Effects of intravenous and oral disopyramide on paroxysmal atrioventricular nodal tachycardia

Supraventricular tachycardia

Supraventricular tachycardias (SVT) comprise those tachycardias that originate above the bifurcation of the bundle of His. They can be classified broadly as AV node dependent and AV node independent. The mechanism and clinical manifestation of SVTs, which is essential to their correct diagnosis, is reviewed. The therapeutic management of SVTs, including acute and chronic drug therapy and catheter ablation, is discussed also.

Adenosine and the treatment of supraventricular tachycardia

Adenosine has recently become widely available for the treatment of paroxysmal supraventricular tachycardia. In order to evaluate its role in the management of arrhythmias, we have reviewed the literature on the cellular mechanisms, metabolism, potential for adverse effects, and clinical experience of the efficacy and safety of intravenous adenosine. Adenosine produces transient atrioventricular nodal block when injected as an intravenous bolus. This is of therapeutic value in the conversion to sinus rhythm of the majority of paroxysmal supraventricular tachycardias, which involve the atrioventricular node in a re-entrant circuit. The mean success rate was 93% from over 600 reported episodes. Compared with other antiarrhythmic agents, adenosine is remarkable for its rapid metabolism and brevity of action, with a half-life of a few seconds. It commonly produces subjective symptoms, particularly chest discomfort, dyspnea, and flushing, which are of short duration only. No serious adverse effect has been reported. Arrhythmias may recur within minutes in a minority of patients. Comparative studies have shown that adenosine is as effective as verapamil in the treatment of supraventricular tachycardia, and has less potential for adverse effects. Patients with supraventricular tachycardia should initially be treated using vagotonic physical maneuvers. Immediate electrical cardioversion is indicated if the arrhythmia is associated with hemodynamic collapse. Adenosine is the preferred drug in those patients in whom verapamil has failed or may cause adverse effects, such as those with heart failure or wide-complex tachycardia. The safety profile of adenosine suggests that it should be the drug of first choice for the treatment of supraventricular tachycardia, but only limited comparative data to support this view are available at present.

Epinephrine-induced reversal of verapamil's electrophysiologic and therapeutic effects in patients with paroxysmal supraventricular tachycardia

The purpose of our study was to determine whether an infusion of epinephrine reverses the electrophysiologic effects of verapamil and whether reversal of verapamil's effects on the induction of paroxysmal supraventricular tachycardia (PSVT) by epinephrine during electropharmacologic testing is predictive of stress-related recurrences of PSVT during long-term treatment with verapamil. The infusion rates of epinephrine used in this study were 25 and 50 ng/kg/min, which previously have been demonstrated to result in plasma epinephrine concentrations in the range that occurs during a variety of stresses in humans. The subjects of this study were 17 patients with recurrent PSVT who underwent an electrophysiologic study in the control state and after at least 2 days of treatment with 240-480 mg/day verapamil. After assessing the response to verapamil, epinephrine was infused and testing was repeated. Verapamil significantly slowed atrioventricular conduction and prolonged refractoriness in the atrium and atrioventricular node. The effects of the two infusion rates of epinephrine were generally similar in magnitude and, therefore, the results were pooled. Epinephrine partially or completely reversed all of verapamil's electrophysiologic effects. Verapamil suppressed the induction of sustained PSVT in 15 patients. Epinephrine facilitated the induction of PSVT in seven of these 15 patients. All 15 patients were treated on a long-term basis with verapamil. The eight patients in whom epinephrine did not facilitate the induction of PSVT had no recurrences of PSVT during 9-18 months of follow-up.(ABSTRACT TRUNCATED AT 250 WORDS)

Pacemaker syndrome with AAI rate variable pacing: importance of atrioventricular conduction properties, medication, and pacemaker programmability

A patient who received an AAI Activitrax rate variable pacemaker for treatment of symptomatic sinus bradycardia is described. disopyramide prolonged the anterograde effective refractory period of the fast conducting atrioventricular (AV) nodal pathway to such an extent, that conduction switched to the slow AV nodal pathway at low atrial pacing rates. This gave rise to symptoms of the pacemaker syndrome during moderate exercise because the paced atrial event was conducted with a long, spike to Q interval with occurrence of the paced atrial event just after the preceding QRS complex. A change of medication solved this problem. Programming a bipolar electrode configuration avoided sensing of far-field QRS signals with the associated problems of resetting the basic pacing interval as well as the upper rate interval. AAI rate variable pacing requires careful evaluation of AV conduction properties, AV conduction intervals as well as the influence of medication to be given. The use of multiprogrammable pacemakers with marker channel capability will significantly facilitate the understanding and resolution of anomalous behavior.

