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His-Purkinje-related ventricular arrhythmias are a subset of ventricular tachycardias that use the specialized cardiac conduction system. These arrhythmias can occur in various different forms of structural heart disease. Here, we review the basic science discoveries and their analogous clinical observations that implicate the His-Purkinje system as a crucial component of the arrhythmia circuit. While mutations serve the molecular basis for arrhythmias in the heritable cardiomyopathies, transcriptional and posttranslational changes constitute the adverse remodeling leading to arrhythmias in acquired structural heart disease. Additional studies on the electrical properties of the His-Purkinje network and its interactions with the surrounding myocardium will improve the clinical diagnosis and treatment of these arrhythmias.

Persistent left superior vena cava (PLSVC) poses technical challenges to implantation of transvenous cardiac implantable electronic devices. His‐bundle pacing is a physiologic pacing strategy to avoid or treat pacing‐induced cardiomyopathy. We report a case of His‐bundle lead implantation in a patient with PLSVC, absent right SVC, and pacing‐induced cardiomyopathy. [ABSTRACT FROM AUTHOR]

The left ventricular summit (LVS) is a challenging location for catheter‐based percutaneous ablation due to its anatomical location. There have been case reports of cryoablations performed in this region, but the technique may be underutilized when radiofrequency ablation fails. A 45‐year‐old male was found to have 25 000 premature ventricular contractions (PVCs) a day despite previous ablation and a reduced ejection fraction of 40% despite medical therapy. Coronary sinus epicardial mapping revealed the coronary sinus distal region generated activations earlier than the QRS onset by 28 ms. Two separate, 4‐minute cryoablations were delivered that suppressed the PVCs within 5 seconds. Alternate energy modalities such as cryo may offer a safer and more viable approach for ablation of LVS in select patients. [ABSTRACT FROM AUTHOR]

The article presents the case of a 65-year-old woman who was rushed to a department due to complaints of recurrent syncope following palpitation episodes to discuss epicardial ablation of recurrent left atrial macroreentrant tachycardia from Bachmann's bundle region after endocardial ablation. Topics include the link between atrial fibrillation and complex left atrial tachycardias (AT) and how epicardial mapping and ablation may enhance the procedural process.

Background: Controversy exists regarding how atrial activation mode and heart rate affect optimal atrioventricular (AV) delay in cardiac resynchronization therapy. We studied these questions using high-reproducibility hemodynamic and echocardiographic measurements.Methods: Twenty patients were hemodynamically optimized using noninvasive beat-to-beat blood pressure at rest (62 ± 11 beats/min), during exercise (80 ± 6 beats/min), and at three atriallypaced rates: 5, 25, and 45 beats/min above rest, denoted as A paced,r + 5, A paced, r + 25, and A paced,r + 45, respectively. Left atrial myocardial motion and transmitral flow were timed echocardiographically.Results: During atrial sensing, raising heart rate shortened optimal AV delay by 25 ± 6ms (P < 0.001). During atrial pacing, raising heart rate from A paced,r+5 to A paced,r+25 shortened it by 16±6 ms; A paced,r+45 shortened it 17 ± 6 ms further (P<0.001).In comparison to atrial-sensed activation, atrial pacing lengthened optimal AV delay by 76±6 ms (P<0.0001) at rest, and at ~20 beats/min faster, by 85±7 ms(P<0.0001), 9±4 ms more (P = 0.017). Mechanically, atrial pacing delayed left atrial contraction by 63±5 ms at rest and by 73±5 ms (i.e.,by 10±5 ms more, P<0.05) at ~20 beats/min faster.Raising atrial rate by exercise advanced left atrial contraction by 7±2 ms (P=0.001). Raising it by atrial pacing did not (P=0.2).Conclusions: Hemodynamic optimal AV delay shortens with elevation of heart rate. It lengthens on switching from atrial-sensed to atrial-paced at the same rate, and echocardiography shows this sensed-paced difference in optima results from a sensed-paced difference in atrial electromechanical delay. The reason for the widening of the sensed-paced difference in AV optimum may be physiological stimuli (e.g.,adrenergic drive) advancing left atrial contraction during exercise but not with fast atrial pacing. [ABSTRACT FROM AUTHOR]

