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Researchers examine the risk factors for sudden cardiac death and management of at-risk patients

Despite advances in the prevention and treatment of heart disease, sudden cardiac death (SCD)—usually caused by ventricular arrhythmias (irregular heart beats)—accounts for one-fourth of all deaths in the United States. SCD occurs most often in patients diagnosed with heart disease, especially those who have suffered a heart attack or congestive heart failure.

Seven studies were published recently that focus on risk factors for SCD and management of patients at high risk for SCD. The studies are from the Sudden Cardiac Death Patient Outcomes Research Team (PORT), led by Mark Hlatky, M.D., principal investigator, and Kathryn McDonald, M.M., project director, of Stanford University. The studies, which were supported in part by the Agency for Healthcare Research and Quality (HS07373 and HS08362), are described here.

Every, N., Hallstrom, A., McDonald, K.M., and others (2002). "Risk of sudden versus nonsudden cardiac death in patients with coronary artery disease." American Heart Journal 144, pp. 390-396.

Patients at high risk of sudden cardiac death (SCD), yet at low risk of nonsudden cardiac death (non-SCD, for example, heart failure), benefit most from antiarrhythmic drugs such as amiodarone or devices like the implantable cardioverter-defibrillator (ICD), which shocks the heart into a normal rhythm. Standard clinical evaluation is not very good at distinguishing patients at risk for SCD versus non-SCD, since these patients have similar clinical profiles, according to this study.

The researchers identified all cardiac deaths during a 3.3-year followup of 30,680 patients discharged alive after a stay in a cardiac care unit of a Seattle hospital. They reviewed the medical charts of 1,093 subsequent out-of-hospital SCDs, 973 non-SCDs, and 442 randomly selected control patients. Patients who died during followup, either suddenly or nonsuddenly, differed in numerous ways from the randomly selected control patients. For example, patients who died were significantly older, more likely to have had a prior heart attack or congestive heart failure, more likely to have diabetes, and less likely to have been discharged on beta-blockers or aspirin.

Yet very few factors distinguished patients with subsequent SCD from those who died not suddenly. Cardiac test results and discharge medications of patients who died suddenly were quite similar to those of patients who died nonsuddenly. Women, patients who had angioplasty or bypass surgery, and patients prescribed beta-blockers were 20 to 30 percent less likely to die suddenly than other patients. Those with heart failure, frequent ventricular ectopy, or a discharge diagnosis of heart attack were 20 to 30 percent more likely to die suddenly than other patients. However, a model containing all clinical variables had only a modest ability to predict mode of death.

Heidenreich, P.A., Keeffe, B., McDonald, K.M., and others (2002). "Overview of randomized trials of antiarrhythmic drugs and devices for the prevention of sudden cardiac death." American Heart Journal 144, pp. 422-430.

By preventing or terminating ventricular arrhythmias (irregular heart beats) in patients who have already suffered a heart attack, the type III antiarrhythmic agent amiodarone and the ICD substantially reduce SCD, according to this study. The investigators reviewed randomized trials and quantitative overviews of type I and type III antiarrhythmic drugs and randomized trials of ICDs and combined these outcomes in a quantitative overview. The Cardiac Arrhythmia Suppression Trial (CAST) and meta-analyses of other studies suggested that type I agents increased by 21 percent the mortality rate of heart attack patients who had no symptoms of irregular heart beat but were at risk of sudden death.

Randomized trials of amiodarone suggested a moderate 13 to 19 percent decrease in mortality rate relative to placebo, and sotalol, another type III agent, was effective in several small trials. Trials of pure type III agents, however, showed no reduced mortality.

An overview of ICD trials revealed a 24 percent reduction in mortality rate compared with amiodarone. The benefit of the device was greater in patients with an ejection fraction (a measure of cardiac output) of 35 percent or less. The evidence supporting the efficacy of the ICD was strongest in patients who had experienced an episode of sustained ventricular tachycardia (abnormally rapid heart beat) or ventricular fibrillation (irregular heart beat).

The researchers suggest that type I agents be reserved for patients with symptomatic atrial arrhythmias and, even in these patients, other therapies may be preferred when the ejection fraction is substantially reduced. They conclude that amiodarone remains an acceptable therapeutic option, particularly as preventive therapy, in patients at high risk of SCD who have not experienced an episode of sustained ventricular tachycardia or fibrillation. The ICD is effective in patients with prior episodes of sustained ventricular tachycardia or fibrillation.

