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ABSTRACT Background Aims Methods Results Conclusion Cardiac implantable devices (CIED) such as pacemakers, implantable cardioverter‐defibrillators, or cardiac resynchronization devices are implanted in selected patients with bradyarrhythmia and advanced heart failure. The invasive character of these procedures poses a risk of early complications such as pneumothorax, bleeding, infections, or dislocations.There are no available data that analyzed the impact of the organization of procedures on the early complications risk after permanent pacing procedures. The aim of this study was to investigate if organizational aspects can impact early complications risk in CIED implantations.This retrospective study analyzed the medical records of 1673 patients who underwent CIED implantation at the Department of Cardiology of Cardinal Wyszynski Hospital in the years 2016–2020 (before the conduction system pacing era).The regression analysis revealed the predictive value of the number of leads on complication risk overall (β = 0.65, p < 0.001). Even though the significant differences in complications count were also observed for the consecutive days of the week (p = 0.002) and procedure order within the same day (p = 0.01), the regression analysis did not confirm their predictive value on complications’ risk. However, the subgroup analysis regarding the device type revealed the significant predictive value of procedure order on complications in the single‐chamber pacemaker subgroup (β = 1.10, p = 0.01). Moreover, the subgroup analysis confirmed the predictive value of the number of leads on pneumothorax (β = 0.89, p = 0.04) and dislocation (β = 0.67, p = 0.01), age of the patient, and the assist with the less experienced operator on hemopericardium (β = 0.11, p = 0.02, and β = 2.34, p = 0.04, respectively).The study showed that the number of leads is the main factor of early complications after CIED implantations. In the simplest devices such as single‐chamber pacemakers, the order of the procedure within the same day can also play a role in early complications risk. [ABSTRACT FROM AUTHOR]

Backgrounds: Two technologies, cardiac contractility modulation (CCM) and subcutaneous implantable cardioverter‐defibrillator (S‐ICD), can be successfully combined and applied to patients with advanced heart failure (HF) with reduced left ventricular ejection fraction (LVEF). Case Report: We reported a case of a 51‐year‐old man with reduced ejection fraction (LVEF = 33%) and a narrow QRS complex who first underwent simultaneous implantation of CCM and S‐ICD. Conclusion: Our case report aimed to reveal that the simultaneous implantation of CCM and S‐ICD could be successfully used in patients with advanced HF, which could significantly improve the clinical symptoms of such patients during one surgery. [ABSTRACT FROM AUTHOR]

Pulsed electrical field (PEF) ablation is a promising novel ablation modality for the treatment of arrhythmia, especially for atrial fibrillation (AF). There have been several important advances in PEF ablation over the past several years, such as the parameters of PEF delivery and electrode Design. And the results in almost all clinical studies of PEF for AF ablation are optimistic, both in terms of effectiveness and safety. This article provides a brief overview of the mechanism and technical progress of PEF ablation in cardiac arrhythmia treatment, and discuss it's potential applications and the future development. [ABSTRACT FROM AUTHOR]

Background: Cardiac contractility modulation (CCM), being reserved for patients with symptomatic chronic heart failure (HF) and narrow QRS complex under guideline directed medical therapy, can recover initially reduced left ventricular ejection fraction (LVEF); however, the influence of pre‐implantation LVEF on long‐term outcomes is not fully understood. This study aimed to compare the effects of lower and higher preimplantation LVEF on long‐term outcomes in CCM‐therapy. Methods: One‐hundred seventy‐two patients from our single‐centre registry were retrospectively included (2002–2019). Follow‐up data were collected up to 5 years after implantation. Patients were divided into Group 1 (baseline LVEF≤ 30%) and Group 2 (≥ 31%). Both groups were compared based on differences in survival, echocardiographic‐ and clinical parameters including LVEF, tricuspid annular plane systolic excursion (TAPSE), NYHA class or Minnesota living with heart failure questionnaire‐score (MLWHFQ). Results: 11% of the patients did have a LVEF ≥31%. Mean LVEF ± SD for both groups were 21.98 ± 5.4 versus 35.2 ± 3.7%, respectively. MLWHFQ (47 ± 21.2 vs. 42±21.4) and mean peak oxygen consumption (VO2, 13.6 ± 4.1 vs. 12.7 ± 2.8 ml/kg/min) were comparable between both groups. LVEF‐grouping did not influence survival. Lower baseline LVEF resulted in significantly better recovery of echocardiographic parameters such as LVEF and TAPSE. Irrespective from baseline LVEF, both groups showed nearly comparable improvements for clinical parameters like NYHA‐class and MLWHFQ. Conclusion: Long‐term biventricular systolic recovery potential in CCM‐therapy might be better for preimplantation LVEF values ≤30%, whereas clinical parameters such as NYHA‐class can improve irrespective from baseline LVEF. [ABSTRACT FROM AUTHOR]

Background: Phrenic nerve (PN) injury is a potential complication that can occur during superior vena cava (SVC) isolation to cure atrial fibrillation (AF). Avoiding radiofrequency (RF) energy delivery is the safer alternative but may result in failed isolation. High-output PN pacing above the ablation site (upstream PN pacing) to confirm whether the PN is intact is a promising technique to avoid PN injury. This study was conducted to elucidate the safety of delivering RF energy at the site of capture of the right PN using upstream high-output pacing during electrical SVC isolation. Methods: SVC isolation was conducted in 41 drug-resistant AF patients. When high-output pacing (25 mA) from the distal tip of the ablation catheter captured the PN at the right atrial-SVC junction, upstream PN pacing (cycle length: 1000-1500 ms) was applied during RF delivery. The application of RF energy was stopped upon the failure or weakness of diaphragmatic twitching. The feasibility of SVC isolation using upstream PN pacing was investigated. Results: In all 41 patients, SVC isolation was successfully achieved. RF energy was delivered at the PN capture site in 26 patients (154 ± 138 second, 18 ± 5 W), and upstream PN pacing was successfully applied in all of the patients. Out of 46 SVC isolations, including five repeated sessions, PN injury occurred in one patient, who recovered spontaneously within 2 weeks. Conclusions: Upstream PN pacing may be effective for the safe completion of SVC isolation and to reduce the severity of PN injury. (PACE 2012; 35:1053-1060) [ABSTRACT FROM AUTHOR]

Introduction: The strength duration curve has been studied for right ventricular endocardial stimulation. There are differences between left ventricular epicardial and right ventricular endocardial stimulation due to different electrophysiologic properties and different electrode-tissue interface. The strength duration curve for epicardial left ventricular stimulation has not been studied so far. Methods: One hundred and three patients were studied. The strength duration curves were determined for left ventricular epicardial and right ventricular endocardial stimulation. The studied points were chronaxie, rheobase, and voltage threshold at 0.5 ms. Left ventricular leads Guidant 4512, 4513, 4537, 4538 (unipolar, area 3.5 mm2; Guidant Corp., St. Paul, MN, USA), Medtronic 4193 (unipolar, area 5.8 mm2; Medtronic Inc., Minneapolis, MN, USA), Guidant 4518, 4542, 4543 (bipolar, area 4 mm2), St. Jude Medical (bipolar, area 4.8 mm2; St. Jude Medical, St. Paul, MN, USA), and Medtronic 4194 (bipolar, area 5.8 mm2) were studied. Results: The Guidant unipolar leads with a distal electrode area of 3.5 mm2 had a lower chronaxie than the other studied leads. The left ventricular epicardial and right ventricular endocardial chronaxie for 15 patients with Medtronic left ventricular leads 4194 or 4193 (5.8 mm2) and right ventricular leads 6947 (5.7 mm2) were 0.52 ± 0.36 ms and 0.62 ± 0.46 ms (P > 0.05). Conclusion: The left ventricular epicardial chronaxie depends on the lead. The left ventricular epicardial chronaxie is similar to the right ventricular endocardial chronaxie for leads with similar electrode stimulation area. [ABSTRACT FROM AUTHOR]

