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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.

Transvenous lead extraction (TLE) is used for lead infection, lead debulking, venous recanalization and device upgrades. Lead extraction is performed using specialized tools including locking stylets, mechanical or rotating sheaths, femoral snares or laser sheaths. The most feared complications associated with lead extraction are bleeding, vascular tear, cardiac avulsion and tamponade. Despite technological progress, the incidence of major procedural complications including death remains slightly above 1%. This case depicts an asymptomatic left common carotid artery (LCCA) to left innominate vein arteriovenous fistula (AVF) after laser‐assisted TLE successfully treated with an endovascular covered stent. [ABSTRACT FROM AUTHOR]

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]

Background: Pacemaker implantation in the U.S. is rising due to an aging population. The aim of this analysis was to identify risk factors associated with increased mortality and complications in hospitalized patients requiring pacemaker implantation. Methods: We performed a retrospective analysis using the National Inpatient Sample database, identifying hospitalized patients who underwent pacemaker implantation using International Classification of Disease, Tenth Revision, Clinical Modification codes. Independent predictors of inpatient mortality were identified using multivariate logistic regression analysis. Results: There were 242,980 hospitalizations with pacemaker implantation during 2016 and 2017. The most frequently encountered indications for hospitalizations involving pacemaker insertion included sick sinus syndrome (SSS) (27.60%), complete atrioventricular (AV) block (21.57%), and second‐degree AV block (7.83%). Chronic liver disease was associated with the highest adjusted odds of inpatient mortality (aOR = 5.76, 95% CI: 4.46 to 7.44, p <.001). Comorbid anemia had the highest statistically significant adjusted odds ratio (aOR) for predictors of post‐procedural cardiac complications (aOR = 3.17, 95% CI: 2.81 to 3.58, p <.001). Mortality in hospitalized patients needing pacemaker implantation was 1.05%. About 3.36% of hospitalizations developed post procedural circulatory complications (PPCC), 2.45% developed sepsis, and 1.84% developed mechanical complications of cardiac electronic devices. Conclusions: We identified several predictors of inpatient mortality in hospitalized patients undergoing pacemaker implantation, including chronic liver disease, protein‐calorie malnutrition, chronic heart failure, anemia, and history of malignancy. Anemia, chronic liver disease, and congestive heart failure were independent predictors of adverse outcomes in such patients. [ABSTRACT FROM AUTHOR]

Background: Ventricular tachycardia (VT) is a common arrhythmia in heart failure with reduced ejection fraction but its incidence, predictors, and significance have not been determined in heart failure with preserved ejection fraction (HFpEF). Methods: We performed a retrospective review of arrhythmias in two cohorts of patients with an HFpEF diagnosis. Patients in cohort 1 (n = 40) underwent routine arrhythmia surveillance with a 14‐day ambulatory electrocardiogram (ECG) monitor. Patients in cohort 2 (n = 85) had cardiac pacemakers and underwent routine device interrogations. Results: In cohort 1, 13 patients (32.5%) had one or more episodes of nonsustained VT (NSVT) on ambulatory ECG. In cohort 2, 38 patients (44.7%) had NSVT on cardiac pacemaker interrogations. During a median (interquartile range) follow‐up of 3.0 (1.6 to 5.1) years, 15 (12%) patients died (20% of patients with NSVT versus 6.8% of those without NSVT; P =.03). In logistic regression analysis, NSVT was associated with a 3.4‐fold higher odds of death (95% confidence interval 1.08 to 10.53; P =.04) in HFpEF. Conclusions: In conclusion, patients with HFpEF have a relatively high, and possibly underappreciated, burden of NSVT, which confers a higher risk of mortality. The frequent episodes of NSVT in these patients may provide insight into the mechanism of sudden cardiac death in HFpEF. [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: Consensus statements on lead extraction give consideration to open surgical removal in the setting of large vegetations, to mitigate the risk of massive embolism that may occur with percutaneous lead removal. Vacuum‐assisted debulking (VD) of large vegetations as an adjunct to percutaneous lead extraction may provide an opportunity to mitigate these risks. Methods: We retrospectively identified all patients undergoing lead extraction at our institution for endovascular infection from 2012 to 2018 and stratified them into two groups based on presence of adjunctive VD (n = 6) or without VD (no‐VD, n = 39). VD was performed with the AngioVac system (Angio‐Dynamics, Latham, NY, USA). Results: Across the cohort, mean age was 62 ± 15 years, ejection fraction was 41 ± 16%, and 39% had end‐stage renal disease on dialysis. Defibrillator systems were present in 71%, and 22% had cardiac resynchronization devices. Mean duration of the oldest extracted lead was 6.3 ± 4.9 years. There were no significant differences in baseline covariates between groups. Those in the VD group were significantly less likely to have Staphylococcus aureus as a causative organism (P =.04). In the VD group, vegetations targeted for debulking ranged in size from 1.8 to 6 cm (longest dimension). There were no operative deaths or clinically evident embolic events in either group. The overall nonfatal complication rate in the VD group was higher (33.3% vs 2.3%, P =.043). Conclusion: : VD can be performed as an adjunct to percutaneous lead extraction with a reasonable safety profile. The relative safety and efficacy of this approach removal requires further study. [ABSTRACT FROM AUTHOR]

