Hemodynamic effects of intravenous sematilide in patients with congestive heart failure: a class III antiarrhythmic agent without cardiodepressant effects

Atrial Fibrillation in Patients with Congenital Heart Disease

Advances in surgical techniques have led to the survival of most patients with congenital heart disease (CHD) up to their adulthood. During their lifetime, many of them develop atrial tachyarrhythmias due to atrial dilatation and scarring from surgical procedures. More complex defects and palliative repairs are linked to a higher incidence and earlier occurrence of arrhythmias. Atrial fibrillation (AF) is common in patients who have atrial septal defects repaired after age 55 and in patients with tetralogy of Fallot repaired after age 45. Patients with dextrotransposition of the great arteries who undergo Mustard or Senning atrial switch procedures have an increased risk of atrial flutter due to atrial baffle suture lines. Patients with Ebstein's anomaly are also prone to supraventricular tachycardias caused by accessory bypass tracts. Patients with a single ventricle who undergo Fontan palliation are at risk of developing persistent or permanent AF due to extreme atrial enlargement and hypertrophy. In addition, obtaining vascular access to the pulmonary venous atrium can present unique challenges during radiofrequency ablation for patients with a Fontan palliation. Patients with cyanotic CHD who develop AF have substantial morbidity because of limited hemodynamic reserve and a high viscosity state. Amiodarone is an effective therapy for patients with arrhythmias from CHD, but its use carries long-term risks for toxicity. Dofetilide and sotalol have good short-term effectiveness and are reasonable alternatives to amiodarone. Pulmonary vein isolation is associated with better outcomes in patients taking antiarrhythmic medications. Anticoagulants are challenging to prescribe for patients with CHD because of a lack of data that can be extrapolated to this patient population. Surgical ablation is the gold standard for invasive rhythm control in patients with CHD and should be considered at the time of surgical repair or revision of congenital heart defects. When possible, patients with complex CHD should be referred for care to an adult congenital heart disease center of excellence.

Antiarrhythmic drugs: new agents and evolving concepts

Properties of several new antiarrhythmic drugs are summarised in this review article. Recent concepts concerning their safety and efficacy of antiarrhythmics are discussed. A brief perspective on possible future strategies for pharmacotherapy of arrhythmias is provided.

Hemodynamic effects of antiarrhythmic compounds: intrinsic effects and autonomic modulation

Besides their proarrhythmic side-effects, most antiarrhythmic drugs exert varying degrees of depressant action on hemodynamics, which may limit their utility, especially in patients with compromised left ventricular function. Antiarrhythmic drugs have not only myocardial inotropic effects but also act on the coronary and peripheral circulation and the heart rate. Thus, sophisticated and appropriate experimental conditions are necessary to define the effect of their direct negative inotropic actions versus their circulatory effects and the impact of drug-induced autonomic modulation. This study describes an extended comparison of amiodarone, d-sotalol, d,l-sotalol, and dofetilide as class III antiarrhythmic drugs with the actions of several class I antiarrhythmic drugs in an open-chest model. The experimental model permits not only measurements in the intact circulation but also measurements of isovolumic indexes of contractility, which are independent of drug-induced changes in ventricular preload and afterload. Furthermore, after autonomic blockade, hemodynamic effects can be measured independently of modulatory adrenergic effects in such a model. d-Sotalol and amiodarone had cardiodepressant effects only at doses significantly higher than the highest doses used clinically. Dofetilide did not have a negative inotropic effect at doses up to 40 ng/kg. However, these results might be modified in experimental models with severely compromised left ventricular function, as was shown for class I antiarrhythmic drugs and for d,l- and d-sotalol. The sensitivity to a drug's negative inotropic action is markedly increased in functionally impaired myocardium. Furthermore, in a model of postischemic myocardial dysfunction, the depressant effect of d-sotalol could largely be avoided by previous autonomic blockade, indicating the importance of the residual beta-blocking potency of d-sotalol in the doses used in our experiments. Thus, in clinically relevant doses amiodarone, d-sotalol, and dofetilide were found to be devoid of negative inotropic actions in the setting of normal left ventricular myocardium. In failing hearts, such effects become more readily evident than they do in normal hearts after high doses of amiodarone and d-sotalol. From beta-blocking experiments in hearts with left ventricular dysfunction, it could be inferred that residual beta-blocking and other negative inotropic mechanisms may produce a net negative inotropic action, thus masking the minor positive class III effects postulated from in vitro experiments. These observations may have significant clinical implications, because they suggest that the intrinsic myocardial effects of antiarrhythmic drugs may be modified by autonomic effects, the status of ventricular function, and changes in preload and afterload.

