Benefits of implantable defibrillators are overestimated by sudden death rates and better represented by the total arrhythmic death rate

Indications for an implantable cardioverter defibrillator (ICD)

Since the first clinical use of implantable defibrillator in human, the technology and the function of implantable cardioverter-defibrillator (ICD) have been much improved and now, ICD can be implanted within the chest wall. ICD is the most reliable therapy to prevent sudden cardiac death (SCD) in patients with documented VT/VF and the efficacy is most clear in patients with depressed heart function. It is now extended as a tool of the primary prevention of SCD in high risk patients after myocardial infarction. However, such beneficial effect is not applicable to DCM though patients might have depressed heart function. ICD is not free from procedure- or device-related problems which need to be resolved. From unknown causes, VT/VF might recur in an incessant form and an emergency admission is needed. Therefore, even during ICD therapy, patients often require antiarrhythmic drugs or catheter ablation.

Implantable cardioverter defibrillators

Implantable cardioverter defibrillators have proven to be an effective therapy for life-threatening ventricular arrhythmias. Given the ever-increasing number of patients who have these devices, increasing numbers of patients are likely to present to emergency departments with defibrillator-related problems. This article discusses normal device function, indications for implantation, and technique of implantation. It also focuses on the evaluation and management of patients with these devices presenting to the emergency department.

Mortality benefit of implantable cardioverter-defibrillator therapy in patients with persistent malignant ventricular arrhythmias despite amiodarone treatment

Implantable cardioverter defibrillators (ICDs) are very effective in preventing sudden cardiac death. However, debate continues as to whether ICD implantation is superior to amiodarone in prolonging survival in patients with life-threatening ventricular arrhythmias. Of 442 consecutive patients treated with amiodarone, we identified 48 patients with symptomatic ventricular arrhythmias who met all of the following inclusion criteria: (1) had inducible sustained ventricular tachycardia at baseline electrophysiologic study, (2) had an oral amiodarone load of at least 10 g over 10 to 14 days, (3) remained inducible with a hemodynamically unstable ventricular arrhythmia at follow-up electrophysiologic study, and (4) were advised to continue amiodarone therapy and undergo ICD implantation. Patients who agreed to undergo ICD implantation (n = 28) had a lower ejection fraction (29 +/- 9% vs 40 +/- 12% p <0.005) and were younger (61.0 +/- 10 vs 69 +/- 7 years, p <0.01) than patients who refused device implantation (n = 20). Using a Cox proportional-hazards model, defibrillator therapy was the strongest independent predictor of improved survival in patients with an ejection fraction < or =40% (RR = 0.42; 95% confidence interval 0.22 to 0.79). Thus, patients with depressed ejection fraction and continued inducibility of sustained ventricular tachycardia despite oral amiodarone loading have a poor prognosis. In such patients, ICDs are associated with a 58% reduction in total cardiac mortality.

Comparison of long-term outcomes of patients treated with nonthoracotomy and thoracotomy implantable defibrillators

In 193 consecutive patients treated with implantable defibrillators at our institution, thoracotomy approaches were used in 87 patients and nonthoracotomy approaches in 106 patients. Long-term outcomes of the 2 groups were compared by the intention-to-treat analysis. Surgical mortality (30-day mortality) rates were 5.7% in the thoracotomy group and 0% in the nonthoracotomy group. Six of 106 patients who underwent nonthoracotomy implantation had a high defibrillation threshold and did not receive nonthoracotomy defibrillators. The duration of follow-up was 52 +/- 31 months in the thoracotomy group, and 23 +/- 15 months in nonthoracotomy group. Actuarial survival rates at 6 and 24 months were, respectively, 90% and 81% in nonthoracotomy patients and 89% and 80% in thoracotomy patients (p = NS). In patients with left ventricular ejection fraction <30%, surgical mortality was 0% by the nonthoracotomy and 10% by the thoracotomy approach. Despite the 10% difference in 30-day mortality, survival rates at 6 months were 85% in nonthoracotomy patients and 81% in thoracotomy patients. At 24 months they were 73% in nonthoracotomy patients and 74% in thoracotomy patients. Thus, this nonrandomized study suggests that while short-term survival is better in nonthoracotomy patients than thoracotomy patients, the difference in survival diminishes quickly during the first few months and disappears by 6 months. The results were similar in patients with severe ventricular dysfunction. Several important implantable-cardioverter defibrillator (ICD) trials initially utilized thoracotomy ICDs. Although questions may be raised with regard to applicability of such a trial in the era of nonthoracotomy ICDs, this study suggests that the results of such ICD trials will be largely applicable to patients treated with nonthoracotomy ICDs.

Comparison of d,l-sotalol and implantable defibrillators for treatment of sustained ventricular tachycardia or fibrillation in patients with coronary artery disease

BACKGROUND

Implantable cardioverter-defibrillators (ICDs) and d,l-sotalol are widely used to treat ventricular tachyarrhythmia and ventricular fibrillation (VT/VF). The purpose of this study was to compare the long-term efficacy of d,l-sotalol and ICDs in patients with coronary artery disease.

METHODS AND RESULTS

In a case-control study, 50 patients treated with oral d,l-sotalol were matched to 50 patients treated with ICDs. Both groups were matched for sex (82 men), age (58 +/- 10 years), ejection fraction (40 +/- 12%), extent of coronary artery disease, presenting arrhythmia, and year that treatment began. In all patients in the sotalol group, VT/VF was inducible in the drug-free electrophysiological study. Induction of sustained VT/VF was suppressed by d,l-sotalol (438 +/- 95 mg/d). In the ICD group, either VT/VF was not inducible (n = 5) or inducible sustained VT/VF was refractory to antiarrhythmic drug treatment (n = 45). Sotalol treatment led to a marked reduction in arrhythmic events. Whereas 83% of the patients in the sotalol group were free of sudden death and nonfatal VT at 3 years, only 33% of the ICD patients did not receive appropriate ICD therapies (P < .005). Actuarial rates for absence of sudden death at 3 years were 85% in the sotalol group and 100% in the ICD group (P < .005). Actuarial rates for overall survival at 3 years were 75% in the sotalol group and 85% in the ICD group (P = .02).

CONCLUSIONS

In this case-control study, ICD therapy was more effective tha electrophysiologically guided antiar-rhythmic treatment with d,l-sotalol in prevention of sudden death and reduction of total morality in patients with coronary artery disease. Prospective studies are needed to confirm these results.

