Cardiac death and stored electrograms in patients with third-generation implantable cardioverter-defibrillators

Forensic perspectives on postmortem CIED interrogation: A systematic review and meta-analysis

BACKGROUND

Cardiac implantable electronic devices (CIED) are a heterogeneous group of medical devices with increasingly sophisticated diagnostic capabilities, which could be exploited in forensic investigations. However, current guidelines are lacking clear recommendations on the topic. The first aim of this systematic review is to provide an updated assessment of the role of postmortem CIED interrogation, and to give practical recommendations, which can be used in daily practice. Secondly, the authors aim to determine the rates of postmortem CIED interrogation and autopsy investigations, the type of final rhythm detected close to death (with a focus on the significance of documented arrhythmias), as well as the role of postmortem CIED interrogation in the determination of final cause/time of death, and any potentially fatal device malfunctions.

METHODS

A systematic search in MEDLINE and Scopus aiming to identify reports concerning postmortem human CIED interrogation was performed, including a systematic screening of reference lists. Case reports, letters to the editors, commentaries, review articles or guidelines were excluded, along with studies related to cardiac devices other than CIED. All data were pooled and analyzed using fixed-effects meta-analysis models, and the I2 statistic was used to assess heterogeneity.

RESULTS

A total of 25 articles were included in the systematic review, enrolling 3194 decedent CIED carriers. Ten studies (40%) had a 100% autopsy rate, whereas in further 6 studies autopsy findings were variably reported; CIED interrogation was available from 22 studies (88%), and it was never performed prior to autopsy. The overall rate of successful postmortem CIED interrogation was 89%, with high heterogeneity among studies, mainly due to device deactivation/battery discharge. Twenty-four percent of CIED carriers experienced sudden cardiac death (SCD), whereas non-sudden cardiac and non-cardiac death (NSCD, NCD) were reported in 37% and 30% of decedents, respectively. Ventricular tachyarrhythmias were recorded in 34% of overall successfully interrogated CIED, and in 62% of decedents who experienced a SCD; of all ventricular tachyarrhythmias recorded, 40% was found in NSCD or NCD. A clear interpretation of the etiological role of recorded arrhythmias in the causation of death required integration with autopsy findings. Overall, potentially fatal device malfunctions were detected in 12% of cases.

CONCLUSIONS

Postmortem CIED interrogation is a valuable tool for the determination of the cause of death, and may complement autopsy. Forensic pathologists need to know the potential utility, pitfalls, and limitations of this diagnostic examination to make this tool as much reliable as possible.

Detecting deceased patients on cardiac device remote monitoring: A case series and management guide for cardiac device services

BACKGROUND

Remote monitoring (RM) of implantable cardiac devices provides substantial and complex information, presenting new challenges such as detection of a patient's death.

OBJECTIVE

This study aims to describe RM transmissions indicating death and propose a management strategy for services.

METHODS

The study included consecutive ambulatory outpatients whose deaths were detected via RM. Clinical and device data were collected from electronic records, and ethical approval was obtained from the service's institutional review board.

RESULTS

Over a 9-year period (2014-2023), 28 patients were detected. The deceased patients had implantable cardioverter-defibrillators, pacemakers, and implantable loop recorders. In 54% of the cases, the patient's death had already been recognized. Alert transmissions indicating death were commonly related to ventricular arrhythmia events, but also due to lead measurements, and implantable loop recorder battery status. Several diagnostic features may indicate a patient's death. The most reliable was the presenting electrogram, demonstrating base rate pacing with no capture. Device diagnostics, lead parameters, and arrhythmia recordings may indicate death; however, not all cases present with recordings and diagnosis may not be conclusive. A majority (82%) had ventricular arrhythmia at the time of death. In cases where defibrillator shocks were delivered, the arrhythmia reinitiated shortly after successful cardioversion. Delayed therapy was observed, and some patients did not receive defibrillator shocks because of discriminators or because the arrhythmia rate fell below the shock zone.

CONCLUSION

Detecting a patient death via RM presents unique challenges and considerations for services. Standard operational policies and legal consultation should be established to address the implications.