Background: Cardiac resynchronization therapy (CRT) improves cardiac performance and survival in patients with congestive heart failure. Recent observations suggest that diabetes is associated with a worse outcome in these patients. The aim of the study was to investigate the effect of diabetes and insulin treatment on outcome after CRT. Methods: Diabetic status and insulin treatment were assessed in 447 patients who underwent CRT (males 80.8%, mean age 65.7 ± 9.7 years, ejection fraction 29.9 ± 6.11%). Patients were stratified in three groups according to the presence or absence of diabetes and insulin treatment. Results: Nondiabetic patients were 366 (79.6%), noninsulin-treated diabetic patients 62 (13.9%), insulin-treated diabetic patients 29 (6.5%). The estimated death rate was 5.15 per 100 patients-year in the nondiabetic group, 8.63 in noninsulin-treated diabetics (HR 1.59, P = 0.240), and 15.84 in insulin-treated diabetics (HR 3.05, P = 0.004). Cardiac mortality accounted for 81% of deaths in nondiabetic patients and for 56% of deaths in diabetic patients. Diabetic patients tended to have a worse recovery of left ventricular ejection fraction over time (P = 0.057) and of the distance at 6-minute walking test (6MWT) (P = 0.018). Conclusions: Insulin-treated diabetes is associated with a worse functional recovery and a higher mortality in patients with advanced heart failure after CRT. While cardiac death accounts for the majority of deaths in nondiabetic patients, a relevant proportion of the mortality in diabetic patients seem to result from noncardiac causes. [ABSTRACT FROM AUTHOR]

Introduction: Right ventricular (RV) anodal capture (AC) has been reported in cardiac resynchronization therapy (CRT), when left ventricular (LV) pacing uses pseudobipolar (LV tip to RV proximal electrode) configuration. The aim of the study was to analyze the prevalence of AC and its implications for device programming. Methods and Results: When AC occurred, the resulting QRS morphology was evaluated with the following pacing modes: (1) LV tip pacing plus RV AC, (2) Biventricular (BiV) pacing (i.e., both LV and RV tip pacing), and (3) BiV pacing plus RV AC. Several interventricular pacing (VV) intervals from 50 ms of LV preactivation to 30 ms of RV preactivation were tested in modes 2 and 3. From 38 consecutive patients, AC was achieved in 14 (in 74% of the pacemakers and in none of the defibrillators). LV tip pacing plus RV AC obtained narrower QRS than BiV pacing at all VV intervals in seven of the patients with AC (50%). When BiV pacing is combined with RV AC, it produced a ventricular depolarization through two wave fronts (one from the LV tip and the second from either the ring or the tip of the RV lead depending on the VV interval programmed). Conclusions: AC obtained the narrowest QRS of all tested pacing modes in a significant proportion of patients undergoing CRT. Though the stimulus was delivered from three sites (BiV pacing plus RV AC mode), only two wave fronts of ventricular activation were seen by ECG. [ABSTRACT FROM AUTHOR]

Background: Angiotensin converting enzyme (ACE) inhibitors and Angiotensin II (AII) receptor blockers have previously been shown to be beneficial in treating patients with not only hypertension but also with cardiovascular diseases. Therefore, such drugs may potentially be used in patients with an implantable cardioverter defibrillator (ICD) who show cardiac dysfunctions. Objective: This study aimed to determine effects of short-term administration of the ACE inhibitor (CV-3317) and the AII receptor blocker (CV-11974, an active form of candesartan) on internal defibrillation threshold (DFT) in anesthetized canine hearts. Methods: DFTs were evaluated using a “hot can” defibrillation lead system in: (a) seven dogs following three intravenous administrations of 20 cc saline; (b) 11 dogs that received intravenous CV-3317 doses of 1 mg/kg, 10 mg/kg, and 50 mg/kg; and in (c) 10 dogs that were intravenously given 0.1 mg/kg, 1 mg/kg, and 10 mg/kg CV-11974. DFTs were determined using a “down-up down-up” protocol. Results: Mean DFT delivered energies at baseline and following three consecutive intravenous saline injections were 16.4 ± 9.3 J, 15.3 ± 7.5 J, 15.9 ± 7.1 J, and 15.5 ± 5.6 J, respectively. Those at baseline and following 1 mg/kg, 10 mg/kg, and 50 mg/kg intravenous CV-3317 were 12.9 ± 6.4 J, 12.2 ± 6.4 J, 11.0 ± 6.6 J, and 11.9 ± 6.6 J, respectively. Similarly, those at baseline and after 0.1 mg/kg, 1 mg/kg, and 10 mg/kg CV-11974 were 13 ± 6.6 J, 12.5 ± 6 J, 12.9 ± 5.8 J, and 13.2 ± 6.6 J, respectively. There were no significant differences between DFT at baseline and the others in each treatment group. Conclusions: Since an ACE inhibitor and an AII receptor blocker did not alter DFT, such drugs may be useful in ICD patients without a decrease in safety margins. [ABSTRACT FROM AUTHOR]

Aim: The purpose of this study was to determine the factors associated with the induction of ventricular flutter/fibrillation (VFl/VF) and its prognostic significance in post-myocardial infarction. Methods: Programmed ventricular stimulation was performed after myocardial infarction (MI) for syncope (n = 232) or systematically (n = 755); 230 patients had an induced VFl/VF and were followed during 4 ± 2 years. Results: VFl/VF was induced in 49/232 patients (21%) with syncope versus 181/755 asymptomatic patients (24%) (NS) and 94/410 patients (23%) with left ventricular ejection fraction (LVEF) <40% versus 136/577 patients (22.5%) with LVEF >40% (NS). Cardiac mortality was 9%; LVEF was 33 ± 15% in patients who died, 43 ± 13% in alive patients (P < 0.004). In patients with LVEF <40%, induced VFl/VF, mortality rate was 31% in those with syncope, 10% in asymptomatic patients (P < 0.001), because of an increase of deaths by heart failure; patients with LVEF >40% with or without syncope had a low mortality (5% and 3%). After linear logistic regression, VFl/VF and LVEF were predictors of total cardiac mortality, but only LVEF <40% predicted sudden death. Conclusion: Syncope and the level of LVEF did not increase the incidence of VFl/VF induction after MI, but modified the cardiac mortality: induced VF increased total cardiac mortality in patients with syncope and LVEF <40%, but did not increase sudden death. In patients with LVEF >40%, induced VFl/VF has no significance neither in asymptomatic patients nor in those with syncope. [ABSTRACT FROM AUTHOR]

