Response of resistant ventricular tachycardia to bretylium. Relation to site of ectopic focus and location of myocardial disease

What is New in Pharmacologic Therapy for Cardiac Resuscitation?

Antiarrhythmic therapy can be a critical component of cardiac resuscitation. Therapies in this area have seen little advance in the last decade. Bretylium, a very old drug, has been reintroduced for ventricular tachycardia/ventricular fibrillation (VT/VF) therapy. There are still important questions to be addressed with bretylium: when to administer (first- or second-line) and at which dose. These questions and the development of newer agents will be areas of future research.

Efficacy of bretylium tosylate for ventricular tachycardia

In 20 patients with inducible ventricular tachycardia (VT), intravenous bretylium tosylate infused as a 10-mg/kg bolus followed by 2 mg/min caused no change in refractory periods and did not suppress inducibility of VT. The use of bretylium for the treatment of VT should be reexamined.

Evolution and revolution in drug labeling: regulation of antiarrhythmic drugs by the Food and Drug Administration 1962-1996

Between 1962, when the Kefauver-Harris Drug Amendments were passed, and 1996, 20 pharmaceutical compounds were approved and labeled by the FDA as effective antiarrhythmic drugs for some specified cardiac arrhythmia. Drug research and development in the 1970s and 1980s were focused on treatment of premature ventricular beats as a marker for sudden cardiac death and ventricular tachycardia. The Cardiac Arrhythmia Suppression Trial in 1989 irrevocably altered this approach. Recent drug development programs have targeted atrial fibrillation (AF) as epidemiologic data have predicted an increase in the incidence of AF as the United States population ages, and as treating premature ventricular beats has fallen from favor. The FDA, the scientific community, and the pharmaceutical industry have all participated in and been affected by this evolution in drug development.

Bretylium: relations between plasma concentrations and pharmacologic actions in high-frequency ventricular arrhythmias

Although it is widely assumed that the early arrhythmogenic and pressor responses to bretylium are caused by catecholamine release from the adrenergic neuron, this assumption has not been systematically studied in humans. Pharmacologic responses to a placebo infusion and 3 separate bretylium infusions (2.5, 5.0, 10 mg/kg over 60 minutes) were assessed in 6 patients with recurrent, nonsustained ventricular tachycardia. Plasma bretylium concentration, blood pressure (BP), plasma norepinephrine (NE) concentration, arrhythmia frequency and adrenergic neuronal blockade (assessed by the presence or absence of reflex venoconstriction) were measured. Adrenergic blockade was seen with every bretylium infusion and at a time when relatively small amounts of bretylium had been administered (range 160 to 750 mg, median 252). Temporal relations (p less than 0.03) were noted among the time of onset of adrenergic neuronal blockade, onset of the pressor response, increase in NE plasma concentration and increase in ventricular arrhythmia frequency. BP responses during the infusions were linearly related to change in plasma NE at the time of development of adrenergic neuronal blockade. Bretylium plasma concentrations higher than 3 micrograms/ml were frequently associated with a short-lived pressor response. There was a significant relation (p less than 0.06) between the increase in plasma NE during the infusion and an increase in ventricular arrhythmia frequency. Reduction in arrhythmia frequency was seen in only 1 patient, beginning 6 hours after the development of adrenergic neuronal blockade.(ABSTRACT TRUNCATED AT 250 WORDS)

Therapy with conventional antiarrhythmic drugs for ventricular arrhythmias

Conventional antiarrhythmic drugs are an important tool for the clinical cardiologist for the treatment of ventricular arrhythmias. Knowledge of the different properties of these drugs will help decrease the incidence of adverse effects and increase the frequency of successful therapy.

Electrophysiologic effects of bretylium on canine ventricular muscle during acute ischemia and reperfusion

Electrophysiologic effects of bretylium were assessed on a recently developed animal model for analysis of conduction of premature impulses and excitation threshold. Bretylium was administered intravenously 10 mg/kg over 10 minutes followed by 2 mg/min of infusion immediately after coronary ligation. Conduction of the premature impulse was recorded in the epicardial and endocardial sites both in the base-to-apex and apex-to-base directions, in the normal, in the center, and across the border of ischemic myocardium. Compared to the control group of animals, bretylium did not cause any significant change in the conduction characteristics in the ischemic myocardium; however, it delayed the conduction of premature impulses in the normal myocardium. Thus the disparity in conduction times between the normal and the ischemic myocardium was lessened by bretylium. Further, conduction of impulses from normal tissue across the border of ischemia was also delayed. Bretylium also decreased the excitability threshold in the ischemic myocardium, although the normal myocardial excitation threshold was unaffected. These unique effects of bretylium on conduction and excitability in the normal, in the center, and across the border of ischemic myocardium, when a therapeutic dosage of the drug is used, further validate its antiarrhythmic potential and offer an insight into its mechanism of action in the setting of acute myocardial ischemia.

