HomeCirculationVol. 147, No. 23Occam's Razor: Two Arrhythmias in a Single Heart? Free AccessCase ReportPDF/EPUBAboutView PDFView EPUBSections ToolsAdd to favoritesDownload citationsTrack citationsPermissions ShareShare onFacebookTwitterLinked InMendeleyReddit Jump toFree AccessCase ReportPDF/EPUBOccam's Razor: Two Arrhythmias in a Single Heart? Aviram Hochstadt, Michael Geist and Sami Viskin Aviram HochstadtAviram Hochstadt Correspondence to: Aviram Hochstadt, MD, MPH, Department of Cardiology, Edith Wolfson Medical Center, Ha-Lokhamim St 62, Holon, Israel, 5822012. Email E-mail Address: [email protected] https://orcid.org/0000-0002-9404-3145 Department of Cardiology, Edith Wolfson Medical Center, Holon, Israel (A.H., M.G.). Sackler School of Medicine, Tel Aviv University, Israel (A.H., M.G., S.V.). , Michael GeistMichael Geist Department of Cardiology, Edith Wolfson Medical Center, Holon, Israel (A.H., M.G.). Sackler School of Medicine, Tel Aviv University, Israel (A.H., M.G., S.V.). and Sami ViskinSami Viskin https://orcid.org/0000-0002-2623-5540 Tel Aviv Sourasky Medical Center, Israel (S.V.). Sackler School of Medicine, Tel Aviv University, Israel (A.H., M.G., S.V.). Originally published5 Jun 2023https://doi.org/10.1161/CIRCULATIONAHA.123.064278Circulation. 2023;147:1779–1781ECG ChallengeA 68-year-old man with arterial hypertension treated with verapamil but no evident heart disease presented with a 2-hour history of palpitations. His physical examination was normal except for a heart rate of 100 bpm. His ECG showed a fairly regular narrow complex tachycardia (Figure 1). The P-P interval is 395 milliseconds (best seen in lead I), representing a regular atrial rate of 152 bpm, whereas the ventricular rate is "only" 100 bpm and fairly regular. What is the best explanation for this tachycardia involving a rapid rhythm in the atria and the ventricles at different rates?Download figureDownload PowerPointFigure 1. Regular narrow complex tachycardia recorded at presentation. The ventricular rate approaches 100 bpm and is fairly regular. Note the regular discrete P waves (best observed in lead I) with a rate of 150 bpm.Please turn the page to read the diagnosis.Response to ECG ChallengeDiscrete P waves with a rate of 152 bpm during palpitations of sudden onset suggest the diagnosis of paroxysmal atrial tachycardia (AT). The challenge is to explain the ventricular rhythm that, with a rate of ≈100 bpm, appears to be dissociated from the atrium.Bitachycardia (simultaneous yet dissociated tachyarrhythmias of the atria and the ventricles) is seen sometimes during ventricular tachycardia. The obvious example is the patient with chronic atrial flutter who develops ventricular tachycardia. However, the narrow QRS complexes recorded in this case exclude ventricular tachycardia and would imply the coexistence of a junctional ectopic tachycardia with AT or the presence of atrioventricular node reentry tachycardia with retrograde block to the atrium during ongoing AT. Both options are unlikely in a sustained tachycardia. A more likely possibility is AT with physiological atrioventricular nodal block in the form of Wenckebach conduction.During AT, physiological conduction block at the atrioventricular node leads to Wenckebach conduction. The hallmark of AT with Wenckebach is a constant P-P interval with a varying RR interval caused by a PR interval that gradually increases until a P wave is ultimately blocked, creating an obvious ventricular pause. For that reason, 3:2 Wenckebach atrioventricular conduction results in "group beating" with alternating short and long RR intervals (Figure 2).Download figureDownload PowerPointFigure 2. Illustration of 3:2 Wenckebach conduction and mathematical exercise to explain 3:2 Wenckebach conduction with regular R-R interval. A, Diagram of atrial tachycardia with 3:2 atrioventricular conduction. Consecutive P waves are annotated as P1, P2, P3, etc. The P-P interval is regular. The PR interval of each beat is annotated as PR1, PR2, etc. Because of Wenckebach conduction, PR2 is longer than PR1 (the difference is ΔPR). P3 is blocked. PR4 and PR5 are equal to PR1 and PR2, respectively. The regular PP interval with varying PR conduction leads to a sequence of short and long RR intervals (R1R2 in red and R2R3 in black, respectively). B, Mathematical calculations explaining how 3:2 Wenckebach conduction can result in a regular RR interval: (1) The R1-to-R2 interval is the sum of the P1-to-P2 interval minus the PR interval of P1 plus the PR interval of P2. (2) ΔPR is the difference between PR1 and PR2. (3) Accordingly, the R1-to-R2 interval is the sum of the P-to-P interval plus ΔPR. (4) The R2-to-R3 interval is equal to the interval from P2 to P3 plus the interval from P3 to P4 (from P2 to P4) minus the PR interval of the second P wave (PR2) plus the PR interval of the fourth P wave (PR4). (5) Because all the P-P intervals are the same, then P2P3+P3P4=2PP (twice the PP interval). (6) Accordingly, the R2-to-R3 interval equals twice the PP interval minus ΔPR. (7) Assuming that the R1-to-R2 interval is equal to the R2-to-R3 interval, then (8) PP plus ΔPR=2PP−ΔPR. (9) Accordingly, the P-to-P interval is double the ΔPR. (10) Thus, for a 3:2 Wenckebach conduction to lead to regular RR intervals, the increment in consecutive PR intervals must be half the PP interval during tachycardia.A mathematical exercise showing how a regular RR interval