AGACDIKEN, A., et al.: Effect of Cardiac Resynchronization Therapy on Left Ventricular Diastolic Filling Pattern in Responder and Nonresponder Patients . Background: The aim of this study was to investigate the short- and long-term effects of cardiac resynchronization therapy (CRT) on left ventricular (LV) diastolic filling pattern and the relation between the diastolic filling pattern and the response to CRT. Methods: Twenty-three patients with systolic heart failure and complete left bundle-branch block underwent implantation of biventricular pacemaker devices. In order to follow the changes in diastolic function, mitral inflow, pulmonary venous flow, and LV flow propagation (Vp) velocities were measured with pulsed-wave and color M-mode Doppler echocardiography 1 week before and 1 and 6 months after pacemaker implantation. At the 6-month follow-up, patients were divided into two groups according to their response to CRT defined as a relative increase in LV ejection fraction (LVEF) ≥25% versus baseline. Results: After biventricular pacemaker implantation, significant clinical improvement was observed in all patients. Compared to baseline, the ratio of early-to-late peak velocities (E/A) decreased significantly at the 6th month (E/A ratio: from 1.5 ± 0.9 to 0.8 ± 0.5 at the 6th month (P = 0.02)). Pulmonary systolic flow to diastolic flow ratio (PVs/PVd) increased with CRT after 6 months (PVs/PVd ratio: from 0.9 ± 0.4 to 1.3 ± 0.7 at the 6th month (P = 0.02)). E/Vp ratio decreased significantly at the 1st and 6th month (E/Vp ratio: from 2.7 ± 0.8 to 2 ± 0.8 at the 1st (P < 0.002) and to 1.9 ± 0.7 at the 6th month (P < 0.02)). In responders (n: 17, 74%), E wave and PVra velocity decreased, E-wave deceleration time increased, and E/Vp ratio improved significantly, whereas in nonresponders, changes in LV diastolic parameters remained insignificant. However, diastolic filling pattern improved significantly at the 1st and 6th month of CRT in both responders and nonresponders. Conclusion: CRT enhances diastolic filling patterns in both responder and nonresponder patients. This may be related to improvement in symptoms even in nonresponders who have a relative increase in LVEF <25%. (PACE 2005; 28:654–660) [ABSTRACT FROM AUTHOR]

BOODHOO, L., et al.: Improving the Acceptability of the Atrial Defibrillator: Patient-Activated Cardioversion Versus Automatic Night Cardioversion With and Without Sedation (ADSAS 2). Acceptability of the atrial defibrillator is partly limited by concerns about shock related anxiety and discomfort. Sedation and/or automatic cardioversion therapy during sleep may ease shock discomfort and improve patient acceptability. Three atrial cardioversion techniques were compared: patient-activated cardioversion with sedation, automatic night cardioversion with sedation, and automatic night cardioversion without sedation. Sedation was oral midazolam (15 mg). Fifteen patients aged 60 ± 13 years were assigned each strategy randomly for three consecutive episodes of persistent atrial fibrillation requiring cardioversion. Patients completed questionnaires for multiple parameters immediately and again at 24 hours postcardioversion. Atrial cardioversion strategies with oral sedation (patient-activated and automatic) significantly reduced shock recall by 77% (P < 0.005), therapy dissatisfaction by 57%-71% (P < 0.03), shock discomfort by 61%-73% (P < 0.01), shock pain by 79%-83% (P < 0.001), and shock intensity by 73%-77% (P < 0.03), compared to automatic night cardioversion without sedation (P < 0.02). Atrial shock pain was short-lived and caused little disruption to the patients' daily routines. Automatic night cardioversion without sedation, resulted in sleep disturbances not seen with the other strategies (42% vs 0%, P < 0.001) as well as concerns about future pain or discomfort. Twelve patients (80%) chose patient-activated cardioversion with sedation as their preferred treatment, and three (20%) remainder chose automatic night cardioversion with sedation. Ninety percent of patients chose automatic night cardioversion without sedation as the least acceptable therapy. Sedation significantly increases atrial shock acceptability regardless of cardioversion method. Shocks without sedation are significantly less acceptable to patients using the atrial defibrillators. (PACE 2004; 27:910–917) [ABSTRACT FROM AUTHOR]

RÜB, N., et al.: Addition of a Defibrillation Electrode in the Low Right Atrium to a Right Ventricular Lead Does Not Reduce Ventricular Defibrillation Thresholds. Transvenous unipolar active can defibrillation systems have proven to be effective in treating ventricular tachyarrhythmias. However, a further reduction of ventricular defibrillation thresholds (V-DFT) would increase the longevity, reduce the size of pulse generators, and help to avoid additional leads in patients with inacceptable high V-DFTs. In a finite difference computer model, the extension of the right ventricular (RV) defibrillation coil into the low right atrium led to a 40% reduction of unipolar V-DFT. To evaluate this finding, we conducted a prospective, randomized study in 11 patients receiving an ICD. Extension of the RV electrode was simulated by adding a second coil placed in the low right atrium with the same polarity. Using a binary search protocol, V-DFT was determined with and without the additional electrode in each patient. Total shock impedance was significantly lower in the two coil (low RA) configuration, compared to the single coil (RV) configuration. Corresponding values were 49.9 ± 6.7 Ohm and 61.1 ± 9.3 Ohm, respectively (P < 0.01, paired t-test). However, there was no reduction, but even a nonsignificant increase in V-DFTs. Mean V-DFT in the RV configuration was 12.0 ± 5.6 J and 16.3 ± 7.8 J in the low RA configuration (P = 0.09, paired t-test). Despite a reduction in total impedance, the addition of a defibrillation coil in the low right atrium does not reduce ventricular defibrillation thresholds. (PACE 2004; 27:346–351) [ABSTRACT FROM AUTHOR]

BREMBILLA-PERROT, B., et al.: Significance of External Cardioversion Induced Atrial Tachyarrhythmias. External cardioversion is used to stop VT or VF in emergency. Supraventricular tachyarrhythmias are sometimes noted after cardioversion in patients known to be previously in sinus rhythm. The purpose of the study was to evaluate the significance of supraventricular tachyarrhythmias induced by external cardioversion. The study population consisted of 22 patients who developed supraventricular tachyarrhythmias after transthoracic cardioversion (300 J) delivered to stop a VT or VF induced by electrophysiological study. Defibrillation used monophasic waveform. Supraventricular tachyarrhythmias complicated 6% of cardioversions for VT; before cardioversion, all patients were in sinus rhythm. After cardioversion, three patients developed a paroxysmal reentrant supraventricular tachycardia (PSVT), which was stopped by atrial pacing. The remaining patients developed AF that lasted from 3 minutes to 24 hours (n = 4). One patient remained in AF. AF developed after a sinus pause or bradycardia, which was due to the interruption of VT or VF in nine patients or was noted just when VT or VF stopped (n = 10). The analysis of clinical data indicated that all three patients who presented a PSVT had a history of PSVT. Among patients who developed a sinus pause dependent AF, two had a history of AF. Among ten patients who developed AF at the time of cardioversion, three had a history of AF. During follow-up (1–9 years), no patient without a history of AF developed spontaneous AF, but patients with history of tachycardias had arrhythmia recurrences. The mechanism of cardioversion related tachycardias can be a pause related dispersion of atrial refractoriness or an adrenergic reaction induced by VT or VF, factors that precipitate arrhythmias in patients with history of atrial arrhythmias (one third of patients). In conclusion, supraventricular tachyarrhythmia is relatively frequent after external cardioversion for ventricular tachyarrhythmia, has no prognostic significance in patients without previous history of atrial arrhythmias, but in those with history of tachycardias is associated with a high risk of recurrence. (PACE 2003; 26:2111–2115) [ABSTRACT FROM AUTHOR]