Background: Catheter ablation improves symptoms and quality of life in patients with atrial fibrillation (AF); however, despite its benefit, women are less likely than men to undergo catheter ablation. Women with AF have been described to have more frequent and severe symptoms with a lower quality of life than men, and it is therefore unclear why women are less likely to undergo catheter ablation. We prospectively characterized gender differences in AF symptoms among men and women undergoing ablation at UNC using questionnaire data. Methods: Functional capacity was assessed with the Duke Activity Status Index (DASI) and quality of life was assessed with the Canadian Cardiovascular Society Symptoms of AF score (CCS‐SAF) and the AF Effect on Quality‐of‐Life Questionnaire Tool (AFEQT). Results: Among 191 patients in the study, women were less likely to undergo catheter ablation and had higher rates of paroxysmal AF and higher CHADS2‐VASc scores than men. Women had a worse functional capacity with significantly lower DASI scores than men; quality of life was also worse among women, with higher CCS‐SAF scores and lower AFEQT scores than men. After adjustment for AF type, there was a persistent gender difference for functional capacity and symptom measures. Conclusions: At the time of catheter ablation, women with AF had a significantly lower functional status with worse symptoms and a lower quality of life than men. The role of this symptom difference on the gender gap in enrollment for catheter ablation is unclear and likely due to multiple patient and provider factors. [ABSTRACT FROM AUTHOR]

Atrial fibrillation (AF) presents a growing clinical and public health burden for which better rhythm control therapies are needed. Focal impulse and rotor mapping (FIRM), currently marketed as a part of the Topera Rotor Mapping system (Abbott Laboratories, Austin, TX, USA), represents a potentially transformational approach to guide the invasive treatment of AF. However, many years after its initial marketing clearance, the clinical utility of this technology remains uncertain. In this article, we review the scientific rationale for this novel approach to AF ablation, evaluate the current clinical evidence for FIRM‐guided ablation, and characterize its premarket regulatory assessment. Lessons for clinicians considering adoption of newly marketed mapping systems are presented. [ABSTRACT FROM AUTHOR]

This study provides a review of the contemporary literature for the effects of most commonly used anesthetic drugs for sedation and anesthesia during adult electrophysiologic (EP) studies where supraventricular tachycardias (SVT) need to be induced for diagnostic purposes and/or catheter ablation. Some medications may affect cardiac electrophysiology and conduction, altering the ability to induce the arrhythmia, and may have negative impact on mapping and ablation treatment. The objective of the study is to determine the best sedative choice during SVT ablations. The authors searched MEDLINE, PubMed, and Google Scholar databases for published articles within the past 20 years (1998‐2018) that have evaluated the effects of common anesthetic drugs during SVT ablations. Further articles were identified through crossreferencing, discussion with electrophysiologists, and hand‐searching key electrophysiology and anesthesia journals. Eight review articles, two randomized control trials, six prospective observational studies, one retrospective observational study, and two case reports were included in this review. Seven of the studies focused on the pediatric population. The findings about the effects of the commonly used anesthetics are discussed further in detail. Sevoflurane had no clinically important effects on sinoatrial (SA) node activity, or the normal atrioventricular (AV), or accessory pathway. Midazolam and fentanyl, alone or in combination, neither alter the inducibility of reentrant tachycardia nor have they shown to affect the SA node, refractory periods of AV conduction, or accessory pathways. Similar findings were reported by investigators with propofol, except for ectopic atrial tachycardia in children, which remained un‐inducible in one of the studies. Remifentanil and dexmedetomidine lengthened both sinus cycle and AV conduction. Dexmedetomidine increased the atrial refractory period and diminished atrial excitability. Ketamine shortened atrial conduction and successfully returned prolongation of sinus node conduction due to dexmedetomidine. In conclusion, the current literature regarding sedation for SVT studies in the adult population is sparse. Midazolam, propofol, fentanyl, and remifentanil can be used safely in patients undergoing EP studies without significant interference with electrophysiological variables or the inducibility of reentrant tachycardias in usual clinical doses. Low‐dose ketamine has potential use as an adjunctive medication in the EP lab and additional studies would be beneficial. The effects of dexmedetomidine on conduction and arrhythmia inducibility during SVT ablation is not as clear as studies have yielded conflicting results, and may not be the best choice for sedation in this patient population. [ABSTRACT FROM AUTHOR]