We present a case of an 89‐year‐old man with a left ventricular assist device and cardiac resynchronization therapy device (CRT‐D) who presented with multiple presyncopal events. On the night of admission, telemetry revealed a 13‐s pause with appropriately timed pacing spikes but with failure to capture, followed by intermittent ventricular contraction with different QRS morphology. What was the mechanism for his ventricular asystole? [ABSTRACT FROM AUTHOR]

Ventricular fibrillation (VF) commonly ends in death. Isolated case reports describe the uncommon occurrence of spontaneous termination of VF. Torsades de pointes (TdP), a peculiar form of polymorphic ventricular tachycardia associated with a prolonged QT interval on the surface electrocardiogram, most often spontaneously terminates and then returns to the underlying rhythm. Here, we present an unusual case of TdP degenerating into VF, reorganizing into TdP, and then spontaneously terminating. Our case suggests that the mechanisms underlying the maintenance of TdP and VF are not dissimilar. The precipitants to this event and the likely mechanisms operative are discussed. [ABSTRACT FROM AUTHOR]

A 52-year-old woman presented with left ventricular (LV) dysfunction and incessant narrow complex tachycardia. Electrocardiogram and clinical picture were suggestive of a permanent form of junctional reciprocating tachycardia, but electrophysiology study showed the tachycardia to be a fast-slow form of atrioventricular nodal reentrant tachycardia (AVNRT). Slow pathway ablation terminated the tachycardia and the LV dysfunction resolved completely at follow-up. Fast-slow AVNRT has not been reported to present in incessant form, and the mechanism in this patient was absent retrograde fast pathway conduction resulting in easy initiation and maintenance of tachycardia. (PACE 2013; 36:e4-e6) [ABSTRACT FROM AUTHOR]

Background: Atrial fibrillation (AF), the most common arrhythmia encountered in clinical practice, is often managed with a rhythm control strategy. Despite the emphasis on symptom relief as the motivation for a rhythm controlling strategy in AF, it remains unclear what factors affect the patient's experienced severity of AF symptoms. We hypothesize that demographic variables may affect AF symptom severity as many AF symptoms (palpitations, dyspnea, fatigue) are nonspecific and may require particular patient insight. Methods: We assessed demographic variables, cardiac and noncardiac comorbidities, AF burden, and AF-specific self-reported symptom severity in a cohort of 300 outpatients with AF presenting to outpatient electrophysiology clinics. Results: In unadjusted analyses, decreased educational attainment, unemployed working status, and non-Caucasian race were associated with worsened AF symptom severity. After adjusting for potential confounders, the association of decreased educational attainment with worsened AF symptom severity persisted. Conclusions: Possible links between these demographic features and AF symptom severity are socioeconomic status and health literacy. Further study into the relationship between educational attainment and AF symptom severity is warranted. (PACE 2012; 35:1090-1096) [ABSTRACT FROM AUTHOR]

An unusual case of electromagnetic interference is presented. As a result of a lightning shock to a Shower House, our patient received two shocks. An elucidation of the different mechanisms for the two shocks is presented. (PACE 2012; 35:e159-e162) [ABSTRACT FROM AUTHOR]

The article presents a case study of a 40 year old man with history of multiple episodes of paroxysmal tachycardia who was referred to a hospital for electrophysiologic studies and catheter ablation. A discussion of diagnostic testing which was conducted on the patient, and of medical treatment which he received, is presented.