BORIANI, G., et al. : Late Improvement in Ventricular Performance Following Internal Cardioversion for Persistent Atrial Fibrillation: An Argument in Support of Concealed Cardiomyopathy. --> The aim of the study was to evaluate the time course of atrial and ventricular function improvement following internal atrial cardioversion in patients with structural heart disease. Twenty‐nine patients with chronic persistent atrial fibrillation (AF) and underlying structural heart disease were followed by serial echocardiograms performed at 1 and 6 hours, 1 day, 1, 2, and 3 weeks, and 1, 2, 3, and 6 months after successful cardioversion. Sinus rhythm was maintained at 6 months in 24 patients. Following cardioversion the time course of left atrial mechanical function (peak A wave, percent A wave filling) differed from that of left ventricular ejection fraction: peak A wave values (cm/s) increased significantly at 1 week (51 ± 23vs35 ± 15at 1 hour,P < 0.05), percent A wave filling (%) increased significantly at 2 weeks (34 ± 12vs22 ± 9at 1 hour,P < 0.05), whereas left ventricular ejection fraction (%) increased later (at 1 month 60 ± 14vs55 ± 14at baseline,P < 0.05and at 2 months60 ± 14vs56 ± 14at 1 hour,P < 0.05). In conclusion, restoration of sinus rhythm results in an improvement in left ventricular ejection fraction during follow‐up, even in patients with structural heart disease without fast ventricular rates at baseline. The dissociation between the time course of atrial and ventricular function improvement suggests that the latter was partly due to regression of a concealed form of cardiomyopathy and/or of a ventricular dysfunction due to chronic AF. (PACE 2003; 26:1218–1226) [ABSTRACT FROM AUTHOR]

A small electrode surface reduces pacing current drain and can extend generator longevity. The study evaluated the performance of a tined, quadripolar defibrillation lead (model 6944) that has a small-surfaced, steroid-eluting electrode tip for high impedance pacing. In a prospective, controlled study, 34 patients with conventional ICD indications were randomized one to one to receive the high impedance model 6944 or a tined defibrillation lead with a conventional sized, steroid-eluting electrode tip model 6942. Lead performance was evaluated at implant, prior to hospital discharge, and 1, 3, 6, and 12 months thereafter. Baseline characteristics did not differ significantly between patients implanted with lead model 6942 (n = 16) or model 6944 (n = 17). One patient randomized to receive the model 6942 was excluded from the study and was implanted with an active-fixation lead after stable lead positioning was neither possible with the 6942 nor with the 6944 electrode. No other lead related adverse events were observed. At implant, there were no significant differences between pacing thresholds, sensing performance, defibrillation impedances, and defibrillation thresholds in both groups, but pacing impedance of the model 6944 (988.6 ± 217.7 Ω) was approximately twice as high as in the model 6942 (431.7 ± 83.7 Ω; P < 0.0001). This difference remained highly significant throughout the observation period of 12 months, while R wave amplitudes and pacing thresholds remained equal in both lead models. The use of a tined defibrillation lead with a small, steroid-eluting electrode tip appears safe and results in a high pacing impedance without compromising system performance. [ABSTRACT FROM AUTHOR]

This study investigated the safety and feasibility of transvenous biventricular defibrillation in ICD patients. Some patients may have high DFTs due to weak shock field intensity on the LV. Animal studies showed a LV shocking electrode dramatically lowered DFTs. This approach might benefit heart failure patients already receiving a LV lead or conventional ICD patients with high DFTs. A modified guidewire was used as a temporary left venous access defibrillation electrode (LVA lead). In 24 patients receiving an ICD. the LVA lead was advanced through a guide catheter in the coronary sinus (CS) and into a randomized LV vein (anterior or posterior) using a venogram for guidance. Paired DFT testing compared a standard right ventricular defibrillation system to a biventricular defibrillation system. There were no complications or adverse events. As randomized, LVA lead insertion success was 87% and 71% for anterior and posterior veins, respectively, and 100% after crossover. Total insertion process time included venogram time (32.5 ± 26.9 minutes, range 5-115, mode 15 minutes) and LVA lead insertion time (15 ± 14 minutes, range 1-51, mode 7 minutes). An apical LVA lead position was achieved in 11 (45%) of 24 patients and 7 (64 %) of these 11 displayed a DFT reduction; however, mean DFTs were not statistically different. Transvenous biventricular defibrillation is feasible and was safe under the conditions tested. Additional clinical studies are justified to determine if optimized LV lead designs, lead placement, and shock configurations can yield the same large DFT reductions as observed in animals. [ABSTRACT FROM AUTHOR]

Focuses on early reinitiation of atrial fibrillation (AF) after eletrical defibrillation. Causes and characteristics of AF after electrical defibrillation; Steps for the suppression of early reinitiation of AF; Potential mechanisms of the condition and clinical implications.

Cycle periods in ECG during VF are correlated with periods of reentrant activation. The ECGs recorded from different locations on the thorax were contributed to from electrical activations within the heart in approximately inverse proportion of their distance from the recording sites. Similarity in cycle periods between ECGs recorded from two locations, therefore, can be used as an index of spatiotemporal similarity in the rate of activation. In the present study coherence was used, which is a mathematical function that measures the degree of similarity that two signals exhibit at specific cycle periods, to test if spatiotemporal similarity in cycle periods between pairs of orthogonal ECGs was correlated with defibrillation shock outcome. The authors estimated time-varying coherence from orthogonal ECGs during 10 seconds of electrically induced VF, which was terminated with a defibrillation shock with a 50% probability of successful outcome. Defibrillation shocks were delivered between a coil electrode placed at the right ventricular apex and a subdermal patch electrode. Time-varying coherencies between pairs of ECGs were estimated using an adaptive least mean square algorithm, time-coherence surfaces were integrated within a frequency region centered at the dominant frequency. Data were collected from ten dogs during 206 (48%) successful and 221 (52%) unsuccessful trials. The results showed that coherencies between the sagittal-transverse pair were 10%-15% higher (P < 0.05) for successful than unsuccessful trials. The correlation between coherence and defibrillation outcome suggests that more defibrillation shocks occurred when the degree of spatial similarity in the rate of activations was higher terminated VF, than those that occurred at other times. These results are consistent with a hypothesis, recently proposed by others, that more uniform activation within regions of the heart that receive low potential gradients during shock may increase the probability of successful defibrillation. [ABSTRACT FROM AUTHOR]

AutoCapture (AC) and Ventricular Capture Management (VCM) are pacing algorithms that attempt to automatically optimize pacing output, providing consistent capture and enhancing device longevity. This report describes potentially serious consequences from use of these algorithms. In one pacemaker dependent patient, AC malfunction led to failure of ventricular capture. This was fixed with a software correction. The potential seriousness of AC malfunction leads to the recommendation that this software be downloaded into all susceptible pacemakers. In a second patient, VCM malfunction resulted in unnecessary high output pacing. Our experience illustrates the need for postmarketing surveillance when embracing newer technology. [ABSTRACT FROM AUTHOR]

Features the consensus statement issued by the North American Society of Electrophysiology and Pacing, in conjunction with the American College of Cardiology, about implantable cardioverter defibrillators (ICD). Indications for ICD therapy; Guidelines for use of ICD; Recommendations for follow-up of ICD; Prehospital discharge assessment; Access to ICD therapy.

