Sanjay Deshpande

Electroanatomically Guided Catheter Ablation of Ventricular Tachycardias Causing Multiple Defibrillator Shocks

SRA, J., et al.: Electroanatomically Guided Catheter Ablation of Ventricular Tachycardias Causing Multiple Defibrillator Shocks. With conventional techniques, RF catheter ablation is difficult in patients with unstable VT or with multiple VTs. The feasibility of RF catheter ablation guided by three‐dimensional electroanatomic mapping technique in patients whose implanted ICD continued to deliver multiple shocks due to VT despite use of antiarrhythmic medications was assessed in 19 patients (15 men, 4 women; mean age [± SD] 70 ± 7 years). All had a prior history of MI and subsequently had received an ICD due to VT. During the 12‐week preablation period, these patients received 31 ± 15 shocks (range 4–62 shocks) due to refractory monomorphic VTs. An electroanatomic mapping technique using the CARTO system was performed to delineate scar tissue. RF catheter ablation was then performed at appropriate sites identified by pacemapping and by substrate mapping. Seventeen patients were on amiodarone at the time of ablation. Twenty‐seven VTs were documented clinically, and 45 were induced during electrophysiological evaluation. Of the 45 tachycardias induced, 38 VTs were targeted for ablation. Catheter ablation was performed during sinus rhythm in 31 episodes and during VT in 7 episodes. During a mean follow‐up of 26 ± 8 weeks (range 18–48 weeks), 13 (66%) patients had no recurrence of VT (P < 0.0001) and antiarrhythmic drugs were discontinued or the number of medications reduced in 17 patients (P < 0.0001). Electroanatomic mapping is helpful in identifying sites for catheter ablation in highly symptomatic patients with refractory VT associated with myocardial scarring.

Spontaneous Reinitiation of Atrial Fibrillation Following Transvenous Atrial Defibrillation

Spontaneous reinitiation of atrial fibrillation (AF) has not been systematically looked at in patients undergoing transvenous AF. This study involved 11 patients, the mean age 60 ± 8 years. 3 male and 8 female, in whom transvenous atrial defibrillation successfully converted AF to sinus rhythm. Eight patients had paroxysmal AF and three patients had chronic persistent AF for 4 weeks or more. Four patients were taking antiarrhythmic medications at the time of testing. Multipolar transvenous catheters were positioned inside the coronary sinus, right atrium, and the right ventricle. Atrial defibrillation testing was performed using the METRIX atrial defibrillation system in nine patients and the Ventritex HVSO2 in the remaining two patients. A total of 64 therapeutic shocks (range 3–11) were delivered in the 11 patients, and 31 of these successfully converted AF to sinus rhythm. In four patients spontaneous AF was reinitiated following 12 successful transvenous atrial defibrillation episodes. The mean time to reinitiation of AF following shock delivery and restoration of sinus rhythm was 8.26 ± 5.25 seconds, range 1.8–19.9 seconds. All 12 episodes of spontaneous AF were preceded by a spontaneous premature atrial complex. The coupling interval of the premature atrial complexes was 443 ± 43 ms, range 390–510 ms. None of the patients taking antiarrhythmic medications or those demonstrating no premature atrial complexes had spontaneous reinitiation of AF. In conclusion, spontaneous reinitiation of AF can occur in a significant proportion of patients with AE undergoing transvenous atrial defibrillation. This phenomenon is preceded by the occurrence of atrial premature complex. Findings of this study may have significant clinical implications.(PACE 1998; 21:1105–1110)

Atrial fibrillation: Epidemiology, mechanisms, and management

The incidence of AF, the most common sustained arrhythmia in clinical practice, increases with age and coronary artery disease, hypertension and valvular heart disease are common underlying substrates; however, occasionally, AF may occur without any underlying heart disease. The most widely accepted theory of its mechanism is Moes multiple wavelet hypothesis, although recent studies are helping to shed light on other mechanisms, including the focal origin of AF in some patients. Most patients experience palpitations, but fatigue, dyspnoea, and dizziness may also occur. Therapy includes prevention of thromboembolism, control of rate, and restoration and maintenance of sinus rhythm. The risks and benefits of each treatment modality need to be assessed according to each patients circumstances. Unlike other arrhythmias, there is still no highly successful therapy for treating AF. However, significant advances are being made using non-pharmacological approaches to either prevent or cure this troublesome arrhythmia.

Sudden cardiac death.

