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

The incidence and impact of implantable cardioverter defibrillator shocks in the last phase of life: An integrated review

BACKGROUND

Although the implantable cardioverter defibrillator is successful in terminating life threatening arrhythmias, it might give unwanted shocks in the last phase of life if not deactivated in a timely manner.

AIMS

This integrated review aimed to provide an overview of studies reporting on implantable cardioverter defibrillator shock incidence and impact in the last phase of life.

METHODS AND RESULTS

We systematically searched five electronic databases. Studies reporting on the incidence and/or impact of implantable cardioverter defibrillator shocks in the last month of life were included. Fifteen studies were included. Two American studies published in 1996 and 1998 reported on the incidence of shocks in patients who died non-suddenly: incidences were 24% and 33%, respectively, in the last 24 hours, and 7% and 14%, respectively, in the last hour of life. Six American studies and one Danish study published between 1991-1999 reported on patients dying suddenly: incidences were 41% and 68% in the last 24 hours and 22-66% in the last hour. Four American studies and two Swedish studies published between 2004-2015 did not distinguish the cause of death: incidences were 17-32% in the last month, 3-32% in the last 24 hours, and 8% and 31% in the last hour of life. Three American studies published between 2004-2011 reported that shocks in dying patients are painful and distressing for patients, and distressing for relatives and professional caregivers.

CONCLUSION

If the implantable cardioverter defibrillator is not deactivated in a timely manner, a potentially significant proportion of implantable cardioverter defibrillator patients experience painful and distressing shocks in their last phase of life.

Role of omega-3 ethyl ester concentrate in reducing sudden cardiac death following myocardial infarction and in management of hypertriglyceridemia: an Indian consensus statement

INTRODUCTION

Sudden cardiac death (SCD) is the most lethal manifestation of heart disease. In an Indian study the SCDs contribute about 10% of the total mortality and SCD post ST elevation myocardial infarction (MI) constitutes for about half of total deaths.

OBJECTIVE

Given the limitations of existing therapy there is a need for an effective, easy to use, broadly applicable and affordable intervention to prevent SCD post MI. Leading cardiologists from all over India came together to discuss the potential role of n-3 acid ethyl esters (90%) of eicosapentaenoic acid (EPA) 460 mg & docosahexaenoic acid (DHA) 380 mg in the management of post MI patients and those with hypertriglyceridemia.

RECOMMENDATIONS

Highly purified & concentrated omega-3 ethyl esters (90%) of EPA (460 mg) & DHA (380 mg) has clinically proven benefits in improving post MI outcomes (significant 15% risk reduction for all-cause mortality, 20% risk reduction for CVD and 45% risk reduction in SCD in GISSI-Prevenzione trial) and in reducing hypertriglyceridemia, and hence, represent an interesting option adding to the treatment armamentarium in the secondary prevention after MI based on its anti-arrhythmogenic effects and also in reducing hypertriglyceridemia.

The dilemma of ICD implant testing

Ventricular fibrillation (VF) has been induced at implantable cardioverter defibrillator (ICD) implant to ensure reliable sensing, detection, and defibrillation. Despite its risks, the value was self-evident for early ICDs: failure of defibrillation was common, recipients had a high risk of ventricular tachycardia (VT) or VF, and the only therapy for rapid VT or VF was a shock. Today, failure of defibrillation is rare, the risk of VT/VF is lower in some recipients, antitachycardia pacing is applied for fast VT, and vulnerability testing permits assessment of defibrillation efficacy without inducing VF in most patients. This review reappraises ICD implant testing. At implant, defibrillation success is influenced by both predictable and unpredictable factors, including those related to the patient, ICD system, drugs, and complications. For left pectoral implants of high-output ICDs, the probability of passing a 10 J safety margin is approximately 95%, the probability that a maximum output shock will defibrillate is approximately 99%, and the incidence of system revision based on testing is < or = 5%. Bayes' Theorem predicts that implant testing identifies < or = 50% of patients at high risk for unsuccessful defibrillation. Most patients who fail implant criteria have false negative tests and may undergo unnecessary revision of their ICD systems. The first-shock success rate for spontaneous VT/VF ranges from 83% to 93%, lower than that for induced VF. Thus, shocks for spontaneous VT/VF fail for reasons that are not evaluated at implant. Whether system revision based on implant testing improves this success rate is unknown. The risks of implant testing include those related to VF and those related to shocks alone. The former may be due to circulatory arrest alone or the combination of circulatory arrest and shocks. Vulnerability testing reduces risks related to VF, but not those related to shocks. Mortality from implant testing probably is 0.1-0.2%. Overall, VF should be induced to assess sensing in approximately 5% of ICD recipients. Defibrillation or vulnerability testing is indicated in 20-40% of recipients who can be identified as having a higher-than-usual probability of an inadequate defibrillation safety margin based on patient-specific factors. However, implant testing is too risky in approximately 5% of recipients and may not be worth the risks in 10-30%. In 25-50% of ICD recipients, testing cannot be identified as either critical or contraindicated.