Cost-effectiveness of implantable defibrillator as first-choice therapy versus electrophysiologically guided, tiered strategy in postinfarct sudden death survivors. A randomized study

BACKGROUND

Rising costs of health care, partly as a result of costly therapeutic innovations, are of concern to both the medical profession and healthcare authorities. The implantable cardioverter-defibrillator (ICD) is still not remunerated by Dutch healthcare insurers. The aim of this study was to evaluate the cost-effectiveness of early implantation of the ICD in postinfarct sudden death survivors.

METHODS AND RESULTS

Sixty consecutive postinfarct survivors of cardiac arrest caused by ventricular tachycardia or fibrillation were randomly assigned either ICD as first choice (n = 29) or a tiered therapy starting with antiarrhythmic drugs and guided by electrophysiological (EP) testing (n = 31). Median follow-up was 729 days (range, 3 to 1675 days). Fifteen patients died, 4 in the early ICD group and 11 in the EP-guided strategy group (P = .07). For quantitative assessment, the cost-effectiveness ratio was calculated for both groups and expressed as median total costs per patient per day alive. Because effectiveness aspects other than mortality are not incorporated in this ratio, other factors related to quality of life were used as qualitative measures of cost-effectiveness. The cost-effectiveness ratios were $63 and $94 for the early ICD and EP-guided strategy groups, respectively, per patient per day alive. This amounts to a net cost-effectiveness of $11,315 per patient per year alive saved by early ICD implantation. Costs in the early ICD group were higher only during the first 3 months of follow-up, but as a result of the high proportion of therapy changes, including arrhythmia surgery and late ICD implantation, costs in the EP-guided strategy group became higher after that. Patients discharged with antiarrhythmic drugs as sole therapy had the lowest total costs. This subset, however, showed extremely high mortality, resulting in a poor cost-effectiveness ratio ($196 per day). Invasive therapies and hospitalization were the major contributors to costs. If quality-of-life measures are taken into account, the cost-effectiveness of early ICD implantation was even more favorable. Recurrent cardiac arrest and cardiac transplantation occurred in the EP-guided strategy group only, whereas exercise tolerance, total hospitalization duration, number of invasive procedures, and antiarrhythmic therapy changes were significantly in favor of early ICD implantation.

CONCLUSIONS

In terms of cost-effectiveness, early ICD implantation is superior to the EP-guided therapeutic strategy in postinfarct sudden death survivors.

Influence of the implantable cardioverter/defibrillator on sudden death and total mortality in patients evaluated for cardiac transplantation

BACKGROUND

Implantable cardioverter/defibrillators (ICDs) may reduce sudden tachyarrhythmic death in patients with severe left ventricular dysfunction. It is uncertain whether this improves survival, particularly in patients awaiting cardiac transplantation.

METHODS AND RESULTS

The effect of treatment for spontaneous ventricular arrhythmias (ICD [n = 59], antiarrhythmic drugs [n = 53], or no antiarrhythmic treatment [n = 179]) on total mortality and mode of cardiac death was analyzed in 291 consecutive patients evaluated for cardiac transplantation between January 1986 and January 1995. There were 109 deaths (37.4%) (63 [21.6%] sudden, 40 [13.7%] nonsudden, and 6 [2.1%] noncardiac) during mean follow-up of 15 months (range, 1 to 118 months). Baseline clinical variables, medical therapies for heart failure, and actuarial rates of transplantation were similar between treatment groups. Kaplan-Meier sudden death rates were lowest in the ICD group, intermediate in the no antiarrhythmic treatment group, and highest in the drug treatment group throughout follow-up (12-month sudden death rates, 9.2%, 16.0%, and 34.7%, respectively; P = .004). Total mortality and nonsudden death rates did not differ. Cox proportional-hazards model revealed that antiarrhythmic drug treatment was associated with sudden death (relative risk, 2.1; 95% CI, 1.04 to 3.39; P = .04) and ICD was associated with nonsudden death (relative risk, 2.26; 95% CI, 1.12 to 4.62; P = .02).

CONCLUSIONS

Sudden death rates were lowest in patients treated with ICDs compared with drug treatment or no antiarrhythmic treatment. However, although ICDs reduced sudden death in selected high-risk patients with severe left ventricular dysfunction, the effect on long-term survival was limited, principally by high nonsudden death rates.

Drugs versus devices: contemporary practice in light of contemporary trials

In years past, the secondary prevention of life-threatening ventricular arrhythmias was limited to empiric drug therapy. In close temporal proximity to the birth of electrophysiologic study-guided treatment strategies to manage these arrhythmias, devices to convert arrhythmias were envisioned and designed. Now, advanced generation implantable defibrillators provide synchronized, low-energy cardioversion, antitachycardia pacing, and pacing support for bradycardia. Over the past decade and half, this technology that was once applied as a therapy of last resort has evolved and emerged as a therapy of first choice. Recently, however, enthusiasm for drug treatment strategies has also increased, especially the use of amiodarone. Most experts now agree that drug therapy chosen by electrophysiologic study guidance provides superior survival compared to the empiric use of Class I drugs, as long as a drug that suppresses arrhythmia inducibility is found. The empiric use of amiodarone and beta blockers may also improve outcome. This review examines some of the recent clinical trials utilizing pharmacologic and nonpharmacologic methods. The importance of ongoing and future clinical trials is emphasized.

Endocardial carbon-braid electrodes. A new concept for lower defibrillation thresholds

BACKGROUND

In the treatment of patients with life-threatening ventricular arrhythmia, transvenous implantable cardioverter/defibrillators provide significant advantages over devices requiring a thoracotomy. This study tested the hypothesis that a new carbon-fiber electrode, designed at the Technische Universität in Munich, Germany, has a lower defibrillation threshold (DFT) than standard transvenous defibrillation electrodes.

METHODS AND RESULTS

In 8 mongrel dogs (weight, 25.2 +/- 0.8 kg; heart weight, 192 +/- 19 g), we examined the efficacy and electrical characteristics of a right ventricular endocardial carbon prototype defibrillation electrode (9.5F, 4.4-cm2 surface) compared with a standard CPI 0062 Endotak electrode and a Medtronic 6966 Transvene endocardial right ventricular defibrillation electrode. The new electrode consists of 24 braided, tubular carbon filaments, each containing 1000 highly isotropic carbon fibers of 7-microns diameter, yielding a theoretical electrical surface of 480 cm2. The DFTs were determined in random order between each of the three right ventricular electrodes and a subcutaneous wire array anode placed on the left thorax. A standard step-down/up DFT protocol of 20-V shock steps was applied. Two different biphasic waveforms with a 1-ms delay between phases were tested: 3.2-ms first phase/2.0-ms second phase, and 6.0-ms first phase/6.0-ms second phase. For the 3.2/2.0-ms waveform, we found a significantly lower DFT for the carbon lead (4.96 +/- 1.58 J) compared with the CPI 0062 (6.93 +/- 1.67 J) and the Medtronic 6966 (7.49 +/- 0.99 J) leads. For the 6.0/6.0-ms waveform, the DFT for the carbon electrode (5.97 +/- 2.09 J) was significantly lower than for the Medtronic 6966 lead (8.55 +/- 1.93 J) but not for the CPI 0062 lead (6.30 +/- 1.41 J). The impedance with carbon was lower than with the other two leads for the 6.0/6.0-ms waveform but not for the 3.2/2.0-ms waveform. For the carbon electrode, the 3.2/2.0-ms waveform had a lower DFT than the 6.0/6.0-ms waveform.