Low energy internal atrial cardioversion can be performed by delivering biphasic shocks between transvenous catheters positioned within the cardiac chambers or great vessels. Delivery of shocks results in effective cardioversion at energies < 6–10 J and the procedure can be effective even when external cardioversion has failed. Shock induced discomfort varies from patient to patient, but the procedure can be usually performed without general anesthesia and eventually under mild sedation. Nevertheless, tolerability has to be improved by obtaining a substantial reduction in defibrillating thresholds. With regard to safety, delivery of shocks for defibrillating the atria implies a potential risk of inducing ventricular fibrillation; to minimize this risk, shock delivery must be synchronous to the QRS and should be avoided during rapid RR cycles (< 300 ms). Presently, transvenous low energy cardioversion is an investigational procedure, but a widening of indications is expected in the near future. The cost of the procedure, which remains invasive and requires a brief hospital stay, must be balanced with the benefit of restoring sinus rhythm and the possibility of maintaining sinus rhythm for the medium- to long-term. Experimental and clinical investigations of low energy internal cardioversion have resulted in the development of devices for atrial defibrillation whose clinical role and cost-benefit ratio is currently under evaluation. [ABSTRACT FROM AUTHOR]

Atrial fibrillatory frequency reflects the atrial refractory period during AF. This study was conducted to investigate noninvasively the diurnal fluctuations of fibrillatory frequency in persistent human atrial fibrillation and to determine the relationship between changes in ventricular rate and fibrillatory frequency. Ambulatory ECGs were recorded in 30 patients (18 men, 12 women, mean age 60 ± 11 years) with persistent AF (> 24 hours). AF frequency was measured in 1-minute ECG segments by subtracting averaged QRST complexes an d applying Fourier analysis to the resulting signals at 4 PM, 10 PM, 4 AM, and 10 AM. Peak frequency was determined in the 3–12 Hz frequency band. Mean fibrillatory frequency measured 6.6 ± 0.6 Hz (range 5.0–7.8 Hz). Two different frequency patterns were distinguished comparing maximal diurnal versus nocturnal fibrillatory frequency. In six (20 %) patients an increase (P = 0.045) in nocturnal fibrillatory frequency (type I) was found. In the remaining 24 (80%) patients a decrease (p < 0.001), in fibrillatory frequency occurred (type II). Type I AF showed a strong inverse correlation between relative changes (percent) in ventricular rate and fibrillatory frequency obtained from two consecutive measurement points (r = -0.88 to -.97, P < 0.01), whereas in type II AF a moderate positive correlation (r = 0.36 to 0.41, P < 0.05) was detected. These data indicate a circadian pattern in AF frequency that concurs with ventricular rate changes suggesting a modulating influence of the autonomic nervous system an atrial electrophysiology in persistent human AF. [ABSTRACT FROM AUTHOR]

In a patient without apparent heart disease, a ventricular extrastimulus delivered from the left ventricular apex where the electrogram was recorded 30 ms after the onset of the QRS complex during VT advanced the second QRS complex, but not the first QRS complex. The morphology of the second QRS complex was the same as that of VT. The postpacing interval was the same as the cycle length of the VT. These findings indicated that the site of stimulation was at the inner loop of the reentry circuit of the VT. A ventricular extrastimulus with a shorter coupling interval advanced the first and second QRS complexes, indicating that the ventricle was activated by antidromic and orthodromic activation from the extrastimulus. Radiofrequency ablation at that site of stimulation terminated the VT and no further VT could be induced. [ABSTRACT FROM AUTHOR]

Dual AV node physiology often persists after successful slow pathway (SP) ablation, and the mechanism of tachycardia elimination is unresolved. Therefore, AV node conduction curves were analyzed following successful ablation (4 ± 1 energy applications) in 85 consecutive patients (58 women, age 50 ± 2 years) with typical AVNRT. Twenty-seven patients (32%) had complete elimination (group 1) whereas 58 (68%) patients had persistence (group 2) of dual AV node physiology. A significant increase in the AV node Wenckebach cycle length (WB-CL) was observed in both groups (310 ± 9 to 351 ±15 ms in group 1, and 325 ± 8 to 369 ± 9 ms in group 2.P < 0.05). A decrease in the fast pathway (FP) ERP (339 ± 15 to 279 ± 12 ms) and an increase in the maximum FP AH interval (141 ± 5 to 171 ±7) were observed only in group 1 (P < 0.05). In group 2, no change in the SP FRP (267 ± 7 to 280 ± 10 ms) was observed, and the change in the maximum SP-AH following ablation showed a significant inverse relation to the maximum SP-AH at baseline in group 2. In conclusion, (1) an increase in the WB-CL is observed independent of the persistence or elimination of dual physiology after successful ablation; (2) when dual physiology is eliminated, significant changes in the FP ERP and the maximum FP-AH occur; (3) when dual physiology persists, FP physiology and the SP FRP remain unchanged, and a significant inverse relation between the change in the maximum SP-AH following ablation and the maximum baseline SP-AH is observed. [ABSTRACT FROM AUTHOR]

Explains that in the search for an answer to the question of optimal right atrial pacing sites, several aspects should be considered. Which site favors atrial pacing performance; Which site provides suitable atrial sensing performance; Site-specific differences of lead dislodgement rate; Do some sites improve hemodynamic function; Are certain sites required for atrial arrhythmia suppression.

Defibrillation in the middle cardiac vein (MCV) has been shown to reduce ventricular defibrillation thresholds (DFTs). Low amplitude auxiliary shock (AS) from an electrode sutured to the left ventricle at thoracotomy have also been shown to reduce DFT if delivered immediately prior to a biphasic shock (between the ventricular RV and superior vena caval (SVC) electrodes). This study investigates the impact on DFT of an AS shock from a transvenously placed MCV lead system. A standard defibrillation electrode was positioned in the RV in eight anesthetized pigs (35-43 kg). A 50 × 1.8-mm electrode was inserted in the MCV through an 8 Fr angioplasty guide catheter. A 150-V (leading edge) monophasic AS was delivered (95 µF capacitor) from the MCV → Can with three different pulse widths (3, 5, 7 ms). A primary biphasic shock (PS) (95µF capacitor, phase I: 44% tilt, 1.6-ms extension and phase 2: 2.5-ms fixed duration) was delivered from the RV → Can ± AS. The four configurations were randomized and DFTs (PS + AS) assessed using a modified binary search. Ventricular fibrillation (VF) was induced with 60 Hz AC followed 10 seconds later by the test shock. The DFTs were compared using repeated measures analysis of variance (ANOVA). All configurations incorporating AS produced significant (P < 0.05) reduction in the DFT compared to no AS (13.8 ± 7.4 J). There was no difference in the efficacy of differing pulse widths (P > 0.05); 3 ms (11.0 ± 5.4 J), 5 ms (11.5 ± 6.0), and 7 ms (10.6 ± 5.3 J). In conclusion, delivering an AS from a transvenous lead system deployed in the MCV reduces the DFT by 23% compared to a conventional RV → Can shock alone. [ABSTRACT FROM AUTHOR]