Background: Electrocardiograms (ECGs) are sent via facsimile by pediatricians and psychiatrists to cardiologists for assessment. The validity of this method of transmission has not been established. Methods: ECGs were collected from 100 consecutive patients from the cardiology clinic of the Children's Hospital at Montefiore. The ECGs were faxed and also electronically faxed (efax) and printed. Two electrophysiologists (EP1 and EP2) interpreted the intervals on original, faxed, and efaxed ECGs and intervals (RR, PR, and QT) were compared. A three-way analysis of variance to examine differences between raters, among ECG intervals, and among methods (repeated factor) was performed. Because no interaction terms were significant, a Duncan's multiple range test was used to evaluate where differences occurred among the three intervals and three methods, given these main effects were significant. Results: The difference between raters EP1 and EP2 was not significant (P = 0.6681). Although the interval measurements of the faxed and efaxed ECGs were not significantly different from each other (P > 0.05), each was significantly different from the original across all three ECG intervals and both raters (P = 0.0138). The RR interval yielded mean (SD) values for the original, faxed, and efaxed methods of 0.6986 seconds (0.2074), 0.6646 seconds (0.1938), and 0.6838 seconds (0.1935), respectively. For the QT interval, the mean (SD) values for the original, faxed, and efaxed methods were 0.3370 seconds (0.0524), 0.32134 seconds (0.0466), and 0.3284 seconds (0.0515), respectively. Conclusions: ECG transmission via facsimile or efax may introduce significant distortion of the intervals. Alternative means of sending ECGs for interpretation should be considered. PACE 2011; 34:1283-1287) [ABSTRACT FROM AUTHOR]

A 74-year-old man with past history of near syncope presented with frequent periods of second-degree atrioventricular block (2° AVB). An electrophysiological study revealed prolonged atrial-His and His-ventricular (HV) intervals and frequent His bundle (H) extrasystoles. The latter manifested in the surface electrocardiogram as premature atrial, junctional, or ventricular beats, as well as 2° AVB that mimicked Wenckebach or Mobitz II block. Procainamide markedly suppressed H extrasystole. However, because of the presence of prolonged HV interval and history of presyncope, a permanent pacemaker was inserted. The case illustrates the varied manifestation of H extrasystole and presents guidelines for management. (PACE 2010; 1-4) [ABSTRACT FROM AUTHOR]

The relationship between QRS narrowing and response to cardiac resynchronization therapy (CRT) has been controversial. We sought to analyze the relationship between QRS narrowing and reverse remodeling in patients undergoing CRT, taking into account potential confounders including pre-CRT QRS duration and underlying QRS morphology. We reviewed pre- and postimplant electrocardiograms and echocardiograms in a cohort of 233 patients undergoing the new implantation of a CRT device between December 2001 and September 2006. For inclusion in the final cohort, patients had New York Heart Association classes II-IV heart failure, left ventricular ejection fraction (LVEF) ≤ 40%, and QRS duration ≥120 ms. Response to CRT was defined as a reduction in left ventricular end-systolic volume (LVESV) of ≥10%. A multivariate model was constructed to determine the relationship between QRS change and response to CRT. Patients with QRS narrowing had significantly greater reductions in left ventricular end-diastolic volume (LVEDV) (mL) (−26.5 ± 52.5 vs −4.8 ± 44.0, P = 0.002) and LVESV (mL) (−34.0 ± 55.5 vs −9.9 ± 45.8, P = 0.002) and improvement in LVEF (%) (8.9 ± 12.8 vs 4.5 ± 9.0, P = 0.007) than patients without narrowing. In univariate analysis, female gender (P = 0.0002), percent QRS narrowing from baseline (P = 0.008), lack of nitrate (P≤ 0.0001) and antiarrhythmic medication use (P = 0.01), lack of a nonspecific intraventricular conduction delay (=0.02), nonischemic cardiomyopathy (P = 0.003), and lower pre-CRT LVEDV (P = 0.006) and LVESV [P = 0.01]) were associated with responders. In a multivariate model, QRS narrowing, indexed to the baseline QRS duration, remained strongly associated with response (odds ratio 0.08 [0.01-0.56], P = 0.01). After adjusting for potential confounders, QRS narrowing, indexed to baseline QRS duration, is associated with enhanced reverse ventricular remodeling following CRT. (PACE 2011; 34:604-611) [ABSTRACT FROM AUTHOR]