Abstract SCD continues to be an important cause of death and morbidity. Despite expanding insight into the mechanisms causing SCD, the population at high risk is not being effectively identified. Although there is still much to do in the management phase of SCD (predicting the efficacy of various therapies), recent clinical trials have helped define the relative risks and benefits of therapies in preventing SCD. Trials are underway to determine whether treating other patient populations, including asymptomatic patients after MI, will improve survival rate. The approach to reducing mortality rate will always be multifaceted; primary prevention of coronary artery disease and prompt salvage of jeopardized myocardium are 2 important aspects of this approach. In addition to interventions for MI, such as myocardial revascularization when indicated, simple and easily administered therapies that are likely to remain the most effective prophylactic interventions are aspirin, ACE inhibitors, β-blockers, and cholesterol-lowering agents. However, the MADIT and AVID data clearly demonstrate a role for ICD therapy in a subgroup of patients who have VT/VF and are at risk of cardiac arrest. Even though the absolute magnitude of benefit associated with ICDs is still to be determined, the AVID study and other recent reports provide convincing evidence that patients who have VT/VF fare better with ICDs than with antiarrhythmic drug therapy. For the high-risk population described in this article, in addition to aggressive antiischemic and heart failure therapy, ICDs are now a mainstay of life-saving treatment. Still to be surmounted is the challenge of identifying patients who have nonischemic substrates and of providing them with the appropriate therapy. Guided by genetic studies and new insight into the mechanisms of such problems as congenital long QT syndrome, life-saving and life-enhancing therapies may soon be available for the management of SCD.

Driving safety among patients with neurocardiogenic (vasovagal) syncope.

The purpose of this study was to evaluate the risk of injury due to syncope while driving and the driving habits of patients with neurocardiogenic (vasovagal) syncope. Neurocardiogenic syncope is one of the most common causes of syncope. However, the important issue of driving related injury due to syncope in this population is not well defined. Risk of injury due to syncope while driving and driving behavior was evaluated in 155 consecutive patients (92 women and 63 men; mean age 49 ± 19 years) with history of syncope in whom hypotension and syncope or presyncope could be provoked during head‐up tilt testing. Patients with syncope and positive head‐up tilt table test were treated with pharmacological therapy. All participants were asked to fill out a detailed questionnaire regarding any driving related injuries and their driving behavior before tilt table testing and during follow‐up. Prior to head‐up tilt testing two patients had syncope while driving, and one of these patients had syncope related injury during driving. The mean duration of syncopal episodes was 50 ± 14 months (range 12–72 months). Of the 155 patients, 52 (34%) had no warning prior to syncope, while 103 (6%) had warning symptoms such as dizziness prior to their clinical syncope. Following a diagnosis of neurocardiogenic syncope established by head‐up tilt testing, six patients stopped driving on their own. During a median follow‐up of 22 months recurrent syncope occurred in five (3.2%) patients. No patient had syncope or injury during driving. In conclusion, syncope and injury while driving in patients with neurocardiogenic syncope is rare. The precise mechanism of this is unclear but may be related to posture during driving. Consensus among the medical community will be needed to provide specific guidelines in these patients.

Sudden death in patients with implantable cardioverter-defibrillators

UNLABELLED Of the 733 patients with implantable cardioverter-defibrillators (ICDs) from 1982 to 1995 in our center, 20 died suddenly while the ICD was activated. This number included 16 men and four women with a mean age of 60 +/- 8 years and ejection fractions of 24.2% +/- 8.6%. ICDs were implanted for drug refractory ventricular tachycardia (VT) in 13 patients and for resucitated cardiac arrest in seven patients. The clinical VT was associated with syncope in 7 of 13 patients. VT was induced in 18 patients and was hemodynamically unstable in 12 patients. Shock therapies associated with syncope were delivered in 7 of 15 patients during the follow-up. This subgroup of patients survived a median of only 18 months after ICD implant. Ventricular fibrillation-defibrillation was found to surround death in nine patients. CONCLUSIONS (1) Sudden death victims of the ICD population are characterized by poor left ventricular function and hemodynamically unstable ventricular tachyarrhythmias. (2) Ventricular tachyarrhythmias are the major cause of sudden death in ICD patients.

Electroanatomic Mapping to Identify Breakthrough Sites in Recurrent Typical Human Flutter

