Patients with malignant or potentially malignant ventricular arrhythmias: opportunities and limitations of drug therapy in prevention of sudden death

From randomized trials to registry studies: translating data into clinical information

All clinicians face the challenge of practicing evidence-based medicine and are confronted with data from a variety of studies, ranging from prospective randomized and registry studies to retrospective analyses. Unfortunately, the data frequently provide conflicting recommendations. How then should one interpret the information so that study findings can be applied directly in patient care? To evaluate the relevance of the abundance of studies published and how they apply to an individual patient, physicians must understand subtle nuances of study design and their effect on the interpretation of the results. In this Review, we examine the strengths and weaknesses of different study designs with the aim of providing the reader with a greater understanding how best to apply study results in the clinical setting.

[Epidemiology of sudden cardiac death in Spain]

Sudden cardiac death is a remarkable public health problem though its incidence in Spain is lower than in other industrialised countries. Approximately 12% of all natural deaths occur suddenly, and 88% of them are of cardiac origin. This is the form of death in more than 50% of coronary heart disease patients. Moreover, it is the first symptom in 19-26% of cases. This close relationship with coronary heart disease results in cardiovascular risk factors being also risk factors for sudden death. Several factors, such as physical activity or certain drugs may act as sudden death triggers. The more effective strategy addressed to sudden cardiac death prevention includes identification high-risk subgroups of patients (i.e. patients with previous coronary heart disease, heart failure, out-of-hospital sudden death survivors and patients who developed a ventricular fibrillation or tachycardia after a myocardial infarction) and development of efficacious therapeutic interventions. Given that most sudden death are related to coronary heart disease, those primary preventive measures directed to reduce the coronary heart disease incidence rates will also prevent sudden cardiac deaths in population. Finally, community programs directed to reduce the time to reach cardiac emergencies by trained personnel, and to train general population in cardio-respiratory reanimation have shown to be efficacious owing to the fact that most sudden cardiac deaths occur out of hospitals.

Medical costs of coronary artery disease in the United States

A model has been developed to determine the cost of coronary artery disease (CAD) based on the 5 primary events identified in the Framingham Study: acute myocardial infarction, angina pectoris, unstable angina pectoris, sudden death and nonsudden death. The costs for diagnostic and therapeutic service for patients with CAD were linked to medical decision algorithms outlining the diagnosis and management of patients with CAD. Because CAD is a changing illness not represented by a single event, the algorithm tracked patients for 5 years after the time of diagnosis, or until death, to develop average cost estimates. The estimated 5-year costs (in 1986 United States dollars) of the 5 CAD events were: acute myocardial infarction $51,211, angina pectoris $24,980, unstable angina pectoris $40,581, sudden death $9,078 and nonsudden death $19,697. The costs of major CAD surgical procedures were also calculated because of their impact on health care costs for patients with CAD. These include: coronary artery bypass surgery per case over 5 years $32,465, and angioplasty per case over 5 years $26,916. The high cost of CAD reflects the improved technology and more effective and expensive therapies now available.

Classification of deaths after myocardial infarction as arrhythmic or nonarrhythmic (the Cardiac Arrhythmia Pilot Study)

The Cardiac Arrhythmia Pilot Study (CAPS) was a randomized, double-blind trial of antiarrhythmic drugs (encainide, flecainide, moricizine, imipramine and placebo) in 502 patients with at least 10 ventricular premature complexes/hour, 6 to 60 days after acute myocardial infarction. CAPS tested the feasibility of performing a larger study to determine if suppression of ventricular ectopic activity after acute myocardial infarction could improve survival. Patients in CAPS were followed for 1 year. All death or cardiac arrest events were evaluated by at least 2 investigators using a classification scheme that characterized the underlying mechanism as cardiac arrhythmic, cardiac nonarrhythmic or noncardiac. Forty-five patients (9%) died or had cardiac arrest during the 1-year follow-up, 29 (64%) within 1 hour from the onset of symptoms and 16 greater than 1 hour from the onset of symptoms. Twenty-three deaths (51%) were classified as arrhythmic, 19 (42%) as nonarrhythmic and 3 (7%) as noncardiac. Acute myocardial ischemia or infarction was associated with the death/cardiac arrest event in 16 patients (36%), 8 in the arrhythmic death group. Discrepancies in classification among reviewers were particularly common in patients with long-standing symptoms of congestive heart failure, in whom it was frequently difficult to identify the precise moment of the onset of symptoms in the death/cardiac arrest event. Using only the temporal relation of symptoms to categorize deaths or cardiac arrests, the mechanism of 12 (27%) of the 45 patients was in disagreement with the classification based on the Events Committee review. Classification of death as sudden or nonsudden is not equivalent to the classification of death as arrhythmic or nonarrhythmic.

Prognostic importance of cardiac arrhythmias in systemic sclerosis

Ambulatory electrocardiography was performed in 183 patients with systemic sclerosis recruited from five centers who were selected to reflect a balanced population with respect to disease extent and duration. Ventricular ectopy occurred in 67 percent of patients and was strongly correlated by both univariate and multivariate analyses with total mortality and with sudden death. By multivariate analysis, ventricular ectopy was strongly associated with increasing patient age and with other evidence of cardiac and pulmonary involvement but not with clinical and laboratory measures of duration and extent of systemic sclerosis. Evidence of myocardial fibrosis thought to be secondary to microvascular alteration is common in systemic sclerosis, but the clinical implications of myocardial involvement are less well appreciated. The present data suggest the need for ambulatory electrocardiography in the clinical assessment of selected patients with systemic sclerosis, especially those with cardiac or pulmonary involvement, as well as for studies of the effects of antiarrhythmic therapy.