is possible despite 3:2 Wenckebach conduction is presented in Figure 2. According to this model, a ΔPR that is half the length of the P-P interval will result in a regular R-R interval. Figure 3 shows a ladder diagram demonstrating the P-P and ΔPR required for a perfectly regular ventricular rate. The figure also shows an enlarged rhythm strip of the clinical arrhythmia.Download figureDownload PowerPointFigure 3. Ladder diagram of an ideal AT with 3:2 Wenckebach conduction and regular ventricular rate and rhythm strip of the clinical arrhythmia with slightly irregular-regular ventricular rate but no obvious pauses despite 3:2 conduction. Top, Ladder diagram for an imaginary atrial tachycardia (AT) with 3:2 Wenckebach conduction when the ΔPR is exactly half the P-P interval, leading to a regular ventricular rate. The P-P interval (shown in red numbers) is 400 milliseconds. Consequently, assuming that the tachycardia begins at time 0, then the successive P waves appear after 400, 800, 1200, 1600 (and so on) milliseconds, shown in black numbers. The PR interval of the first P wave (PR1) is 160 milliseconds long (blue). Therefore, the first QRS appears 560 milliseconds after time 0 (400+160 milliseconds ). The second PR interval (PR2) is 160 milliseconds long (blue). Therefore, the second QRS appears 1160 milliseconds from time 0 (800+360 milliseconds). The third P wave is blocked at the level of the atrioventricular node. The same sequence of events occurs for the fourth, fifth, and sixth P wave and so on. Note that the difference between PR1 and PR2 (which is the ΔPR) is 200 milliseconds (360–160 milliseconds), exactly half the P-P interval. The net result is that, despite a 3:2 conduction, the ventricular rate is perfectly regular, with an R-R interval (red numbers) of 600 milliseconds. Bottom, An enlarged segment (lead I) of the clinical arrhythmia. The P-P is regular. As opposed to the ideal arrhythmia (top), in our patient, the ΔPR is slightly less than half the P-P interval. As a result, in our patient, the ventricular rate is not completely regular, and careful observation reveals group beating.In the first report of regular AT despite Wenckebach conduction,1 a PP interval approximating 380 milliseconds and a ΔPR of 190 milliseconds (from 160 to 350 milliseconds for the 2 conducted beats) created a regular ventricular rate of 106 bpm. In the second report,2 a PP interval of 700 milliseconds and a PR increasing from 250 to 600 milliseconds (ΔPR 350 milliseconds) produced a regular ventricular rhythm. This phenomenon is rare. During electrophysiological studies, accelerated atrial pacing creating 3:2 Wenckebach creates a regular ventricular rate in 1% of trials.1 In our own case, the PP interval is 400 milliseconds and the ΔPR is 190 milliseconds, not exactly twice the ΔPR. Careful analysis reveals that the RR interval is not exactly regular. Dual atrioventricular node physiology is a likely requirement to achieve the required ΔPR.The patient was transferred to the electrophysiologic laboratory. He arrived in AT with 2:1 atrioventricular conduction. The tachycardia was ablated at the crista terminalis. The teaching point of this case is that, during AT with apparently discordant rates in the atrium and the ventricle, atrioventricular conduction (rather than independent speeding of both chambers) is the likely explanation even if the type of atrioventricular conduction is not readily apparent at first. AT with 3:2 Wenckebach conduction leads to a regular ventricular rhythm when the ΔPR is half the P-P interval.Article InformationSources of FundingNone.Disclosures None.FootnotesFor Sources of Funding and Disclosures, see page 1781.Circulation is available at www.ahajournals.org/journal/circCorrespondence to: Aviram Hochstadt, MD, MPH, Department of Cardiology, Edith Wolfson Medical Center, Ha-Lokhamim St 62, Holon, Israel, 5822012. Email [email protected].comReferences1. Fuest S, Gleva MJ, Noheria A. Regular tachycardia despite Wenckebach atrioventricular conduction.J Electrocardiol. 2018; 51:126–128. doi: 10.1016/j.jelectrocard.2017.08.034CrossrefMedlineGoogle Scholar2. Littmann L, Tenczer J. Regular ventricular rate and "reverse bigeminy" in 3:2 Wenckebach periodicity.J Electrocardiol. 2020; 62:73–78. doi: 10.1016/j.jelectrocard.2020.08.011CrossrefMedlineGoogle Scholar eLetters(0)eLetters should relate to an article recently published in the journal and are not a forum for providing unpublished data. Comments are reviewed for appropriate use of tone and language. Comments are not peer-reviewed. Acceptable comments are posted to the journal website only. Comments are not published in an issue and are not indexed in PubMed. Comments should be no longer than 500 words and will only be posted online. References are limited to 10. Authors of the article cited in the comment will be invited to reply, as appropriate.Comments and feedback on AHA/ASA Scientific Statements and Guidelines should be directed to the AHA/ASA Manuscript Oversight Committee via its Correspondence page.Sign In to Submit a Response to This Article Previous Back to top Next FiguresReferencesRelatedDetails June 6, 2023Vol 147, Issue 23 Advertisement Article InformationMetrics © 2023 American Heart Association, Inc.https://doi.org/10.1161/CIRCULATIONAHA.123.064278PMID: 37276252 Originally publishedJune 5, 2023 PDF download Advertisement SubjectsArrhythmiasElectrophysiology

