Metoprolol--a new cardioselective beta-adrenoceptor blocking agent for treatment of tachyarrhythmias

Drug therapy of sustained ventricular tachyarrhythmias. Is there still a role?

This article provides a review of the risks faced by patients with sustained ventricular tachycardia (VT) or ventricular fibrillation (VF) in the absence of a reversible or transient cause so that the goals of therapy can be clearly defined. The therapeutic approaches that have been proposed to achieve these goals are outlined and evidence comparing these various approaches to therapy is then summarized in order to propose an algorithm for the optimal use of antiarrhythmic drug therapies as primary therapy for selected VT/VF patients. Options for the ancillary uses of antiarrhythmic drug therapies in ICD patients are considered.

Multifocal atrial tachycardia: mechanisms, clinical correlates, and treatment

MAT is an uncommon arrhythmia most often seen in elderly patients with chronic pulmonary disease who are critically ill due to acute respiratory or cardiac decompensation. Its importance lies in the fact that it is commonly mistaken for AF, since both disorders are characterized by narrow ventricular complexes, irregular rates, and (depending on the ECG lead observed in MAT) by an apparent lack of P wave activity. This may lead to treatment with digoxin, a drug known to be ineffective in the therapy of MAT, with the potential for producing toxicity in patients who are predisposed. The incidence of MAT in hospitalized patients in various studies ranges from 0.13% to 0.40%. The mechanism of the arrhythmia is thought to be triggered activity arising from increased intracellular calcium stores that may be produced by hypokalemia, hypoxia, acidemia, and increased catecholamines, characteristics commonly found in patients with MAT. COPD, coronary artery disease, CHF, and infection (both pulmonary and nonpulmonary) are the most common clinical settings of MAT. Mortality is very high in all patients studied, ranging from 38% to 62%, and is due to their underlying disease processes and not to the arrhythmia. The need for intubation and mechanically assisted ventilation portends a particularly poor prognosis for survival. Treatment should initially consist of correction of the precipitating causes, as it is common for patients to convert to sinus rhythm both spontaneously and after these measures are taken.(ABSTRACT TRUNCATED AT 250 WORDS)

Antiarrhythmic efficacy of solitary beta-adrenergic blockade for patients with sustained ventricular tachyarrhythmias

To assess the efficacy and predictability of solitary beta-adrenergic blocker (BB) therapy for ventricular tachyarrhythmia (VT), 30 patients (16 men and 14 women) with a mean age of 55 years, who initially had sustained ventricular tachycardia (70%) or ventricular fibrillation (30%), were studied. Results of baseline arrhythmia tests showed VT on ECG monitoring in 57% of the patients, during exercise in 50%, induced by programmed stimulation in 69%, increasing to 86% during isoproterenol. BB therapy prevented inducible VT during programmed stimulation in 37% of the patients, prevented VT on ECG monitoring in 54%, and prevented VT during exercise in 83%. Long-term BB therapy was given to 24 of 30 patients, whereas six other patients with hemodynamically unstable VT during BB therapy received other long-term treatment. During a mean follow-up of 824 days, 6 of 24 patients had recurrent VT. BB therapy was discontinued in two patients because of side effects. Long-term success was predicted by left ventricular ejection fraction greater than 45%, absence of coronary disease, and age less than 60 years (all p less than 0.02). Neither suppression of arrhythmia during exercise testing, nor results of programmed stimulation or ECG monitoring were predictive of outcome. Thus beta-adrenergic blockers can be effective as solitary antiarrhythmic therapy in selected patients with VT.

Cardiac dysrhythmia associated with general anaesthesia for oral surgery. Its prevention by the prophylactic use of an oral beta-adrenergic blocker

Ninety patients, divided randomly into three groups, received either no metoprolol, 50 mg or 100 mg metoprolol as an oral premedication. The electrocardiogram was monitored throughout the procedure. It was found that both doses of metoprolol significantly reduced the incidence of cardiac dysrhythmia.

The use of a selective beta-adrenergic receptor blocker for the preoperative preparation of thyrotoxic patients

Metoprolol, a cardioselective beta-blocker, was used in two asthmatic, thyrotoxic patients in preparation for thyroidectomy. Adequate reduction in resting heart rate was achieved in both individuals without inducing clinically significant airway obstruction. Beta-1-blockade can be selectively employed in this clinical setting, but patients should be hospitalized and closely monitored for adverse effects on pulmonary function. Metoprolol therapy in patients with reversible airway obstruction is discussed with reference to recent studies on relative cardioselectivity.

Metoprolol in anaesthesia for oral surgery. The effect of pretreatment on the incidence of cardiac dysrhythmias

Metoprolol, a cardioselective beta-adrenergic blocking drug, was given, with a placebo as an alternative, in a double-blind trial to 60 patients who were undergoing removal of third molar teeth under general anaesthesia. Dyshythmias occurred in significantly fewer patients in the metoprolol group than in the control group, and when ventricular dyshythmias occurred they were abolished in every case by the administration of metoprolol. It is concluded that metoprolol is effective in preventing cardiac dysrhythmias occurring during oral surgery carried out under general anaesthesia.

Effects of metoprolol on heart rate in patients with digitalis treated chronic atrial fibrillation

Adequate control of ventricular rate in patients with chronic atrial fibrillation (AF) may not be achieved with digitalis alone. In the present study the additional effect of two different doses (50 mg and 50 +/- 50 mg) of oral metoprolol, a new selective beta-blocking agent, on ventricular rate in patients with longstanding AF has been studied. A decrease in the mean ventricular rate during rest and during exercise at various work loads was observed after both doses. The effect was more pronounced at the highest work load of 80 W, both after 50 mg (p less than 0.002) and after 50 +/- 50 mg (p less than 0.01) of the drug. A high initial heart rate at rest or during exercise was reduced more by the drug than a lower one. Exercise tolerance was reduced in 2 patients. These results suggest that patients with AF in whom satisfactory control of heart rate cannot be achieved with digitalis alone may benefit from addition of individualized metoprolol therapy.