Martin Fromer

Narrow, slow-conducting isthmus dependent left atrial reentry developing after ablation for atrial fibrillation: ECG characterization and elimination by focal RF ablation.

Introduction: The complete circuit of reentrant left atrial tachycardias (LATs) occurring after ablation for atrial fibrillation (AF) has not been well described. Identifying discrete isthmuses critical to these LATs may simplify their elimination by catheter ablation.

ACC/AHA/ESC 2006 Guidelines for Management of Patients With Ventricular Arrhythmias and the Prevention of Sudden Cardiac Death-Executive Summary.

Ventricular Arrhythmias and the Prevention of Sudden Cardiac Death—Executive Summary A Report of the American College of Cardiology/American Heart Association Task Force and the European Society of Cardiology Committee for Practice Guidelines (Writing Committee to Develop Guidelines for Management of Patients With Ventricular Arrhythmias and the Prevention of Sudden Cardiac Death) Developed in Collaboration With the European Heart Rhythm Association and the Heart Rhythm Society

Ultrarapid subthreshold stimulation for termination of atrioventricular node reentrant tachycardia.

OBJECTIVES We investigated the efficacy and safety of ultrarapid subthreshold electrical stimuli in terminating sustained atrioventricular (AV) node reentrant tachycardia. BACKGROUND Subthreshold stimuli, singly and in trains, have been reported to prolong the effective refractory period, inhibit the response to subsequent suprathreshold extrastimuli and to terminate ventricular tachycardia and reciprocating tachycardia. METHODS Seventeen consecutive patients with inducible sustained slow-fast AV node reentrant tachycardia (mean tachycardia cycle length 358 +/- 61 ms) were studied. Trains of subthreshold stimuli were tested at various right atrial sites. RESULTS Trains of subthreshold stimuli reproducibly terminated AV node reentrant tachycardia in 15 patients without administration of adjunctive pharmacologic agents. Effective subthreshold current strength ranged from 0.5 to 1.5 mA (mean 0.9 +/- 0.3). The cycle length of effective subthreshold stimuli trains ranged from 30 to 80 ms (mean 57 +/- 17), and the number of stimuli in the train ranged from 4 to 16 (mean 8 +/- 4). The site of successful termination was the proximal coronary sinus in 6 patients and the right low atrial septum in 12. During successful subthreshold termination, no atrial capture could be detected. Neither atrial fibrillation nor flutter nor tachycardia acceleration occurred. CONCLUSIONS Low current, high frequency trains of stimuli, when applied at a site presumed to be close to the reentrant circuit, provided a safe and effective method of terminating the common type of AV node reentrant tachycardia. This technique could be used to identify critical parts of the reentrant circuit suitable for ablation and further investigations with this method are warranted.

Heart Rate Dynamics at the Onset of Ventricular Tachyarrhythmias as Retrieved From Implantable Cardioverter-Defibrillators in Patients With Coronary Artery Disease

BACKGROUND The recent availability of implantable cardioverter-defibrillators (ICDs) that record 1024 R-R intervals preceding a ventricular tachyarrhythmia (VTA) provides a unique opportunity to analyze heart rate variability (HRV) before the onset of VTA. METHODS AND RESULTS Fifty-eight post-myocardial infarction patients with an implanted ICD for recurrent VTA provided 2 sets of 98 heart rate recordings in sinus rhythm: (1) before a VTA and (2) during control conditions. Three subgroups were considered according to the antiarrhythmic (AA) drug regimen. A state of sympathoexcitation was suggested by the significant reduction in HRV before VTA onset compared with control conditions. beta-Blockers and dl-sotalol enhanced HRV in control recordings; nevertheless, HRV declined before VTA independent of AA drugs. A gradual increase in heart rate and decrease in sinus arrhythmia at VTA onset were specific findings of patients who received dl-sotalol. CONCLUSIONS The peculiar heart rate dynamics observed before VTA onset are suggestive of a state of sympathoexcitation that is independent of AA drugs.