This study assessed the influence of rates of reperfusion on excitability of the myocardium using dominant frequency (DF) (in Hz) of VF and the relationship of DF to the minimum defibrillation energy (MDE) (in J). Our hypothesis was that increasing flow during reperfusion increases DF that raises MDE. Initially, six Langendorff perfused swine hearts were serially fibrillated and perfusion arrested for 4 minutes followed by reperfusion and defibrillation to establish reproducibility of the model. The epicardial ECG was analyzed for DF. In subsequent studies (n = 8), no flow VF was followed by 1-minute reperfusion at normal flow or 10% flow (low flow) and shocked with increasing energy via epicardial pads until defibrillation. The DF at onset of no flow VF was 9.5 ±1.4 and decreased to 3.6 ±1.4 after 4 minutes. Reperfusion at normal flow increased the DF of VF compared to low flow after 1 minute (10.8 ± 1.1 vs 4.5 ± 1.1 Hz, P = 0.0002) and was associated with increased defibrillation energy requirements (13.5 ± 5.0 vs 7.3 ± 6.2 J, P = 0.047). In summary, defibrillation energy requirements are lower when myocardial excitability is reduced during low flow reperfusion. [ABSTRACT FROM AUTHOR]

Although it is generally assumed that defibrillation becomes more difficult when the duration of VF is prolonged, after a failed defibrillation attempt, there is little information on the defibrillation efficacy of multiple shocks delivered at the same energy. The purpose of this study was to systematically examine the efficacy of a second shock delivered at the same or reversed polarity after a failed first shock. Defibrillation was attempted after 10 seconds of VF in 12 pigs (30-56 kg) using biphasic waveforms and a nonthoracotomy lead system. Shock energy was held constant for the first and second shocks at 50%-90% of the DFT. The second shock was delivered 10 seconds after a failed first shock. First and second shock polarity (first phase) was randomized to (+,+), (+,-), (-,-), (-,+). The incidence of successful defibrillation (for all polarities) was 12.3% for first and 49.1% for second shocks (P < 0.0001). Anodal first shocks had a 17.2% incidence of success as opposed to a 7.4% incidence of success with cathodal first shocks (P = 0.001). Anodal second shocks had a 55.5% incidence of success compared to a 42.7% incidence of success with cathodal second shocks (P = 0.008). There was no significant benefit from polarity reversal after a failed first shock (P = 0.29). In conclusion, less energy is required for successful defibrillation by a second shock after a failed first. The optimal configuration for first and second shocks is with the RV as anode. Polarity reversal of a second shock after a failed first does not affect the probability of second shock success. [ABSTRACT FROM AUTHOR]

There are conflicting results on the effect of polarity change on the defibrillation efficacy of biphasic shocks possibly caused by different shock durations. The goal of the present study was to investigate the influence of polarity reversal on defibrillation efficacy for different biphasic shock durations in a porcine animal model. In eight anesthesized pigs using a transvenous/ submuscular lead system DETs for 4 phase 1 durations were determined: 8.1 ms, 6 ms, 3.8 ms and 1.7 ms. The phase 1/phase 2 ratio was constant at 60%/40%. For cathodal shocks, the defibrillation coil in the right ventricular apex was the cathode during phase 1 and for anodal shocks it was the anode. For both polarities, the strength-duration curve revealed a DFT minimum at 3.8 ms (cathodal shocks: 21.3 ± 6.4 J, P < 0.001; anodal shocks: 21.9 ± 8 J, P = 0.05). For anodal shocks and phase 1 durations of 1.7, 3.8, and 6 ms there was no significant difference of the stored energy at the DFT compared to cathodal shocks. In contrast, significantly lower DFTs were observed for anodal shocks with a phase 1 duration of 8.1 ms (28.8 ± 6.4 J compared to 33.1 ± 5.9 J for cathodal shocks, P = 0.006). The effect of lower defibrillation energy requirements with polarity reversal depends on the total biphasic shock duration; for the pulse duration with the lowest DFT, polarity reversal does not increase defibrillation efficacy of biphasic shocks. [ABSTRACT FROM AUTHOR]

Biphasic defibrillation wavaforms have provided a reduction in defibrillation thresholds in transvenous ICD systems. Although a variety of hiphasic waveforms have been tested, the optimal pulse durations and tilts have yet to be identified. A multicenter clinical study was conducted to evaluate the performance of a new ICD hiphasic waveform and new HV active fixation steroid eluting lead system. Fifty-three patients were entered into the study. Mean age was 63 years with a mean ejection fraction of 36.8%. Primary indication for implantation was monomorphic ventricular tachycardia alone (54.7%). Forty-eight patients (90.6%) were implanted with an RV shocking lead and active can alone as the anodal contact. The ICD can was the cathode. In four cases (7.5%), an additional SVC or CS had was used due to a high DFT with the RV lead alone. In an additional case, a chronic SVC lead was used although the HV-Can DFT was acceptable. DFT for all cases at implant was 9.8 ± 3.7 J. Repeat testing at 3 months for a subset of patients showed a reduction in DFT (7.4 ± 3.0J), P value = 0.03. Sensing and pacing characteristics of the HV lead system remained excellent during the study period (acute 0.047 ± 0.005 ms at 5.4 V and 9.9 ± 6.2 mV R wave; chronic 0.067 ± 0.11 ms at 5.4 V and 9.3 ± 5.4 mV R wave). It is concluded that this lead system provides good acute and chronic sensing and pacing characteristics with good DFT values in combination with this waveform. [ABSTRACT FROM AUTHOR]

Examines the relationship of afterdepolarizations to cardiac arrhythmia in the intact heart. Mechanisms responsible for digitalis-induced delayed afterdepolarizations; Cellular electrophysiologic characteristics of digitalis-induced delayed afterdepolarizations; Comparison of digitalis-induced repetitive ventricular responses in intact animals and delayed afterdepolarizations in isolated tissues.

Examines the role of electronically-mediated transmission and block processes in determining the behavior of the atrioventricular (AV) node. Impulse transmission across excitable tissues; Source of the nonhomogeneity of cardiac tissues; Model for AV nodal conduction using the sucrose gap preparation; Example of electronic inhibition in a sucrose gap preparation.