Determinants of survival in patients with malignant ventricular arrhythmia associated with coronary artery disease

The long-term survival data in patients with coronary artery disease and a history of malignant ventricular arrhythmia, defined as noninfarction ventricular fibrillation (VF) or hemodynamically compromising ventricular tachycardia (VT) followed for up to 9 years, were analyzed. In this group of 161 patients there was a total of 57 deaths, of which 35 (63%) were sudden. Life-table analysis demonstrated a 10% sudden death rate for all patients in the first year and a 7% annual rate in the subsequent 4 years. In patients managed noninvasively, the overall mortality rate was 27% over 9 years, or 3% per year. Suppression of ventricular tachycardia on both ambulatory monitoring and exercise testing was associated with improved survival. In patients evaluated by electrophysiologic testing the sudden death rate was 1.4% per year over an average of 5 years. This survival rate was not different compared with the noninvasive group (p = 0.09). Measures of left ventricular dysfunction and the frequency of ventricular arrhythmia before and after drug therapy were associated with a risk of sudden cardiac death by univariate analysis. Multivariate regression analysis identified 4 variables as independent predictors of sudden cardiac death: rales (p = 0.009), the number of runs of VT during exercise testing while receiving antiarrhythmic drug therapy (p = 0.0003), a history of congestive heart failure (p = 0.0009) and the number of premature beats on Holter monitoring (p = 0.01). These findings support the concept that suppression of repetitive arrhythmia on Holter monitor and exercise testing is a marker for improved survival among patients with malignant ventricular arrhythmia.(ABSTRACT TRUNCATED AT 250 WORDS)

Prognostic significance of ventricular ectopic activity in survivors of acute myocardial infarction

Twenty-four hour ambulatory electrocardiography was performed on 3,290 survivors of acute myocardial infarction participating in the Beta-Blocker Heart Attack Trial (BHAT). History of myocardial infarction before the qualifying event, congestive heart failure and age were independently associated with the frequency and complexity of ventricular premature beats. Of the 1,640 patients randomized to placebo therapy, 163 died (76 suffered sudden death) during a 25 month average follow-up period. Ventricular ectopic activity was an independent predictor of total mortality after taking into consideration 16 other prognostic factors describing past history, risk factors, physical examination and laboratory investigations. Seven categoric definitions of ventricular ectopic activity predicted mortality, with similar odds ratios ranging from 2.27 to 2.69. A reciprocal relation of the sensitivity and specificity of each definition in predicting mortality was observed. Three clinical criteria (ST depression, cardiomegaly and prior infarction) allowed stratification of patients into four subsets with respective mortality rates of 35.5% (three criteria present), 19.0% (two criteria), 11.5% (one criterion) and 4.7% (none). Presence of ventricular ectopic activity (greater than or equal to 10 ventricular premature beats/h or pairs, ventricular tachycardia or multiform complexes) was associated with higher mortality rates in all four risk strata. The relative risk was higher (3.86) in the lowest risk stratum (mortality 2.4% without and 9.1% with ventricular ectopic activity). Thus, in survivors of acute myocardial infarction, ventricular ectopic activity was more pronounced in patients with prior myocardial infarction and congestive heart failure. It predicted mortality independently of other factors. Although mortality ratios were similar for all seven arrhythmia definitions, a reciprocal relation between sensitivity and specificity of the definitions in predicting mortality existed; ventricular ectopic activity was associated with increased mortality in all risk strata, but with a higher risk ratio in the numerically larger, low risk subset.

Prophylactic antiarrhythmic therapy of high-risk survivors of myocardial infarction: lower mortality at 1 month but not at 1 year

To determine whether prophylactic antiarrhythmic therapy influences mortality in high-risk patients after acute myocardial infarction, 143 such patients were randomized in a double-blind individually dose-adjusted, placebo-controlled trial an average of 14 +/- 7 days after myocardial infarction and followed for 1 year. Patients were judged to be at high risk on the basis of (1) ejection fraction less than 40% (n = 60), (2) arrhythmias of Lown class 3 or higher (n = 26), or (3) both (n = 57). Aprindine was chosen because of its long half-life, few side effects, and antiarrhythmic efficacy. Baseline characteristics in the treatment arms did not differ. Holter-detected arrhythmias were reduced in aprindine-treated patients at 3 months (p less than .001) and at 1 year (p less than .001). One patient was lost to follow-up; in the remaining patients 1 year mortality was 20% (28/142; 12 aprindine and 16 placebo). There was no significant difference between the two study arms in overall mortality and sudden death. However, among those who died, median duration of survival was longer in aprindine-treated patients (86 vs 21.5 days) (p = .04). Although antiarrhythmic treatment with aprindine of high-risk patients after myocardial infarction does not affect 1 year survival, mortality appears to be delayed; thus there may be a role for short-term treatment before more definitive therapy such as surgery.

Ambulatory electrocardiographic monitoring: can we predict sudden death?

Cardiac arrhythmias can be accurately detected and quantified using ambulatory electrocardiographic monitoring. From a review of major studies, it appears that the presence of advanced ventricular arrhythmias identifies a subset of patients with coronary heart disease who are at a relatively higher risk for sudden death than are those patients without such arrhythmias. Left ventricular dysfunction is an independent and additive risk factor for subsequent development of sudden cardiac death. The presence of high grade ventricular arrhythmias appears to increase the risk for sudden death in patients with hypertrophic and dilated cardiomyopathy. Ambulatory monitoring can be used to identify a subset of patients with coronary disease or cardiomyopathy who are at increased risk for sudden cardiac death. Because of the relatively low overall incidence of sudden cardiac death in such patients, and the low sensitivity and specificity for accurately classifying patients, the practical applicability of this technique to large population subgroups is limited.