Sudden cardiac death: etiologies, pathogenesis, and management

Long-term prognosis after out-of-hospital cardiac arrest and primary percutaneous coronary intervention

AIMS

To study the long-term survival after out-of-hospital cardiac arrest and successful cardiopulmonary resuscitation (CPR) in patients with acute ST-segment elevation myocardial infarction (STEMI) treated with primary percutaneous coronary intervention (PCI).

MATERIAL AND METHODS

In-hospital and 2-year survival of 40 patients treated with primary PCI after out-of-hospital cardiac arrest and STEMI was compared with that of a reference group of 325 STEMI patients, without cardiac arrest, also treated with primary PCI in the same period.

RESULTS

In the group with out-of-hospital cardiac arrest, both in-hospital and 2-year mortality was 27.5%. In the reference group, in-hospital and 2-year mortality was 4.9 and 7.1%, respectively. After discharge from hospital there was no significant difference in mortality between the groups.

CONCLUSION

Long-term prognosis is good in selected patients after successful out-of-hospital CPR and STEMI treated with primary PCI.

Application of noninvasive and invasive tests for risk assessment in patients with ventricular arrhythmias

Sudden cardiac death remains a major public health problem in western society. Because most patients who experience cardiac arrest are not successfully resuscitated, primary prevention of sudden death remains an important challenge. A number of noninvasive risk stratification techniques have been suggested as providing useful information in patients with underlying structural heart defects. Unfortunately, the positive predictive value of most of these techniques has been limited. Left ventricular ejection fraction, the presence of nonsustained ventricular tachycardia on Holter monitoring, and inducible sustained ventricular tachycardia at electrophysiologic testing in patients with coronary artery disease remain the best established prognostic test. However, with the exception of two ICD studies using the combination of these markers, prospective studies have not yet completely validated the use of these and other prognostic markers. Further understanding of the pathophysiology of ventricular fibrillation and other risk stratification techniques will be necessary before a clear algorithm can be developed for application to patients at risk for sudden death.

The azimilide post-infarct survival evaluation (ALIVE) trial

The AzimiLide post-Infarct surVival Evaluation (ALIVE) trial is a new clinical trial using an innovative design to examine the potential of azimilide, a novel type of antiarrhythmic, for improving survival in post myocardial infarction (MI) patients at high risk of sudden cardiac death. Azimilide is the first of a unique class of antiarrhythmic drugs that blocks both slow and rapid components of the delayed rectifier potassium currents in human myocardium. Preclinical studies have shown the drug to be effective in reducing cardiac tachyarrhythmias, even under ischemic conditions. Currently, azimilide is in Phase III trials for the treatment of supraventricular arrhythmias. The ALIVE study design is based on lessons learned from the Cardiac Arrhythmia Suppression Trials (CAST), the Survival With Oral d-Sotalol (SWORD) trial, and the European Myocardial Infarction Amiodarone Trial (EMIAT) and identifies recent post-MI patients at high risk of sudden cardiac death. The hypothesis underlying this trial is that azimilide will improve survival in this patient population. The ALIVE trial is designed as a double-blind, placebo-controlled, multinational trial that will overcome the shortcomings of previous antiarrhythmic trials by using left ventricular ejection fraction and heart rate variability as predictors to target a post-MI patient population at high risk of sudden death. The major inclusion criteria for the study are adult patients of either gender with a left ventricular ejection fraction of 15-35% who have had a recent MI (within 6-21 days). Additional stratification will be based on patients with heart rate variability < or = 20 U (heart rate variability index). Exclusion criteria include factors that may predispose a patient to nonarrhythmia-induced death or to low risk of sudden cardiac death caused by arrhythmia. Sample size is based on the assumption that the all-cause mortality rate (the primary endpoint) for 1 year in placebo patients at high risk for sudden cardiac death (heart rate variability < or = 20 U) is 15% and that azimilide will decrease all-cause mortality by at least 45% in these patients. The trial consists of 3 groups-patients receiving 75 mg azimilide orally each day, patients receiving 100 mg azimilide orally each day, and patients receiving placebo. No dose adjustments for age, gender, renal or hepatic failure, or concomitant use of warfarin or digoxin are thought necessary with azimilide. Enrollment for the trial is expected to continue for 24 months, and treatment is scheduled to be administered for a 1-year follow-up period.