CONCLUSIONS

The present canine study found a lower DFT for a new carbon electrode compared with DFTs for endocardial defibrillation electrodes made of standard metal. Further long-term animal studies and clinical studies are needed to determine whether carbon materials and braided-lead technology are practical and beneficial in patients.

Choosing the optimal monophasic and biphasic waveforms for ventricular defibrillation

INTRODUCTION

The truncated exponential waveform from an implantable cardioverter defibrillator can be described by three quantities: the leading edge voltage, the waveform duration, and the waveform time constant (tau s). The goal of this work was to develop and test a mathematical model of defibrillation that predicts the optimal durations for monophasic and the first phase of biphasic waveforms for different tau s values. In 1932, Blair used a parallel resistor-capacitor network as a model of the cell membrane to develop an equation that describes stimulation using square waves. We extended Blair's model of stimulation, using a resistor-capacitor network time constant (tau m), equal to 2.8 msec, to explicitly account for the waveform shape of a truncated exponential waveform. This extended model predicted that for monophasic waveforms with tau s of 1.5 msec, leading edge voltage will be constant for waveforms 2 msec and longer; for tau s of 3 msec, leading edge voltage will be constant for waveforms 3 msec and longer; for tau s of 6 msec, leading edge voltage will be constant for waveforms 4 msec and longer. We hypothesized that the best phase 1 of a biphasic waveform is the best monophasic waveform. Therefore, the optimal first phase of a biphasic waveform for a given tau s is the same as the optimal monophasic waveform.

METHODS AND RESULTS

We tested these hypotheses in two animal experiments. Part I: Defibrillation thresholds were determined for monophasic waveforms in eight dogs. For tau s of 1.5 msec, waveforms were truncated at 1, 1.5, 2, 2.5, 3, 4, 5, and 6 msec. For tau s of 3 msec, waveforms were truncated at 1,2,3,4,5,6, and 8 msec. For tau s of 6 msec, waveforms were truncated at 2,3,4,5,6,8, and 10 msec. For waveforms with tau s of 1.5, leading edge voltage was not significantly different for the waveform durations of 1.5 msec and longer. For waveforms with tau s of 3 msec, leading edge voltage was not significantly different for waveform durations of 2 msec and longer. For waveforms with tau s of 6 msec, there was no significant difference in leading edge voltage for the waveforms tested. Part II: Defibrillation thresholds were determined in another eight dogs for the same three tau s values. For each value of tau s, six biphasic waveforms were tested: 1/1, 2/2, 3/3, 4/4, 5/5, and 6/6 msec. For waveforms with tau s of 1.5 msec, leading edge voltage was a minimum for the 2/2 msec waveform. For waveforms with tau s of 3 msec, leading edge voltage was a minimum for the 3/3 msec waveform. For waveforms with tau s of 6 msec, leading edge voltage was a minimum and not significantly different for the 3/3, 4/4, 5/5, and 6/6 msec waveforms.

CONCLUSIONS

The model predicts the optimal monophasic duration and the first phase of a biphasic waveform to within 1 msec as tau s varies from 1.5 to 6 msec: for tau s equal to 1.5 msec, the optimal monophasic waveform duration and the optimal first phase of a biphasic waveform is 2 msec, for tau s equal to 3.0 msec, the optimal duration is 3 msec, and for tau s equal to 6 msec, the optimal duration is 4 msec. For both monophasic and biphasic waveforms, optimal waveform duration shortens as the waveform time constant shortens.

Comparison and frequency of ventricular arrhythmias after defibrillator implantation by thoracotomy versus nonthoracotomy approaches

Postoperative exacerbation of ventricular arrhythmias has been reported in some patients treated with thoracotomy implantable cardioverter-defibrillators (ICDs). This phenomenon, which may be related to epicardial patch electrodes, may be less frequent after nonthoracotomy ICD implantation. In this nonrandomized study, postoperative arrhythmias in thoracotomy approaches (n = 52) were compared with those in nonthoracotomy approaches (n = 59). Preoperatively, all patients were clinically stable receiving an antiarrhythmic regimen chosen by serial drug testing. Nine of 52 patients in the thoracotomy group developed sustained ventricular tachycardia postoperatively while receiving the same antiarrhythmic regimen chosen preoperatively, and 1 patient eventually died. Two additional patients developed frequent and prolonged episodes of nonsustained ventricular tachycardia requiring changes in the antiarrhythmic regimen. In the nonthoracotomy group, only 3 of 59 patients developed sustained ventricular tachycardia and 1 developed frequent nonsustained ventricular tachycardia. Thus, only 4 of 59 patients in the nonthoracotomy group developed clinically significant ventricular arrhythmia during the postoperative period compared with 11 of 52 patients in the thoracotomy group (p < 0.05). Surgical mortality was 6% in the thoracotomy group, and 0% in the nonthoracotomy group. In the remaining clinically stable patients, a marked (sevenfold) increase in asymptomatic ventricular arrhythmias was noted in 15 of 39 patients in the thoracotomy group, and in 3 of 55 patients in the nonthoracotomy group (p < 0.05). Thus, postoperative exacerbation of ventricular arrhythmia, sometimes noted with thoracotomy approaches, is very rare with nonthoracotomy approaches.

An AVID dissent

Despite declarations to the contrary, AVID appears to be a study that is seriously flawed. It is unfairly biased against the ICD; it entails unresolved ethical questions; and it poses a basic question that is inappropriate and subject to broad misinterpretation. Whatever the outcome of the study, harm is likely to follow unless the results are viewed very circumspectly. Rather than conducting such a study, we instead should be directing research funds toward identifying subsets of patients who might best benefit from the ICD. To optimize the use of the ICD, we need to do more patient selection, not less. We need to define subsets of patients in whom the prevention of sudden death by the ICD yields a prolonged overall survival, as well as subsets of patients in whom the device offers little or no benefit. AVID not only fails to do this, but it also threatens to inappropriately curtail (or less likely, to inappropriately expand) the proper use this efficacious tool, the ICD.

