Sustained ventricular arrhythmias: differences between survivors of cardiac arrest and patients with recurrent sustained ventricular tachycardia.

Clinical, angiographic, echocardiographic and electrophysiologic data were examined in 101 patients with a history of sustained ventricular arrhythmia not associated with acute myocardial infarction. These patients included 66 survivors of out of hospital cardiac arrest and 35 patients presenting with hemodynamically well tolerated sustained ventricular tachycardia. On univariate analysis, patients in the cardiac arrest group had a lower incidence of previous myocardial infarction and left ventricular aneurysm and a higher ejection fraction compared with the ventricular tachycardia group. During electrophysiologic testing, the arrhythmia induced in the patients in the cardiac arrest group was fast and polymorphic and frequently degenerated into ventricular fibrillation. In contrast, in the ventricular tachycardia group, a slower, monomorphic and hemodynamically well tolerated ventricular tachycardia was commonly induced. On multivariate analysis, a polymorphic pattern of the induced ventricular arrhythmia was the only independent variable that distinguished the survivors of cardiac arrest from those presenting with sustained ventricular tachycardia. These results suggest that 1) the survivors of cardiac arrest and patients presenting with sustained well tolerated ventricular tachycardia are clinically distinct groups; and 2) the polymorphic tachycardia induced during programmed electrical stimulation in the survivors of cardiac arrest may indicate an unstable tachycardia mechanism. This may explain why these patients present with ventricular fibrillation and cardiac arrest, whereas others present with hemodynamically stable ventricular tachycardia.

Tocainide for drug-resistant sustained ventricular tachyarrhythmias.

Eighty-two patients with drug-resistant ventricular tachycardia or fibrillation were treated with oral tocainide. Treatment in 54 patients, all with inducible ventricular tachycardia or fibrillation at baseline electrophysiologic testing, was based on the results of invasive electrophysiologic testing. Twenty-eight additional patients with frequent spontaneous ventricular tachycardia or no inducible arrhythmia during electrophysiologic testing were treated on the basis of the findings of electrocardiographic (ECG) Holter monitoring. Tocainide was effective in 7 (13%) and partially effective in 5 (8%) of the 54 patients in the electrophysiologic study group and was effective in 17 (61%) of the 28 patients in the ECG monitoring group. History of previous myocardial infarction and failure of response to lidocaine correlated with failure to respond to tocainide. Side effects were common both during initial therapy and during long-term treatment and necessitated discontinuation of tocainide therapy in 17% of the patients. At a mean follow-up period of 14 months, 13 patients are still receiving tocainide and are arrhythmia-free. In conclusion, the usefulness of oral tocainide in the management of drug-refractory sustained ventricular tachycardia or fibrillation is limited because of its low effectiveness and frequent side effects.

Intraoperative comparison of sequential-pulse and single-pulse defibrillation in candidates for automatic implantable defibrillators.

Sixteen survivors of cardiac arrest underwent intraoperative comparison of the effectiveness of sequential-pulse and single-pulse defibrillation. Defibrillation was tested alternately with the single-pulse or sequential-pulse technique 10 seconds into an episode of ventricular fibrillation that was induced with alternating current. The sequential-pulse defibrillation technique using truncated exponential pulses was performed with a right ventricular endocardial catheter and a left ventricular epicardial patch electrode. The first pulse was delivered between the right ventricular apical and the superior vena caval electrode on the right ventricular endocardial catheter. The second pulse was delivered between the right ventricular apical electrode and the left ventricular patch electrode 0.2 ms after termination of the first pulse. Single-pulse defibrillation was performed with a standard intracardiac defibrillation system in which a single truncated exponential pulse was delivered across 2 epicardial patch electrodes positioned over the anterolateral right ventricle and the posterolateral left ventricle. During defibrillation threshold determination, voltage and current waveforms were recorded and integrated to determine delivered energy. Average defibrillation threshold leading-edge voltage for the sequential pulse technique was 496 +/- 140 V, compared with 365 +/- 157 V for the single-pulse technique (p less than 0.005). Defibrillation threshold leading-edge current for the sequential-pulse technique was 6.0 +/- 2.3 A, compared with 10.6 +/- 5.1 A for the single-pulse method (p less than 0.0005).(ABSTRACT TRUNCATED AT 250 WORDS)

Intravenous adenosine in the prehospital treatment of paroxysmal supraventricular tachycardia.

STUDY OBJECTIVE: To determine the clinical efficacy and safety of IV adenosine administration in the field for the treatment of paroxysmal supraventricular tachycardia (PSVT). DESIGN: Prospective, consecutive case series. SETTING: An urban emergency medical services system. PARTICIPANTS: Thirty-seven adult patients in whom paramedics made the diagnosis of PSVT. INTERVENTIONS: Six milligrams of adenosine was administered by rapid IV bolus. If there was no effect within two minutes, a 12-mg bolus was given. This dose was repeated once if necessary. If there still was no effect, the medical command physician was contacted for further management. MEASUREMENTS: Vital signs, symptoms, and a single-channel ECG were recorded before, during, and after the administration of adenosine. RESULTS: On review of the ECG tracings, 26 patients (70%) were in PSVT. Eleven had rhythms other than PSVT on review, including five with atrial fibrillation, four with sinus tachycardia, and two with ventricular tachycardia. Of the 26 patients with PSVT, 23 (88%) converted to sinus rhythm after adenosine administration. Eleven patients were hypotensive at presentation. Seven of these were in PSVT and became hemodynamically stable on conversion with adenosine. The four hypotensive patients with rhythms other than PSVT (two with atrial fibrillation and two with ventricular tachycardia) had no change in blood pressure after adenosine administration. Nine patients were subsequently found to have wide-complex tachycardia. None of these patients suffered hemodynamic compromise after adenosine administration, and side effects were infrequent, mild, and transient. CONCLUSION: Adenosine appears to be effective and safe for the pre-hospital treatment of PSVT.