Thomas Guarnieri

Prognostic importance of defibrillator shocks in patients with heart failure.

BACKGROUND Patients with heart failure who receive an implantable cardioverter-defibrillator (ICD) for primary prevention (i.e., prevention of a first life-threatening arrhythmic event) may later receive therapeutic shocks from the ICD. Information about long-term prognosis after ICD therapy in such patients is limited. METHODS Of 829 patients with heart failure who were randomly assigned to ICD therapy, we implanted the ICD in 811. ICD shocks that followed the onset of ventricular tachycardia or ventricular fibrillation were considered to be appropriate. All other ICD shocks were considered to be inappropriate. RESULTS Over a median follow-up period of 45.5 months, 269 patients (33.2%) received at least one ICD shock, with 128 patients receiving only appropriate shocks, 87 receiving only inappropriate shocks, and 54 receiving both types of shock. In a Cox proportional-hazards model adjusted for baseline prognostic factors, an appropriate ICD shock, as compared with no appropriate shock, was associated with a significant increase in the subsequent risk of death from all causes (hazard ratio, 5.68; 95% confidence interval [CI], 3.97 to 8.12; P<0.001). An inappropriate ICD shock, as compared with no inappropriate shock, was also associated with a significant increase in the risk of death (hazard ratio, 1.98; 95% CI, 1.29 to 3.05; P=0.002). For patients who survived longer than 24 hours after an appropriate ICD shock, the risk of death remained elevated (hazard ratio, 2.99; 95% CI, 2.04 to 4.37; P<0.001). The most common cause of death among patients who received any ICD shock was progressive heart failure. CONCLUSIONS Among patients with heart failure in whom an ICD is implanted for primary prevention, those who receive shocks for any arrhythmia have a substantially higher risk of death than similar patients who do not receive such shocks.

Intravenous amiodarone for the prevention of atrial fibrillation after open heart surgery: the amiodarone reduction in coronary heart (ARCH) trial

OBJECTIVES This study was designed to test whether intravenous (i.v.) amiodarone would prevent atrial fibrillation and decrease hospital stay after open heart surgery. BACKGROUND Atrial fibrillation commonly occurs after open heart procedures and is thought to be a significant determinant for prolongation of hospitalization. Oral amiodarone given preoperatively appears to reduce the incidence of atrial fibrillation. This study was designed to test whether the more rapid-acting i.v. formulation of amiodarone given postoperatively would reduce the incidence of atrial fibrillation. METHODS Three hundred patients undergoing standard open heart surgery were randomized in a double-blind fashion to i.v. amiodarone (1 g/day for 2 days) versus placebo immediately after open heart surgery. The primary end points of the trial were incidence of atrial fibrillation and length of hospital stay. Baseline clinical variables and mortality and morbidity data were collected. RESULTS Atrial fibrillation occurred in 67/142 (47%) patients on placebo versus 56/158 (35%) on amiodarone (p = 0.01). Length of hospital stay for the placebo group was 8.2 +/- 6.2 days, and 7.6 +/- 5.9 days for the amiodarone group (p = 0.34). No differences were noted in baseline variables, morbidity or mortality. CONCLUSIONS Low-dose i.v. amiodarone was safe and effective in reducing the incidence of atrial fibrillation after heart surgery, but did not significantly alter length of hospital stay.

Predictors of first discharge and subsequent survival in patients with automatic implantable cardioverter-defibrillators.

BackgroundTwo hundred eighteen patients were evaluated in a two-phase approach (time to first appropriate discharge, survival after discharge) to identify factors that may be related to maximal benefit derived from use of an automatic implantable cardioverter-defibrillator (AICD). Methods and ResultsOne hundred ninety-seven patients survived implantation of AICD, with or without concomitant cardiac surgery. One hundred five patients had an AICD discharge associated with syncope, presyncope, documented sustained ventricular tachycardia or fibrillation, or sleep at 9.1 ± 11.1 months after implantation. Patients survived 23.8 ± 18.0 months after AICD discharge. Left ventricular dysfunction (p =0.008 for ejection fraction less than 25%) was associated with earlier AICD discharge and shortened survival after AICD discharge (p =0.008 for ejection fraction less than 25%;p=0.01 for New York Heart Association functional class III and IV). B-Blocker administration (p =0.006) and coronary bypass surgery (p =0.06) were associated with later AICD discharge. Coronary bypass surgery (p =0.035) but not P-blockers was associated with more prolonged survival after AICD discharge. ConclusionsThese data suggest that a relatively easy algorithm can be applied to predict which patient will benefit most from AICD implantation.