Sudden death in recipients of first-generation implantable cardioverter defibrillators: analysis of terminal events. Participating investigators

Clinical factors and terminal events associated with sudden death in 51 patients were analyzed from among a multicenter experience of 864 recipients of first generation automatic implantable cardioverter defibrillator (AICD) devices (single zone, committed, monophasic pulse with > or = 1 epicardial patch electrode) during the period May 1982-February 1988. For these 51 patients, mean age was 58 years and atherosclerotic heart disease was present in 84%, with a history of ventricular fibrillation (VF) in 61%, and inducible sustained ventricular tachycardia (VT) in 84%; mean left ventricular ejection fraction was 0.26. Nearly 80% experienced one or more appropriate AICD shocks during the median 9 month (range 0-46 months) period prior to death. Of 30 monitored deaths, the first documented terminal rhythm was VF in 12 (40%), VT in 8 (27%), and asystole or electromechanical dissociation in the remaining 10 (33%). Shocks were documented during terminal events in 21 (66%) of 32 witnessed cases of sudden death with activated devices. The proportion of monitored or witnessed sudden deaths that were known or presumed to be tachyarrhythmic (based on terminal VT, VF, or shocks) ranged from 69% (11/16 cases with activated/nondepleted devices and a defibrillation threshold [DFT] < or = 20 J) to 81% (29/36 cases on intention-to-treat basis). Of 27 patients with known or presumed sudden tachyarrhythmic death, the AICD had been deactivated prior to death in 4 (15%); activated, but depleted in 4 (15%); activated/nondepleted, but with DFT of 25 J in 4 (15%); and activated/nondepleted, but without DFT testing in 4 (15%). The remaining 11 (41%) known or presumed sudden tachyarrhythmic deaths occurred in patients with activated/nondepleted devices and DFT < or = 20 J; however, definite or suspected contributory factors (e.g., hematoma under epicardial patch, generator component failure, or drug-induced DFT rise) could be identified in 6 (55%) of 11 cases. Thus, in this first-generation AICD experience: 1) most sudden deaths occurred on the basis of a known or presumed tachyarrhythmia; and 2) an understanding of apparent "failure" of ICD therapy could often be gained through an integrated analysis of associated clinical factors and management practices, as well as device "hardware" function. These observations are likely to remain relevant, even with respect to newer generation ICDs.

Comparison of defibrillator therapy and other therapeutic modalities for sustained ventricular tachycardia or ventricular fibrillation associated with coronary artery disease

Outcomes of 282 patients referred to the arrhythmia service at Montefiore Medical Center for sustained ventricular tachycardia (n = 214) or ventricular fibrillation (n = 68) associated with coronary artery disease were analyzed retrospectively. All patients underwent serial drug trials by electrophysiologic testing and Holter monitoring. Sixty-eight patients who did not respond to drug therapy were treated with implantable cardioverter-defibrillators (ICD group), and 214 patients were treated with other methods guided by electrophysiologic testing and Holter monitoring (non-ICD group). The non-ICD group included 49 patients who responded to drug therapy as judged by electrophysiologic testing, as well as patients who did not respond and were not treated with defibrillator therapy for various reasons. Ten patients died in the hospital (2 patients in the ICD group, 8 in the non-ICD group). Actuarial survival rates free of total cardiac death at 1, 2, and 3 years were, respectively, 94%, 87%, and 85% in the ICD group, and 82%, 78%, and 73% in the non-ICD group (p = NS). Survival rates free of total death at 1, 2, and 3 years were 90%, 82%, and 76% in the ICD group, and 82%, 76%, and 70% in the non-ICD group, respectively (p = NS). Survival rates free of total cardiac and total deaths of 49 patients treated with an effective regimen determined by electrophysiologic testing were not significantly different from those of the ICD group. This retrospective study suggests that outcomes of patients treated with ICDs may not be dramatically different from those of patients treated with other methods guided primarily by electrophysiologic testing.(ABSTRACT TRUNCATED AT 250 WORDS)

The role of implantable cardioverter defibrillators in dilated cardiomyopathy

Depending on the severity of the disease, patients with dilative cardiomyopathy (DCM) have a poor prognosis. No definite data are available to show that complex ventricular ectopy, the presence of ventricular late potentials, or programmed electrical stimulation in patients without symptoms with DCM identify patients at risk of sudden cardiac death. Although poor left ventricular function seems to be the most potent predictor of total cardiac death, the prediction of sudden death in patients without symptoms with DCM is poor. Studies with either class I antiarrhythmic drugs or amiodarone have not yet demonstrated a reduction in total mortality rates or sudden death. The usefulness of an implantable cardioverter defibrillator (ICD) in patients without symptoms with DCM is currently under investigation. The usefulness of serial electropharmacologic testing for patients with documented sustained ventricular tachycardia or ventricular fibrillation and DCM is still controversial. Because most patients with DCM and VT or out-of-hospital cardiac arrest have either no inducible ventricular tachyarrhythmia at baseline or the reproducibility of ventricular tachycardia/ventricular fibrillation induction is poor, implantation of an ICD should be considered in most of these patients. The indication for implantation of an ICD should be made on clinical judgment of the patient's functional status and other prognosis-limiting factors, such as rapid progression of heart failure, end-stage heart failure, and age.

Mortality benefits and the implantable cardioverter-defibrillator

The automatic implantable cardioverter-defibrillator (ICD) is highly effective in reducing sudden death rates in patients with life-threatening ventricular tachyarrhythmias. However, the magnitude of the ability of the ICD to improve overall survival is less certain. Data supporting the contention that the ICD prolongs survival are reviewed. It is evident that the mortality benefit consequent to the marked reduction in sudden death varies widely across subpopulations in a predictable manner. This observation reflects the powerful influence of other clinical factors that constrain survival in typical ICD patients. The implications for future studies on the ICD are discussed.

Antiarrhythmic drugs versus implantable defibrillators: the need for a randomized controlled study

The implantable cardiac defibrillator was first used in 1980 and has gained widespread acceptance. However, no randomized controlled trials have been reported that compare the implantable cardiac defibrillator with antiarrhythmic drugs. Most published studies have used historical control subjects or nonrandomized concurrent patients for comparison with patients who received an implantable defibrillator. To reduce bias, studies are needed that compare therapies randomized between antiarrhythmic drugs and implantable defibrillators. The Antiarrhythmics Versus Implantable Defibrillators (AVID) Study was designed to evaluate the nonthoracotomy, tiered-therapy implantable defibrillator compared with drug therapy (amiodarone or sotalol). Patients are eligible for randomization if they have a history of recent cardiac arrest caused by ventricular fibrillation or have hemodynamically serious ventricular tachycardia. A pilot study to enroll 200 patients began on June 1, 1993, before the start of the main study of 1000 patients. Analysis of the main study by intention to treat will assess the primary endpoint of total mortality.