Electrophysiologic testing of bretylium tosylate in sustained ventricular tachycardia

We used programmed ventricular stimulation to test intravenous bretylium tosylate in 10 consecutive patients with inducible sustained ventricular tachycardia (usually refractory to type I antiarrhythmic agents). These 10 patients had previously documented sustained ventricular tachycardia and/or ventricular fibrillation complicating stable heart disease. Following control inductions of sustained ventricular tachycardia, bretylium 10 mg/kg was infused over 30 minutes. Thirty minutes after this infusion, sustained ventricular tachycardia could be induced in 9 of the 10 patients (one of these nine patients also had bretylium-potentiated spontaneous ventricular tachycardia). Tachycardia induced in the nine patients after bretylium was similar to control tachycardia with respect to morphology and cycle length (333 +/- 16 msec after bretylium versus 330 +/- 16 msec during control). However, five of the nine patients tolerated induced tachycardia less well after bretylium (exacerbated hypotension). In one patient, ventricular tachycardia could not be induced after intravenous bretylium.

Severe hypotension due to the use of bretylium for postcardiotomy ventricular arrhythmias

We describe three patients who developed refractory hypotension after the administration of bretylium tosylate for postoperative ventricular ectopy. In one patient, the administration of vasopressors and fluid restored the blood pressure, but in the other two patients these measures failed, necessitating open-heart cardiac massage. The hemodynamic effects of bretylium are unpredictable; therefore, this drug should be used cautiously in the treatment of postcardiotomy ventricular arrhythmias.

Electrocardiographic ischemic ST-T changes and ventricular premature systoles

41928 consecutive electrocardiograms were statistically analyzed for the presence of ventricular premature systoles (VPSs) and ischemic ST-T changes in different age groups. VPSs were found in 2314 tracings, whereas signs of myocardial ischemia were noted in 10448 records. VPSs appeared to be more prevalent in the presence of ischemic changes than in the absence of ischemia, and those VPSs in cases with ischemic changes showed a higher correlation with aging. 456 electrocardiograms were then selected to correlate the morphology of VPSs and the areas of myocardial ischemia based on the following criteria: (1) VPSs with the same morphology were present in both limb and precordial leads, and (2) only one representative record was used on each patient who had more than one tracing showing VPSs. It was found that, especially in cases with inferior or anterolateral wall ischemia, right bundle branch block (RBBB) type VPSs appeared to arise from these ischemic areas, whereas such a correlation was less evident in left bundle branch block (LBBB) type VPSs. Although LBBB type VPSs were generally considered benign, those with superiorly oriented QRS axes appeared to be more closely associated with organic cardiac lesions than those with inferiorly oriented axes. Clinical significance of the morphology of VPSs may thus be substantiated.

Bretylium tosylate as initial treatment for cardiopulmonary arrest: randomized comparison with placebo

To evaluate the therapeutic effectiveness of intravenous bretylium tosylate as a first-line drug for patients in cardiopulmonary arrest, a randomized, double-blind study was conducted, comparing bretylium with a normal saline placebo. Fifty-nine patients presenting to the emergency department with cardiopulmonary arrest due mainly to ventricular fibrillation or asystole initially received either bretylium (10 mg/kg) or placebo in a rapid intravenous bolus and were then otherwise treated according to standard American Heart Association guidelines. If ventricular fibrillation or asystole persisted, a second bolus of bretylium or normal saline was given after 20 minutes. Thirty-five percent of patients presenting with ventricular fibrillation or asystole who received bretylium were successfully resuscitated, whereas 6% of patients who received placebo survived (P less than 0.05). These findings serve to suggest that the early use of bretylium tosylate in cardiopulmonary arrest improves survival.

Comparison of bretylium tosylate and lidocaine in management of out of hospital ventricular fibrillation: a randomized clinical trial

Bretylium tosylate was compared with lidocaine hydrochloride as initial drug therapy in 146 victims of out of hospital ventricular fibrillation in a randomized blinded trial. An organized rhythm was achieved in 89 and 93 percent and a stable perfusing rhythm in 58 and 60 percent of the patients who received bretylium and lidocaine, respectively. After initiation of advanced life support, an organized rhythm was first established after an average of 10.4 minutes and 10.6 minutes in the two respective groups, requiring an average of 2.8 defibrillatory shocks in those who received bretylium and 2.4 in the lidocaine-treated patients. Comparable numbers of patients were discharged from the hospital: 34 percent of those given bretylium and 26 percent of the patients whose initial therapy was lidocaine. No instance of chemical defibrillation was observed with either drug. In this study, bretylium afforded neither significant advantage nor disadvantage compared with lidocaine in the initial management of ventricular fibrillation.