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]

Abstract: Background: Despite data supporting the use of simulation training in procedural specialties and accreditation requirements, few options exist for electrophysiology (EP) training. We aimed to develop a low‐cost, accessible simulator for training in EP mapping, and to test the simulator in a group of novice users. Methods: Our mapping simulator is composed of three components: an acrylic case representing torso and thigh; three‐dimensional (3D) printed cardiac models; and a commercially available mapping system. Using a proprietary flexible material that mimics the consistency of human heart tissue, we created an anatomically accurate model of a normal right atrium (RA) from computed tomography data. We developed a test protocol consisting of two activities: creation of a RA shell and timed navigation to specific locations within the RA shell. Seventeen participants were randomized to either practice versus no practice on the simulator, and repeated simulator and self‐assessment tests were performed after 1 week. We measured volume of the RA map and time taken and distance from the target sites for each target location. Results: Both groups showed improvement in generation of geometry, volume, time to target, and self‐assessed comfort level after initial exposure to the simulator. Compared with no‐practice, the practice group demonstrated an improved sense of confidence in mapping. Conclusions: Focused training in EP mapping using a novel simulator created with 3D printed heart models and a standard mapping system is feasible for use in the training environment. Exposure to the simulator is associated with improved mapping skills and trainee comfort level. [ABSTRACT FROM AUTHOR]

Background Cardiac implantable electronic device (CIED) hematomas are associated with many adverse outcomes. We examined the incidence and risk factors associated with hematoma formation post-CIED implantation, and explored the preventative effect of prophylactic pressure bandaging (PPB) in a large tertiary center. Methods 1,091 devices were implanted during October 2011-December 2014. Clinically significant hematomas (CSH) were those that necessitated prolonged admission, including those due to reoperation, and clinically suspicious hematomas were swellings noted by medical/nursing staff. We screened for variables affecting hematoma incidence prior to conducting multivariate logistic regression analyses, one for all hematomas and one for CSH. Results 61 hematomas were identified (5.6% of patients), with 12 of those clinically significant (1.1% of patients). Factors significantly increasing the odds of developing any hematoma were stage 2 (odds ratio [OR] = 2.93, 95% confidence interval [CI] [1.08-7.94], P = 0.034) and 3 chronic kidney disease (CKD) (OR = 3.39 [1.20-9.56], P = 0.021), unfractionated heparin/therapeutic enoxaparin (OR = 3.15 [1.22-8.14], P = 0.018), and dual antiplatelets-aspirin + clopidogrel (OR = 2.95 [1.14-7.65], P = 0.026) + other combinations. Body Mass index (BMI) 25.0-29.9 (OR 0.52 [0.28-0.98], P = 0.044) and >30 were associated with decreased hematoma risk (OR 0.43 [0.20-0.91], P = 0.028). Factors significant for CSH formation were unfractionated heparin/therapeutic enoxaparin (OR = 9.55 [1.83-49.84], P = 0.007) and aspirin + clopidogrel (OR = 7.19 [1.01-50.91], P = 0.048). PPB nonsignificantly increased the odds of total hematoma development (OR = 1.53 [0.87-2.69], P = 0.135), and reduced CSH (OR = 0.67 [0.18-2.47], P = 0.547). Conclusions Heparin and dual antiplatelet use remain strong predictors of overall hematoma formation. CKD is a comparatively moderate predictor. BMI > 25 may decrease the risk of hematoma formation. PPB had nonsignificant effects on hematoma development. [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]

Background Adenosine (ADO) can uncover dormant conduction following pulmonary vein (PV) isolation. We sought to identify the value of dormant conduction for predicting atrial fibrillation (AF) recurrence and chronic PV reconnection. Methods One hundred fifty-two patients (80 male; age 60 ± 11 years) undergoing PV isolation for AF were studied. After PV isolation, sites of ADO-induced PV reconnection were recorded and targeted with additional ablation. In patients undergoing repeat ablation for recurrent AF, chronic PV reconnection was assessed. Results Forty-five (30%) patients had ADO-induced PV reconnection following PV isolation. Dormant conduction was successfully eliminated with additional ablation in 41 (91%) of these patients. After follow-up of 598 ± 270 days, 60 (39%) patients had recurrent AF. Dormant PV conduction was not a significant predictor of AF recurrence (hazard ratio 1.51; 95% confidence interval: 0.89-2.56; P = 0.12) although three of four (75%) patients with residual dormant conduction following initial ablation developed recurrent AF. Twenty-six patients with recurrent AF underwent repeat ablation with 52 of 99 (53%) PVs found to have chronic reconnection. Nine of 11 (82%) PVs with dormant conduction and 43 of 88 (49%) PVs without dormant conduction at initial procedure had chronic reconnection at repeat ablation. Conclusions When additional ablation is performed to eliminate ADO-induced PV reconnection after PV isolation, dormant conduction is not a significant predictor of recurrent AF. Although PVs with dormant conduction at initial procedure may develop chronic reconnection, the majority of PVs that show conduction recovery at repeat ablation occur in nondormant PVs. [ABSTRACT FROM AUTHOR]