Acute hemodynamic effects of intravenous ibutilide in patients with or without reduced left ventricular function

Many antiarrhythmic agents have adverse hemodynamic effects which limit their use in patients with impaired ventricular function or during tachyarrhythmias. Ibutilide is an intravenous, selective class III antiarrhythmic agent that is effective for conversion of atrial fibrillation or flutter. This multicenter, randomized, placebo-controlled, dose-ranging study evaluated the effects of intravenous ibutilide on hemodynamic parameters during invasive monitoring in 47 patients with or without reduced left ventricular ejection fraction (LVEF) > 35% or < or = 35%. Patients received either placebo or ibutilide as a 10-minute loading and a 30-minute maintenance infusion using 1 of the following dosing regimens: placebo then placebo (n = 12); 0.01 then 0.002 mg/kg (n = 12); 0.02 then 0.004 mg/kg (n = 12); or 0.03 then 0.006 mg/kg (n = 11). Ibutilide significantly increased QT and QTc intervals in a dose-related manner with mean increases ranging from 51 to 99 ms, but did not alter the PR interval or QRS duration. During ibutilide infusion, a few small but statistically significant changes from baseline in several hemodynamic variables were present. However, the changes in cardiac output, pulmonary artery or capillary wedge pressures, blood pressure, or heart rate in patients receiving ibutilide were not significantly different from the changes in patients receiving placebo. Thus, ibutilide did not cause clinically important adverse hemodynamic effects, even in patients with depressed ventricular function. One patient developed 2 episodes of nonsustained torsades de pointes during ibutilide. These results demonstrate that with careful monitoring for proarrhythmia, ibutilide can be used safely from a hemodynamic standpoint in the acute treatment of arrhythmias, even in patients with reduced ventricular function.

Hemodynamic effects of the class III antiarrhythmic drug, d-sotalol, in patients with congestive heart failure

In contrast to Vaughan Williams class I drugs, class III drugs, such as d-sotalol, may not be negative inotropic. These drugs block potassium ion channels and prolong repolarization, theoretically leading to improved contractility. We investigated the hemodynamic actions of acute intravenous administration of 1.5 mg/kg of d-sotalol in 28 patients with congestive heart failure randomized to receive placebo (n = 10) or active drug (n = 18) in a double-blind study. A Swan-Ganz catheter was placed in all patients > or = 16 hours before drug administration. All hemodynamic variables were assessed at baseline and 30 minutes and 1, 2, 4, 8, and 12 hours after administration of the drug. Electrocardiograms were obtained before and 1, 2, 4, and 12 hours after drug administration. The QT interval increased from 370 +/- 9 to 426 +/- 14 ms at 1 hour, whereas the QTc increased from 433 +/- 5 to 470 +/- 12 ms (both p < 0.001). The increase was still statistically significant at 12 hours. There was no change in the placebo group. Although heart rate decreased in the d-sotalol group (84 +/- 2 to 76 +/- 2 at 1 hour, p < 0.001), there were no changes in blood pressure or right atrial pressure. Cardiac index decreased slightly (2.0 +/- 0.2 to 1.9 +/- 0.1 mm Hg), consistent with the lower heart rate. Pulmonary capillary wedge pressure decreased from 18.9 +/- 2.4 to 17.9 +/- 1.9 mm Hg at 1 hour despite reduced cardiac index. We conclude that in contrast to class I, II, and IV antiarrhythmic drugs, d-sotalol exerts no clinically important acute hemodynamic actions at doses that produce electrophysiologic effects.