Downgrade of cardiac defibrillator devices to pacemakers in elderly heart failure patients: clinical considerations and the importance of shared decision-making

Implantable cardioverter defibrillators are implanted on a large scale in patients with heart failure (HF) for the prevention of sudden cardiac death. There are different scenarios in which defibrillator therapy is no longer desired or indicated, and this is occurring increasingly in elderly patients. Usually device therapy is continued until the device has reached battery depletion. At that time, the decision needs to be made to either replace it or to downgrade to a pacing-only device. This decision is dependent on many factors, including the vitality of the patient and his/her preferences, but may also be influenced by changes in recommendations in guidelines. In the last few years, there has been an increased awareness that discussions around these decisions are important and useful. Advanced care planning and shared decision-making have become important and are increasingly recognised as such. In this short review we describe six elderly patients with HF, in whose cases we discussed these issues, and we aim to provide some scientific and ethical rationale for clinical decision-making in this context. Current guidelines advocate the discussion of end-of-life options at the time of device implantation, and physicians should realise that their choices influence patients’ options in this critical phase of their illness.

Death with an implantable cardioverter-defibrillator: a MADIT-II substudy

AIMS

There are limited data regarding factors that identify implantable cardioverter-defibrillator (ICD) patients who will experience either ventricular tachyarrhythmic (VTA) or non-arrhythmic (NA) mortality, and the commonly used clinical classification of sudden cardiac death (SCD) vs. non-sudden cardiac death (NSCD) may not be accurate enough. We aimed to correlate clinical adjudication of mortality events to device interrogation data and to identify risk factors for VTA mortality in Multicenter Automatic Defibrillator Implantation Trial II (MADIT-II).

METHODS AND RESULTS

Of the 746 patients who received an ICD in MADIT-II, 44 died from cardiac causes and had available interrogation data at the time of death. Sudden cardiac death vs. NSCD was defined by an adjudication committee. Ventricular tachyarrhythmic and NA arrhythmic deaths were categorized by the presence or absence of ventricular tachycardia or fibrillation (VT/VF) during the terminal event. Mode of death was found to be inaccurate when validated by device interrogation for VTA events: 50% patients adjudicated as SCD did not have a VTA event at the time of death; and 25% of adjudicated NSCD were found to have VT/VF during the mortality event. Multivariate analysis showed that factors independently associated with VTA mortality included: VT/VF >72 h prior to the mortality event [hazard ratio (HR) 8.0; P < 0.001], hospitalization for heart failure (HR 6.7; P = 0.001), and a history of hypertension (HR 4; P = 0.04).

CONCLUSION

Current classification of SCD vs. NSCD fails to identify VTA events at the time of death in a significant proportion of patients, and simple clinical parameters can be used to identify ICD recipients with increased risk for VTA mortality.

Post mortem pro life - Should we analyse the implantable devices after death? A systematic review

AIM

Post-mortem interrogation of the cardiac implantable electronic devices (CIEDs) in combination with autopsy findings can provide additional information regarding device functioning after implantation or the mechanism of death. The aim of the study is to review the available data on the post-mortem interrogation of CIEDs and its possible clinical implications.

METHODS AND RESULTS

A systematic review of the published studies has been performed. Out of 762 unique citations 14 have been retained for final analysis. Post-mortem CIED interrogation reliably detects both serious device malfunctions and lead disorders but also improper device programming. As the need for CIED implantation is growing in the low-income countries, currently available data on battery longevity of devices explanted and destined for re-use have been reviewed.

CONCLUSIONS

Post-mortem CIED interrogation provides a unique opportunity to explore different mechanisms of death, often unavailable for distinction during regular in-hospital observation or in autopsy analysis.

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.

Postmortem ICD interrogation in mode of death classification

BACKGROUND

The definition of sudden death due to arrhythmia relies on the time interval between onset of symptoms and death. However, not all sudden deaths are due to arrhythmia. In patients with an implantable cardioverter defibrillator (ICD), postmortem device interrogation may help better distinguish the mode of death compared to a time-based definition alone.

OBJECTIVE

This study aims to assess the proportion of "sudden" cardiac deaths in patients with an ICD that have confirmed arrhythmia.

METHODS

We conducted a literature search for studies using postmortem ICD interrogation and a time-based classification of the mode of death. A modified QUADAS-2 checklist was used to assess risk of bias in individual studies. Outcome data were pooled where sufficient data were available.

RESULTS

Our search identified 22 studies undertaken between 1982 and 2015 with 23,600 participants. The pooled results (excluding studies with high risk of bias) suggest that ventricular arrhythmias are present at the time of death in 76% of "sudden" deaths (95% confidence interval [CI] 67-85; range 42-88).