Introduction Mechanisms underlying atrial fibrillation (AF) and dementia are unknown. Some genetic risk factors convey risk for AF and cerebral ischemic events. These markers may identify AF patients at risk for dementia either directly or through a gene-gene interaction with the ApoE ε4 variant, a known marker of dementia risk. Methods Caucasian patients with AF and a subsequent dementia diagnosis (n = 112) were matched 1:2 on sex, AF onset age, and follow-up period to AF patients without dementia. AF patients with dementia and AF patients without dementia were matched 1:1 on sex and age at dementia diagnosis (n = 112). Genotyping employed Taqman real-time polymerase chain reaction. Multivariable conditional logistic regression was used to examine associations between AF/dementia groups and single nucleotide polymorphism (SNP), as well as gene-gene interactions. Results In dementia patients, there was an association between the PITX2 loci and AF (rs2634073: odds ratio [OR] = 2.11; P = 0.025 and rs2200733: OR = 2.27; P = 0.029). In patients with AF, there was an association between PITX2 loci, rs2200733, and dementia (OR = 2.15, P = 0.008). There was no association between ApoE ε4 allele and AF in patients with dementia, although confirmation of the association between the carriage of ApoE ε4 allele and dementia was found (OR = 1.79; P = 0.026) in patients with AF. There were no significant interactions between ApoE ε4 allele and both the PITX2 loci and ZFHX3. Conclusions These findings support prior studies of ApoE risk of noncerebral vascular accident-related dementia/Alzheimer's risk in the Caucasians and provide support to suggest an association between PITX2-related SNPs and dementia, which may in part be attributed to silent cerebral ischemic events, a hypothesis deserving further testing. [ABSTRACT FROM AUTHOR]

Background Little is known about the effect of nifekalant, a pure IKr-selective blocker, on typical atrial flutter (AFL) and its termination mechanism. Methods The effects of nifekalant on AFL were elucidated in 17 patients. During AFL, the conduction time from the lateral to septal cavotricuspid isthmus (IS) and that through the reminder of the right atrium (nIS); AFL-cycle length (CL) variability, which was quantified by the standard deviation; and the maximum difference in AFL-CL were measured before and after administration of nifekalant (0.2-0.3 mg/kg). A single extrastimulus was delivered from the lateral cavotricuspid isthmus to elucidate the resetting response curves and atrial effective refractory period (AERP) before and after administration of nifekalant. Results There was no significant difference in AFL-CL, IS, and nIS before and after nifekalant; however, AERP was increased after nifekalant (155 ± 22 ms vs 184 ± 32 ms, P < 0.001). The standard deviation and the maximum difference in AFL-CL were both increased after nifekalant (1.7 ± 0.7 ms vs 3.6 ± 2.3 ms, P < 0.001 and 4.1 ± 1.9 ms vs 8.5 ± 5.2 ms, P < 0.001). The total excitable gap decreased (94 ± 17 ms vs 66 ± 21 ms, P < 0.001) with rightward shift of the resetting response curves and loss of full excitability after nifekalant. In 11 patients (65%), AFL was terminated spontaneously (n = 7) or by a single extrastimulus (n = 4), which was not observed before nifekalant. Termination was associated with orthodromic block in the cavotricuspid isthmus in all patients. Conclusions Nifekalant increases AERP and AFL-CL variability by abolishing a fully excitable gap, without prolongation of AFL-CL. These unique effects facilitate the termination of AFL. [ABSTRACT FROM AUTHOR]

Ectopic foci arising from pulmonary veins (PVs) are the predominant sources for the initiation and maintenance of atrial fibrillation (AF) in a vast majority of cases. However, ectopic foci also exist in the non-PV areas like superior vena cava (SVC) in 10-20% of the cases. We report the significance of SVC isolation in a patient with persistent AF and anomalous pulmonary venous connection of the right superior pulmonary vein into the SVC. (PACE 2013; 36:e146-e149) [ABSTRACT FROM AUTHOR]

