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 ) .
C0018827
ventricular
C0018787
hearts