CONCLUSION

Postmortem ICD interrogation identifies 24% of "sudden" deaths to be nonarrhythmic. Postmortem device interrogation should be considered in all cases of unexplained sudden cardiac death.

Team-Based Care for Managing Cardiac Comorbidities in Heart Failure

The need for HF management is predicted to increase as the HF population ages. Balancing HF and the multiple cardiac comorbidities remains difficult for any single provider, but becomes Fig. 6. Five-year rates of death or urgent heart transplantation by deciles of total cholesterol in heart failure. (From Horwich TB, Fonarow GC, Hamilton MA, et al. Low serum total cholesterol is associated with marked increase in mortality in advanced heart failure. J Card Fail 2002;8(4):222; with permission.) easier with the involvement of a team. Collaboration between physicians, nurses, nurse practitioners, physician assistants, pharmacists, and other health care workers reduces the burden of care coordination and simultaneously improves delivery of care. Team-based approaches increase cost-effectiveness, reduce hospitalization rates, and equally important, give patients more resources and support, which research shows may ultimately improve compliance and outcomes.

Out-of-hospital cardiac arrest -optimal management

Out-of-hospital cardiac arrest (OHCA) has attracted increasing attention over the past years because outcomes have improved impressively lately. The changes for neurological intact outcomes has been poor but several areas have achieved improving survival rates after adjusting their cardiac arrest care. The pre-hospital management is certainly key and decides whether a cardiac arrest patient can be brought back into a spontaneous circulation. However, the whole chain of resuscitation including the in-hospital care have improved also. This review describes aetiologies of OHCA, risk and potential protective factors and recent advances in the pre-hospital and in-hospital management of these patients.

Implantable cardioverter-defibrillator therapy before death: high risk for painful shocks at end of life

BACKGROUND

Several trials have demonstrated improved survival with implantable cardioverter-defibrillator (ICD) therapy. The cause and nature of death in the ICD population have been insufficiently investigated. The objective of this study was to analyze ICDs from deceased patients to assess the incidence of ventricular tachyarrhythmias, the occurrence of shocks, and possible device malfunction.

METHODS AND RESULTS

We prospectively analyzed intracardiac electrograms in 125 explanted ICDs. The incidence of ventricular tachyarrhythmia, including ventricular fibrillation, and shock treatment was assessed. Ventricular tachyarrhythmia occurred in 35% of the patients in the last hour of their lives; 24% had an arrhythmic storm, and 31% received shock treatment during the last 24 hours. Arrhythmic death was the primary cause of death in 13% of the patients, and the most common cause of death was congestive heart failure (37%). More than half of the patients (52%) had a do-not-resuscitate order, and 65% of them still had the ICD shock therapies activated 24 hours before death. Possible malfunctions of the ICD were found in 3% of all patients.

CONCLUSIONS

More than one third of the patients had a ventricular tachyarrhythmia within the last hour of life. Cardiac death was the primary cause and heart failure the specific cause of death in the majority of the cases. Devices remained active in more than half of the patients with a do-not-resuscitate order; almost one fourth of these patients received at least 1 shock in the last 24 hours of life.

Intraoperative defibrillation threshold testing during implantable cardioverter-defibrillator insertion: do we really need it?

BACKGROUND

The assessment of defibrillation efficacy using a safety margin of 10 J has long been the standard of care for insertion of implantable cardioverter-defibrillator (ICD), but physicians are concerned about complications related to induction test. Therefore, the need for testing has been recently questioned. The aim of our study was to assess the impact of defibrillation threshold (DFT) testing of ICD on the efficacy of ICD therapy.

METHODS

We analyzed data obtained from follow-up visits of 122 consecutive patients who underwent ICD implantation at our institute from April 1996 to June 2008, with (n = 42) or without (n = 80) DFT testing. Patients in the DFT group were less likely to be men (83.3% vs 96.3%, P < .031) than those in the non-DFT group. Conversely, the 2 groups were similar in age, left ventricular ejection fraction at baseline, functional class, and underlying cardiovascular disease. Results during a 12-month follow-up, 13 (31.0%) and 30 (37.5%) ventricular tachyarrhythmic episodes were recorded in the DFT and non-DFT groups, respectively (P = .472). Antitachycardia pacing (ATP) terminated most of episodes, reducing the need of defibrillation at 7.7% in the DFT group and 3.3% in the non-DFT group (P = .533). Similar percentages of inappropriate ATP interventions (7.1% vs 3.8%, P = .413) and shock deliveries (2.4% vs 5.0%, P = .659) were recorded between DFT and non-DFT groups.