BACKGROUND:Limited information exists about detailed clinical characteristics and management of the small subset of Brugada syndrome (BrS) patients who had an arrhythmic event (AE). OBJECTIVES:To conduct the first nationwide survey focused on BrS patients with documented AE. METHODS:Israeli electrophysiology units participated if they had treated BrS patients who had cardiac arrest (CA) (lethal/aborted; group 1) or experienced appropriate therapy for tachyarrhythmias after prophylactic implantable cardioverter defibrillator (ICD) implantation (group 2). RESULTS:The cohort comprised 31 patients: 25 in group 1, 6 in group 2. Group 1: 96% male, mean CA age 38 years (range 13-84). Nine patients (36%) presented with arrhythmic storm and three had a lethal outcome; 17 (68%) had spontaneous type 1 Brugada electrocardiography (ECG). An electrophysiology study (EPS) was performed on 11 patients with inducible ventricular fibrillation (VF) in 10, which was prevented by quinidine in 9/10 patients. During follow-up (143 ± 119 months) eight patients experienced appropriate shocks, none while on quinidine. Group 2: all male, age 30-53 years; 4/6 patients had familial history of sudden death age < 50 years. Five patients had spontaneous type 1 Brugada ECG and four were asymptomatic at ICD implantation. EPS was performed in four patients with inducible VF in three. During long-term follow-up, five patients received ≥ 1 appropriate shocks, one had ATP for sustained VT (none taking quinidine). No AE recurred in patients subsequently treated with quinidine. CONCLUSIONS:CA from BrS is apparently a rare occurrence on a national scale and no AE occurred in any patient treated with quinidine.