Habitual Cocaine Use Is Associated with High Defibrillation Threshold During ICD Implantation

BACKGROUND

Habitual cocaine use can lead to dilated cardiomyopathy (DCM) and sudden cardiac death. Based on prior clinical observations, we hypothesized that prior habitual cocaine use is a strong predictor of high defibrillation threshold (DFT) during implantable cardioverter-defibrillator (ICD) implant.

METHODS

We reviewed the medical records of 130 consecutive patients undergoing initial ICD implantation or revision at Parkland Hospital and the Dallas VA Hospital, Dallas, TX, from January 2002 to November 2005. Patient characteristics and DFT data were collected retrospectively.

RESULTS

The study group includes 11 patients (8.46%) who were identified as having a history of prior habitual cocaine use as demonstrated by history and urine toxicology; the rest (119 patients) form the control group. Cocaine-using patients tended to be younger (48.2 +/- 10 vs 60.1 +/- 12.3 years; P = 0.0026), were less likely to have coronary disease (36.3% vs 72.2%; P = 0.032), and had less comorbidity. The average DFT was 27.9 +/- 7.8 J for all cocaine-using patients and 14.5 +/- 4.1 J for noncocaine-using patients (P = 0.00018). In the cocaine-using group, three out of 11 patients required a subcutaneous array compared to none in the control group.

CONCLUSIONS

Our results suggest that patients with a history of habitual cocaine use may be at increased risk to have a high DFT during ICD implantation. This is the first study to demonstrate such association. ICD implantation in patients with this history should be planned with these findings in mind, as larger output generators or subcutaneous arrays might be required.

Intraoperative testing of the implantable cardioverter-defibrillator: how much is enough?

INTRODUCTION

Defibrillation testing of the implantable cardioverter-defibrillator (ICD) is considered a standard and required practice at the time of implantation. How much testing, if any in some cases, should be performed, however, remains unknown.

METHODS AND RESULTS

Included in this retrospective analysis were 835 patients (77% men; age 65 +/- 13 years) who received transvenous ICDs between January 1996 and December 2003. One hundred twenty-nine (15.5%) had intraoperative defibrillation threshold (DFT) testing, 503 (60.2%) had limited defibrillation safety margin testing, and 203 (24.3%) had no defibrillation testing. We compared the outcome (success of ICD therapies against spontaneous VT/VF events and survival) of the three groups of patients, who in some respects had important clinical differences. The success of the first delivered shocks against VT/VF was similar for DFT (91%), safety margin testing (91%), and no-testing (92%) groups; and the second shocks terminated the remaining episodes in all three groups. Sudden-death-free survival rates were similar in the three groups, however, the overall long-term survival rate was significantly lower in the no-testing group (58%) than in the DFT (74%) and safety margin testing (69%) groups (P < 0.0005). Multivariate analysis found no strong predictors of sudden death, but there were several independent predictors of overall mortality including lack of ICD testing (HR: 2.031, CI: 1.253-3.290, P = 0.004).

CONCLUSION

In this select patient cohort, success of ICD therapies and sudden-death-free survival were similar in patients who had DFT, safety margin testing, and no testing, but overall survival was significantly lower in the no-testing group. Thus in the absence of prospective mortality data, a minimum of safety margin ICD testing should remain standard practice.

Is defibrillation testing required for defibrillator implantation?

The assessment of defibrillation (DFT) efficacy has long been the standard of care during defibrillator implantation. To ensure an acceptable DFT safety margin, early defibrillator systems frequently required that the shock polarity and the location, type, or number of electrodes had to be altered. Advances in defibrillator and lead technology have resulted in lower and more consistent DFT thresholds in the range of 10 J, with an infrequent requirement to modify the DFT system. Yet, one can make an argument for and against continuation of DFT testing at the time of defibrillator implantation. The goal of this paper is to address both the data that do support and the data that do not support continuation of DFT testing at the time of device implantation. Scientifically, DFT testing should be abandoned only when prospective evidence demonstrates that defibrillator implantation without testing is as safe and has the same mortality benefits as implantation with testing. The most attractive aspect of eliminating DFT efficacy testing is that more patients may have the opportunity to be treated with this life-saving therapy. Perhaps there are alternative strategies to improve accessibility to defibrillator therapy without possibly eroding its effectiveness. In the end, will lives be saved or lost if we discontinue DFT efficacy testing and lower the barriers to implantable defibrillator therapy?

