Antiarrhythmic drug therapy for congestive heart failure with focus on moricizine

Interactions between pharmacologic and nonpharmacologic antiarrhythmic therapy

Whether patients with serious ventricular arrhythmias should be treated first with antiarrhythmic drugs or an implantable cardioverter-defibrillator (ICD) is not known. Many patients are ultimately treated with both an antiarrhythmic drug and on ICD. Early studies reported that 40-70% of patients who received an ICD were ultimately treated with an antiarrhythmic drug, although fewer patients are now being treated with both modalities. The beneficial interactions between antiarrhythmic drugs and an ICD are slowing of ventricular tachycardia, which yields improved hemodynamic tolerance; improved antitachycardia pacing and low energy cardioversion success; lowering of antiarrhythmic drug doses, which reduces the risk of side effects; limiting the number of arrhythmia episodes, which minimizes patients discomfort and prolongs ICD battery life; and preventing or slowing supraventricular tachyarrhythmias, which reduces the number of inappropriate shocks from the ICD. The disadvantages of combining pharmacologic therapy and the use of an ICD are the cost and side effects of both therapies. Adverse interactions between an ICD and antiarrhythmic drugs include slowed ventricular tachycardia, which may lead to failure to detect the arrhythmia; increased defibrillation and pacing thresholds; worsened hemodynamic tolerance of ventricular tachycardia; lengthened PR, QRS, or QT intervals causing multiple counting; and decreased size of the intracardiac electrogram, leading to failure to detect the ventricular tachycardia or fibrillation. Caution must be used when combining pharmacologic therapy with an ICD. Repeat electrophysiologic testing is frequently necessary after the initiation of antiarrhythmic drug therapy in a patient with an ICD to ensure successful therapy with the ICD.

Cardioversion, defibrillation, and overdrive pacing of ventricular arrhythmias: the effect of moricizine in dogs with sustained monomorphic ventricular tachycardia

The purpose of this investigation is to define whether the antiarrhythmic drug moricizine has beneficial or adverse effects on currently used antitachycardia and antifibrillatory devices. These studies were performed in a dog model of sustained monomorphic ventricular tachycardia (VT). In 11 dogs, the left anterior descending artery and all surrounding epicardial collateral feeder vessels were ligated. Defibrillator patches were implanted and the dogs were allowed to recover. After a 7-day recovery period, effective refractory period (ERP), end diastolic threshold (EDT), VT induction, and VT and ventricular fibrillation (VF) termination data were collected before and after moricizine infusion (2 mg/kg). In this experimental model, moricizine caused the following electrophysiological changes: a prolongation of the ERP from 173 +/- 14 to 182 +/- 15 (P < 0.02) with no significant effect on the EDT for pacing; a prolongation of the VT cycle length from 175 +/- 18 to 201 +/- 23 msec (P < 0.003); an increased cycle length required for overdrive pacing from 136 +/- 20 to 157 +/- 22 msec (P < 0.01); no effect on the energy required to cardiovert VT; an increase in the defibrillation threshold from 7.5 +/- 4 to 9.4 +/- 4 joules (P < 0.006) and; in 5 of the 8 dogs with VT, the VT could be initiated with somewhat less aggressive stimulation. Significant beneficial electrophysiological physiological effects were noted on the VT cycle length, including a proportionately prolonged overdrive pacing cycle length for VT termination.(ABSTRACT TRUNCATED AT 250 WORDS)

Ventricular arrhythmia in congestive heart failure

The importance of ventricular arrhythmia is based on its association with sudden death. In certain groups of patients, ventricular arrhythmia--primarily runs of nonsustained ventricular tachycardia (NSVT)--is associated with an increased risk for sudden death. Although this relationship has been most often reported in patients with recent myocardial infarction, it has also been recognized in patients with dilated cardiomyopathy, regardless of etiology. Therefore, ventricular arrhythmia is common in patients with CHF due to cardiomyopathy. A number of studies have reported that 70-95% of patients with cardiomyopathy and congestive heart failure (CHF) have frequent ventricular premature beats, and 40-80% will manifest runs of NSVT. Many factors are responsible for ventricular arrhythmia in such patients, including structural abnormalities, electrolyte imbalance, hemodynamic impairment, activation of neurohormonal mechanisms, and pharmacologic therapy. Many studies have reported a high yearly mortality in patients with cardiomyopathy and CHF; greater than 40% of deaths are sudden, most often the result of sustained ventricular tachyarrhythmia. Most studies have noted an association between presence (and frequency) of NSVT and risk of sudden cardiac death in these patients. Unfortunately, other techniques--such as the signal-averaged electrocardiogram and electrophysiologic testing--are not helpful in identifying the individual at risk. Although several drug interventions will reduce mortality from progressive CHF, these drugs have not been shown to reduce sudden death and, indeed, have a variable effect on ventricular arrhythmia. Although NSVT is a marker for increased risk for sudden death, it is uncertain if antiarrhythmic drugs will prevent this outcome. Antiarrhythmic drugs have not been shown to be effective for preventing sudden death, although there are as yet no well-controlled randomized trials. Several studies suggest that amiodarone and beta blockers are beneficial, but this requires confirmation. For patients who have been resuscitated following an episode of sudden death due to a sustained ventricular tachyarrhythmia, antiarrhythmic therapy guided by invasive and noninvasive techniques appears to reduce risk of recurrent arrhythmia. However, the response rate to antiarrhythmic agents is low and side effects are common in patients with CHF. Especially important is the increased risk of precipitating CHF and aggravating the arrhythmia being treated. For many such patients who have had serious ventricular tachyarrhythmia, the automatic implantable cardioverter defibrillator may prove a better option. Other drugs used for management of CHF reduce overall mortality, but not risk of sudden death.

Sudden death in patients with congestive heart failure: future directions

Sudden, unexpected cardiac death continues to be a major clinical problem in patients with congestive heat failure. This review summarizes the current state of knowledge regarding the identification and management of these patients. The roles of ambulatory ECG monitoring, electrophysiological testing, signal-averaged ECG, and other methods of predicting increased risk of sudden death are discussed. The modes of sudden cardiac death and the potential mechanisms of ventricular arrhythmias in congestive heart failure are reviewed. Current therapeutic options including antiarrhythmic drugs, neurohormonal blockade, and automatic implantable cardioverter defibrillators are discussed. Finally, future directions and ongoing clinical investigations of the management of these complex patients are considered.

Pharmacology and clinical use of a new group of antiarrhythmic drugs: derivatives of tricyclic nitrogen-containing systems

This paper is concerned with a new group of antiarrhythmic drugs: derivatives of phenothiazine and dibenzazepine which belong to tricyclic nitrogen-containing systems. It has been discovered that the transition from omega-aminoalkyl to omega-aminoacyl phenothiazine derivatives results in a decrease in psychotropic activity and an increase in cardiovascular, particularly antiarrhythmic, action. Based on structural and antiarrhythmic activity studies, the new and effective drugs ethmozine, ethacizine and bonnecor have been selected and extensively studied. Data on spectra and mechanisms of their action, obtained in different arrhythmia models, have been confirmed by clinical studies. Correlation between pharmacological properties and electrophysiological mechanisms, and differences in action of the drugs studied on brain and heart plasma membrane receptors may serve as a starting point for the further directed search for new antiarrhythmic drugs among tricyclic nitrogen-containing structures.