Cardiac resynchronization therapy (CRT) is an effective treatment for heart failure (HF); however, a third of patients are non-responders. The development of quadripolar left ventricular (LV) lead was shown, mainly in single manufactures’ registry, to improve LV remodeling and overall mortality. However, limited reports exist on the impact of quadripolar LV leads on HF hospitalization rates in real-life cohorts. We evaluated the clinical outcomes associated with quadripolar LV leads in a large nation-wide registry including all patients implanted with a cardiac resynchronization therapy with defibrillator (CRT-D).

Introduction Life expectancy of less than 1 year is usually a contraindication for implantable cardioverter defibrillator (ICD) implantation. The aim was to identify patients at risk of death during the first year after implantation. Methods and Results Conclusions Data were derived from a prospective Israeli ICD Registry. Two groups of patients were compared, those who died and those who were alive 1 year after ICD implantation. Factors associated with 1-year mortality were identified on a derivation cohort. A risk score was established and validated. A total of 2617 patients have completed 1 year of follow-up after ICD or cardiac resynchronization therapy defibrillator (CRT-D) implantation. Age greater than 75 years (hazard ratio [HR], 2.7; 95% confidence interval [95% CI], 1.6 to 4.4), atrial fibrillation (AF; HR, 1.9; 95% CI, 1.12 to 3.17), chronic lung disease (HR, 2.0; 95% CI, 1.1 to 3.76), anemia (HR, 2.3; 95% CI, 1.3 to 3.93) and chronic renal failure (CRF; HR, 3.4; 95% CI, 1.74 to 6.6) were independent risk factors for 1-year mortality. We propose a simple AAACC ("triple A double C") score for prediction of 1-year mortality after ICD implantation: Age greater than 75 years (3 points(pts)), anemia (2 pts), AF (1 pt), CRF (3 pts) and chronic lung disease (1 pt). Mortality risk increased with rising number of points (from 1% with 0 pts to 12.5% with >4 pts). The risk score was evaluated with receiver operating characteristic curve and the area under the curve of the validation curve is 0.71 (95% CI, 0.66 to 0.76). Age greater than 75, AF, chronic lung disease, anemia, and CRF were independent risk factors for 1-year mortality. AAACC risk score identifies patients at high risk of death during 1 year after ICD implantation.

There are limited data regarding the effect of diabetes mellitus (DM) on the risks of both appropriate and inappropriate implantable cardioverter defibrillator (ICD) therapy. The present study was designed to compare the outcome of appropriate and inappropriate ICD therapy in patients with or without DM.

