Electrophysiologic and electrocardiographic consequences of congestive heart failure

In order to determine the effect of altered autonomic tone in patients with reduced left ventricular function and congestive failure on atrioventricular conduction, the refractory periods of the A-V conducting system were compared in forty-five patients with normal left ventricular function and fifteen patients with a left ventricular end-diastolic pressure greater than 12 mmHg and a left ventricular ejection fraction less than 50% with symptoms of congestive failure. All patients in the study had resting heart rates of 90 beats per minute or less. Patients with congestive failure were found to have a significant reduction in the functional refractory period of the A-V node (390 +/- 29 msec versus 430 +/- 38 msec; P less than 0.01) and the effective refractory period of the total A-V conducting system (275 +/- 34 msec versus 311 +/- 45 msec; P less than 0.01). In addition, patients with congestive failure had a higher incidence of aberrant conduction of premature atrial contractions (14 of 15 versus 22 of 45; P less than 0.01) and a significantly higher incidence of left bundle branch aberration (50% versus 20%; P less than 0.01). The results indicate significant facilitation of A-V nodal conduction in patients with congestive failure probably due to enhanced sympathetic activity and decreased parasympathetic inhibition. These findings may increase the ability of the clinician to understand electrophysiologic changes in congestive heart failure.