No Benefit From Defibrillation Threshold Testing in the SCD-HeFT (Sudden Cardiac Death in Heart Failure Trial)

OBJECTIVES This study investigated whether defibrillation threshold (DFT) testing during implantable cardioverter-defibrillator (ICD) implantation predicts clinical outcomes. BACKGROUND Defibrillation testing is often performed during insertion of ICDs to confirm shock efficacy. There are no prospective data to suggest that this procedure improves outcomes when modern ICDs are implanted for primary prevention of sudden death. METHODS The analysis included the 811 patients who were randomized to the ICD arm of the SCD-HeFT (Sudden Cardiac Death in Heart Failure Trial) and had the device implanted. The DFT testing protocol in SCD-HeFT was designed to limit shock testing in a primary prevention heart failure population. RESULTS Baseline DFT data were available for 717 patients (88.4%). All 717 patients had a DFT of < or =30 J, the maximum output of the device in this study. The DFT was < or =20 J in 97.8% of patients. There was no survival difference between patients with a lower DFT (< or =10 J, n = 547) and a higher DFT (>10 J, n = 170) (p = 0.41). First shock efficacy was 83.0% for the first clinical ventricular tachyarrhythmia event; there were no differences in shock efficacies when the cohort was subdivided by baseline DFT. CONCLUSIONS Low baseline DFTs were obtained in patients with stable, optimally treated heart failure during ICD implantation for primary prevention of sudden death. First shock efficacy for ventricular tachyarrhythmias was high regardless of baseline DFT testing results. Baseline DFT testing did not predict long-term mortality or shock efficacy in this study.

Clinical interactions between pacemakers and automatic implantable cardioverter-defibrillators

Concomitant use of a pacemaker and an automatic implantable cardioverter-defibrillator (AICD) is common. Seventeen percent of patients receiving an AICD at The Johns Hopkins Hospital also had a permanent pacemaker implanted before (16 patients), at the same time as (2 patients) or after (12 patients) AICD implantation. Four types of interactions were noted: 1) transient failure to sense or capture immediately after AICD discharge (seven patients); 2) oversensing of the pacemaker stimulus by the AICD, leading to double counting (one patient); 3) AICD failure to sense ventricular fibrillation resulting from pacemaker stimulus oversensing (three patients, one only at high asynchronous output); and 4) pacemaker reprogramming caused by AICD discharge (three patients). No clinical sequelae of these interactions were noted during follow-up study. Thus, potentially adverse clinical interactions are common and routine screening is recommended. With proper attention to lead placements and programming of the devices, clinical consequences of these interactions can be avoided.

Treatment of Malignant Ventricular Arrhythmias with Endocardial Resection and Implantation of the Automatic Cardioverter-Defibrillator

Although ventricular resection guided by endocardial mapping has been a successful treatment for drug-refractory ventricular arrhythmias, 20 to 30 percent of patients still have postoperative sustained ventricular tachycardia or sudden death. To improve the outcome of the procedure, we implanted an automatic cardioverter-defibrillator in conjunction with endocardial resection in 28 patients, all of whom had had previous myocardial infarctions and between one and five cardiac arrests. There were three perioperative deaths. During follow-up of 8 to 51 months (mean, 25), 4 of the 25 survivors had recurrences of hypotensive ventricular tachycardia, which in all instances were automatically terminated by the implanted device. One patient, whose automatic cardioverter-defibrillator was not functional, died suddenly. We conclude that patients undergoing mapping-directed endocardial resection can be provided with additional protection against recurrent ventricular tachyarrhythmias or sudden death by implantation of an automatic cardioverter-defibrillator.

