Impaired force-frequency relations in patients with hypertensive left ventricular hypertrophy - A possible physiological marker of the transition from physiological to pathological hypertrophy

Background-The extent to which force-frequency and relaxation-frequency rel ations (FFR and RFR, respectively) and exercise-induced adrenergic stimulat ion affect myocardial inotropic and lusitropic reserves has not been establ ished in patients with left ventricular (LV) hypertrophy (LVH). Methods and Results-We calculated the maximum first derivative of LV pressu re (LV dP/dt(max)) and the LV pressure half-time (T-1/2) during pacing, exe rcise, and isoproterenol infusion in 17 patients with hypertensive WH and 9 control subjects to investigate the influence of increases in heart rate ( HR) and adrenergic stimulation on inotropic and lusitropic reserves. Group A consisted of 10 LVH patients who showed a progressive increase in the HR- LV dP/dt(max) relation. Group B consisted of 7 LVH patients in whom the HR- dP/dt(max) relation at physiological pacing rates was biphasic. The LV mass index was larger and the LV ejection fraction was smaller in group B than in group A (244+/-72 g/m(2) versus 172+/-22 g/m(2) and 55 +/- 18% versus 72 +/-6%, respectively; both P<0.05). The increase in LV dP/dt(max) was seater during exercise than pacing alone for similar increases in HR in all group s (P<0.05) (group A, 111+/-22% versus 25+/-14%; group B, 105+/-355 versus 1 4+/-10%; control, 111+/-24% versus 25+/-12%). T-1/2 was shorter (P<0.05) du ring exercise than with pacing alone in all groups (group A, 41+/-6% versus 11+/-3%; group B, 38+/-9% versus 14+/-4%; control, 44+/-6% versus 12+/-5%) . Isoproterenol infusion caused similar increases in LV dP/dt(max) and simi lar decreases in T-1/2 in all groups. Conclusions-The FFR was biphasic in patients with seven LVH irrespective of LV function but was preserved in patients with less severe LVH and control subjects. Importantly, the RFR and adrenergic control of both inotropic an d lusitropic reserves were well preserved in all LVH patients. A biphasic F FR at physiological pacing rates may be one of the earliest markers of the transition from physiological adaptation to the pathological process in LVH patients.