CONCLUSIONS

At 1-year follow-up, the performance of DFT testing does not seem to add any significant efficacy advantage in patients undergoing ICD implantation. Prospective randomized trials and long-term follow-up are warranted to clarify whether routine DFT testing may be safely abandoned leading to a revision of current guidelines.

Mechanisms of ventricular fibrillation initiation in MADIT II patients with implantable cardioverter defibrillators

BACKGROUND

The availability of stored intracardiac electrograms from implantable defibrillators (ICDs) has facilitated the study of the mechanisms of ventricular tachyarrhythmia onset. This study aimed to determine the patterns of initiation of ventricular fibrillation (VF) in Multicenter Automatic Defibrillator Implantation Trial (MADIT) II patients along with associated electrocardiogram (ECG) parameters and clinical characteristics.

METHODS

Examination of stored electrograms enabled us to evaluate the rhythm preceding each episode of VF and to calculate (intracardiac) ECG parameters including QT, QT peak (QTp), coupling interval, and prematurity index.

RESULTS

Sixty episodes of VF among 29 patients (mean age 64.4 +/- 2.5 years) were identified. A single ventricular premature complex (VPC) initiated 46 (77%) episodes whereas a short-long-short (SLS) sequence accounted for 14 (23%) episodes. Of the 29 patients studied, 23 patients had VF episodes preceded by a VPC only, two patients with SLS only, and four patients with both VPC and SLS-initiated episodes. There were no significant differences between initiation patterns in regards to the measured ECG parameters; a faster heart rate with SLS initiation (mean RR prior to VF of 655 +/- 104 ms for SLS and 744 +/- 222 ms for VPC) approached significance (P = 0.06). The two patients with SLS only were not on beta-blockers compared to 83% of the VPC patients.

CONCLUSION

Ventricular fibrillation is more commonly initiated by a VPC than by a SLS sequence among the MADIT II population. Current pacing modes designed to prevent bradycardia and pause-dependent arrhythmias are unlikely to decrease the incidence of VPC-initiated episodes of VF.

[Risk of venous thromboembolism in acute medical illnesses. Part 2: Situations at risk in ambulatory, hospital and internal medicine settings]

PURPOSE

The increased risk of thromboembolism in acute medical illnesses (AMI) is difficult to assess because of the diversity of medical conditions. The first part of this review of the literature was dedicated to methods of risk analysis based on our current pathophysiological knowledge. This second part describes more specifically the risk of venous thrombosis linked to AMI in hospital, ambulatory and internal medicine settings.

CURRENT KNOWLEDGE AND KEY POINTS

The incidence of venous thromboembolism is higher in hospital than in ambulatory setting, albeit the latter remains significant. Stroke and affections leading to intensive care management represent conditions at great risk. Several mechanisms leading to a prothrombotic state have been identified, explaining the increased risk observed during relapses of pathologies specifically treated in internal medicine such as lupus erythematosus, Wegener granulomatosis, inflammatory bowel diseases and Behcet's disease.

FUTURE PROSPECTS AND PROJECTS

Next to the pathophysiological understanding of venous thrombosis, the assessment of the specific thrombogenic burden of an AMI is an additive tool to screen medical patients at high risk. This systematic review of the literature shows uncertainties towards some risk factors as bedrest or acute inflammatory response. Taking into account the methodological difficulties inherent to prospective and epidemiological studies, a meta-analysis focusing on these factors would be useful to refine prevention guidelines for venous thromboembolism in medical setting.

Acute Pulmonary Embolism Is an Independent Predictor of Adverse Events in Severe Decompensated Heart Failure Patients

BACKGROUND

Congestive heart failure (CHF) is a well-recognized risk factor for venous thromboembolism (VTE) and is associated with higher mortality in patients with an acute pulmonary embolism (PE). There are very few data on how acute PE affects the clinical course of patients with heart failure. The purpose of this study was to determine the impact of an acute PE on the short-term prognosis of patients hospitalized for decompensated CHF.

METHODS

This was a prospective cohort study of 198 patients admitted to a coronary care unit between July 2001 and March 2003 with severe decompensated CHF. The primary outcome measure was death or rehospitalization at 3 months.