Full title: Clinical Outcomes in Patients with Severe Renal Dysfunction Including Dialysis Following Defibrillator Implantation Published in Am J Nephrol 2015;42:295–304 Submission for the "Best Research by Young Electrophysiologists" session BACKGROUND: Renal dysfunction is associated with increased mortality in heart failure (HF) patients. However, there are limited data regarding clinical and arrhythmic outcomes associated with implantable cardioverter defibrillator (ICD) therapy in this population. Methods: We evaluated outcomes associated with the severity of renal dysfunction with or without dialysis among 2,289 patients who were enrolled and prospectively followed up in the Israeli ICD Registry. The primary endpoint of the study was all-cause mortality. Secondary endpoints included cardiac mortality, HF hospitalization, non-cardiac hospitalization, and appropriate and inappropriate ICD therapy. Results: Severe renal dysfunction patients (estimated glomerular filtration rate <30 ml/min/x200B;1.73 m2; n = 144 patients; 6%) were older, with higher comorbidities prevalence, and more likely to suffer from advanced HF. Among severe renal dysfunction patients, those on dialysis had a lower prevalence of wide QRS and complete left bundle branch morphology, resulting in lower cardiac resynchronization therapy defibrillator (CRTD) implantation rates. Dialysis was associated with an overall increased risk for all-cause mortality (hazard ratio (HR) 3.22; 95% CI 1.69–6.13; p < 0.01) and for noncardiac hospitalizations (HR 2.80; p < 0.001) compared to all other study patients. However, within the subgroup of patients with severe renal dysfunction, the presence of dialysis was not an independent risk factor for all-cause mortality (HR 0.99; p = 0.97) as compared to non-dialysis. The rate of appropriate ICD therapy for ventricular tachyarrhythmias increased with declining renal function, with the highest rate observed among those undergoing dialysis.

BACKGROUND:Renal dysfunction is associated with increased mortality in heart failure (HF) patients. However, there are limited data regarding clinical and arrhythmic outcomes associated with implantable cardioverter defibrillator (ICD) therapy in this population.METHODS:We evaluated outcomes associated with the severity of renal dysfunction with or without dialysis among 2,289 patients who were enrolled and prospectively followed up in the Israeli ICD Registry. The primary endpoint of the study was all-cause mortality. Secondary endpoints included cardiac mortality, HF hospitalization, non-cardiac hospitalization, and appropriate and inappropriate ICD therapy.RESULTS:Severe renal dysfunction patients (estimated glomerular filtration rate<30 ml/min/1.73 m2; n=144 patients; 6%) were older, with higher comorbidities prevalence, and more likely to suffer from advanced HF. Among severe renal dysfunction patients, those on dialysis had a lower prevalence of wide QRS and complete left bundle branch morphology, resulting in lower cardiac resynchronization therapy defibrillator (CRTD) implantation rates. Dialysis was associated with an overall increased risk for all-cause mortality (hazard ratio (HR) 3.22; 95% CI 1.69-6.13; p<0.01) and for noncardiac hospitalizations (HR 2.80; p<0.001) compared to all other study patients. However, within the subgroup of patients with severe renal dysfunction, the presence of dialysis was not an independent risk factor for all-cause mortality (HR 0.99; p=0.97) as compared to non-dialysis. The rate of appropriate ICD therapy for ventricular tachyarrhythmias increased with declining renal function, with the highest rate observed among those undergoing dialysis.CONCLUSIONS:The present findings suggest that dialysis does not significantly modify the adverse outcomes associated with severe renal dysfunction following ICD/CRTD implantation.

Atrial fibrillation (AF) is the most commonly encountered arrhythmia. Atrial fibrillation has significant implications in terms of morbidity and effects on quality of life, especially due to the risk of embolic phenomena and in particular embolic stroke that may have significant prognostic implications. The prevalence of AF increases with age and in patients with cardiac disease. Atrial fibrillation ablation is becoming a viable option and the number of procedures is on the rise in suitable patients. In this review we describe the rationale behind this procedure in terms of underlying mechanisms of AF, various techniques and risks vs. benefits in different patient groups. Whether atrial fibrillation ablation, should be used as first line therapy is still controversial. In addition, it should be remembered that even after a presumably successful ablation, it is not an indication to stop anticoagulation therapy. Anticoagulation should be maintained if appropriate guideline indications exist. e