Clinical efficacy of radiofrequency current in the treatment of patients with atrioventricular node reentrant tachycardia

Eight women (mean age 41 years, range 24 to 62) with drug-resistant atrioventricular (AV) node reentrant tachycardia underwent radiofrequency catheter ablation. Radiofrequency energy was delivered in a unipolar mode with use of a back paddle as the anode placed between the two scapulae. The total applied energy was 2,233 +/- 1,919 J. The AH interval increased from 87 +/- 13 to 113 +/- 17 ms (p less than 0.05) and the PQ interval increased from 141 +/- 15 to 169 +/- 34 ms (p less than 0.05). The anterograde Wenckebach cycle length increased from 300 +/- 41 to 320 +/- 42 ms (p less than 0.05). Retrograde conduction was abolished in five patients. Atrioventricular node tachycardia was still inducible in three patients. During a follow-up period of 9 +/- 3 months, four patients remained clinically asymptomatic without drug therapy and four patients had recurrent symptoms. Three of the latter responded to previously unsuccessful antiarrhythmic drugs and the fourth patient underwent surgical cure for persistence of tachycardia. Right bundle branch block occurred in five patients; it was permanent in four and transient in one. In conclusion, radiofrequency catheter ablation represents a valuable but still investigational therapy in patients with drug-refractory AV node reentrant tachycardia.

Ten-Years Follow-Up of 20 Patients with Idiopathic Ventricular Tachycardia

The follow‐up and characteristics of 20 patients with ventricular tachycardia (VT) and no detectable heart disease is reported. These were 16 men and four women with a mean age of 44 years. Symptoms were present in 18 patients (eight had syncope and ten palpitations or dizziness), VT was sustained in 11 patients and a left bundle branch block morphology with inferior axis was found in 17 patients. In three patients, VT had a right bundle branch block morphology and left‐axis deviation. The VT was inducible in 13 patients during the electrophysiological testing (EP) and was sustained in five patients. Medical treatment was introduced in 19 patients. During a mean follow‐up of 10 years from the onset of the symptoms and 6 years from the EP testing, one patient died suddenly. He had stopped taking amiodarone 5 months before. In seven patients symptoms recurred and were due to discontinuation of therapy in two cases and inefftcacy of previous effective treatment in five patients. After modification of the treatment (three cases), implantation of a pacemaker (one case) and catheter ablation (one case), all patients became asymptomatic. Eleven patients became asymptomatic with the first administered antiarrhythmic therapy. One patient continues to be asymptomatic in spite of discontinuation of his medical therapy. We conclude that patients with VT and no detectable heart disease have a good long‐term prognosis and that appropriate therapy can be found in almost all patients.

Dual Chamber Pacing in Hypertrophic Obstructive Cardiomyopathy: Beneficial Effect of Atrioventricular Junction Ablation for Optimal Left Ventricular Capture and Filling

Clinical improvement with dual chamber pacing bas largely been reported in patients suffering from hypertrophic obstructive cardiomyopathy and mainly attributed to the reduction of the subaortic pressure gradient. To be effective, pacing must induce a permanent and complete capture of the LV. In two patients of our collective, symptoms (angina and dyspnea NYHA Class III and/or syncopes) persisted or relapsed despite pacing. This was related to the inability to obtain full LV capture due to a too‐short native PR interval. RF ablation of the AV junction was therefore performed in botb patients, resulting in permanent AV block in one and prolonged PR interval up to 310 ms in the second. Pacing was thereafter associated with an immediate and significant clinical improvement related to permanent LV capture, whatever the patients activity. After RF ablation, the AV delay was set up to induce the best LV filling, as assessed by Doppler analysis of mitral flow. Our observations suggest that RF ablation or modification of the AV junction can be a successful procedure in some patients with residual or recurrent symptoms, when the latter result from a loss of capture or from the inability to program an AV delay tbat does not compromise the active component to LV filling. Doppler echocardiography is a simple and effective mean to assess the hemodynamic effect of AV interval modulation in this setting.