Influence of left ventricular function on survival and mode of death after implantable defibrillator therapy (Cleveland Clinic Foundation and Montefiore Medical Center experience)

To determine the influence of left ventricular (LV) function on survival and mode of death in patients with an implantable cardioverter-defibrillator (ICD), sudden death, surgical mortality, total arrhythmia-related death, total cardiac death and total death were retrospectively evaluated in 377 consecutive patients. The outcomes were also compared between patients with an LV ejection fraction > or = 30% (214 patients, group 1) and < 30% (148 patients, group 2). Surgical mortality was 3.9% (1.8% in group 1, 7% in group 2). During the follow-up of 25 +/- 20 months, actuarial survival rates of all patients at 3 years were 96% for sudden deaths, 81% for total cardiac deaths and 74% for total mortality. When the 2 groups were compared, survival rates of groups 1 and 2 at 3 years, respectively, were 99 and 90% for sudden death (p < 0.05), 97 and 84% for sudden death and surgical mortality (p < 0.01), 94 and 80% for the total arrhythmia-related death (p < 0.001), 88 and 68% for total cardiac death (p < 0.0001), and 81 and 62% for total mortality (p < 0.002). In group 2, 73% of total cardiac deaths within 1 year were causally related to the arrhythmia. Thus, in patients with an ICD, sudden death rates were very low. However, total cardiac death and total death rates were relatively higher. The outcomes of patients with an ICD were strongly influenced by the degree of LV dysfunction.(ABSTRACT TRUNCATED AT 250 WORDS)

Future developments in implantable cardioverter defibrillators: the optimal device

Despite recent therapeutic advances, SCD remains the leading cause of mortality in industralized nations. The most frequent cause of SCD is ventricular tachyarrhythmias in the setting of advanced structural heart disease due to chronic coronary heart disease or idiopathic dilated cardiomyopathy. Although high-risk groups can be prospectively identified, attempts at primary prevention have been largely unsuccessful. Effective treatment strategies for SCD survivors include antiarrhythmic drug therapy guided by programmed stimulation, endocardial resection, and ICDs. Device therapy has proven extremely effective in preventing recurrent sudden death from ventricular tachyarrhythmias. Widespread application of ICD therapy, perhaps even to include members of high-risk populations that have not experienced cardiac arrest, will depend on many factors including the demonstration that device therapy improves total mortality, not just arrhythmia-related mortality, reduction in cost, and improvements in the devices themselves. Some of the important characteristics of the optimal ICD of the future are nonthoracotomy lead placement; subpectoral generator placement; multiprogrammable, tiered therapy; improved diagnostic specificity, whether based on electrogram or hemodynamic-sensing algorithms; improved integration of brady- and tachy-sensing systems; and enhanced electrogram storage capability with trans-telephonic retrieval of electrogram recordings. The creation of this ideal ICD will obviously require continued technological advances; however, given the tremendous improvements realized over the first three generations of ICD systems, optimism for the future seems warranted.

Interventional electrophysiology--state-of-the-art 1993

The field of clinical electrophysiology has broadened significantly in the last several years, spawning a new discipline known as Interventional or Therapeutic Electrophysiology. In the United States, Electrophysiology has its own training path and accreditation requirements. One of the reasons for the growth of interest in electrophysiology is the exciting introduction of nonpharmacologic methods of arrhythmia therapy, including curative radiofrequency catheter ablation and implanted devices for antitachycardia pacing/defibrillation. The arrhythmia specialist now has at his/her disposal a wide range of options for patients with symptomatic or life-threatening cardiac arrhythmias.

Do patients with an implantable defibrillator live longer?

OBJECTIVES

This study was done to provide information on the potential benefit of implantable cardioverter-defibrillator therapy regarding sudden and arrhythmia-related deaths and to examine whether such therapy improves survival.

BACKGROUND

Implantation of automatic cardioverter-defibrillators is reported to abort sudden cardiac death due to malignant tachyarrhythmias.

METHODS

Between 1989 and 1992, 107 patients were screened for implantation of a third-generation implantable cardioverter-defibrillator combined with endocardial leads. Mean age was 57 +/- 13 years and mean ejection fraction was 40 +/- 15%. Sudden death, total arrhythmia-related death and total cardiac death were compared with the occurrence of fast ventricular tachyarrhythmias (> 240 beats/min), assuming that most of these arrhythmias would have been fatal without treatment by the implantable cardioverter-defibrillator.

RESULTS

The surgical mortality rate was 2.7% in all 107 patients and 1% in the 99 patients who qualified for endocardial leads. During a follow-up period of 12 +/- 8 months, actuarial survival rate free of events at 6 months as well as at 12 and 18 months was 100% for sudden death, 97% for total arrhythmia-related death and 95% for total cardiac death. In contrast, after 6, 12 and 18 months, the rate of survival free of fast ventricular tachycardia was only 83%, 74% and 69%, respectively, and the rate of survival free of any ventricular tachyarrhythmia was only 59%, 49% and 40%, respectively.

CONCLUSIONS

The outcome of patients treated with an implantable cardioverter-defibrillator and endocardial defibrillation leads is excellent. For many patients, this treatment is probably lifesaving.

Comparison of frequency of aggravation of ventricular tachyarrhythmias after implantation of automatic defibrillators using epicardial versus nonthoracotomy lead systems

The time of onset of 4,471 episodes of ventricular tachycardia (VT) or fibrillation (VF) in 40 of 65 patients with an implantable cardioverter-defibrillator (ICD) with endocardial defibrillation electrodes (group 1) and in 53 of 123 with epicardial defibrillation electrodes (group 2) was analyzed to examine whether the incidence of VT/VF immediately after surgery is greater than during further follow up and whether the site of lead placement exerts an influence on the occurrence of these arrhythmias. Actuarial survival rates free of VT/VF were 77, 65, and 54% at 1, 3 and 6 months, respectively, for group 1, and 84, 66 and 52%, respectively, for group 2. The probability of VT/VF was increased only during the first week after surgery; in that week, 12.8% of all patients had VT/VF, without significant differences between groups 1 and 2. Until the end of the first month, this percentage increased to 23%, whereas only 12 to 15% of patients had VT/VF during subsequent months. In 19 patients with third-generation devices capable of terminating tachycardias by overdrive pacing, 326 of 412 VT/VF episodes occurring in the first week after surgery were terminated by antitachycardia pacing, and only 86 had to be terminated by cardioversion or defibrillation. No postoperative exacerbation of inappropriate ICD therapies was observed in any group; 2 to 5% of patients per month received ICD therapies for atrial fibrillation or sinus tachycardia. Patients who received appropriate ICD therapies in the first week after surgery were at high risk of recurrence of VT/VF.(ABSTRACT TRUNCATED AT 250 WORDS)

Implantable cardioverter-defibrillator therapy in survivors of out-of-hospital sudden cardiac death without inducible arrhythmias

OBJECTIVES

The aim of this study was to determine the efficacy of implantable cardioverter-defibrillator (ICD) therapy in survivors of sudden cardiac death in whom no ventricular arrhythmias can be induced with programmed electrical stimulation.