BACKGROUND:Defibrillation threshold (DFT) testing during placement of an implantable cardioverter-defibrillator (ICD) has been considered mandatory. Accumulating data suggest a more limited role for DFT. OBJECTIVE:The purpose of this study was to compare the outcome of ICD recipients who underwent DFT testing compared with those who did not. METHODS:In this prospective cohort analysis of patients who received an ICD between July 2010 and March 2013, we compared patients who underwent DFT testing and those who did not. Primary end-points were death and malignant ventricular arrhythmias. Secondary end-points included the composite end-points and inappropriate ICD discharges. RESULTS:Of the 3596 patients in the registry, 614 patients (17%) underwent DFT testing during ICD placement vs 2982 (83%) who did not. Variables associated with ICD testing were implantation for secondary prevention (relative risk [RR] 1.87), prior ventricular arrhythmias (RR 1.81), use of antiarrhythmic medication (RR 1.59), and sinus rhythm (RR 2.05). Factors predisposing against testing were cardiac resynchronization therapy defibrillator implantation (RR 0.56) and concomitant diuretic use (RR 0.71). ICD testing was not associated with 1-year mortality (5.3% vs 5.1%, P = .74), delivery of appropriate shocks (8.6% vs 5.6%, P = .16), combined outcomes of ventricular arrhythmias and death (12.9% vs 11.3%, P = .45), or inappropriate ICD discharges (3.9% vs 2.1%, P = .2) compared to no DFT testing. CONCLUSION:No significant differences in the incidence of mortality, malignant ventricular arrhythmias, or inappropriate ICD discharges were observed between patients who underwent DFT testing compared to those who did not. Our results may support avoiding DFT testing during ICD placement, but this requires confirmation by additional prospective studies.

Renal Function and Outcomes After Defibrillator Implantation. Background: Implantable cardioverter defibrillators (ICDs) and cardiac resynchronization therapy (CRT) reduce mortality in patients with heart failure (HF) and left ventricular dysfunction. However, their efficacy in patients with chronic kidney disease (CKD) is controversial.Objective: We examined the association between renal dysfunction and clinical outcomes in patients undergoing ICD and CRT defibrillator (CRTD) implantation.Methods: Data were collected from the Israeli ICD registry. Estimated glomerular filtration rate (eGFR) at implantation was assessed using the modification of diet in renal disease formula. Primary outcome was all-cause mortality. Secondary outcomes included the composite endpoints of death or HF and death or ventricular arrhythmias (ventricular tachycardia/ventricular fibrillation [VT/VF]); any hospitalizations; first appropriate and inappropriate ICD therapy.Results: During the study period (July 2010-November 2012), 2,811 patients were implanted with ICD or CRTD. One-year follow-up data were available for 730 ICD patients and 453 CRTD patients. Patients with eGFR < 30 mL/minute/1.73 m(2) (n= 54, 4.6%) were older, had a higher prevalence of diabetes, hypertension, or ischemic heart disease. eGFR < 30 mL/minute/1.73 m(2) was associated with increased mortality risk in ICD (HR 5.4; 95% CI 1.5-19.2), but not in CRTD patients (HR 0.9; 95% CI 0.1-7.5). Renal dysfunction was associated with the composite endpoints of death or HF and death or VT/VF in ICD, but not in CRTD patients. Mean eGFR during follow-up decreased by 8.0 +/- 4.3 mL/minute/1.73 m(2) in ICD patients (P = 0.06) and by 1.8 +/- 1.3 mL/minute/1.73 m(2) in patients with CRTD (P = 0.2).Conclusion: Based on this retrospective analysis, CKD is associated with adverse prognosis after ICD implantation, but not after CRTD implantation. GFR decreased in patients with ICD, but not in CRTD patients.

