Ambulatory sudden cardiac death: mechanisms of production of fatal arrhythmia on the basis of data from 157 cases

Prognostic role of inducible ventricular tachycardia in patients with dilated cardiomyopathy and asymptomatic nonsustained ventricular tachycardia

We studied the prognostic relevance of inducible ventricular tachycardia in 32 patients with dilated cardiomyopathy and spontaneous nonsustained asymptomatic ventricular tachycardia. Programmed ventricular stimulation included basic drive cycle lengths of 600, 500, 430, 370, 330 and 300 msec at single, double, and triple extrastimuli. Ventricular tachycardia (greater than or equal to 6 beats) was initiated in 7 patients (22%), with sustained monomorphic ventricular tachycardia being seen in 4 of them. During median follow-up of 21 months (13-44), 14 patients died. Sudden cardiac death occurred in two of the seven patients with inducible tachycardia and in only one of the 25 patients in whom it was not possible to induce tachycardia. Although patients with inducible tachycardia did not differ clinically from those in whom tachycardia could not be induced, the projected mean survival time was significantly shorter in those with inducible tachycardia (10 months vs. 32 months, P = 0.04). For late sudden cardiac death, the positive predictive value of inducible tachycardia was 28%. The negative predictive value was 96%. We conclude that induction of ventricular tachycardia by programmed stimulation might indicate poorer prognosis in patients with dilated cardiomyopathy.

Electrocardiographic J waves after resuscitation from cardiac arrest

A patient was monitored prior to, during, and after cardiac arrest with a Holter monitor and an electrocardiograph. The arrest occurred without any premonitory signs on the ECG. At the onset of the arrest, torsades de pointes ventricular tachycardia occurred, which quickly degenerated into ventricular fibrillation. After a successful second defibrillation, the patient developed Osborn waves, which subsided within a few minutes.

Clinical profile of patients with Chagas' disease before and during sustained ventricular tachycardia

Sustained ventricular tachycardia was diagnosed in 15 patients undergoing ordinary activity with Chagas' disease seen at our Institute from 1978 to 1989. Palpitations were observed in 11 (66%) of the patients, dyspnea in 7 (46%), atypical chest pain in 5 (33%) and syncope in 2 (13%). Cardiac arrhythmia was detected in 4 (26%) on physical examination. The resting electrocardiogram showed premature ventricular contractions in 13 (86%) patients, ST-T changes in 12 (80%), left axis deviation in 9 (60%) and right bundle branch block in 4 (26%). Chest X-rays showed mild cardiomegaly in 8 (53%) and moderate cardiomegaly in 3 (20%) patients. Mild left ventricular dysfunction was detected echocardiographically in 1 (10%), moderate in 3 (30%) and severe in 1 (10%) of the 10 patients studied. During sustained ventricular tachycardia, dyspnea was found in 7 of 15 (46%) patients, palpitations in 6 (40%), atypical chest pain in 6 (40%), syncope in 1 (6%), systemic arterial hypotension in 3 (20%) and cardiogenic shock in 2 (13%). The electrocardiographic findings were as follows: mean heart rate was 201 bpm; mean QRS lengthening was 0.16 sec; right bundle branch block plus right axis deviation was seen in 5 of 15 (33%) patients; right bundle branch block plus left axis deviation in 4 (26%); and a positive concordance of all precordial leads in 5 (33%) patients. Based on these findings, we conclude that the majority of patients with Chagas' disease who develop sustained ventricular tachycardia do not have severe myocardial disease, show an uncommon electrocardiographic pattern of this arrhythmia, and most importantly, have a benign clinical course.

Incidence of ventricular arrhythmias during transient myocardial ischemia in patients with stable coronary artery disease

To determine the incidence of ventricular arrhythmias related to episodes of transient myocardial ischemia during ambulatory electrocardiographic (ECG) monitoring, 97 patients with stable angina pectoris, angiographically proved coronary artery disease and an abnormal exercise test were studied. A total of 573 episodes with ST segment depression were documented: in 118 episodes (21%) the patients were symptomatic and in 455 (79%) they remained asymptomatic. Ventricular arrhythmias (greater than 5 premature ventricular beats/min, bigeminy, couplets or salvos of premature ventricular beats) occurred during 27 (5%) ischemic episodes in a subset of 10 patients (10%) (group A). The other 87 patients (90%) (group B) showed exclusively ischemic episodes without ventricular arrhythmias. Comparison of patients in group A and group B showed no differences in hemodynamic, angiographic, exercise testing and ambulatory ECG monitoring data. Ischemic episodes with and without ventricular arrhythmias showed a similar duration and amplitude of ST segment depression and a comparable heart rate at the onset of ischemia. Both types of ischemic episodes, with and without arrhythmias, occurred predominantly during the morning hours between 6:00 AM and noon, and both types remained asymptomatic to within similar percentages. The data demonstrate that ventricular arrhythmias are related to transient myocardial ischemia in only a few patients with stable angina pectoris; these arrhythmias are related neither to the degree of ischemia during ambulatory ECG monitoring nor to the occurrence of anginal symptoms.

Recasting the approach to the treatment of potentially malignant ventricular arrhythmias after the CAST study

The best therapeutic approach to the therapy of potentially malignant ventricular arrhythmias is still unknown, particularly in view of the increased mortality with flecainide and encainide shown in the CAST study. Various ongoing studies, particularly with amiodarone, will show whether better results can be obtained with other agents. Flecainide and encainide do, however, have a restricted place when other agents cannot be used. Low-dose amiodarone with low-dose flecainide may be worth trying.