RESULTS

PE was confirmed in 18 of 198 patients enrolled (9.1%). The groups with and without PE were comparable with regards to demographics, the prevalence of comorbid conditions, and severity of CHF (p > 0.05). The prevalence of cancer (p = 0.0001), previous VTE (p = 0.003), and right ventricular overload (p = 0.006) was higher in the PE group. The presence of PE was also associated with a longer hospital stay (37.5 +/- 71.6 days vs 15.4 +/- 15.0 days, p = 0.001) [mean +/- SD] and a higher incidence of death or rehospitalization at 3 months (72.2% vs 43.9%, p = 0.02). In a multiple logistic regression analysis, PE remained an independent predictor of death or rehospitalization at 3 months (odds ratio, 4.0; 95% confidence interval, 1.1 to 15.1; p = 0.038).

CONCLUSIONS

Acute PE commonly complicates the hospital course of patients with severe CHF, increasing the length of hospital stay and the chance of death or rehospitalization at 3 months.

The history, science, and innovation of Holter technology

Holter technology has endured for more than 40 years, and proven to be a valuable adjunctive noninvasive diagnostic technology to record the ambulatory or long-term electrocardiogram in the study of living creatures. During this span of time, many scientists, physicians, and innovators contributed to the development and evolution of Holter technology. This essay seeks to document a view of the history and evolution of the technology during that time, and concomitantly give recognition to the scientists, physicians, and engineers who contributed so greatly.

Incidence and Clinical Predictors of Pulmonary Embolism in Severe Heart Failure Patients Admitted to a Coronary Care Unit

OBJECTIVES

To determine the incidence of clinical pulmonary embolism (PE) in a population with severe congestive heart failure (CHF) admitted to a coronary care unit (CCU), and to identify clinical predictors of PE in this population.

DESIGN AND SETTING

Prospective, observational study performed in a CCU of a tertiary care hospital between July 2001 and March 2003.

PATIENTS

One hundred ninety-eight patients with severe decompensated CHF.

MEASUREMENTS AND RESULTS

Of 198 patients recruited, 18 patients (9.1%) received a diagnosis of PE during their hospitalization. Deep vein thrombosis was demonstrated in 8 of 18 patients (44.4%) with PE. Thromboprophylaxis was used by 12 of 18 patients (66.7%) with PE and 126 of 180 patients (70%) without PE (p = 0.77). Both groups were similar with respect to mean age (68.2 +/- 14.1 years vs 69.6 +/- 13.4 years [+/- SD]), proportion of male patients (61.1% vs 55.1%), markers of CHF severity (New York Heart Association functional class > II, ejection fraction < 30%, Na < 136 mEq/L, ischemic etiology), and comorbid conditions (diabetes mellitus, atrial fibrillation, chronic renal failure, hypertension) [p = not significant]. The presence of PE was significantly associated with cancer (relative risk [RR], 8.4; 95% confidence interval [CI], 3.9 to 18.1), immobilization (RR, 5.4; 95% CI, 2.0 to 14.4), previous venous thromboembolism (VTE) [RR, 4.4; 95% CI, 1.7 to 11.3], COPD (RR, 3.1; 95% CI, 1.03 to 9.2), and right ventricle (RV) abnormality (RR, 3.3; 95% CI, 1.3 to 8.0). In a multiple logistic regression analysis, only cancer (odds ratio [OR], 26.9; 95% CI, 4.9 to 146.8), RV abnormality (OR, 9.7; 95% CI, 2.2 to 42.6), and previous VTE (OR, 9.1; 95% CI, 1.28 to 64.7) remained independently associated with PE.

CONCLUSIONS

In patients with severe decompensated CHF admitted to a CCU, the incidence of clinical PE is very high despite adequate prophylaxis. Traditional risk factors seemed to play an important role in determining the risk of PE in this population.

Electrical therapy for post defibrillatory pulseless electrical activity

BACKGROUND

Defibrillation may convert ventricular fibrillation (VF) only to reveal profound mechanical dysfunction. Survival following this dysfunction, known as pulseless electrical activity (PEA) and electromechanical dissociation (EMD), is uncommon. We sought to evaluate an electrical therapy for primary post shock PEA following short duration VF.