Background Current 3D mapping systems have difficulty rendering complex cardiac structures. Different electroanatomical mapping software has been recently developed which uses a mathematical algorithm to improve interpolation between mapped points and delineation of closely spaced structures. This study tested the feasibility and accuracy of this software in comparison to traditional software. Methods In vivo 3D impedance-based mapping using a multielectrode catheter with a single geometry point cloud was performed in the left atria and pulmonary veins (PV) in 23 patients undergoing catheter ablation for atrial fibrillation. The maps were analyzed with traditional (NavX, St. Jude Medical, Minnetonka, MN, USA), either with or without multichamber mapping versus St. Jude OneModel™ software and dimensions of cardiac chambers in human studies were compared to preprocedural computed tomographic (CT) or magnetic resonance (MR) scans to determine the relative accuracy of the maps. Results Maps created by the OneModel software provided greater detail of complex cardiac structures compared to traditional software. Comparison of the left atrial/pulmonary vein electroanatomical maps with the CT and MR scans as reference standard demonstrated significantly less error in measurement of all PV ostial long- and short-axis dimensions, inter-PV distance, and ridge width (left PV to left atrial appendage) with the OneModel versus traditional software (P < 0.001 for all dimensions measured). Conclusions The OneModel software produces maps that are more accurate in rendering complex cardiac structures compared to traditional software. [ABSTRACT FROM AUTHOR]

We report a 43-year-old man with an implantable cardioverter defibrillator for aborted sudden cardiac death. He represents in extreme electrical storm with 111 different ventricular fibrillation episodes. Successful treatment was achieved with multiple antiarrhythmic agents, mechanical ventilation, external shocks, and ultimately overdrive pacing. A cardiac magnetic resonance scan revealed two cardiac lesions that were later diagnosed as metastatic fibrosarcoma. This case highlights two very important and increasingly common cardiological dilemmas: the management of extreme electrical storm and the role of magnetic resonance imaging in aborted cardiac death patients with an apparent 'normal' heart. [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]

A 58-year-old man was referred to our emergency room with hemodynamically unstable sustained ventricular tachycardia (VT). The morphology of the VT exhibited a left bundle branch block and inferior axis deviation. He had no past history of cardiovascular disease. Echocardiography, cardiac catheterization, cardiac biopsy, gallium scintigram, myocardial scintigram, T1,T2-weighted magnetic resonance imaging (MRI), and gadolinium-enhanced cine MRI did not detect any structural heart disease or abnormal cardiac function. However, delayed-enhancement MRI (DE-MRI) detected a focal intramural scar within the septal ventricular outflow tract. An electrophysiological study revealed a sustained VT with several morphologies and the entrainment phenomenon. Radiofrequency catheter ablation to the site corresponding to the focal scar detected by DE-MRI successfully eliminated the VT. (PACE 2012;35:e349-e352) [ABSTRACT FROM AUTHOR]

Background: Traditionally fluoroscopy has been used for navigation of catheters during electrophysiological procedures. Recent advances in electroanatomic mapping technologies resulted in a decrease and even in elimination of fluoroscopy exposure during these procedures. Methods: Electrophysiological procedures were performed with the use EnSite NavX™ or Velocity™ (St. Jude Medical, St. Paul, MN, USA) systems. Following construction of the right atrial geometry, other relevant geometries were formed (right ventricle, coronary sinus, or left atrium). Fluoroscopy was used in patients with complex congenital heart disease, in younger children, and during transseptal punctures. Cryoablation or radiofrequency was used for catheter ablation. Results: A total of 305 patients underwent catheter ablation for various supraventricular and ventricular tachyarrhythmia substrates using EnSite system guidance. No fluoroscopy was used in 191 (63%) of these cases. The mean fluoroscopy time in the rest of the procedures was 13.9 ± 11.6 minutes (0.2-60 minutes). The mean procedure time was 184 ± 71 minutes. No complications were noted except for temporary diaphragmatic paralysis in one patient and temporary AV block in another patient following cryoablation. Acute success rate in achieving complete elimination of arrhythmia substrates was 95% (290/305). The recurrence rate was (31/271) 11.4% at a mean follow-up time of 42 ± 23 months. Conclusions: Fluoroscopy can be significantly decreased or even eliminated in the majority of catheter ablation procedures. Long-term results demonstrate that this can be done efficiently and safely. (PACE 2012; 35:1067-1073) [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]

A 57-year-old woman with refractory vasovagal syncope and a sinus pause of 6.8 seconds during tilt-table test accepted the suggestion of atrial vagal denervation. Radiofrequency pulses were delivered on positive vagal reflex sites according to the standard of heart rate (HR) drop ≥20% after high frequency stimulation (HFS). The endpoint of inexistence of HR decrease at repeating HFS was achieved in 18 sites. No syncope attacked during 12 months and three tilt-table tests performed at 1, 6, and 12 months were negative. Extensive ablation on atrial endocardium for vagal denervation is suggested to be efficient in cardioinhibition type of VVS. (PACE 2012;1-5) [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]