We present a case of atrioventricular node reentrant tachycardia that displays spontaneously alternating antegrade and retrograde conduction via 1:2 manners. (PACE 2011; 34:e43-e46) [ABSTRACT FROM AUTHOR]

United States approval of the Model 3830, 4.1-French (Fr) diameter, lumenless, pacing lead (Medtronic Inc., Minneapolis, MN, USA) in patients under 17 years of age, and those with congenital heart disease (CHD), was in 2005. To date, long-term performance at alternative pacing sites (APS) is limited and chronic efficacy comparisons with more established leads is lacking. The purpose of this study was to evaluate these factors. Implant and follow-up data on leads were compared: group 1 (non-3830 leads) and group 2 (Model 3830 leads). These included acute and chronic sensing and pacing, impedances, implant sites, and complications. Groups were compared using Fischer's exact test, paired, and nonpaired t-tests, with significance defined at P < 0.05. A total of 119 patients (ages 5-48 years) received 171 leads: group 1 (n = 80) and group 2 (n = 91). At implant, there were no differences in patient age, CHD, sensing, or pacing thresholds between groups. Implant lead impedances differed between groups but all were within normal values for each lead design. Chronic data showed no difference in sensing, pacing thresholds, or impedances. There were five (6%) early lead dislodgements in group 1 and one (1%) in group 2. APS were achieved in group 2 with mean 1.6 ± 1.3 minutes fluoroscopy time. The new 4.1-Fr lumenless lead shows similar performance indices to established leads even at APS, yet is thinner and achieves APS with technical ease, permitting more efficient chronic pacing in children and all patients with CHD. (PACE 2010; 33:1467-1474) [ABSTRACT FROM AUTHOR]

Radiofrequency ablation of atrial flutter is a commonly performed procedure. Ablation success depends upon complete transmural atrial tissue injury to achieve bidirectional cavotricuspid isthmus (CTI) block. Transmural ablation increases risk of injury to the adjacent right coronary artery (RCA). Distance between the RCA and the endocardium within the CTI area is not well described. We aimed to perform in vivo measurements of the distance between the CTI area and adjacent RCA. Thirty-three consecutive patients underwent electrocardiogram-gated contrast-enhanced computed tomography. CTI area was divided into nine segments based on three common catheter locations (paraseptal, central, and lateral or 5, 6, and 7 o'clock) and ventricular to atrial ablation line. Mean age was 64 ± 11 years and 97% of the participants were male. Paraseptal, central, and lateral measurements at the tricuspid annulus ridge showed endocardial to RCA distance 9 ± 3, 6 ± 2, and 5 ± 3 mm, respectively (range 2-17 mm). Corresponding measurements for the ventricular side were 5 ± 3, 4 ± 2, and 4 ± 2 mm and atrial side measurements were 3 ± 2, 3 ± 2, and 3 ± 3 mm. Distance was ≤2 mm in 14% of segments on the ventricular side and 39% of segments on the atrial side. Paired t-test showed significant difference (P < 0.001) between tricuspid annulus ridge measurements and adjacent atrial or ventricular measurements. Distance between endocardium and RCA lumen is reduced in areas adjacent to the tricuspid annulus ridge. (PACE 2010; 1319-1323) [ABSTRACT FROM AUTHOR]

Currently available implantable loop recorders (ILRs) are hampered by limited memory, sensing artifacts, and need for manual memory download. Remote monitoring techniques that automatically transfer stored recordings for review may enhance ILR utility. However, automatic electrocardiograph (ECG) detection and transmission of an excessive number of tracings directly to physicians may be burdensome. This pilot study assessed the utility of direct ILR transmission to a central ECG monitoring center on the burden of data to be reviewed by the physician. Patients with unexplained syncope were implanted with a novel ILR with automatic (i.e., independent of patient intervention) wireless telemetry download. Transmitted recordings underwent a two-step review process: initial algorithmic filtering followed by human overread at a monitoring center using predefined criteria. Forty patients were enrolled and followed for 8.5 ± 5.1 months. A total of 223,226 ECG recordings were transmitted to the monitoring center (on average 660 per patient per month). Algorithmic filtering eliminated 191,305 ECGs as artifact (89%), with monitoring center overread of 31,921 strips. Ultimately, 117 relevant ECGs were selected for further evaluation by the physician (0.0053%). One or more relevant ECGs were identified for 20 patients (50%). Automatic ILR recording and wireless technique is feasible for remote ECG monitoring by ILRs. However, sensitive criteria for recording and transmission may result in an excessive ECG burden. The two-step screening process in this pilot study minimized physician overread time while providing clinically relevant recordings in a substantial proportion of patients. (PACE 2010; 1347-1352) [ABSTRACT FROM AUTHOR]