Hlatky, M.A., Saynina, O., McDonald, K.M., and others (2002). "Utilization and outcomes of the implantable cardioverter defibrillator, 1987-1995." American Heart Journal 144, pp. 397-403.

Introduced into clinical use in 1980, the ICD has become smaller and simpler to implant, while providing better methods to detect and treat sustained ventricular tachyarrhythmias (rapid, irregular heart beat). This study found that ICD use expanded more than 10-fold in clinical practice from 1987 to 1995, with improved mortality rates but high medical expenditures and rates of surgical revision. The investigators 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. They linked the initial hospital admission for each ICD patient to previous and subsequent admissions and to mortality files to determine the outcomes of ICD use.

During the study period, over 31,000 ICDs were implanted in Medicare patients, most of whom had been hospitalized for heart attack, congestive heart failure, or ventricular tachycardia at that time or during the previous year. Between 1987 and 1995, the number of hospitals performing the procedure increased from roughly 100 to 500, and the volume of ICD implantations per hospital also rose. Patients who died within 30 days of implantation decreased from 6 to 2 percent, and mortality rates within a year of implantation fell from 19 to 11 percent. Mortality rates at 3 years declined as well, but less sharply, from 38 percent in 1987 to 33 percent in 1992.

Subsequent hospitalizations for ICD complications or surgical replacement were very common and within the first year remained about 5 percent. However, the rate of revision/replacement at 3 years declined from 34 percent from 1987 to 1989 to 18 percent for devices implanted from 1990 to 1992, largely as a result of fewer generator replacements due to improvements in device and battery life. Medicare expenditures for these patients within 30 days of ICD implantation have remained close to $40,000 in 1993 dollars, and 3-year expenditures averaged almost $50,000.

McDonald, K.M., Hlatky, M.A., Saynina, O., and others (2002). "Trends in hospital treatment of ventricular arrhythmias among Medicare beneficiaries, 1985-1995." American Heart Journal 144, pp. 413-421.

Survival of patients who sustain a ventricular arrhythmia is poor but slowly improving due to in-hospital use of medications and ICDs. However, this more intensive hospital treatment has been accompanied by increased hospital expenditures, finds this study. The researchers analyzed Medicare databases from 1985 to 1995 to identify elderly patients hospitalized with ventricular arrhythmias (index admission). They created a longitudinal patient profile by linking the index hospital admission with all earlier and subsequent admissions and with death records.

During this time, about 85,000 elderly patients went to U.S. emergency departments (EDs) with ventricular arrhythmias each year. Only about 20,000 of these patients lived to be admitted to the hospital from the ED, and then about 14 percent died within the first day. From 1987 to 1995, the demographic and clinical characteristics of patients and the use of coronary angioplasty and bypass graft surgery for these patients were largely unchanged. However, the use of electrophysiology studies (EPS) grew from 3 to 22 percent and use of ICDs increased from 1 to 13 percent. A growing number of patients survived, particularly in the medium term, with 1-year survival rates increasing from 53 percent in 1987 to 58 percent in 1994, or half a percentage point each year.

At the same time, hospital expenditures rose 8 percent per year, primarily because of the increased use of EPS and ICD procedures. By 1993, Medicare was reimbursing hospitals an average of $15,627 for care for each patient during the year after admission for ventricular tachycardia/fibrillation. During the subsequent year, another $14,739 on average was spent for these patients. The increased intensity of care for these patients led to a rise in the average expenditure per patient of about $1,000 per year (in 1993 dollars) from 1987 to 1995.

Alexander, M., Baker, L., Clark, C., and others (2002). "Management of ventricular arrhythmias in diverse populations in California." American Heart Journal 144, pp. 431-439.

Several studies have shown lower use of cardiac procedures in racial/ethnic minorities, and this study is no exception. It found that in a large population of California patients hospitalized for life-threatening ventricular arrhythmia (LTVA), blacks received significantly fewer invasive electrophysiological studies (EPS) and ICD procedures than whites and had higher mortality rates a year later. The researchers analyzed discharge abstracts of patients admitted to non-Federal California hospitals for ventricular tachycardia or ventricular fibrillation (VT/F) between 1992 and 1994.

