title: Characterization of oscillations in ventricular refractoriness in man after an abrupt increment in heart rate.
abstract: Oscillations in ventricular myocardial refractoriness after a change in rate have not been described in man. During 25 baseline paced cycle lengths (SB-SB) of 400 to 800 msec in 14 patients, a shorter cycle length (S'-S') was introduced that was 10 to 20 msec (mean 15 +/- 5) greater in duration than the ventricular effective refractory period (VERP) determined after 12 beats of the respective baseline cycle length (group 1 trials). In addition, during 14 of the 25 baseline cycle lengths, a second shorter cycle length was introduced that was 50 to 80 msec (mean 65 +/- 10) greater than the VERP of the respective baseline cycle length (group 2 trials). In all 39 group 1 and group 2 trials the VERP was determined after each of at least 3 beats (S'1, S'2, S'3) of the shorter cycle length and in six of the 25 group I trials the VERP was determined after each of at least 12 beats of the shorter cycle length. In all group 1 trials oscillations of the VERP were observed, with a mean S'1 VERP of 202 +/- 28 msec, an S'2 VERP of 228 +/- 25 msec (p less than .001 vs S'1 VERP), and an S'3 VERP of 210 +/- 26 msec (p less than .001 vs S'2 VERP). Oscillations dampened within 4 beats, but persisted at a lower amplitude in four of the six group I trials during which the shorter cycle length was maintained for at least 12 beats.(ABSTRACT TRUNCATED AT 250 WORDS)
mesh_terms: D000200:Action Potentials; D000328:Adult; D002304:Cardiac Pacing, Artificial; D005260:Female; D006321:Heart / Q000502:physiology; D006339:Heart Rate; D006801:Humans; D008297:Male; D008875:Middle Aged; D009200:Myocardial Contraction; D013997:Time Factors