Background: Nonreproducibility of precordial electrocardiogram (ECG) leads in serial ECGs has led to emphasis on the limb leads for some applications. Since modern electrocardiographs measure leads I and II and calculate on line the other four limb leads, the former can substitute for the set of six limb leads. Furthermore, based on the mathematical relationship of lead aVR and leads I and II, it was hypothesized that aVR could be used as a representative index of the set of the six limb leads. The aim of this study was to evaluate whether ECG lead aVR could function as an index of all limb leads, in clinical electrocardiography. Methods: Automation-derived and manually derived QRS voltage amplitude measurements of all limb leads in ECGs of a series of 100 randomly selected consecutive patients, and ECGs of 36 patients with various edematous states (EDST), congestive heart failure (CHF), or undergoing hemodialysis (HD), and aVR were inter-correlated with the sums of leads I and II (ΣI&II), and the entire set of the six limb leads (Σ6LbLds). Results: Correlation of aVR with ΣI&II and Σ6LbLds was excellent (P < 0.00005); also, aVR was found to be a reliable index of the six limb leads in repeat ECGs in the patients with various EDST, CHF, or undergoing HD, in whom changes in aVR correlated with changes in patients’ body weight. Conclusion: aVR could be taken as an index of all ECG limb leads in analysis in general, and in monitoring patients with EDST, CHF, and HD in particular. [ABSTRACT FROM AUTHOR]

Background: Attenuation of electrocardiogram (ECG) QRS complexes is observed in patients with a variety of illnesses and peripheral edema (PERED), and augmentation with alleviation of PERED. Serial ECGs in stable individuals display variation in the amplitude of QRS complexes in leads V1–V6, stemming from careless placement of recording electrodes on the chestwall. Electrocardiographs record only leads I and II, and mathematically derive the other four limb leads in real time. This study evaluated the sum of the amplitudes of ECG leads I and II, along with other sets of ECG leads in the monitoring of diuresis in patients with congestive heart failure (CHF). Methods: Twenty patients with CHF had ECGs and weights recorded on admission and at discharge. The amplitude of the QRS complexes in all ECG leads were measured and sums of I and II, all limb leads, V1–V6, and all 12 leads were calculated. Results: There was a good correlation between the weight loss and the increase in the sums of the amplitudes of the QRS complexes from leads I and II (r = 0.55, P = 0.012), and the six limb leads (r = 0.68, P = 0.001), but a poor correlation with the V1–V6 leads (r = 0.04, P = 0.85) and all 12 leads (r = 0.1, P = 0.40). Conclusions: Sums of the amplitudes of the ECG QRS complexes from leads I and II constitute a reliable, easily obtainable, ubiquitously available, bedside clinical index, which can be employed in the diagnosis, monitoring of management, and follow-up of patients with CHF. [ABSTRACT FROM AUTHOR]

A 63-year-old male patient with inferior infarction revealed transient attenuation of the Q-waves in II, III, and aVF, and R-waves in V1–V3 during an exercise stress test. Myocardial scintigraphy disclosed ischemia of the anterior wall and coronary arteriography, a 90% stenosis of the left main coronary artery (LMCA). The mechanism involved appears to be a transient failure of the anterior wall to generate adequate depolarization forces for the genesis of Q-waves in the inferior leads and R-waves in the anterior leads. This electrocardiogram sign is diagnostic of severe anterior wall ischemia due to left anterior descending or LMCA stenosis. [ABSTRACT FROM AUTHOR]

