Adrenergic control of the force-frequency and relaxation-frequency relations in patients with hypertrophic cardiomyopathy

Exercise-induced enhancement of the force-frequency and relaxation-frequency relations has been studied in conscious animals but not in intact diseased human hearts. We evaluated left ventricular (LV) isovolumic contraction (dP/dt(max)) and relaxation (tau) during atrial pacing and dynamic exercise...

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Published inCirculation (New York, N.Y.) Vol. 96; no. 9; pp. 2959 - 2968
Main Authors IZAWA, H, YOKOTA, M, TAKEICHI, Y, INAGAKI, M, NAGATA, K, IWASE, M, SOBUE, T
Format Journal Article
LanguageEnglish
Published Hagerstown, MD Lippincott Williams & Wilkins 04.11.1997
American Heart Association, Inc
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Summary:Exercise-induced enhancement of the force-frequency and relaxation-frequency relations has been studied in conscious animals but not in intact diseased human hearts. We evaluated left ventricular (LV) isovolumic contraction (dP/dt(max)) and relaxation (tau) during atrial pacing and dynamic exercise in 13 patients with nonobstructive hypertrophic cardiomyopathy (HCM) and 7 control subjects to investigate the influence of exercise on the force-frequency and relaxation-frequency relations. Group A consisted of 6 patients in whom the heart rate (HR)-dP/dt(max) relation was markedly enhanced during exercise (88+/-30%) compared with during pacing (34+/-15%). Group B consisted of 7 patients in whom the HR-dP/dt(max) relation showed similar enhancement during exercise (28+/-7%) and atrial pacing (28+/-11%). There was no difference in the HR-tau (derivative method [TD] and pressure half-time method [T(1/2)]) relation between pacing and exercise in groups A and B. Both the mean maximal wall thickness and the hypertrophy score in group B were greater than in group A (27+/-5 versus 19+/-2 mm and 7+/-1 versus 5+/-1 points, respectively; both P<.01). There was no difference in the LV peak systolic pressure, end-diastolic pressure, or the plasma level of catecholamines at baseline, at 50 W of exercise, and at peak pacing between groups A and B. The HR-dP/dt(max) relation in the control group was markedly enhanced during exercise (80+/-27%) compared with during pacing (32+/-14%). The HR-tau relation in the control group was enhanced during exercise (TD, 35+/-9%; T(1/2), 34+/-8%) compared with during pacing (TD, 12+/-7%; T(1/2), 14+/-7%). Exercise-induced enhancement of the relaxation-frequency relation was inhibited in all HCM patients, regardless of the degree of LV hypertrophy. The patients without exercise-induced enhancement of the force-frequency relation had more severe LV hypertrophy than the patients with the enhancement, indicating that the adrenergic control of the force-frequency relation may, at least in part, depend on the severity of LV hypertrophy or the stage of HCM.
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ISSN:0009-7322
1524-4539
DOI:10.1161/01.CIR.96.9.2959