BACKGROUND

Survivors of sudden cardiac death in whom ventricular arrhythmias cannot be induced with programmed electrical stimulation remain at risk for recurrence of serious arrhythmias. Optimal protection to prevent sudden death in these patients is uncertain. This study compares survival in the subset of survivors of sudden cardiac death with that of patients treated with or without an ICD.

METHODS

A retrospective study was performed on 194 consecutive survivors of primary sudden death who had < or = 6 beats of ventricular tachycardia induced with programmed electrical stimulation with at least three extrastimuli. Ninety-nine patients received an ICD and 95 did not.

RESULTS

There were no significant differences between the two groups in presenting rhythm, number of prior myocardial infarctions or use of antiarrhythmic agents. Patients treated with an ICD were younger (55 +/- 16 vs. 59 +/- 11 years, p = 0.03) and had a lesser incidence of coronary artery disease (48% vs. 63%, p = 0.04) and a lower ejection fraction (0.43 +/- 0.16 vs. 0.48 +/- 0.18, p = 0.04). There were no significant differences between the groups in the use of revascularization procedures or antiarrhythmic agents after the sudden cardiac death. Patients treated with an ICD had an improvement in sudden cardiac death-free survival (p = 0.04) but the overall survival rate did not differ from that of the patients not so treated (p = 0.91). A multivariate regression analysis that adjusted for the observed differences between the groups did not alter these results.

CONCLUSIONS

Survivors of sudden cardiac death in whom no arrhythmias could be induced with programmed electrical stimulation remained at risk for arrhythmia recurrence. Although the proportion of deaths attributed to arrhythmias was lower in the patients treated with an ICD, this therapy did not significantly improve overall survival.

Sudden cardiac death and the use of implantable cardioverter-defibrillators in pediatric patients. The Pediatric Electrophysiology Society

BACKGROUND

During the past decade, the implantable cardioverter-defibrillator (ICD) has emerged as the primary therapeutic option for survivors of sudden cardiac death (SCD). Investigation of the clinical efficacy of these devices has primarily assessed outcome in adults with coronary artery disease. The purpose of this cooperative, international study was to evaluate the impact of ICDs on the pediatric population of SCD survivors, based on an analysis of the clinical characteristics and outcomes of young patients who underwent ICD implantation following an episode of life-threatening ventricular tachycardia or resuscitation from SCD.

METHODS AND RESULTS

An initial data base, established by contacting the manufacturers of the various commercially and investigationally available devices, identified 177 patients who were less than 20 years of age at the time of initial implantation of an ICD. With this data base as a reference, detailed responses were subsequently obtained from physicians involved in the care of 125 (71%) of these patients. The patients ranged in age from 1.9 to 19.9 years (mean, 14.5 +/- 4 years) and weighted 9.7-117 kg (mean, 44.6 +/- 14 kg). Of the 125 patients, 76% were survivors of SCD, 10% had drug refractory ventricular tachycardia, and 10% had syncope with heart disease and inducible sustained ventricular tachyarrhythmias. The most common types of associated cardiovascular disease were hypertrophic and dilated cardiomyopathies (54%), primary electrical diseases (26%), and congenital heart defects (18%). Ventricular function was abnormal in 46% of the patients. During a mean follow-up of 31 +/- 23 months, at least one ICD discharge occurred in 85 of the 125 (68%) patients. Seventy-three patients (59%) received at least one appropriate ICD discharge, and 25 patients (20%) had one or more spurious or indeterminate discharges. Duration of follow-up > 24 months (p = 0.001) and inducibility of a sustained ventricular arrhythmia (p = 0.05) were correlated with appropriate ICD discharges. There were nine deaths during the study period: five sudden, two due to recurrent ventricular arrhythmias, and two related to congestive heart failure. Abnormal ventricular function (p = 0.002) and prior ICD discharge (p = 0.01) were univariate correlates of patient mortality; by multivariate logistic regression, abnormal ventricular function was the only significant correlate of death (p = 0.005). By actuarial analysis, the estimated overall post-ICD implant survival rates at 1, 2, and 5 years were 95%, 93%, and 85%, respectively. The corresponding sudden death-free survival rates were 97%, 95%, and 90%.

CONCLUSIONS

Pediatric patients resuscitated from SCD appear to remain at risk for recurrence of life-threatening tachyarrhythmias. During a mean follow-up of 31 months, the ICD provided an effective therapy for such arrhythmias in the majority of patients in this study. Following ICD implant, impaired ventricular function was the primary factor correlated with mortality. The patterns of ICD discharge observed in young patients and, thus, inferred risk of recurrent life threatening arrhythmias are similar to those of adult survivors of SCD. Thus, the use of ICDs in pediatric patients, with implant selection criteria similar to adults, appears valid.

A population-based estimate of candidacy rates for the implantable cardioverter-defibrillator

The implantable cardioverter-defibrillator (ICD) increases survival of patients who receive the device. However, candidacy rates have not been calculated for a defined population, and the potential effect of the device on the survival of all patients with heart disease has not been estimated. To make these calculations, medical records were reviewed for 1976 to 1988 in a population demographically similar to the white population of the United States. Definite and possible candidates were identified on the basis of American Heart Association/American College of Cardiology guidelines. Candidacy rates ranged from 3.3/100,000 (counting only definite candidates for the entire period) to 8.7/100,000 (counting definite and possible candidates after 1980). Extrapolated to the 1990 U.S. population, estimates ranged from 8,207 to 21,637 new candidates each year. During an average follow-up of 5 years, half of all deaths among candidates had the potential to be delayed by an ICD. In a similar population that has a death rate from heart disease of approximately 280/100,000, 0.6 to 1.6% of subjects have the potential to have their deaths delayed to some extent by an ICD.