A 51-year-old woman presented with an episode of syncope. Upon further review she was found to have a typical Brugada type pattern on her electrocardiogram. She did not have evidence for structural heart disease. At electrophysiological testing she was found to have marked infrahisian conduction disease and had easily inducible polymorphic ventricular tachycardia. She underwent implantation of a dual-chamber implantable cardioverter defibrillator (ICD) and family screening was recommended. Genetic analysis revealed a novel nonsense mutation in the gene encoding for the sodium channel (SCN5A). Five months after ICD implantation the patient had an episode of ventricular fibrillation documented on ICD interrogation. This case is unique as it is consistent with an overlap syndrome, namely both Brugada Syndrome and distal atrioventricular (AV) conduction disease secondary to a novel SCN5A mutation in a young female. This finding highlights the phenotypic heterogeneity of novel SCN5A mutations. [ABSTRACT FROM AUTHOR]

With the ageing of the population and expanding use of deep brain stimulation in the treatment of various neurological and neuropsychiatric conditions, there will be an increasing number of patients with these devices who present with cardiac conditions necessitating electrophysiology studies (EPS). However, neurostimulator devices have been shown to cause significant artifacts on electrocardiography recordings. We present the case of a 53-year-old Parkinsonian woman with a brain neurostimulator device who underwent a successful EPS with radiofrequency ablation. (PACE 2013; 36:e1-e3) [ABSTRACT FROM AUTHOR]

We report two cases of intermittent Wolff-Parkinson-White (WPW) syndrome. In one patient, early repolarization (ER) was masked during preexcitation whereas in the other, J wave-like notches were observed in the right precordial leads only during preexcitation. The clinical significance of ER is not apparent in WPW syndrome but some possible mechanisms are discussed. (PACE 2012; 35:e231-e233) [ABSTRACT FROM AUTHOR]

The article presents a case study of an 88 year old man with no known history of structural heart disease who was admitted to the emergency department complaining of regular palpitations. A discussion of diagnostic testing which was conducted on the man, and resulted in him receiving a diagnosis of a regular wide QRS complex tachycardia, is presented.

The emergence of Brugada pattern on electrocardiogram in response to class IA or IC antiarrhythmic agents is widely utilized to diagnose concealed Brugada syndrome and recognized as a risk factor for sudden death. Phenytoin, a class IB antiarrhythmic agent, has not been reported to induce Brugada pattern. We report a patient who presented with Brugada electrocardiogram at supratherapeutic phenytoin level. Considering that patients with syncope may falsely be labeled to have seizures and some epilepsy patients are at increased risk of sudden death, all patients with supratherapeutic phenytoin level should be evaluated with an electrocardiogram for emergence of Brugada pattern. [ABSTRACT FROM AUTHOR]

A case is presented revealing the common phenomenon of heart rate-dependent diagnosis of electrocardiographic (ECG) diagnosis of left ventricular hypertrophy (LVH), which consists of satisfaction of LVH criteria only at faster rates whereas ECGs with a slow heart rate do not satisfy such criteria. The mechanism of the phenomenon has been attributed to the tachycardia-mediated underfilling of the left ventricle bringing the electrical 'centroid' of the heart closer to the recording electrodes, which results in augmentation of the amplitude of QRS complexes, particularly in leads V2-V4. (PACE 2013; 36:e136-e137) [ABSTRACT FROM AUTHOR]

In this article the author discusses changes in the QT interval of the human heart which can result from cardiac and noncardiac factors. He is critical of using electrocardiograms to diagnose and monitor congenital and acquired changes in the QT interval and is supportive of having additional research conducted on QRST complexes and their relationship to QT interval changes.

In patients with chronic Chagas' cardiomyopathy, there are forms of the disease that affect the electrical conduction system almost exclusively. The most common disorders include right bundle branch block alone or in association with left anterior fascicular block. We present an unusual case of a patient with Chagas' cardiomyopathy in association with a preexcitation syndrome. (PACE 2012; 35:e38-e39) [ABSTRACT FROM AUTHOR]