Clinical implication of surface morphology of ventricular premature contractions

VPC morphology was studied in the surface 12-leads ECGs (resting) in one hundred and thirty-six patients over a none-month period (January-September, 1978). Seventy four (54%) of these had coronary artery disease proven by cardiac catheterization (61) or by evidence of acute transmural myocardial infarction (13) diagnosed by ECG and serum enzyme study. Twenty-three of the patients (17%) had other organic heart diseases documented by cardiac catheterization. The remaining thirty-nine (29%) were healthy individuals. Three common types of VPCs are recognized as right, left and septal in origin. There is no significant difference in the prevalence of these types in the presence of heart disease (right, 35%, left 31%, and septal 34%). However if septal VPCs are considered along with left VPCs, these are twice as common as right VPCs. VPCs occurring in healthy individuals are overwhelmingly (74%) right ventricular in origin. In general, VPCs are most likely to occur in the presence of ventricular dyssynergy and multiple coronary arterial lesions.

Intravenous disopyramide phosphate and ventricular overdrive pacing in the termination of paroxysmal ventricular tachycardia

Both antiarrhythmic drugs and bursts of rapid ventricular pacing provide alternatives to DC cardioversion for the treatment of paroxysmal ventricular tachycardia. This report considers the individual and combined success of burst ventricular pacing and intravenous disopyramide phosphate in the tretment of 11 examples of paroxysmal ventricular tachycardia. Rapid ventricular pacing, at a rate of up to 50 beats/min faster than the tachycardia rate terminated 7 of the tachycardias. Intravenous disopyramide resulted in increased tachycardiac cycle length (342 +/- 34 ms-385 +/- 56 ms), increased QRS complex width (147 +/- 42 ms-180 +/- 41 ms) and termination of 8 the tachycardias. The remaining 3 tachycardias could be terminated by bursts of ventricular pacing following the infusion of disopyramide. Of these, 2 could not be terminated prior to disopyramide. The use of both techniques allowed the extinction of all 11 tachycardias and prevented the need to proceed to DC conversion.

Superiority of practolol versus propranolol in protection against ventricular fibrillation induced by coronary occlusion

The ability of practolol and propranolol of prevent ventricular fibrillation in experimental anterior myocardial infarction was compared in dogs subjected to ligation of the left anterior descending and first septal coronary arteries. This procedure, which causes ventricular fibrillation in 90 percent of animals within 30 minutes, was performed in control dogs and in dogs pretreated with propranolol (0.5 mg/kg body weight) or with practolol (1.5 to 2.5 mg/kg). These doses produced nearly equivalent shifts in isoproterenol-induced chronotropic dose-response curves, indicating equivalent degrees of beta adrenergic blockade. In 21 dogs with confirmed ligation, cardiogenic shock did not develop. Six of seven control dogs died with ventricular fibrillation. Six of seven dogs pretreated with propranolol also had fibrillation, whereas only one of the seven dogs pretreated with practolol manifested ventricular fibrillation during the 45 minute postligation observation period. Practolol afforded significant protection compared with no treatment or treatment with propranolol (P less than 0.05).

Origin of so-called right and left ventricular arrhythmias in acute myocardial ischemia

The anatomic origin of ventricular arrhythmias occurring immediately after coronary arterial ligation was studied in 32 dogs. The electrocardiogram and seven single or composite bipolar electrograms were recorded from various sites within and surrounding the ischemic area in the left and right ventricles. Delay and fragmentation in the activation of the epicardial ischemic zone of the left ventricle, bridging diastole, preceded the appearance of ventricular arrhythmias and were continuous during the rhythm disorders. So-called left and right ventricular arrhythmias were associated with similar delay and fragmentation in left ventricular ischemic epicardial activity. Multiple and simultaneous activation of both the right and left ventricles produced ventricular fusion premature complexes. Multiple exit points increased before ventricular fibrillation occurred. The ultimate origin of premature ectopic impulse formation in the ventricles is not necessarily related to one or more exit points in either ventricle. Ischemic damage to the heart produces ventricular arrhythmias that appear to originate from both ventricles. The site of origin of ventricular arrhythmias should not be the sole factor in assessing the benign or malignant properties of the arrhythmia.

Resistant ventricular tachycardias and recurrent cardiac arrests. 96 episodes

A 66-year-old man suffered an acute myocardial infarction complicated by multiple episodes of ventricular tachycardia and 96 episodes of ventricular fibrillation requiring cardioversion over a period of 55 days. Following ventricular aneurysmectomy, the ventricular tachycardia persisted. This converted to regular sinus rhythm with a regimen of disopyramide phosphate, quinidine, and propranolol.