Is the adaptation of right ventricular refractoriness to an abrupt increase in heart rate impaired in chronic heart failure?
Chronic heart failure is associated with a high risk of ventricular arrhythmias and sudden death, although the mechanisms leading to these arrhythmias are not fully understood. To determine if the adaptation of ventricular refractoriness to an abrupt increase in heart rate is impaired in heart failure, electrophysiologic findings in 11 patients with structurally normal hearts (group I) were compared to findings in 28 patients with chronic heart failure (mean left ventricular ejection fraction 0.23 +/- 0.05). Heart failure was due to coronary artery disease in 14 patients (group II) and to idiopathic dilated cardiomyopathy in 14 patients (group III). The effective refractory period at the right ventricular apex was measured during unipolar cathodal pacing at twice diastolic threshold following a 12-beat ventricular drive at a cycle length of 600 msec. The pacing cycle length was then decreased to 400 msec for one, two, and three beats and the refractory period was determined for each beat at the faster rate. For each beat the mean refractory periods of group II and III patients were similar and were significantly longer than those of group I patients (p less than 0.01). The refractory period progressively shortened at the 400 msec cycle length and the percent decrease for each beat was similar among all three groups (p greater than 0.10). In the group II and III patients there was no correlation of the refractory period or change in refractory period with the pulmonary artery, right atrial, and pulmonary capillary wedge pressures.(ABSTRACT TRUNCATED AT 250 WORDS)
Denardo
S J
SJ
Department of Medicine, UCLA School of Medicine.
Stevenson
W G
WG
D000328:Adult; D005117:Cardiac Complexes, Premature / Q000503:physiopathology*; D002304:Cardiac Pacing, Artificial; D002311:Cardiomyopathy, Dilated / Q000503:physiopathology; D003327:Coronary Disease / Q000503:physiopathology; D004562:Electrocardiography; D005260:Female; D006329:Heart Conduction System / Q000503:physiopathology; D006333:Heart Failure / Q000503:physiopathology*; D006339:Heart Rate; D006352:Heart Ventricles / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D013575:Syncope / Q000503:physiopathology*; D013617:Tachycardia, Supraventricular / Q000503:physiopathology*