Rate Control

Abstract

The control of ventricular rate plays an important role in the management of patients with atrial fibrillation, decreasing symptoms and improving cardiac function, exercise capacity, and quality of life.1–3 Oral or intravenous agents are routinely administered to achieve adequate control of the ventricular rate by modulating atrioventricular nodal function. The systemic effects of calcium channel antagonists and β-adrenergic receptor antagonists on blood pressure and other adverse effects, however, may limit use of these agents in some patients. In other patients, it may be difficult to achieve adequate rate control with the use of pharmacological agents. Article p 2383 In their article in this issue of Circulation , Sigg et al4 describe the novel approach of delivering pharmacological agents via a luminal catheter secured to the region of the atrioventricular node. Using a steerable electrophysiological catheter, they locate the His bundle potential and the coronary sinus ostium and display these positions in 2 orthogonal planes. The luminal catheter is screwed into the myocardium, and third-degree atrioventricular block resulting from the injection of a 1-mg dose of acetylcholine is used to confirm the proper positioning of the luminal catheter. The authors demonstrate that varying degrees of atrioventricular nodal blockade may be achieved by continuous infusion of acetylcholine at rates between 10 and 200 μg/min. In comparison, the intravenous injection of 1 mg acetylcholine did not cause atrioventricular block in any animal, demonstrating that a significant part of the effect of the direct luminal infusion was local. The authors provide histological evidence that the luminal catheter was positioned within or near the edge of the triangle of Koch, confirming the accuracy of the positioning method. In addition, no significant histological …