Experience with a New Implantable Pacer-, Cardioverter-Defibrillator for the Therapy of Recurrent Sustained Ventricular Tachyarrhythmias: A Step Toward a Universal Ventricular Tachyarrhythmia Control Device

Ten consecutive patients (mean age 57.9 ± 7.6 years) were treated with an investigational tachyarrhythmia control device, the implantable Medtronic Pacer‐, Cardioverter‐, Defibrillator model 7216A or 72170. All patients had coronary artery disease with old myocardial infarctions and presented hemodynamically significant sustained ventricular tachyarrhythmias not suppressed by antiarrhythmic drug therapy and unrelated to acute myocardial infarction. In two patients a nonthoracotomy lead system was implanted. Lowest effective defibrillation energy ranged from 5 to 18 joules (mean 12.2 ± 4 joules) for the epicardial bielectrode systems and were 15 and 18 joules for the nonfhoracotomy lead system implants. The postoperative periods were unremarkable. Follow‐up ranged from 7 to 19 months (mean 13.8 ± 4.5 months). Spontaneous tachyarrhythmia episodes were detected and treated by the device in six patients, five of them received staged therapies. No deaths occurred and no hospital admissions were necessary for device related or ventricular tachyarrhythmia related complications. In conclusion, this integrated device represents a major step toward the development of a universal ventricular arrhythmia control device.

Ventricular arrhythmia in coronary artery disease: limits of a risk stratification strategy based on the ejection fraction alone and impact of infarct localization

AIMS Estimates of the left ventricular ejection fraction (LVEF) in patients with life-threatening ventricular arrhythmias related to coronary artery disease (CAD) have rarely been reported despite it has become the basis for determining patients eligibility for prophylactic defibrillator. We aimed to determine the extent and distribution of reduced LVEF in patients with sustained ventricular tachycardia or ventricular fibrillation. METHODS AND RESULTS 252 patients admitted for ventricular arrhythmia related to CAD were included: 149 had acute myocardial infarction (MI) (Group I, 59%), 54 had significant chronic obstructive CAD suggestive of an ischaemic arrhythmic trigger (Group II, 21%) and 49 patients had an old MI without residual ischaemia (Group III, 19%). 34% of the patients with scar-related arrhythmias had an LVEF > or =40%. Based on pre-event LVEF evaluation, it can be estimated that less than one quarter of the whole study population had a known chronic MI with severely reduced LVEF. In Group III, the proportion of inferior MI was significantly higher than anterior MI (81 vs. 19%; absolute difference, -62; 95% confidence interval, -45 to -79; P < or = 0.0001), though median LVEF was higher in inferior MI (0.37 +/- 10 vs. 0.29 +/- 10; P = 0.0499). CONCLUSION Patients included in defibrillator trials represent only a minority of the patients at risk of sudden cardiac death. By applying the current risk stratification strategy based on LVEF, more than one third of the patients with old MI would not have qualified for a prophylactic defibrillator. Our study also suggests that inferior scars may be more prone to ventricular arrhythmia compared to anterior scars.

Termination of sustained ventricular tachycardia by ultrarapid subthreshold stimulation in humans.

Our purpose was to investigate the efficacy, safety, and electrophysiological mechanism of ultrarapid subthreshold electrical stimulation in terminating sustained ventricular tachycardia (VT) in humans. Fifteen patients with inducible sustained hemodynamically stable VT and whose VT cycle length ranged between 295 and 440 msec (337 +/- 60 msec) were included in this study. The stimulation threshold and ventricular myocardial effective refractory period were determined during VT, and the values ranged between 0.4 and 1.2 mA (mean, 0.7 +/- 0.3 mA) and between 185 and 245 msec (mean, 225 +/- 20 msec), respectively. Trains of ultrarapid subthreshold stimulation were delivered with cycle lengths of 100 to 10 msec in decremental steps of 10 msec. A 5-second pause was allowed between each step (decrement). A 2-msec pulse width was used in all patients, and a 4-msec pulse width was also tested in eight patients. Any apparent captured beat was disregarded. In eight (53%) patients, ultrarapid subthreshold stimulation terminated VT, and in the remaining seven (47%) patients, it did not. The lowest subthreshold stimulation that effectively terminated VT was 0.05 mA. In 10 patients, the site of early activity during VT was determined by endocardial catheter mapping, and subthreshold stimulation more effectively terminated VT in eight patients when it was applied close to the site of early activity. In seven patients who underwent mapping-guided arrhythmia surgery, subthreshold stimulation was applied close to the site of early activity and successfully terminated VT. In no patient did subthreshold stimulation produce acceleration of VT or induce ventricular fibrillation.(ABSTRACT TRUNCATED AT 250 WORDS)