Sudden arrhythmic cardiac death--mechanisms, resuscitation and classification: the Seattle perspective

Ventricular fibrillation (VF) is the first recorded arrhythmia in 75% of patients who have a sudden cardiovascular collapse. Rarely (1%) does sustained ventricular tachycardia (VT) alone cause collapse and unconsciousness. Whether all VF begins as VT is unknown. Early application of cardiopulmonary resuscitation and rapid defibrillation are essential to ensure survival and satisfactory neurologic recovery. During the last 2 years in Seattle, the initial resuscitation rate for VF was 269 of 447 patients (60%), with 114 of 447 patients (26%) surviving long-term. Survivors of VF have a high overall risk of recurrent VF, with many univariate risk factors identified: evidence of poor left ventricular function (history of congestive heart failure, prior myocardial infarction [MI] or low ejection fraction), extensive coronary artery disease, absence of a new MI (either Q wave or non-Q wave) with VF, male gender, advanced age, complex or high-frequency ventricular ectopy on Holter recording, inducibility at electrophysiologic study, exercise-induced angina or hypotension, and smoking. Classification of cardiac deaths as arrhythmic or nonarrhythmic is important in interpreting the therapeutic response. However, because many patients have chronic symptoms, timing of the onset of a new event is difficult. Furthermore, accurate timing of an event does not guarantee correct classification. Sudden death is not necessarily arrhythmic, nor is all arrhythmic death sudden. Total cardiac mortality may be a simpler and more relevant end point to measure the overall effect of antiarrhythmic therapy.

From concept to standard-of-care? Review of the clinical experience with automated external defibrillators

There is now both national and international acceptance of the "principle of early defibrillation," which contends that whoever arrives first at the scene of a cardiac arrest should have a defibrillator. The almost revolutionary technological event that permits widespread implementation of this principle has been the development of automated external defibrillators (AEDs). The simplicity, accuracy, and safety of these devices markedly expands the range of people who can deliver early defibrillation, which includes minimally trained emergency personnel, lay and community responders, and family members of high-risk patients. Even though AEDs now approach the status of "standard of care," the AED, as an example of a new technology, has not followed the classic technology paradigm: conceptualization, experimentation, dissemination, and standard of care. Instead, like many other technical innovations in emergency medicine, the development of AEDs proceeded simultaneously on many fronts, and implementation often occurred before confirmation of important subissues. AEDs may experience the life cycle of many new ideas: initial enthusiasm and widespread adoption, followed by disillusionment and rejection, and finally a mature, proper perspective. Careful implementation and continued evaluation may help emergency personnel avoid periods of disillusionment with AEDs and move steadily and uneventfully to a proper perspective.

Diverse mechanisms of unexpected cardiac arrest in advanced heart failure

To define the mechanisms of unexpected cardiac arrest in advanced heart failure, we reviewed the causes of cardiac arrest as established from electrocardiographic monitoring and from clinical and autopsy data in patients hospitalized for cardiac transplantation evaluation and management of advanced heart failure (mean left ventricular ejection fraction, 0.18 +/- 0.08) who were stable while on vasodilator and diuretic therapy such that hospital discharge to home was anticipated. Twenty-one cardiac arrests occurred in 20 of 216 (9%) such patients during a 4-year period. Heart failure was due to coronary artery disease with prior myocardial infarction in 13 patients and nonischemic cardiomyopathy in seven patients. The rhythm at the time of arrest was severe bradycardia or electromechanical dissociation (BA/EMD) in 13 (62%) patients. The precipitating cause of the BA/EMD arrest was coronary artery thrombosis or embolism in two patients, pulmonary embolism in one patient, hyperkalemia in two patients, and unexplained hypoglycemia in one patient. In seven of 13 (54%) patients, a precipitating cause of the bradycardia arrest could not be established. Only eight of 21 (38%) arrests were due to ventricular tachycardia or fibrillation (VT/VF), and all occurred in patients with prior myocardial infarction (p = 0.02 vs. BA/EMD arrests). Two VT/VF arrests were due to acute or recent infarction, and one patient had hyperkalemia. The patients who suffered a BA/EMD arrest were similar to those who had a VT/VF arrest in age, ventricular arrhythmia history, ventricular function, and serum potassium levels. Serum sodium levels were lower in patients with BA/EMD arrests (129 +/- 3 vs. 133 +/- 4 meq/l, p = 0.025).(ABSTRACT TRUNCATED AT 250 WORDS)

Prevalence of silent myocardial ischemia in survivors of cardiac arrest

The prevalence and type of ischemia (silent vs painful) in survivors of cardiac arrest not associated with acute myocardial infarction were studied to test the hypothesis that survivors may have an increased prevalence of silent ischemia. Of 48 survivors of cardiac arrest over a 4-year period who had undergone exercise testing, 24 met inclusion criteria. These 24 subjects had documented ventricular fibrillation and coronary artery disease proven by cardiac catheterization or a previous electrocardiographic pattern of myocardial infarction. Thirteen of 24 (54%) had a positive treadmill stress test (greater than or equal to 1.0 mm flat or downsloping ST depression). The mean resting left ventricular ejection fraction was 43%. Nine of 11 patients (82%) who had exercise radionuclide studies performed had ischemic abnormalities (less than 5% increase in left ventricular ejection fraction with new or worsened wall motion abnormalities). Thus, 16 of 24 (67%) had a positive treadmill stress test or radionuclide ventriculogram. Only 1 of 16 (6%) had painful ischemia (p less than 0.001 relative to an even distribution of painful vs painless ischemia). Thus, survivors of cardiac arrest have a high prevalence of exercise-induced ischemia, and in most the ischemia is silent.