Background: The implantable loop recorder (ILR) is an important tool for the evaluation of unexplained syncope, particularly in cases of rarely occurring arrhythmia.Objectives: To review the clinical experience of two Israeli medical centers with the ILR.Methods: We reviewed the medical records of patients with unexplained syncope evaluated with the ILR at Rabin Medical Center (2006-2010) and Wolfson Medical Center (2000-2009).Results: The study group included 75 patients (44 males) followed for 11.9 +/- 9.5 months after ILR implantation. Patients' mean age was 64 +/- 20 years. The ILR identified an arrhythmic mechanism of syncope in 20 patients (17 bradyarrhythmias, 3 tachyarrhythmias) and excluded arrhythmias in 12, for a diagnostic yield of 42.7%. It was not diagnostic in 17 patients (22.7%) at the time of explant; 26 patients (34.7%) were still in follow-up. In two patients ILR results that were initially negative were reversed by later ILR tracings. The patients with bradyarrhythmias included 9 of 16 (56.3%) with surface electrocardiogram conduction disturbances and 2 of 12 (16.7%) with negative findings on carotid sinus massage. All bradyarrhythmic patients received pacemakers; the seven patients for whom post-intervention data were available had no or mild symptoms.Conclusions: The ILR has a high diagnostic yield. Pre-ILR findings correlating with the ILR results are conduction disturbances (positive predictor of arrhythmia) and negative carotid sinus massage results (negative predictor of arrhythmia). Proper patient instruction is necessary to obtain accurate results. Caution is advised when excluding an arrhythmia on the basis of ILR tracings, and long-term follow-up is warranted. IMAJ 2012; 14: 488-492

Background: The implantable loop recorder (ILR) is an important tool for the evaluation of unexplained syncope, particularly in cases of rarely occurring arrhythmia. o bjectives: To review the clinical experience of two Israeli medical centers with the ILR. methods: We reviewed the medical records of patients with unexplained syncope evaluated with the ILR at Rabin Medical Center (2006–2010) and Wolfson Medical Center (2000–2009). r esults: The study group included 75 patients (44 males) followed for 11.9 ± 9.5 months after ILR implantation. Patients’ mean age was 64 ± 20 years. The ILR identified an arrhythmic mechanism of syncope in 20 patients (17 bradyarrhythmias, 3 tachyarrhythmias) and excluded arrhythmias in 12, for a diagnostic yield of 42.7%. It was not diagnostic in 17 patients (22.7%) at the time of explant; 26 patients (34.7%) were still in follow-up. In two patients ILR results that were initially negative were reversed by later ILR tracings. The patients with bradyarrhythmias included 9 of 16 (56.3%) with surface electrocardiogram conduction disturbances and 2 of 12 (16.7%) with negative findings on carotid sinus massage. All bradyarrhythmic patients received pacemakers; the seven patients for whom post-intervention data were available had no or mild symptoms. conclusions: The ILR has a high diagnostic yield. Pre-ILR findings correlating with the ILR results are conduction disturbances (positive predictor of arrhythmia) and negative carotid sinus massage results (negative predictor of arrhythmia). Proper patient instruction is necessary to obtain accurate results. Caution is advised when excluding an arrhythmia on the basis of ILR tracings, and long-term follow-up is warranted.

BACKGROUND:Many electrophysiologists recommend implantable cardioverter defibrillators for patients with Brugada syndrome who are cardiac arrest survivors or presumed at high risk of sudden death (patients with syncope or a familial history of sudden death or those with inducible ventricular fibrillation at electrophysiologic study).OBJECTIVES:To assess the efficacy and complications of ICD therapy in patients with Brugada syndrome.METHODS:The indications, efficacy and complications of ICD therapy in all patients with Brugada syndrome who underwent ICD implantation in 12 Israeli centers between 1994 and 2007 were analyzed.RESULTS:There were 59 patients (53 males, 89.8%) with a mean age of 44.1 years. At diagnosis 42 patients (71.2%) were symptomatic while 17 (28.8%) were asymptomatic. The indications for ICD implantation were: a history of cardiac arrest (n = 11, 18.6%), syncope (n = 31, 52.5%), inducible VF in asymptomatic patients (n = 14, 23.7%), and a family history of sudden death (n = 3, 0.5%). The overall inducibility rates of VF were 89.2% and 93.3% among the symptomatic and asymptomatic patients, respectively (P = NS). During a follow-up of 4-160 (45 +/- 35) months, all patients (except one who died from cancer) are alive. Five patients (8.4%), all with a history of cardiac arrest, had appropriate ICD discharge. Conversely, none of the patients without prior cardiac arrest had appropriate device therapy during a 39 +/- 30 month follow-up. Complications were encountered in 19 patients (32%). Inappropriate shocks occurred in 16 (27.1%) due to lead failure/dislodgment (n = 5), T wave oversensing (n = 2), device failure (n = 1), sinus tachycardia (n = 4), and supraventricular tachycardia (n = 4). One patient suffered a pneumothorax and another a brachial plexus injury during the implant procedure. One patient suffered a late (2 months) perforation of the right ventricle by the implanted lead. Eleven patients (18.6%) required a reintervention either for infection (n = 1) or lead problems (n = 10). Eight patients (13.5%) required psychiatric assistance due to complications related to the ICD (mostly inappropriate shocks in 7 patients).CONCLUSIONS:In this Israeli population with Brugada syndrome treated with ICD, appropriate device therapy was limited to cardiac arrest survivors while none of the other patients including those with syncope and/or inducible VF suffered an arrhythmic event. The overall complication rate was high.

