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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)

Characterization of oscillations in ventricular refractoriness in man after an abrupt increment in heart rate.