SRA, J., et al.: Electroanatomic Mapping to Identify Breakthrough Sites in Recurrent Typical Human Flutter. The accuracy of conventional techniques in localizing previous radiofrequency (RF) ablation sites and thus breakthrough sites of recurrent atrial flutter is somewhat limited. We investigated the role of electroanatomic mapping for identifying breakthrough sites or “gaps” at the tricuspid annulus and inferior vena cava (IVC)/eustachian ridge isthmus to help RF ablation in patients with recurrent typical flutter. Twelve patients (8 men, 4 women, age 63 ± 10 years) with recurrent typical atrial flutter were included in the study. An electroanatomic mapping system (CARTO) was used to create a voltage map and activation and propagation patterns in the right atrium. Detailed voltage, activation, and propagation mapping of the tricuspid annulus and IVC/eustachian ridge isthmus allowed precise identification of gaps in all 12 patients at the tricuspid annulus (eight sites), IVC ridges (two sites), mid‐isthmus region (one site), and tricuspid annulus and IVC ridges (one site). Radiofrequency energy directed at these sites eliminated atrial flutter in all 12 patients, confirmed by noninducibility of atrial flutter and demonstration of conduction block during atrial pacing on either side of the lesion lines. During a mean follow‐up of 14.8 ± 3.5 months (range 8–19 months), paroxysmal atrial flutter recurred in only one patient and was subsequently treated with amiodarone, although this had been ineffective prior to ablation. Electroanatomic mapping can precisely identify gaps in the lesion line responsible for breakthrough of recurrent typical atrial flutter at the tricuspid annulus and at the IVC/eustachian ridge isthmus. These sites can be targeted with RF ablation with a high degree of success.

Comparison of outcome of implantable cardioverter defibrillator implantation in patients with severe versus moderately severe left ventricular dysfunction secondary to atherosclerotic coronary artery disease.

This study was undertaken to assess the feasibility and clinical outcome of implantable cardioverter-defibrillators (ICDs) among patients with coronary artery disease and left ventricular ejection fraction (LVEF) of <20%. The morbidity, mortality, and the long-term survival of 117 patients with LVEF of <20% (group 1) were compared with 321 patients with LVEF of 20% to 40% (group 2). Mortality in the first 30 days after ICD implantation was 0% for group 1 and 0.6% in group 2. Actuarial survival (all cause) at the end of 2, 4, and 5 years were 83%, 70%, and 62%, respectively, in group 1 and 90%, 80%, and 71% in group 2 (p = 0.05). Fifty-five patients (47%) in group 1 and 126 patients (39%) in group 2 received appropriate shocks during follow up. Among the patients in group 1, the overall survival at 2 years after an appropriate shock from an ICD was 92% for patients <60 years of age, 77% for patients ages 60 to 69, and 53% for patients >70 years old. Although the overall survival of patients in group 1 was slightly lower compared with those in group 2, in a multivariate analysis, the EF was not an independent predictor of poor survival. The ICD can be implanted with acceptable operative morbidity and mortality in selected patients with LVEF of <20%.

Catheter ablation of ventricular tachycardia

The role and success rate of catheter ablation for monomorphic ventricular tachycardia (VT) depend on the mechanism and origin of the tachycardia (i.e., myocardial versus His-Purkinje system) and whether it occurs in the presence or absence of structural heart diseases. For sustained bundle-branch reentry, a form of VT associated with structural heart disease, radiofrequency catheter ablation of the right bundle-branch can be performed readily and is highly successful in eliminating this arrhythmia. Because of modest success rates of catheter ablation of VT associated with a prior infarction (between 17% and 75%), this treatment modality is usually considered for cases refractory to drug therapy and should be viewed as adjunctive therapy. The target for ablation is a critical area of slow conduction, which is selected based on earliest endocardial activation, mid-diastolic potentials, concealed entrainment, or pace mapping. Radiofrequency catheter ablation may be the treatment of choice in patients with VT and no apparent structural heart disease; this is especially true for young patients who would otherwise require long-life antiarrhythmic therapy. Success rates between 75% and 100% have been reported, especially when the origin is in the right ventricular outflow tract.

Reversing the Initial Phase Polarity in Biphasic Shocks: Is the Polarity Benefit Reproducible?

The effect of initial phase polarity (IPP) reversal using biphasic shocks on DFT at the time of implantation of implantable cardioverter defibrillator and the reproducibility of this effect during predischarge testing was evaluated in a randomized fashion. Twenty‐two patients with ventricular tachycardia or ventricular fibrillation (VF) who received either the Medtronic 7219D (7 patients), 7219C (12 patients), 7223 (1 patient), or CPI Ventak MINI (2 patients) were studied. The DFT was determined in a randomized fashion at implantation and during predischarge testing using a binary search protocol. Initial shock was delivered at 12 J. If successful, subsequent shock was delivered at 6 J, following which the shock was incremented or decremented by 3 J depending upon the success. The DFT for right ventricular (RV)‐and RV + IPP was 10.9 ± 4.1 J and 11.1 ± 4.0 J, respectively, at implant (P = ns) and 9.7 ± 4.3 J and 8.4 ± 6 J, respectively, (P = ns) at predischarge testing. Of the six patients who had better DFT with RV+ at implantation, only one patient maintained the benefit during predischarge testing. The differences observed in IPP in individual patients may not be demonstrable during repeated testing. These findings may have implications on how these devices should be programmed.