Experience of cardioverter-defibrillators inserted without thoracotomy: evaluation of transvenously inserted intracardiac leads alone or with a subcutaneous axillary patch

OBJECTIVES

To compare the efficacy of a purely transvenous cardioverter-defibrillator (ICD) system with that of a system with a supplementary subcutaneous patch. To evaluate clinical follow up of these lead arrangements that do not require thoracotomy.

DESIGN

A simplified defibrillation protocol to test two different lead arrangements during implantation, with routine clinical follow up after implantation.

SETTING

Tertiary referral centre for treatment of arrhythmia.

PATIENTS

22 consecutive patients selected for implantation of an ICD because of life-threatening ventricular arrhythmias (ventricular fibrillation or sustained ventricular tachycardia) of whom 20 entered the test protocol.

INTERVENTION

Implantation of an ICD with transvenously inserted intracardiac leads and a subcutaneous patch and assessment of effective defibrillation followed by testing of the purely transvenous approach.

MAIN OUTCOME MEASURES

Reproducible conversion of ventricular fibrillation to sinus rhythm at a certain energy level, providing a safety margin of at least 10 J for both lead arrangements. Confirmation of efficacy during clinical follow up (mean 6 months).

RESULTS

A transvenous lead system combined with a subcutaneous axillary patch was implanted in 20/22 patients and it provided adequate and acceptable energy levels. In 10/20 tested patients a purely transvenous lead configuration provided an acceptable safety margin as well. Nine patients had clinical recurrences: all these arrhythmias were successfully converted.

CONCLUSION

A transvenous lead system was sufficient in 50% of the patients at the time of implantation. Data on long-term clinical follow up of this arrangement are not available. The approach without thoracotomy with a subcutaneous patch is feasible and effective in most patients selected for ICD treatment.

Complications of implantable cardioverter defibrillator therapy: follow-up of 241 patients

In order to determine the incidence of complications of implantable cardioverter defibrillator (ICD) therapy, 241 patients with a total of 353 ICD implantations were followed for 24 +/- 20 months. Complications were defined as any untoward effects experienced by the patient related to the ICD implantation and function or death within 4 weeks of implant or before hospital discharge. During follow-up, 129 of 241 patients (53%) had a total of 166 complications. An operative procedure was required to correct the complication in 50 of the 241 patients (21%). No patient died intraoperatively, but eight patients died within 4 weeks postoperatively or before hospital discharge. ICD infection required removal of the device in 13 patients (5%). Twenty-six patients (11%) had postoperative respiratory complications. Postoperative bleeding and/or thrombosis occurred in 11 patients (4%). Endocardial lead migration was observed in nine patients (4%) and lead adapter or insulation break occurred in nine patients (4%). Fifty-four patients (22%) experienced ECG-documented discharges for non-VT rhythm. In conclusion, although perioperative mortality in ICD patients is low, the majority of patients have complications during follow-up. Recognition of these complications may allow for advances in ICD technology and management strategies to avoid their occurrence.

Comparison of clinical benefits and outcome in patients with programmable and nonprogrammable implantable cardioverter defibrillators

Technological advances in implantable cardioverter defibrillators (ICDs) have provided a variety of programmable parameters and antitachycardia therapies whose utility and impact on clinical outcome is presently unknown. ICDs have capabilities for cardioversion defibrillation alone (first generation ICDs), or in conjunction with demand ventricular pacing (second generation ICDs), or with demand pacing and antitachycardia pacing (third generation ICDs). We examined the pattern of antitachycardia therapy use and long-term survival in 110 patients with sustained ventricular tachycardia (VT) or ventricular fibrillation (VF). Group I included 62 patients with nonprogrammable first generation ICDs that delivered committed shock therapy after ventricular tachyarrhythmia detection based on electrogram rate and/or morphology was satisfied. Group II included 48 patients with multiprogrammable ICDs (including second and third generation ICDs) that had programmable tachyarrhythmia detection based on rate and tachycardia confirmation prior to delivery of electrical treatment with either programmable shocks and/or, as in the third generation ICDs, antitachycardia pacing. Incidence and patterns of antitachycardia therapy use and long-term survival were compared in the two groups. The incidence of appropriate shocks in patients who completed 1 year of follow-up was significantly greater in group I (30 of 43 patients = 70% vs 11 of 26 patients = 42%; P less than 0.05). In the total follow-up period, a significantly larger proportion of group I patients as compared to group II patients used the shock therapies (46 of 62 patients = 74% vs 25 of 48 patients = 52%; P less than 0.01), with the majority doing so within the first year of implantation (96% and 92%, respectively). Although the frequency of antitachycardia therapy activation was similar, the number of shocks delivered per patient was lower in group II, particularly in the initial 3 months of follow-up (P = 0.06). No clinical variable aided in identifying users from nonusers of antitachycardia therapy. Arrhythmic mortality was virtually eliminated in both groups. Two-year actuarial cardiac survival in the two groups was similar (group I = 78% vs group II = 84%; P greater than 0.2). Survival from cardiac mortality in users and nonusers of antitachycardia therapies was also similar in both groups (P greater than 0.2) and in the total patient group (P greater than 0.2). We conclude that programmable ICDs continue to confer advantages in prevention of sudden death that were observed with nonprogrammable ICDs and can be expected to improve patient tolerance and physician acceptance of device therapy for VT/VF.

How useful are implantable cardioverter-defibrillators?

When use of an implantable cardioverter-defibrillator (ICD) is being considered for a patient with life-threatening ventricular arrhythmias, the potential risks and benefits must be carefully weighed. The risks of implantation of an ICD should be minimal; however, a low risk is highly dependent on patient selection and other factors, and perioperative risk varies significantly from center to center. The referring physician should not hesitate to ask for perioperative mortality statistics from the referral center. The difficulty in successfully documenting the usefulness of the ICD is especially important today. As the ICD becomes more like the pacemaker, there will be a natural tendency to expand the use of this new technology to patients in lower-risk groups. Suboptimal methods were adequate to document the benefit of the ICD in high-risk patients, but similar methods may not be adequate for low-risk patients. Fortunately, the importance of performing adequate studies has been recognized, as evidenced by the several randomized controlled trials that have been undertaken to study the efficacy of the ICD in these new groups of patients.

Implantable defibrillators for prevention of sudden death. Technology at a medical and economic crossroad

Implantable cardioverter-defibrillator therapy is now widely used for the treatment of symptomatic patients with documented or suspected life-threatening VTs. Although sudden death recurrence in ICD recipients is virtually eliminated, the extent of benefit both with respect to cardiac mortality and total survival in this patient population remains to be accurately quantitated, particularly vis-à-vis alternative antiarrhythmic therapies. Advanced device and lead systems can be expected to further improve both patient survival and quality of life after implant. The economic impact of unrestrained proliferation in ICD therapy can be enormous; however, available cost-benefit analyses support judicious use of this therapy with comparable economic impact to other accepted cardiovascular therapies. Such prospective risk stratification becomes economically essential when considering expanding its application to asymptomatic or minimally symptomatic populations at potential risk for future cardiac arrest.