The effectiveness of pacing techniques for termination of ventricular tachycardia is well established, and of great value in the electrophysiologic laboratory, and, to a more limited degree, for chronic therapy using implanted anti-tachycardia devices. Although it appears that most clinical ventricular tachycardias are due to reentrant mechanisms, responses to antitachycardia pacing have often been difficult to understand. In this paper, clinical observations are correlated with hypothetical constructs and considerations, in an attempt to derive some general principles related to the success and failure of pacing for ventricular tachycardia. In these analyses, it appears that properties of conductivity and refractoriness in the myocardium are as important as the properties of the tachycardia circuit. Programmed extrastimuli or rapid pacing result in shortening of the effective refractory period of the myocardium, together with depressed conduction velocity of the stimulated wavefront. However, the changes in wavefront conductivity do not occur in step with changes in the effective refractory period; as a result, the stimulated wavefront arrives at the tachycardia circuit in a pattern which differs from the stimulation pattern. In general, it appears that termination of the tachycardia is favored when the stimulated wavefront arrives at the tachycardia circuit at a point when if cannot enter the circuit in an antegrade direction. Those conditions are favored by a refractory period in the circuit which is moderately long compared to that of the myocardium. Constructions explaining the observation of a tachycardia termination zone are presented, together with explanations for failure to achieve termination, and for various patterns of acceleration. [ABSTRACT FROM AUTHOR]

The past decade has witnessed important advances in the understanding of the mechanism underlying ventricular arrhythmias. It has become clear that sustained ventricular arrhythmias can generally be reproduced with programmed ventricular stimulation in the clinical electrophysiology laboratory. False positive results may, however, occur with very vigorous stimulation techniques, particularly in patients without documented arrhythmias. False negative results are not infrequent in victims of cardiac arrest. Ability or inability to initiate ventricular tachycardia during acute and chronic drug testing has predicted clinical failure or success, at least for conventional antiarrhythmics. Patients with sustained ventriculartachycardia and cardiac arrest occurring outside the peri-infarction period are those most likely to benefit from study. Conventional antiarrhythmic agents are successful in about one-third of patients with a high degree of concordance among these drugs. Amiodarone is frequently effective in patients with drug-refractory ventricular arrhythmias. However, its efficacy cannot be predicted by programmed stimulation. This is in striking contrast to Type 1A anti-arrhythmic agents. [ABSTRACT FROM AUTHOR]

Deals with a form of reentry during which both of the bundle of His and ventricular myocardium are incorporated in the circuit. Mechanism involved in macro-entry His Purkinje system; Distinction of macro reentry His Purkinje system from other reentrant phenomenon following paced ventricular premature stimulation; Longitudinal dissociation within the bundle branches; Electrophysiologic criteria used in identifying ventricular echo and atrioventricular nodal reentry.

His bundle recordings and programmed electrical stimulation were performed in a 70-year-old woman with bidirectional tachycardia; the recordings demonstrated the infra-Hissian origin of the tachycardia. Occurrence of the His deflection slightly after the onset of ventricular depolarization suggested that the origin of the tachycardia was located near the His bundle bifurcation. Recording of three atrial sites during tachycardia allowed the study of retrograde atrial activation. Two sets of fairly constant and alternating VA intervals were recorded. This fact is consistent with two ventricular circuits used alternatively. The tachycardia could also be interrupted with a single atrial or ventricular premature beat. It is postulated that the tachycardia is due to macroreentry involving the two fascicles of the left branch. Thu study suggests that reentry may be a possible mechanism in some cases of bidirectional tachycardia. (PACE, Vol. 5, September-October, 1982) [ABSTRACT FROM AUTHOR]

Two patients underwent permanent endocardial pacing for complete atrioventricular block. In each case a persistent left superior vena cava was either suspected or known to be present. An active fixation electrode was passed down the left superior vena cava and the tip positioned in the apex of the right ventricle. Stable ventricular pacing was achieved for the follow-up period of approximately six months. With the availability of such active fixation electrodes the presence of a persistent left superior vena cava no longer mandates insertion of an endocardial electrode via the right superior vena cava, when present, or implantation of an epicardial pacing system. [ABSTRACT FROM AUTHOR]

The long-term performance of porous and solid ring-tipped electrodes was compared in clinical use over a one-year period Each of the two electrode designs was implanted in 22 patients in conjunction with an output-programmable pacemaker. Implant evaluation included impedance, height of sensed R wave, and a strength-duration curve. Threshold determination by pulse-width programming was performed at the time of implant and at one week, two weeks, two months, six months, and one year. There were no dislodgements with either electrode. No significant differences were noted in the acute parameters or in chronic thresholds. [ABSTRACT FROM AUTHOR]

In order to identify a practical short-duration limit for stimulating myocardium, theoretical and experimental studies were carried out using dog and turtle hearts The strength-duration curves for current, charge and energy were derived from the standard excitable membrane model which employs a parallel resistance and capacitance. From these derivations, the predicted duration for minimum energy was identified. The experimentally measured strength-duration curves for two types of myocardium followed the predicted values closely The duration for minimum energy was calculated to be 1.25 times the membrane time constant. The practical short-duration limit for a pacemaking stimulus is about 30% of the membrane time constant. For dog myocardium the average time constant was 2.4 ms Therefore, a practical stimulus duration for minimum charge in the dog should be no longer than about two-tenths of a millisecond, although shorter duration stimuli are equally effective This minimum charge criterion provides the minimum drain on the stimulator power supply. [ABSTRACT FROM AUTHOR]

The study was designed to assess the effect of various forms of right atrial or ventricular stimulation on the termination of re-entrant "supraventricular" tachycardias. Standard electrophysiological techniques were used in 81 patients to study 86 stable tachycardias. All tachycardias were initiated by single or double atrial or ventricular premature stimuli or incremental atrial pacing. Eight groups of tachycardia circuit were defined in terms of the anterograde and retrograde pathways. Termination of each tachycardia was studied by atrial underdrive, ventricular underdrive, rapid atrial stimulation and single or double atrial and ventricular premature extrastimuli, intranodal re-entrant tachycardias formed 33% of the total and WPW tachycardias as a whole formed 55% of the total number of arrhythmias. The remainder were comprised of atrial tachycardia (5%), tachycardias in association with a partial AV nodal bypass (3%) and pre-excited tachycardias (5%). A single atrial extrastimulus was most effective where the circuit involved the right atrium. Atrial underdrive was consistently less successful than a single atrial extrastimulus in all groups. Rapid atrial pacing was effective in all groups, but caused transient atrial flutter or fibrillation in a proportion of each group except one. Ventricular underdrive stimulation was most effective in those groups where the right ventricle was involved in the circuit, but tended to be less effective than programmed single or double ventricular extrastimuli. Pacemakers designed to deliver appropriately timed single or double extrastimuli may offer an important alternative to other pacing modalities. [ABSTRACT FROM AUTHOR]

In order to avoid the potential risk of a short refractory period and the inconvenience of the electronic blocking mechanism at the highest synchronous rate with the conventional atrial triggered pulse generator, two more functions have been added to the normal atrial triggered (VAT) pulse generator. First, it has been designed to be ventricular inhibited: second, a highest synchronous rate detector has been added. When the highest synchronous rate of about 140 is exceeded, the atrial signals are blocked and the frequency of the basic rate generator is increased to about 330. Two patients could hardly feel the change from atrial triggered pacing to ventricular inhibited stimulation, and both were able to work at higher loads with this type of pacing compared with the conventional atrial triggered pulse generator. [ABSTRACT FROM AUTHOR]

Examines the efficacy of Moore-Corradi procedure, an electrical treatment for aneurysm, a cardiovascular disease manifested by a sac-like widening of an artery. Delivery of electricity through permanently implanted wire; Analysis of essential elements and conditions best suited for the procedure; Evaluation of death risk and disease risk factors from electrical treatment for aneurysm.