Patients with malignant refractory ventricular arrhythmias present a unique therapeutic challenge. In recent years, this challenge has become even more complex due to the wide spread use of implantable cardiac defibrillators. If, in the past, a majority of the patients succumbed due to these arrhythmias, today, due to the defibrillators, they survive and then need further treatment. The defibrillators treat the arrhythmias when they occur but in most cases do not prevent their initiation. In many cases we need to resort to other modalities. We present three patients who exemplify various options of dealing with this complex issue.

Complex RF ablation may be required because of anatomical anomalies, difficult target point approach, difficult diagnosis misleading the ablation procedure, multiple pathways and multiple types of arrhythmias in the same heart. These conditions were met in 17% of 1000 consecutive ablation procedures. The final success was not significantly affected however there was a trend for multiple procedures to achieve the same success level.

OBJECTIVES: To assess the relative contributions of rate control and rhythm regularization to left ventricular function in atrial fibrillation (AF) patients undergoing atrioventricular nodal ablation. This was performed by assessing the effect of ventricular rhythm regularization on left ventricular function during AF, and the effect of varying heart rate on left ventricular function after ablation.PATIENTS AND METHODS: Eleven patients with continuous,AF and V/VI-R pacemakers undergoing therapeutic atrioventricular nodal ablation were studied. Preablation patients underwent two 30 min observation periods in a randomized, blinded fashion during which they were either in baseline,AF (pacer set to default V/VI 50/min) or being paced using a rhythm stabilizing algorithm (RSA) designed to regularize rhythm without changing baseline ventricular rate. Six weeks after ablation, patients were again observed during the two following 30 min periods: pacing at a row clinically indicated rate (69 +/-9 beats/min), and pacing at the rapid, mean preablation rate. During all observation periods, left ventricular function was measured continuously using a nuclear vest that provided validated measures of heart rate, ejection fraction, and normalized endsystolic volume (ESV) and end-diastolic (EDV) volume.RESULTS: Before ablation, RSA successfully regularized rhythm, decreasing the coefficient of variation of interbeat intervals 20 +/-5% to 10 +/-4% (P <0.001). The heart rate with RSA (105 +/- 19 beats/min) was not significantly different From the baseline AF rate (102 +/- 21 beats/min). increased rhythm regularity achieved by RSA significantly improved left ventricular function, decreasing ESV from 62 +/- 12 units to 57 +/- 11 units (P=0.03), and increasing the ejection fraction from 31 +/- 11% to 36 +/- 11% (P=0.03). After ablation, at the clinically indicated low Facing rate of 69 +/-9 beats/min, a much greater improvement in ejection fraction was observed, increasing to 44 +/- 13% (P=0.005 compared with preablation). However, rapid regular Facing at the mean preablation rate of 110 +/- 18 beats/min eradicated this improvement, decreasing the ejection fraction to 31 +/-8% (P=0.003), and increasing ESV from 53 +/- 13 units to 62 +/-8 units (P=0.006).CONCLUSIONS: Rhythm regularity achieved by a regularizing; pacing algorithm can significantly, albeit modestly, improve left ventricular function in AF. However, more marked improvements in left ventricular function seen after ablation are primarily due to rate reduction alone.