Influence of left ventricular function on outcome of patients treated with implantable defibrillators

BACKGROUND

The outcomes of patients treated with implantable defibrillators were compared between patients with left ventricular ejection fraction greater than or equal to 30% and less than 30%.

METHODS AND RESULTS

Of 68 consecutive patients treated with implantable defibrillators, 40 patients (group 1) had left ventricular ejection fraction greater than or equal to 30%, and 28 patients (group 2) had left ventricular ejection fraction less than 30%. Sudden death, surgical mortality, nonsudden arrhythmia-related death (death within 24 hours after an arrhythmic event despite initial termination of the arrhythmia by the implantable defibrillator), total arrhythmia-related death (including sudden death, surgical death, and nonsudden arrhythmia-related death), and total cardiac death were compared between the two groups. Surgical mortality was 4.4% (0% in group 1, 11% in group 2). During the follow-up of 31 +/- 27 months, actuarial survival rates free of events were 97%, 97%, and 97% in group 1 and 96%, 91%, and 82% in group 2 at 12, 24, and 36 months, respectively, for sudden death (p = NS); 97%, 97%, and 97% in group 1 and 85%, 81%, and 72% in group 2 at 12, 24, and 36 months, respectively, for sudden death and surgical mortality (p less than 0.05); 97%, 97%, and 97% in group 1 and 82%, 78%, and 70% in group 2 at 12, 24, and 36 months, respectively, for total arrhythmia-related death (p less than 0.05); and 95%, 95%, and 95% in group 1 and 82%, 69%, and 57% in group 2 at 12, 24, and 36 months, respectively, for total cardiac death (p less than 0.05). Four (57%) of seven nonsudden cardiac deaths during the initial 36-month follow-up period were causally related to arrhythmia (three surgical deaths and one arrhythmia-related nonsudden death).

CONCLUSIONS

The outcome of patients treated with implantable defibrillators is strongly influenced by the degree of left ventricular dysfunction. In group 1 patients, surgical mortality, sudden death, and total cardiac death are rare. In group 2, sudden death rate may not be markedly different from that of group 1 patients. However, the risk of therapy (surgical mortality) is high. Many nonsudden cardiac deaths are causally related to arrhythmia (surgical mortality or nonsudden arrhythmia-related death). Therefore, the survival rate free of total arrhythmia-related death is significantly lower in group 2 (70% versus 97% in group 1 at 3 years). Further studies are needed to determine the roles of defibrillator therapy and other therapies in various clinical settings.

Long-term multicenter experience with a second-generation implantable pacemaker-defibrillator in patients with malignant ventricular tachyarrhythmias. The Guardian Multicenter Investigators Group

A second-generation implantable pacemaker-cardioverter-defibrillator was evaluated in 200 patients with sustained ventricular tachycardia, ventricular fibrillation or prior cardiac arrest. The device permits demand ventricular pacing for bradyarrhythmias and for long QT interval or tachycardia suppression, uses programmable (3 to 30 J) energy shocks for conversion of ventricular tachycardia and ventricular fibrillation and is used with conventional pacing and defibrillation leads. Ventricular tachycardia/fibrillation recognition is based on the ventricular electrogram rate and requires reconfirmation before shock delivery. Two hundred patients (mean age 62 years, mean left ventricular ejection fraction 36%) were enrolled and followed up for 0 to 23 months (mean 12). Epicardial lead system implantation was performed with use of an anterolateral thoracotomy (38%), median sternotomy (26%) and subxiphoid (20%) or subcostal (16%) approach. Perioperative mortality rate was 5.5% (all nonarrhythmic deaths). Implant defibrillation threshold ranged from 3 to 30 J (mean 15), with initial programmed shock energy ranging from 3 to 30 J (mean 22). Ventricular tachycardia/fibrillation sensing threshold ranged from 0.7 to 1.8 mV (median 1) and the tachycardia detection interval from 288 to 416 ms (median 320). Reprogramming of implant variables was necessary for reliable electrographic sensing (54 patients), programmed shock therapy (61 patients) and tachycardia detection rate (63 patients). Device activation for potential shock delivery occurred in 111 patients (55.5%) with actual shock delivery after ventricular tachycardia/fibrillation reconfirmation in 66 patients (33%). During follow-up study, there was a 1% arrhythmia mortality rate, 6.5% cardiac mortality rate and 10.5% total mortality rate. This study demonstrates that the programmable implantable pacemaker-cardioverter-defibrillator is effective in preventing arrhythmic death, yet reduces patient exposure to repeated shock therapy. Reprogramming is usually necessary during follow-up for optimal function.

Exacerbation of ventricular arrhythmias during the postoperative period after implantation of an automatic defibrillator

The postoperative course of 68 consecutive patients treated with an implantable defibrillator during the period from 1982 through 1990 was studied. In 46 patients (group 1), no concomitant surgery was performed during the implantation. In 22 patients (group 2), concomitant surgery (coronary artery bypass [n = 12], valve replacement [n = 3] or arrhythmia surgery [n = 7]) was performed. All patients in group 1 were clinically stable before surgery, receiving an antiarrhythmic regimen chosen by serial drug testings. The same regimen was continued postoperatively. Eight of the 46 patients in group 1 whose condition had been stable in the hospital for 19 +/- 25 days preoperatively developed multiple episodes of sustained ventricular tachycardia 4 +/- 9 days after implantation while receiving the same antiarrhythmic regimen. Although the exacerbation was transient in some patients, six required different antiarrhythmic therapy and one eventually died. Two additional patients had frequent and prolonged episodes of nonsustained ventricular tachycardia that could trigger the defibrillator, requiring changes in the antiarrhythmic regimen. Another patient had progressive cardiac failure and died on day 5. A marked (sevenfold) increase in asymptomatic ventricular arrhythmias was noted in 42% of the remaining 35 patients. In group 2 (combined surgery), one patient developed refractory ventricular tachycardia 3 days postoperatively and died on that day. Three patients developed frequent nonsustained ventricular tachycardia postoperatively, requiring changes in the antiarrhythmic regimen. The overall surgical mortality rate was 4.4% (4.3% in group 1 and 4.5% in group 2) and was due to refractory ventricular tachycardia in two patients and cardiac failure in one.(ABSTRACT TRUNCATED AT 250 WORDS)