Presents the first part of a series article regarding the definitions and glossary about the compendium of pacemaker technology. Definition of electrostimulation; Factors contributing to the threshold, which is the minimum amount of electricity that is just able to stimulate a cell response; Application of the electrical pulse in a pacemaker.

Chest thump is a simple method of treatment of some paroxysmal arrhythmias. Its therapeutic efficacy, electrophysiological bases and clinical utility have been studied in 17 patients during 45 episodes of ventricular tachycardia (VT). Thumping the precordium interrupted the VT in 22 episodes. Three types of interruption of VT have been observed: (1) In 15 episodes, single ventricular premature beats induced by the blow, occurring randomly in the cycle, stopped the arrhythmia; (2) In 5 episodes, a run of premature beats, induced by a rapid succession of blows, interrupted the tachycardia; (3) In 2 episodes, chest thump caused a short period of asystole followed by sinus rhythm. Chest thump is an antiarrhythmic treatment of definite clinical utility. The complications are rare, although there is a possibility of ventricular fibrillation. Therefore, it should be performed only under careful supervision. [ABSTRACT FROM AUTHOR]

The effects of rapid external chest wall stimulation were evaluated in 10 patients with normally-operating unipolar, lithium-powered, QRS-inhibited pacemakers functioning in their control VVI (QRS-inhibited) mode. Stimuli delivered at slow rates resulted in the expected pacemaker inhibition. On the other hand, during rapid (greater than 900/min) external chest wall stimulation, 8 pacemakers reverted to a VOO mode, 1 to a VVI mode and 1 to either a VVI or VOO mode. No pacemaker was totally inhibited by rapid chest wail stimulation. In accordance with the manufacturer's specifications, the rate to which the implanted pacemakers reverted during the VOO modes produced by the fast external stimuli were the same as those of the VOO modes induced by proper application of an external magnet. Although rapid external chest wail stimulation proved to be a safe procedure, more studies are necessary to determine its usefulness in the follow-up of patients with implanted QRS-inhibited (VVI) pacemakers. At present, conclusions cannot be drawn regarding whether these pacemakers will revert to a mode of operation similar to that induced by rapid external chest wall stimulation when subjected to extrinsic sources of strong electromagnetic interference. [ABSTRACT FROM AUTHOR]

Automatic capture verification can prolong pulse generator longevity and increase patient safety. However, the detection of evoked response following pacing is complicated due to afterpotentials caused by polarization of electrodes. This study describes a new capture verification scheme, which neutralizes the charges between the pacing electrodes. The hypothesis of the charge-neutral sensing is that the afterpotentials in the ring and the tip are opposite in polarity when pacing in a bipolar mode between ring and tip. Summing the unipolar signals sensed at the tip and the ring should effectively cancel the afterpotentials. This scheme was implemented in an external computer based system and tested during pacemaker implant/replacement on 23 patients during VVI pacing (17 acutely implanted leads and 6 chronic leads). Surface ECG was recorded to provide a marker for capture and noncapture. The pacing voltage was gradually decreased until a noncapture beat was noted. To avoid fusion beats, the pacing rate was programmed ∼50% higher than the intrinsic rate. The evoked response was high pass filtered and the integral average was calculated for both capture and noncapture beats. The system signal to noise ratio (SNR) was expressed as ratio of the minimum integral average of all capture beats to the maximum integral average of all noncapture beats. The system SNR was 8.6 ± 1.3 (mean ± S.E.M; range 1.5-22.8), indicating that the charge-neutral sensing method has, on average, a ninefold safety margin in providing capture verification. Further, evaluation is needed to fully assess this feature in patients with chronic leads. [ABSTRACT FROM AUTHOR]

Even with the use of biphasic shocks, up to 5% of patients need an additional subcutaneous lead to obtain a defibrillation safety margin of at least 10 f. The number of patients requiring additional subcutaneous leads may even increase, because recent generation devices have a < 34 f maximum output in order to decrease their size. In 20 consecutive patients, a single element subcutaneous array lead was implanted in addition to a transvenous lead system consisting of a right ventricular (RV) and a vena cava superior lead using a single infraclavicular incision. The RV lead acted as the cathode; the subcutaneous lead and the lead in the subclavian vein acted as the anode. The biphasic defibrillation threshold was determined using a binary search protocol. Patients were randomized as to whether to start them with the transvenous lead configuration or the combination of the transvenous lead and the subcutaneous lead. In addition, a simplified assessment of the defibrillation field was performed bv determining the interelectrode area for the transvenous lead only and the transvenous lead in combination with the subcutaneous lead from a biplane chest X ray. The intraoperative defibrillation threshold was reconfirmed after 1 week, after 3 months, and after 12 months. The mean defibrillation threshold with the additional subcutaneous lead was significantly (P = 0.0001) lower (5.7 ± 2.9 f) than for the transvenous lead system (9.5 ± 4.6 f). With the subcutaneous lead, the impedance of the high voltage circuit decreased from 48.9 ± 7.4 (1 to 39.2 ± 5.0 Cl. In the frontal plane, the interelectrode area increased by 11.3% ± 5.5% (P < 0.0001) and in the lateral plane by 29.5% ± 12.4% (P < 0.0001). The defibrillation threshold did not increase during follow-up. Complications with the subcutaneous electrode were not observed during a follow-up of 15.8 ± 2 months. The single finger array lead is useful in order to lower the defibrillation threshold and can be used in order to lower the defibrillation threshold. [ABSTRACT FROM AUTHOR]

Twenty-three patients affected by severe, refractory angina were submitted to permanent spinal cord stimulation (SCS) and then followed in our outpatient clinic for 24 months. During the follow-up period, the number of weekly angina episodes drastically dropped from 9.2 (preimplant) to 1.8 in the 3rd, 2.5 in the 6th. 4.5 in the 12th, and 4.2 in the 24th month, with a statistically significant difference (P < 0.01) between the first and last values. A significant increase in the average exercise time from 320 ± 120 seconds (in baseline condition) to 410 ± 115 seconds (during SCS) was observed at the treadmill stress test (P < 0.01). SCS was well tolerated by all the patients. However, 7 patients died during follow-up (3 myocardial infarctions, 2 noncardiac deaths, and 2 sudden deaths). Three generators were replaced because of battery depletion after 15. 17, and 21 months. No serious complication was observed. In conclusion, in patients with otherwise intractable angina or already submitted to myocardial revascularization, SCS is very effective in reducing the number of angina episodes. The time of the work during exercise stress test is also significantly prolonged. [ABSTRACT FROM AUTHOR]

Reported is a case involving a patient with a previously implanted spinal cord stimulator (SCS) who presented for an implantable cardioverter defibrillator (ICD). The SCS device was located in the left lower abdominal quadrant with a stimulation electrode array placed on the dorsal aspect of the spinal cord at the T-11 thoracic level. Interaction testing demonstrated that the bipolar sensing transvenous lCD system (Medtronic 7221Cx PCD) did not detect the stimulator's output at burst rates ranging from 20-130 pulses/s, even with the ICD set to its maximum sensitivity of 0.15 mV and the stimulator programmed to the highest patient tolerated output combinations of 5 V, 0.45 ms in the bipolar configuration and 3 V. 0.45 ms in the unipolar (i.e., case-electrode) configuration. [ABSTRACT FROM AUTHOR]