METHODS AND RESULTS

Forty-eight episodes of VF, lasting 110 +/- 25 s, were induced in 16 anesthetized dogs. Following defibrillation, 35 episodes met PEA criteria (ABP < or = 36 mmHg diastolic and pulse pressure < or = 14 mmHg in the first 20 s post shock). These post defibrillation PEA episodes were either Not Treated (NT) or Treated (T) with packets of 4-20 monophasic 0.2 ms 50-100 Hz pulses of 20-60 V applied across the tip and coil of an integrated bipolar transvenous defibrillation lead positioned in the right ventricle. The therapeutic endpoint was return of spontaneous circulation (ROSC; self-sustained ABP > or = 60 mmHg diastolic and/or > or = 100 mmHg systolic) for over 2 min. In the Not Treated group, only 4 of 19 (21%) episodes spontaneously recovered to ROSC in 123 +/- 49 s while in the Treated group, 11 of 16 (69%) of the PEA episodes achieved ROSC in 102 +/- 92 s.

CONCLUSIONS

Electrical therapy increased the likelihood of ROSC in primary post defibrillation PEA three-fold (P < 0.01). Recovery occurred in the absence of thoracic compression, mechanical ventilation, or adjunctive drug therapy.

Death in patients with permanent pacemakers for sick sinus syndrome

BACKGROUND

Although more than one million patients in the United States have permanent pacemakers, little is known about their cause of death. We evaluated the cause of death in 404 patients who died in the Mode Selection Trial (MOST).

METHODS

In MOST, patients received a dual-chamber pacemaker randomly programmed to either dual-chamber or ventricular pacing. The circumstances surrounding each death were reviewed by a clinical events committee, which used prospectively defined criteria to adjudicate the cause of death.

RESULTS

A total of 2010 patients with a median age of 74 years were included. After a median follow-up of 33 months, 404 (20%) patients died, including 198 (49%) of noncardiac causes and 143 (35.4%) of cardiac causes. In 63 patients, the cause of death was unknown. Independent predictors of death through the use of a multivariable analysis were (1) demographic factors including age, male sex, and weight; (2) clinical factors including prior myocardial infarction, cardiomyopathy, New York Heart Association class III/IV, and the Charlson Comorbidity Index; and (3) scores from two measures of functional status, the Karnofsky Score and the Mini-Mental State Examination. Independent predictors of cardiovascular death were similar.

CONCLUSIONS

Patients treated with permanent pacemakers for sinus node dysfunction are elderly and have a substantial mortality rate, with more than half the classifiable deaths being noncardiac. Baseline demographic variables and scores from quality-of-life measures can identify patients with the highest risk of death.

Prediction of sudden cardiac death after myocardial infarction in the beta-blocking era

OBJECTIVES

This study assessed the predictive power of arrhythmia risk markers after an acute myocardial infarction (AMI).

BACKGROUND

Several risk variables have been suggested to predict the occurrence of sudden cardiac death (SCD), but the utility of these variables has not been well established among patients using medical therapy according to contemporary guidelines.

METHODS

A consecutive series of 700 patients with AMI was studied. The end points were total mortality, SCD, and nonsudden cardiac death (non-SCD). Nonsustained ventricular tachycardia (nsVT), ejection fraction (EF), heart rate variability, baroreflex sensitivity, signal-averaged electrocardiogram (SAECG), QT dispersion, and QRS duration were analyzed (n = 675). Beta-blocking therapy was used by 97% of the patients at discharge and by 95% at one and two years after AMI.

RESULTS

During a mean (+/-SD) follow-up of 43 +/- 15 months, 37 non-SCDs (5.5%) and 22 SCDs (3.2%) occurred. All arrhythmia risk variables differed between the survivors and those with non-SCD (e.g., the standard deviation of N-N intervals was 98 +/- 32 vs. 74 +/- 21 ms [p < 0.001] and the QRS duration was 103 +/- 22 vs.89 +/- 16 ms [p < 0.001]). Sudden cardiac death was weakly predicted only by reduced EF (<0.40; p < 0.05), nsVT (p < 0.05), and abnormal SAECG (p < 0.05), but not by autonomic markers or standard ECG variables. The positive predictive accuracy of EF, nsVT, and abnormal SAECG as predictors of SCD was relatively low (8%, 12%, and 13%, respectively).

CONCLUSIONS

The common arrhythmia risk variables, particularly the autonomic and standard ECG markers, have limited predictive power in identifying patients at risk of SCD after AMI in the beta-blocking era.