Among 8,713 patients admitted with VT/F, 29 percent had a subsequent EPS procedure, and 9 percent had an ICD implanted. After controlling for potential confounding factors, black patients were 28 percent less likely to undergo EPS and 61 percent less likely to have an ICD implanted than white patients. Within 1 week of admission for VT/F, 22 percent of blacks and 21 percent of Hispanics received EPS compared with 28 percent of Asians and 30 percent of whites, a similar pattern that also was observed within a year of the hospitalization. Within 1 week of hospital admission, 4 percent of blacks, 6 percent of Hispanics, and 7 percent of Asians had received an ICD compared with 10 percent of whites, with the same pattern evident 1 year later.

Even after controlling for multiple confounding risk factors, 20 percent of blacks discharged alive from the hospital died over the next year compared with 15 percent of Hispanics and whites and 13 percent of Asians. Black and Asian patients lived closer to hospitals with EPS/ICD capability than Hispanic or white patients, yet they were no more likely to be admitted to such hospitals. In the study period, implantation of an ICD was usually confined to patients who had undergone a prior EPS procedure. Yet in patients who had undergone an EPS procedure, black patients were still 55 percent less likely to have an ICD implanted than white patients. Use of EPS and ICD procedures was also lower among women, older patients, and Medicaid or uninsured patients.

Hsu, J., Uratsu, C., Truman, A., and others (2002). "Life after a ventricular arrhythmia." American Heart Journal 144, pp. 404-412.

A life-threatening ventricular arrhythmia (LTVA) can have a substantial negative effect on a person's quality of life (QOL). With therapy, most patients can improve their QOL and reduce symptoms, possibly more so after treatment with an ICD, according to this study. However, the costs of treating these patients are very high and include the cost of the ICD. The researchers investigated changes in QOL during the first 2 years after initial arrhythmia, as well as cost and resource use among patients discharged after a first episode of an LTVA between 1995 and 1998 in a managed care population of 2.4 million members.

The researchers evaluated QOL by use of the Duke Activity Status Index (DASI), Medical Outcomes Study SF-36 mental health and vitality scales, and the Cardiac Arrhythmia Suppression Trial (CAST) symptom scale via telephone interviews with patients at discharge and 6, 12, and 24 months later. They also reviewed patient charts at baseline and at 24 months to assess treatment, coexisting illness, and medication use, and they evaluated resource use and costs via health plan databases. The 264 patients with new cases of LTVA received either an ICD or antiarrhythmic medication such as amiodarone, depending on their doctor's recommendation.

Both functional status and symptoms (ranging from palpitations and fainting to joint pains and severe shortness of breath) improved significantly for these patients during the study period, particularly for ICD patients. Patients receiving an ICD had the greatest initial decrease in DASI functional status (16.4 units) but also had the greatest subsequent recovery of their functional status (8.2 units) compared with patients receiving amiodarone. The average symptom score decreased from 44.2 to 29.5 units in the original nine-item CAST instrument, and these improvements were greater in patients receiving an ICD than in patients receiving amiodarone. However, the direct cost of medical care for LTVA patients was very high, averaging $30,193 in 2 years (including the initial cost of an ICD unit for the 94 patients receiving this treatment in the LTVA cohort). These data suggest that most patients treated for newly developed LTVA achieve QOL scores that are similar to those of patients after coronary angioplasty or coronary artery bypass graft surgery.

Owens, D.K., Sanders, G.D., Heidenreich, P.A., and others (2002). "Effect of risk stratification on cost-effectiveness of the implantable cardioverter defibrillator." American Heart Journal 144, pp. 440-448.

Risk stratification based on patient risk of sudden cardiac death alone is not sufficient to predict the cost-effectiveness of the implantable cardioverter defibrillator (ICD) compared with the medication amiodarone. Risk stratification strategies must distinguish patients who die suddenly from those who die nonsuddenly, not just patients who die suddenly from those who live, if they are to successfully identify patients for whom use of the ICD is economically attractive, suggest these researchers.

They developed a mathematical model to evaluate the cost-effectiveness of ICD implantation compared with amiodarone treatment, which incorporated mortality rates from sudden and nonsudden cardiac death, noncardiac death, and costs for each treatment strategy. They found that if the annual total cardiac mortality rate is 12 percent, the cost-effectiveness of the ICD varies from $36,000 per quality-adjusted life year (QALY) gained when the ratio of sudden cardiac death to nonsudden cardiac death is 4 to $116,000 per QALY gained when the ratio is 0.25.

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