Sudden death in recipients of transvenous implantable cardioverter defibrillator systems: terminal events, predictors, and potential mechanisms

INTRODUCTION

Transvenous implantable cardioverter defibrillator (ICD) systems are very effective in preventing sudden death; however, little is known about terminal events and potential causes and mechanisms of sudden death in recipients of these devices.

METHODS AND RESULTS

We analyzed 74 cases of sudden death among patients enrolled in several clinical investigations of transvenous ICD systems. Eighty-one percent were men (mean age 68+/-10 years), 86% had coronary artery disease, mean left ventricular ejection fraction was 0.27+/-0.11, and two thirds presented with sustained ventricular tachycardia. The final event was witnessed in 65 patients (81%). Based on reported ICD shocks, documented rhythm, and/or postmortem device data, sudden death was deemed tachyarrhythmic in 49 cases (66%), nontachyarrhythmic in 12 (16%), and indeterminate in the remaining 13 (18%). Multivariate analysis of several clinical and nonclinical factors found advanced age (> 65 years, P = 0.03, odds ratio [OR] 1.75, 95 % confidence interval [CI] 1.05 to 2.92), reduced left ventricular ejection fraction (< 0.35, P < 0.01, OR 3.51, CI 1.66 to 7.40), and having antibradycardia pacing ICDs (P = 0.02, OR 5.26, CI 1.37 to 20.0) to be independent predictors of sudden death. One or more predisposing factors and/or potential causes of sudden death were identified in 21 patients (28%).

CONCLUSION

In this select group of transvenous ICD recipients, (1) sudden death was associated with ventricular tachycardia/ventricular fibrillation in at least two thirds of cases, (2) nearly one third of patients had one or more factors, some device related, that could have been associated with sudden death, and (3) death ensued despite appropriate ICD therapies and, in many cases, external resuscitation, suggesting acute adverse events as common terminal factors.

Sudden death in implantable cardioverter-defibrillator recipients: clinical context, arrhythmic events and device responses

OBJECTIVES

We sought to investigate the nature of terminal events and potential contributory clinical and nonclinical (e.g., device-related) factors associated with sudden death (SD) in recipients of an implantable cardioverter-defibrillator (ICD).

BACKGROUND

The ICD is very effective in terminating ventricular tachycardia (VT) or ventricular fibrillation (VF), but protection against SD is not absolute. Little is known about the nature and potential causes of SD in patients with ICDs.

METHODS

We analyzed 25 cases of out-of-hospital SD among patients enrolled in the clinical investigation of the Cadence Tiered-Therapy Defibrillator System.

RESULTS

All patients (24 men and 1 woman, mean age 62+/-10 years) received epicardial lead systems. The majority (92%) had coronary artery disease and a previous myocardial infarction (MI), with a mean left ventricular ejection fraction 0.25+/-0.07. At device implantation, the mean defibrillation threshold was 13+/-5 J. Sudden death occurred 13+/-11 months later. Twenty patients (80%) had received appropriate ICD therapies before death, and 18 (72%) were receiving > or = 1 antiarrhythmic drugs at the time of death. Sudden death was tachyarrhythmia-associated in 16 patients (64%), non-tachyarrhythmia-associated in 7 (28%) and indeterminate in 2 (8%). In the 16 patients with tachyarrhythmia-associated SD, the overall first therapy success rate in tachycardia and fibrillation zones was 60% and 67%, respectively. However, despite protracted therapies (> or = 2 shocks) in 7 (66%) of 12 patients who received fibrillation therapies, the final tachyarrhythmic episode was ultimately terminated by the ICD in 15 (94%) of the 16 patients, whereas 1 patient died after multiple (initially successful) internal and external shocks for intractable VT/VF during exercise. In 10 patients (40%) one or more, primarily clinical, factors potentially contributory to SD were identified: heart failure (n=8), angina (n=2), hypokalemia (n=1), adverse antiarrhythmic drug treatment (n=1) and acute MI (n=1). An additional 10 patients (40%) had experienced an increase in frequency of ICD shocks within 3 months of SD. Appropriate battery voltages and normal circuitry function were found in all devices interrogated and analyzed after death.

CONCLUSIONS

In this select group of patients receiving a third-generation ICD, SD was associated with VT or VF events in nearly two-thirds of patients, and death occurred despite ultimately successful, although often protracted, device therapies. These observations, along with evidence of recent worsening clinical status, suggest acute cardiac mechanical dysfunction as a frequent terminal factor. In recipients with ICDs, SD directly attributable to device failure seems to be rare.