Pirmenol in termination of paroxysmal supraventricular tachycardia

An assessment was made of the effect of pirmenol in the termination of paroxysmal supraventricular tachycardia (SVT). Sinus rhythm was restored by intravenous administration in 11 of 17 patients during a spontaneous attack. Another 8 patients were studied electrophysiologically. Pirmenol terminated an induced SVT in 3 of 5 patients having an atrioventricular (AV) intranodal re-entry mechanism but in none of 3 patients having an atrioventricular bypass tract as one re-entrant limb. The overall success in restoring sinus rhythm was 14 of 25 patients (56%). The drug was hemodynamically well tolerated even in cases of continued SVT. Pirmenol increased the atrial effective refractory period and had no obvious effect on AH and HV intervals. The functional refractory period of the AV node was decreased, probably by an anticholinergic effect. The effective and functional refractory periods of retrograde atrioventricular conduction via the AV node and bypass tract were increased in some patients. The mechanism terminating the AV intranodal SVT was a block in the retrograde part of the dual AV nodal pathway, a typical antiarrhythmic Class I effect.

Long-term therapy with disopyramide phosphate: side effects and effectiveness

In this study, the safety and efficacy of long-term therapy with disopyramide phosphate were evaluated in 40 patients with documented, recurrent, symptomatic tachyarrhythmias. Twenty-one (53%) of the patients had organic heart disease, and nine of these patients had compensated congestive heart failure. The tachyarrhythmias which were treated were paroxysmal supraventricular tachycardia (21 patients), paroxysmal atrial fibrillation (six patients), and paroxysmal ventricular tachycardia (13 patients). In each patient there was evidence, from continuous ECG monitoring or electrophysiologic testing, that disopyramide would be effective therapy, and each patient was able to tolerate disopyramide (no side effects or tolerable side effects) during an initial trial period of 1 to 2 weeks. Dosages of disopyramide were 400 to 1600 mg/day (994 +/- 320 mm/day). During long-term therapy, side effects were reported by 28 (70%) of the patients. The side effects were usually anticholinergic, and were usually a continuation of side effects noted during the initial trial period. None of the patients had idiosyncratic reactions to disopyramide. Most of the patients found side effects to be tolerable; however, in seven patients it was necessary to discontinue disopyramide after 1 to 8 (6 +/- 3) months. Actuarial incidence of intolerable side effects was 21 +/- 7% at 12 months. Nine (22%) of the 40 patients had symptomatic recurrences of tachyarrhythmia after 3 to 32 (15 +/- 9) months of therapy. Actuarial incidence of drug ineffectiveness was 32 +/- 10% at 24 months. Disopyramide was both effective and tolerated in 24 (60%) of the patients, who were followed for 2 to 64 (23 +/- 16) months.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute electrophysiologic effects of pirmenol in normal subjects and in patients with Wolff-Parkinson-White syndrome

The acute electrophysiologic effects of pirmenol are reported in 8 normal subjects and in 8 patients with Wolff-Parkinson-White (WPW) syndrome. Standard electrophysiologic testing was performed before and after a 50-mg intravenous bolus and a 60-minute infusion of 150 mg of pirmenol. After pirmenol administration, AH interval, atrial refractory period, atrioventricular (AV) nodal functional refractory period and Wenckebach cycle length did not change; however, sinus cycle length decreased from 743 +/- 169 to 650 +/- 133 ms (p less than 0.001), sinoatrial conduction time from 103 +/- 35 to 78 +/- 37 ms (p less than 0.05) and AV nodal effective refractory period from 308 +/- 51 to 272 +/- 23 ms (p less than 0.01). Pirmenol increased the HV interval from 43 +/- 5 to 48 +/- 6 ms (p less than 0.05) and ventricular functional refractory period from 247 +/- 21 to 260 +/- 21 ms (p less than 0.005). Anterograde effective refractory period of the accessory AV pathway increased in 4 of 6 patients with ventricular preexcitation and retrograde effective refractory period increased in all patients. Pirmenol treatment prolonged the shortest preexcited RR interval from 253 +/- 38 to 459 +/- 19 ms (p less than 0.05) and the average RR interval from 354 +/- 26 to 421 +/- 60 ms (p less than 0.01) during atrial fibrillation in all 6 patients with preexcitation. Pirmenol did not influence the inducibility or cycle length of AV reciprocating tachycardia in the patients with WPW syndrome. The pirmenol infusions were well tolerated.(ABSTRACT TRUNCATED AT 250 WORDS)