Antiarrhythmic drug therapy for sporadic ventricular ectopic arrhythmias

Exercise stress testing and 24-hour ambulatory monitoring have been employed to evaluate antiarrhythmic drug efficacy in patients with sporadic ventricular ectopic arrhythmias (VEA). Twenty-three patients with often recurring VEA were exercised 123 times and subjected to 66 ambulatory monitoring sessions during control periods and while receiving either procaine amide or quinidine. Two dose schedules were employed; procaine amide, 3.0 and 6.0 g daily and quinidine, 1.2 and 1.8 g daily. Though adequate and even high drug blood levels were reached, an effective antiarrhythmic response was observed in only eight patients receiving procaine amide and in seven of those taking quinidine. These modest successful results were associated with a high incidence of troublesome adverse effects which were noted in 11 patients receiving procaine amide and six of those receiving quinidine. It is concluded that these antiarrhythmic drugs should not be employed in the patient with episodic VEA unless the arrhythmias are symptomatic and are clearly life-threatening.

A comparison of the experimental anti-arrhythmic properties of acebutolol (M and B 17,803), propranolol and practolol

1 The beta-adrenoceptor blocking agent, acebutolol (M & B 17,803), has been compared with propranolol, practolol, lignocaine and quinidine for its ability to revert or prevent various types of experimental arrhythmias.2 By intravenous infusion, acebutolol had one half the potency of propranolol in reverting an established ouabain-induced ventricular arrhythmia in the anaesthetized dog. Practolol was ineffective in the conditions used.3 High oral doses of acebutolol or propranolol significantly increased the arrhythmic dose of ouabain in the conscious rabbit. Similar doses of practolol produced a significant decrease (i.e. potentiation) in the dose of ouabain required to produce arrhythmia. Lignocaine and quinidine showed no or little activity in this test.4 Propranolol, acebutolol and practolol were all effective in decreasing the frequency of ectopic beats induced by adrenaline and methylchloroform in the anaesthetized cat. Lignocaine and quinidine were only weakly effective.5 Acebutolol and propranolol were equally effective either intravenously or orally in reducing the incidence of ventricular fibrillation produced by chloroform in mice.6 It is suggested that the wide spectrum of experimental anti-arrhythmic activity of acebutolol coupled with its cardioselectivity may make it an interesting compound in the treatment of cardiac arrhythmias in man.

Electrophysiologic effects of procaine amide in patients with intraventricular conduction delay

In 16 patients with intraventricular conduction delay (IVCD) and cardiac arrhythmias, procaine amide (PA) was infused intravenously at rates of 30-40 mg/min until a maximum dose of 750-1,000 mg was administered. His bundle electrograms and plasma PA levels were obtained every 5 min during infusion and for 25 min thereafter. The mean peak PA level (10.2 ± 3.4 µg/ml) was achieved at the end of infusion. Mean control A-V nodal conduction times (A-H: 99.5 ± 34 msec) and A-H at peak PA levels (90 ± 15.3) did not differ significantly. However, the mean infranodal conduction time (H-Q) at peak PA (68.1 ± 14.8 msec) was significantly higher than control measurements (57.6 ± 13 msec) ( P < 0.001), with a mean percent increase of 18% (11 msec), and maximal prolongation of H-Q occurred at peak PA blood levels. There was no statistically significant correlation between maximum absolute or percent change in H-Q and control H-Q, control QRS duration, or peak PA levels. One patient with sinus bradycardia had further decreases in rate and a junctional rhythm after PA. Intravenous administration of PA appears safe and effective for patients with IVCD in terms of arrhythmia control and absence of high degree A-V block, ventricular ectopic beats, or standstill, but caution should be used in treating patients with sinus bradycardia.

Procaine amide against re-entrant ventricular arrhythmias. Lengthening R-V intervals of coupled ventricular premature depolarization as an insight into the mechanism of action of procaine amide

Nine patients with coupled ventricular premature depolarizations (VPDs) were treated with intravenous procaine amide to abolish the arrhythmia. The effect of procaine amide on the electrocardiogram was carefully observed. Seven patients were treated with intermittent intravenous therapy-100 mg of procaine amide was injected every five minutes-and two were treated by constant intravenous infusion-200 µg/min/kg body weight; blood for plasma procaine amide concentration was obtained 4.5 to 5 min after each dose. As the cumulative dose of procaine amide increased, plasma drug concentration increased and the frequency of coupled VPDs progressively decreased. Moreover, in every patient an interesting electrocardiographic phenomenon was observed: as plasma drug concentration increased, the coupling interval progressively increased until the arrhythmia was completely abolished. A hypothesis for procaine amide's antiarrhythmic action is offered based on this new observation. This hypothesis suggests that procaine amide prolongs conduction in the depressed portion of a re-entrant pathway such that conduction is further delayed and block finally occurs, thereby terminating the arrhythmia.

Long-term use of procaine amide following acute myocardial infarction

The safety of long-term prophylactic antiarrhythmic therapy with procaine amide was studied in 78 patients recovering from acute myocardial infarction. Patients were randomly allocated to a control or treatment group and followed monthly for up to 2 years with ambulatory ECG monitoring and measurement of serum drug level, antinuclear antibody (ANA) titer, LE preparation, blood count, BUN, and SGOT. Early reactions forced discontinuation of therapy in nine of 39 treated patients within the first 3 weeks. Late reactions were observed in 14 of 16 patients who took procaine amide for 3 months or longer. Every patient on therapy for 1 year or longer demonstrated elevation in ANA titer. Comparison of monitoring data between these two groups revealed no difference in the incidence of occasional or frequent premature ventricular beats. However, during the first 6 months, treated patients tended to have fewer major arrhythmias. There were fewer sudden deaths among treated patients, but this difference did not reach statistical significance at the 5% level. It is concluded that the high incidence of toxic reactions precludes widespread use of long-term prophylactic procaine amide therapy. More precise identification of a sudden death-prone population might justify such therapy in such selected cases.