Background: Risk stratification for Wolff-Parkinson-White (WPW) by intracardiac electrophysiology study (ICEPS) carries risks related to catheterization. We describe an alternative approach by using transesophageal electrophysiology study (TEEPS). Methods: The pediatric electrophysiology database was reviewed for patients with WPW and no documented clinical supraventricular tachycardia (SVT) who underwent risk stratification by TEEPS from October 2005 to November 2010. Of those who underwent subsequent ICEPS, only those with data available to compare accessory pathway (AP) conduction during ICEPS and TEEPS were included. Results: Of 65 patients who underwent TEEPS, 42 were found to have an indication for ablation. The most common indication for ICEPS was inducible SVT, which was induced in 67% of patients. Of 42 patients who underwent subsequent ICEPS, 23 had sufficient data for comparison of AP conduction between ICEPS and TEEPS. There was no difference between the baseline minimum 1:1 antegrade conduction through the accessory pathway found at TEEPS versus ICEPS (312 ± 51 ms vs 316 ± 66 ms, P = 0.5). There was no significant difference between the baseline antegrade AP-effective refractory period found at TEEPS versus ICEPS (308 ± 34 ms vs 297 ± 37 ms, P = 0.07). There were no complications related to TEEPS or ICEPS. Conclusion: TEEPS is a safe and feasible alternative to ICEPS for risk stratification in patients with asymptomatic WPW and should be considered before ICEPS and ablation. (PACE 2012; 1-5) [ABSTRACT FROM AUTHOR]

Introduction: Fasciculoventricular pathways (FVPs) are rare causes of preexcitation that do not mediate tachycardias. We report a two-center experience of pediatric patients with FVP and an unexpectedly high association of complex congenital heart defects (CHDs), chromosomal anomalies, and hypertrophic cardiomyopathy. Methods: A retrospective review of the electrophysiology database at two institutions was performed to identify patients with FVP from January 2000 to January 2011. Medical records of these patients were reviewed for clinical history and course, presence of comorbidities, and details of intracardiac electrophysiology (EP) study. Results: A total of 17 patients were identified. The primary indication for EP study was a preexcitation pattern on electrocardiogram. The majority of patients, 12/17 (71%), were found to have associated cardiac and genetic anomalies. Hypertrophic cardiomyopathy was found in 5/17 (29%) patients, with genetic testing in two patients demonstrating the lysosomal-associated membrane protein 2 mutation (Danon syndrome). Underlying complex CHDs were present in 3/17 (18%) patients. One patient (6%) was status post (s/p) cardiac transplant, one patient had hypertension, and another had Trisomy 21. Other electrophysiologic substrates mediating tachycardia were found in 3/17 (18%) patients. Only 5/17 patients (29%) were otherwise healthy with structurally normal hearts. Conclusions: In this largest reported series of FVP in children, there is an unusually high association of FVP with complex CHDs, chromosomal anomalies, and hypertrophic cardiomyopathy. Any patient with such disorders and manifest preexcitation should be evaluated with a high index of suspicion for a FVP. (PACE 2012;1-6) [ABSTRACT FROM AUTHOR]

Pulmonary veins (PVs) usually drain into the left atrium (LA) and are frequently targeted for electrical isolation, since it became evident that PVs may trigger and maintain paroxysmal atrial fibrillation (AF). We present a patient with right-sided PVs anomalously connecting to the right atrium with lack of electrical PV-atrial connection. Therefore, isolation of the left veins was performed resulting in freedom from AF as shown during a midterm follow-up. These findings indicate that PV connection to the LA may be a prerequisite for the arrhythmogenic properties of the PVs causing AF. (PACE 2010; 1-4) [ABSTRACT FROM AUTHOR]

The present case illustrates pulmonary vein isolation guided by real-time three-dimensional transesophageal echocardiography. This imaging modality allowed to navigate in a point-by-point fashion around pulmonary veins to assess both catheter location in relation to pulmonary vein ostia and stability of catheter tip. Also, it offered high-resolution visualization of a thickened, prominent tissue that surrounded the left upper pulmonary vein (the ligament of Marshall). The ability to visualize this anatomical structure along with intracardiac recording of electrical signals allowed to safely modulate in loco radiofrequency energy delivery, thus achieving electrical isolation of the pulmonary vein. (PACE 2011; 1-4) [ABSTRACT FROM AUTHOR]

The article presents a case study of a 62 year old man who presented to physicians with left hemiparesis resulting from a right internal capsule stroke and irregular heart palpitations. A discussion of diagnostic testing which was conducted on the patient, and resulted in him receiving a diagnosis of alternating bundle branch block, is presented.