Cardiopulmonary resuscitation: a review for clinicians

Attempts at cardiopulmonary resuscitation (CPR) date from antiquity, but it is only in the last 50 years that a scientifically-based methodology has been developed. External chest compressions is the standard method for managing circulatory arrest, however, numerous alterations of this technique have been proposed in attempts to improve outcome from CPR. Defibrillation is the single most important therapy for the management of ventricular fibrillation or pulseless ventricular tachycardia. Adrenergic agents used to improve myocardial and cerebral perfusion are also the subject of considerable investigation with new agents entering clinical study. This paper reviews the history, current techniques and pharmacotherapy as well as controversial issues in the management of patients with cardiac arrest.

Treatment of prolonged ventricular fibrillation. Immediate countershock versus high-dose epinephrine and CPR preceding countershock

BACKGROUND

Early countershock of ventricular fibrillation has been shown to improve immediate and long-term outcome of cardiac arrest. However, a number of investigations in the laboratory and in the clinical population indicate that immediate countershock of prolonged ventricular fibrillation most commonly is followed by asystole or a nonperfusing spontaneous cardiac rhythm, neither of which rarely respond to current therapy. The use of epinephrine in doses greater than those currently recommended has recently been shown to improve both cerebral and myocardial perfusion during cardiopulmonary resuscitation (CPR). The purpose of this study was to compare cardiac resuscitation outcome between immediate countershock of prolonged ventricular fibrillation with high-dose epinephrine therapy and conventional CPR before countershock of prolonged ventricular fibrillation in a canine model.

METHODS AND RESULTS

After sedation, intubation, induction of anesthesia, and instrumentation, ventricular fibrillation was electrically induced in 28 dogs. After 7.5 minutes of ventricular fibrillation, animals were randomly allocated to two treatment groups: group 1, immediate countershock followed by recommended advanced cardiac life support (ACLS) interventions, or group 2, 0.08 mg/kg epinephrine and manual closed-chest CPR before countershock and ACLS. In both groups, ACLS was continued until a spontaneous perfusing rhythm was restored or for 20 minutes (total arrest time, 27.5 minutes). A spontaneous perfusing rhythm was restored in three of 14 group 1 animals and in nine of 14 group 2 animals (p = 0.014 by sequential analysis method of Whitehead). Coronary perfusion pressure (aortic minus right atrial pressure during CPR diastole) before countershock was significantly greater in group 2 (21 +/- 7 mm Hg) when compared with mean circulatory pressure in group 1 (9 +/- 8, p less than 0.01).

CONCLUSIONS

The findings of this study suggest that a brief period of myocardial perfusion before countershock improves cardiac resuscitation outcome from prolonged ventricular fibrillation.

Patients with supraventricular tachycardia presenting with aborted sudden death: incidence, mechanism and long-term follow-up

A total of 13 (4.5%) of 290 patients with aborted sudden death had either documented (7; 54%) or strong presumptive evidence of supraventricular tachycardia that deteriorated into ventricular fibrillation. Six (46%) of the 13 had an accessory conduction pathway and either atrial fibrillation (5 patients) or paroxysmal atrioventricular (AV) reentrant tachycardia (1 patient) that deteriorated into ventricular fibrillation. Three patients with AV node reentrant tachycardia and four with atrial fibrillation and enhanced AV node conduction presented with supraventricular arrhythmias that deteriorated into ventricular fibrillation. Patients were treated with medical, surgical or catheter ablative procedures designed to prevent recurrences of supraventricular arrhythmias. Four patients received an implanted automatic defibrillator, but none had an appropriate device discharge. Over a follow-up period of 41.6 +/- 33.6 months, 12 patients are alive without symptomatic arrhythmias. One patient died because of severe chronic lung disease and heart failure. Supraventricular tachycardia was the cause of aborted sudden death in approximately 5% of patients referred for evaluation of sudden cardiac death. Treatment directed at prevention of supraventricular tachycardia was associated with an excellent prognosis. Current treatment techniques appear to obviate the need for automatic defibrillator therapy in these patients.