Management of arrhythmias in heart failure

Arrhythmias continue to contribute significantly to morbidity and mortality in heart failure. Implantable defibrillators have assumed an increasingly important role in preventing sudden death and are recommended for patients who have been resuscitated from cardiac arrest, have unexplained syncope, or exhibit inducible ventricular tachycardia in the setting of prior myocardial infarction. The extension of survival conferred by implantable defibrillators is likely to be limited in patients with advanced heart failure. Ongoing trials will help define the use of these devices in heart failure populations, in whom atrial fibrillation is common and rate control and anticoagulation are of major importance. Among pharmaceutical options, amiodarone and dofetilide are the major agents for maintenance of sinus rhythm. The complexity of coexistent heart failure and arrhythmia management warrants close collaboration between heart failure and arrhythmia specialists.

Utilization and outcomes of the implantable cardioverter defibrillator, 1987 to 1995

BACKGROUND

The patterns of adoption of the implantable cardioverter defibrillator (ICD) and the outcomes of its use have not been well documented in general, unselected populations. The purpose of this study was to document the impact of the ICD in widespread clinical practice.

METHODS

We identified ICD recipients by use of the hospital discharge databases of Medicare beneficiaries for 1987 through 1995 and of California residents for 1991 through 1995. The index admission for each patient was linked to previous and subsequent admissions and to mortality files to create a longitudinal patient profile.

RESULTS

The rate of ICD implantations increased >10-fold between 1987 and 1995, as both the number of hospitals performing the procedure and the volume of ICD implantations per hospital rose. Mortality rates within 30 days of ICD implantation decreased from 6.0% to 1.9%, and mortality rates within 1 year fell from 19.3% to 11.4%. Surgical interventions to revise or replace the ICD within the first year remained about 5%, however, and cumulative expenditures at 1 year ($46,000-$51,000) changed very little. ICD implantation rates varied >3-fold among different regions of the United States.

CONCLUSIONS

ICD use has expanded markedly during the study period, with improved mortality rates, but medical expenditures and rates of surgical revision remain high for ICD recipients.

Sudden death in patients with implantable cardioverter defibrillators: the importance of post-shock electromechanical dissociation

OBJECTIVES

The purpose of this study was to determine the mechanisms of sudden death (SD) in patients with ventricular tachyarrhythmias (ventricular tachycardia/ventricular fibrillation [VT/VF]) treated with an implantable cardioverter defibrillator (ICD).

BACKGROUND

Despite ICD therapy, some patients with VT/VF still die suddenly. Optimal ICD use requires determination of the mechanisms of these residual SDs.

METHODS

We reviewed 320 patient deaths during trials of Medtronic transvenous ICD systems (Medtronic Inc., Minneapolis, Minnesota). Sudden deaths were further categorized according to mechanism. Post-shock electromechanical dissociation (EMD) describes a scenario where VT/VF was appropriately detected and treated by an ICD shock that restored a physiologic rhythm, but death still occurred immediately by EMD.

RESULTS

A mode of death could be ascribed for 317 patients-90 (28%) were sudden, 156 (49%) were non-sudden cardiac, and 71 (22%) were noncardiac. A mechanism of SD was proposed for 68 patients-20 (29%) had post-shock EMD, 17 (25%) had VT/VF uncorrected by shocks, 11 (16%) had primary electromechanical dissociation, 9 (13%) had incessant VT/VF, 5 (7%) had VT/VF after their ICD was deactivated or removed, and 6 (9%) had single instances of various other terminal events. Only New York Heart Association functional class independently predicted SD by post-shock EMD.

CONCLUSIONS

The most common mechanism of SD in patients with an ICD is VT/VF treated with an appropriate shock followed by EMD. As this mechanism accounted for 29% of the SDs to which a cause could be ascribed, this mechanism of SD warrants further investigation.

Implantable cardioverter defibrillators in heart failure

Implantable cardioverter defibrillators provide effective and reliable treatment of spontaneous VT and VF. These devices can be expected to decrease the risk for arrhythmic death in patients with heart failure but do not improve overall survival when death from severe pump dysfunction is imminent. Appropriate patient selection is a major aspect of arrhythmia management. Future devices will incorporate features that have the potential to reduce atrial arrhythmias, improve ventricular function, monitor hemodynamics, and prevent sudden arrhythmic death.