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: Previous studies have observed that short-term exposure to elevated concentrations of particulate matter (PM) air pollution increases risk of acute ischemic heart disease events and heart failure hospitalization, alters cardiac autonomic function, and increases risk of arrhythmias. This study explored the potential associations between short-term elevations in PM exposure and atrial fibrillation (AF). Methods and Results: A case-crossover study design was used to explore associations between fine PM (PM2.5, particles with an aerodynamic diameter ≤2.5 μm) and 10,457 AF hospitalizations from 1993 to 2008 of patients who lived on Utah's Wasatch Front. Patients were hospitalized at Intermountain Healthcare facilities with a primary diagnosis of AF. Concurrent day exposure and cumulative lagged exposures for up to 21 days were explored and the data were stratified by sex, age, and previous or subsequent admission for myocardial infarction. Although the estimated associations between PM2.5 and AF hospitalizations for the various lag structures and strata were consistently positive suggestive of risk, they were not statistically significant and they were extremely small compared to previously observed associations with ischemic heart disease events and heart failure hospitalizations. Further, we observed no additive risk between PM2.5 and AF hospitalization in those with respiratory disease or sleep apnea. Conclusions: Unlike previously observed associations with ischemic heart disease events and heart failure hospitalizations using similar study design and approaches, this study found that hospitalization for AF was not significantly associated with elevations in short-term exposure to fine PM air pollution. (PACE 2011; 34:1475-1479) [ABSTRACT FROM AUTHOR]

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]

Idiopathic ventricular fibrillation (VF) is defined as spontaneous VF in the absence of structural heart disease. No prior reports exist addressing the technical aspects of idiopathic VF ablation in a child. We present the case of a 10-year-old boy with idiopathic VF, who presented a unique management challenge, particularly as regards the technical aspects of the ablation procedure. Ablation of idiopathic VF is feasible in a 10-year-old boy and oral quinidine seems more effective than other antiarrhythmic drugs in this condition. (PACE 2011; 34:e85-e89) [ABSTRACT FROM AUTHOR]

The article presents a case study of a 41-year-old obese woman who underwent elective gastric banding and experienced syncope on the first day following surgery. Telemetry monitoring revealed high-grade atrioventricular (AV) block for which dopamine was administered. Topics include a diagnosis of Lyme cardiac disease, the use of temporary pacing wire (TPW) to wean her off dopamine, and a safety and cost analysis of a TPW versus a permanent pacemaker to treat Lyme cardiac disease.

Idiopathic left ventricular tachycardia is an infrequent form of ventricular tachycardia associated with a structurally normal heart. The prognosis is usually benign; however, sustained cases have been reported. In this report, we describe two cases of persistent idiopathic left ventricular tachycardia complicated by tachycardia-mediated cardiomyopathy. In the first case, the patient developed a right ventricular thrombus with subsequent pulmonary embolism. In the second case, the patient developed acute pulmonary edema. Both cases were cured by catheter ablation. (PACE 2010; 1-4) [ABSTRACT FROM AUTHOR]

This two-part manuscript reviews diagnostic pacing maneuvers for supraventricular tachycardia (SVT). Part one will involve a detailed consideration of ventricular overdrive pacing (VOP), since this pacing maneuver provides the diagnosis in the majority of cases. This will include a review of the post-VOP response, fusion during entrainment, the importance of the VOP site, quantitative results of entrainment such as the postpacing interval, differential entrainment, and new criteria derived from features found at the beginning of the VOP train. There is a considerable literature on this topic, and this review is by no means meant to be all-encompassing. Rather, we hope to clearly explain and illustrate the physiology, strengths, and weaknesses of what we consider to be the most important and commonly employed diagnostic pacing maneuvers, that is, those that trainees in cardiac electrophysiology should be well familiar with at a minimum. (PACE 2011; 1-16) [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]

Little is known about the prevalence of upper extremity vein obstruction or anomalies in patients before first implantation of implantable cardioverter defibrillator (ICD). It remains unclear in which patients contrast venography is warranted before implantation procedure. Results of clinical data and contrast venography of 302 consecutive patients scheduled for first ICD implantation were analyzed. Prevalence of upper vein obstruction was 6.6% (20/302 patients) in a typical patient population undergoing first ICD implantation. Age, left ventricular ejection fraction, underlying heart disease, prior open-heart surgery, or cardiopulmonary resuscitation were not predictors of obstruction. Patients with previous cardiac pacemaker implantation had a higher rate of obstruction, though this was not statistically significant (20% vs 15.7%, P = 0.54). Persistent left vena cava was found in 0.7%. There is no clinical parameter sufficient enough to predict upper extremity venous obstruction. Contrast venography may be considered in patients with previous pacemaker placement but should not be a routine diagnostic tool in unselected patients prior to first ICD-implantation procedure. (PACE 2011; 1-6) [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]