Multifocal atrial tachycardia: a toxic effect of theophylline

Sixteen patients with multifocal atrial tachycardia (MAT) who were taking theophylline were identified over 6 months. After theophylline was discontinued the atrial rate fell and MAT resolved in all sixteen patients. Five patients were challenged with intravenous aminophylline to investigate the role of theophylline in the genesis of MAT. MAT with a rapid ventricular response occurred in all five even though metabolic and respiratory variables did not change. MAT returned on challenge in three patients in whom serum theophylline levels were within the generally accepted therapeutic range (10-20 mg/l). In individual patients, theophylline had a dose-related effect on the atrial rate and the amount of ectopic atrial activity. Thus, theophylline may commonly precipitate MAT and treatment with the drug should be carefully considered in patients with respiratory insufficiency and MAT.

Implanted Automatic Defibrillators: Effects of Drugs and Pacemakers

The automatic implantable cardioverter defibrillator is an effective device for prevention of sudden ive device for prevention of sudden cardiac death. Patients who require the implantation of the device often require permanent pacing for symptomatic bradyarrhythmias and may require antiarrhythmic drug therapy. Antiarrhythmic drugs may after the defibrillation thresholds, arrhythmia cycle length and frequency, pacing thresholds and postshock excitability. Interactions between the defibrillator and the pacemaker may result in sensing problems, leading to multiple counting and inappropriate shocks, or ventricular fibrillation nondetection, sensing or capture failure post defibrillation and pacemaker reprogramming induced by defibrillator discharge. The potential for interactions will increase as the new generation of programmable defibrillators become clinically available, combining features of permanent pacemakers, antitachycardia pacemakers and defibrillators.

Pathologic findings related to the lead system and repeated defibrillations in patients with the automatic implantable cardioverter-defibrillator

The purpose of the present study was to examine at autopsy the effect of multiple defibrillations on the myocardium and the pathologic consequences of short- and long-term placement of the intravascular and interpericardial leads of the automatic implantable cardioverter-defibrillator. Twenty-five patients were examined at autopsy; 8 of them underwent lead implantation only and 17 received both leads and the automatic implantable cardioverter-defibrillator. Twelve patients (48%) died of ventricular tachycardia or ventricular fibrillation; seven (28%) died of other causes. Acute pericarditis occurred in all patients, resulting in a localized, progressive fibrosis around the apical patch lead without giving rise to pericardial restriction. Thrombus formation was associated with the superior vena cava spring electrode in four patients (17%) and the right ventricular rate-sensing electrode in one patient (4%). Asymptomatic pulmonary emboli occurred in two patients (8%). In one patient who underwent defibrillation 59 times, superior vena cava changes consisted of vein wall destruction, fibrosis and thrombus formation. Pathologic changes under the apical patch related to defibrillation were observed in seven patients; two of these had fewer than 5 defibrillations, one had 8 defibrillations and four had 21 to 74 defibrillations. These changes consisted of contraction band necrosis in four patients, vacuolar cytoplasmic clearing and loss of myocytes confined to the myocardium under the patch electrode in five patients who had multiple defibrillations. The observed pathologic changes were estimated to affect less than 2% of the total myocardial mass. Thus, the automatic implantable cardioverter-defibrillator lead system and multiple defibrillations result in localized myocardial injury confined to the tissue under the patch electrode.(ABSTRACT TRUNCATED AT 250 WORDS)

Long‐Term Follow‐Up of Patients with Nonischemic Dilated Cardiomyopathy and Ventricular Tachyarrhythmias Treated with Implantable Cardioverter Defibrillators

We analyzed our 10‐year cumulative experience of 40 consecutive patients with idiopathic dilated Cardiomyopathy and associated ventricular tachyarrhythmias, treated with implantable Cardioverter defibrillators. Dilated Cardiomyopathy was defined as left ventricular ejection fraction (EF) ≤50% with no defineable etiology. Patient characteristics included: 24 male, mean age 52 years, mean EF = 33%, New York Heart Association Class I–III, presenting syndrome—cardiac arrest (n = 28), syncope/near syncope (n = 12). At 2.5 years mean follow‐up, there were 16 deaths: one operative, three sudden, two incessant ventricular tachycardia/ventricular fibrillation (VT/VF), six heart failure, and four noncardiac. The actuarial mortality at 1 and 4 years was 0% and 14% for sudden death, 11% and 34% for cardiac death. The projected mortality was 52% and 78% for same time intervals (P < 0.01). No useful baseline variable predicted who would or would not receive an ICD shock in follow‐up. ICD therapy appears effective in reducing sudden death mortality in this high risk population.