Ventricular tachycardias above the initially programmed tachycardia detection interval in patients with implantable cardioverter-defibrillators: incidence, prediction and significance

OBJECTIVES

This retrospective study was performed to provide data on ventricular tachycardias (VT) with a cycle length longer than the initially programmed tachycardia detection interval (TDI) in patients with implantable cardioverter defibrillators (ICDs).

BACKGROUND

It has been clinical practice to program a safety margin of 30 to 60 ms between the slowest spontaneous or inducible VT and the TDI.

METHODS

Baseline characteristics of 659 consecutive patients with ICDs were prospectively; follow-up information was retrospectively collected.

RESULTS

During a mean follow-up of 31+/-23 months, 377 patients (57.2%) had at least one recurrent VT or ventricular fibrillation; 47 patients (7.1%) suffered 61 VTs above the TDI. The risk of a VT above the TDI ranged between 2.7% and 3.5% per year during the first four years after ICD implantation. The difference between the cycle length of the slowest VT before ICD implantation, spontaneous or induced, and the first VT above TDI was 108+/-58 ms. Fifty-four VTs (88.5%) above the TDI were associated with significant clinical symptoms (angina or palpitation 63.9%, heart failure 6.6% and syncope 8.2%). Six patients (9.8%) had to be resuscitated. Kaplan-Meyer analysis identified New York Heart Association class II or III (p = 0.021), ejection fraction < 0.40 (p = 0.027), spontaneous (p<0.001) or inducible (p<0.001) monomorphic VTs and the use of class III antiarrhythmic drugs (amiodarone, p<0.001; sotalol, p = 0.004) as risk predictors of VTs above the TDI. The risk of recurrent VTs above TDI was 11.8%, 12.5% and 26.6% during the first, second and third year after first VT above TDI, respectively.

CONCLUSIONS

The risk of VTs above the TDI is significantly increased in some patients, and many VTs above TDI cause significant clinical symptoms. A larger safety margin between spontaneous or inducible VTs and the TDI seems to be necessary in selected patients. This is in conflict with an increased risk of inadequate episodes and demands highly specific and sensitive detection algorithms in these patients.

Hybrid therapy for ventricular arrhythmia management

Optimum arrhythmia management has evolved to couple ICD therapy with catheter ablative and drug therapy to attempt to eliminate or reduce arrhythmia risk. No longer should the clinician approach such therapy as a choice among single alternative strategies only. Optimum patient management includes not only recognition of the indications and benefits of such hybrid therapy but also a complete understanding of potential pitfalls of such therapy.

Implantable defibrillators and antiarrhythmic drugs in patients at risk for lethal arrhythmias

The high mortality rate and frequency of ventricular arrhythmias in patients with congestive heart failure has prompted numerous clinical trials aimed at reducing mortality by addressing arrhythmic death. Recently completed trials have suggested that for patients who have survived cardiac arrest, the preferred treatment may be an implantable cardioverter defibrillator (ICD). From the standpoint of primary prevention, implantable defibrillators and amiodarone have received the most attention. It remains unclear, however, to which patients these studies apply, and if and how the results might be generalized. No available studies confirm an additional benefit of pharmacologic or device-based antiarrhythmic therapy beyond that offered by optimal treatment with beta blockers, angiotensin-converting enzyme inhibitors, and lipid-lowering drugs in the majority of patients with cardiomyopathy. Clinical trials are ongoing to address these issues.

Class III drugs and congestive heart failure: focus on the congestive heart failure-survival trial of antiarrhythmic therapy

Patients with congestive heart failure frequently have ventricular arrhythmias on ambulatory electrocardiographic recordings and sudden cardiac death is seen in almost 50% of such patients. Many antiarrhythmic agents have been approved to suppress the arrhythmia in an effort to improve survival. Some sodium-channel blockers not only failed to improve survival but have been shown to be harmful. This led to the development of potassium-channel blockers, such as d-sotalol, amiodarone, dofetilide, and azimilide. d-Sotalol was associated with excess mortality in patients with left ventricular dysfunction; amiodarone seems to be potentially beneficial; and dofetilide has a neutral effect on mortality. The Sudden Cardiac Death Heart Failure Trial (SCD HEFT) is testing the implantable cardioverter defibrillator (ICD) against amiodarone and placebo. The ICDs appear to be superior to antiarrhythmic drugs in certain high-risk patients, although not proved in unstratified patients with heart failure.