Data on the mechanisms of sudden cardiac death are limited and may be biased by delays in rhythm recording and selection bias in survivors. As a result, the relative contributions of monomorphic ventricular tachycardia (VT) (cycle length [CL] > 260 ms), monomorphic fast VT (FVT) (CL ≤ 260 ms), and polymorphic VT (PMVT)/ventricular fibrillation (VF) have not been well characterized nor compared in patients with and without prior arrhythmic events. A retrospective cohort study of implantable cardioverter-defibrillator (ICD) recipients with primary or secondary implant indications was used to evaluate intracardiac electrograms (EGMs) for the first spontaneous VT/VF resulting in appropriate ICD therapy. EGMs were categorized into VT, FVT, and PMVT/VF based on CL and morphologic criteria. Of 616 implants, 145 patients (58 [40%] primary indications) received appropriate ICD therapy for VT/VF over mean follow-up of 3.8 ± 3.2 years. Primary implants had more diabetes (28% vs 12%; P = 0.02) and less antiarrhythmic use (15% vs 33%; P = 0.02). In those patients with spontaneous arrhythmia, PMVT/VF occurred in 20.7% of primary versus 21.8% of secondary implants, FVT in 19.0% versus 21.8%, and VT in 60.3% versus 56.4%, respectively (P = 0.88). Spontaneous VT CL was similar regardless of implant indication (284 ± 56 [primary] vs 286 ± 67 ms [secondary]; P = 0.92). Monomorphic VT is the most common cause of appropriate ICD therapy regardless of implant indication. These results provide insight into the mechanisms of sudden cardiac death and have implications for the use of interventions designed to limit ICD shocks. (PACE 2011; 34:571-576) [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]

Electrophysiological properties of the atrial endocardium compared to epicardium are not well understood. The purpose of this study was to compare the electrophysiological properties and vulnerability to arrhythmia induction from these regions. Transseptal endocardial and percutaneous epicardial mapping were performed in a porcine model (n = 7). Two opposing 4-mm electrophysiological catheters were positioned endocardially and epicardially. A circular mapping catheter (CMC) was positioned at the ostium of the common inferior pulmonary vein (CIPV) recording left atrial (LA)-PV potentials. Endocardial and epicardial effective refractory periods (ERPs) at two basic cycle lengths (CLs) of 600 and 400 ms were recorded from four anatomic locations (CIPV, LA appendage, right superior PV, and LA posterior wall). Atrial repetitive response (ARR) induction was also tested from endocardial and epicardial sites. Overall, 254 ERP measurements (mean 36.3 per animal) and 84 induction attempts (mean 12 per animal) were performed. The ERP was significantly shorter in the epicardium compared to the endocardium at basic CL of 400 ms (P = 0.006) but not at CL of 600 ms (P = 0.2). In addition, only the epicardium demonstrated ERP shortening when the CL of the basic drive was shortened (P = 0.03). ARR could be induced more often from the epicardium (P = 0.002) and fibrillatory activity with epicardial/endocardial dissociation was recorded (n = 3). Also, the earliest PV activation site on the CMC was noted to be different in 16.5% of cases during epicardial and endocardial pacing. The electrophysiological characteristics of the atrial epicardium are different from the endocardium with a shorter ERP and more frequent ARR induction by programed stimulation. (PACE 2011; 37-46) [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]

The article discusses research investigating the patient-centered outcomes of an implantable cardioverter defibrillator (ICD) shock. The authors cite a literature review within the issue examining the effects of ICD shock, which suggests that ICD shock has less of an impact on an individual's quality of life (QOL) than previously hypothesized. An in-depth review of the clinical experiences of ICD patient management is presented.

There is some disagreement concerning the minimal value of the interval between components of double potentials (DPs interval) that allows distinguishing complete and incomplete block in the cavotricuspid isthmus (CTI). To assess clinical utility of the relationship between atrial flutter cycle length (AFL CL) and the DPs interval. Ablation of the CTI was performed in 87 patients during AFL (245 ± 40 ms). Subsequently, DPs were recorded during proximal coronary sinus pacing at sites close to a gap in the ablation line and after achievement of complete isthmus block. We noted strong correlation between AFL CL and the DPs interval after achievement of isthmus block (r = 0.73). The mean DPs interval was 95.3 ± 18.3 ms (range 60-136 ms) and 123.3 ± 24.3 ms (range 87-211 ms) during incomplete and complete isthmus block, respectively (P < 0.001). When expressed as a percentage of AFL CL, this interval was 35.7 ± 3.5% AFL CL (range 28-40.2%) and 50.4 ± 6.9% AFL CL (range 39-72%) during incomplete and complete isthmus block, respectively (P < 0.001). A cutoff value of 40% of AFL CL identified CTI block with 96.7% sensitivity and 100% specificity. The interval between DPs after achievement of block in the CTI correlates with AFL CL. The DPs interval expressed as a percentage of AFL CL allows better distinguishing between complete and incomplete isthmus block compared to standard method based on milliseconds. The DPs interval below 40% of AFL CL indicates sites close to a gap in the ablation line. (PACE 2010; 33:1518-1527) [ABSTRACT FROM AUTHOR]