May 18, 1999

Altered force-frequency relation in hypertrophic obstructive cardiomyopathy

Basic Research in Cardiology
U SchottenC Schumacher

Abstract

The present study was designed to test the hypothesis that in hypertrophied myocardium of patients with hypertrophic obstructive cardiomyopathy (HOCM) a reduced contractile reserve provided by frequency dependent potentiation of force of contraction contributes to the myocardial dysfunction. Myectomy was performed in 8 HOCM patients with normal systolic left ventricular function at rest. Nonfailing myocardium from the hearts of three multiorgan donors was investigated for comparison. In thin myocardial strips we measured the inotropic effects of different stimulation frequencies (0.5-3.0 Hz) at different extracellular Ca2+ concentrations (1.8-16.2 mmol/l). At 1.8 mmol/l extracellular Ca2+ concentration, increasing stimulation rates had no positive inotropic effect in HOCM myocardium, whereas in nonfailing myocardium force of contraction increased up to 3 Hz. Increasing extracellular Ca2+ concentrations induced a positive force-frequency relation in HOCM with a maximum at 5.4 mmol/l Ca2+. A further increase to 16.2 mmol/l Ca2+ resulted in a negative force-frequency relation in these specimens. The time to peak tension and the time to relaxation decreased at increasing stimulation frequencies at all Ca2+ concentrations investigat...Continue Reading

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Mentioned in this Paper

Myocardial Contraction
Extracellular
Calcium
Hypertrophic Cardiomyopathy
Hypertrophy
Contraction (Finding)
Myocardial Dysfunction
Myocardium
Left Ventricular Function
Cardiomyopathies

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