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European Heart Journal 1995 16(Supplement C):2-7; doi:10.1093/eurheartj/16.suppl_C.2
Copyright © 1995 by the European Society of Cardiology.
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© 1995 The European Society of Cardiology

Myocyte reorganization in hypertrophied and failing hearts

N. R. Alpert, L. A. Mulieri, G. Hasenfuss* and C. Holubarsch*

Department of Molecular Physiology and Biophysics, University of Vermont College of Medicine Burlington, Vermont 05405
* University of Freiburg, Division of Cardiology Freiburg, Germany

Correspondence; N. R. Alpert. Department of Molecular Physiology and Biophysics, University of Vermont College of Medicine Burlington, Vermont 05405

In hypertrophied and failing hearts there are major changes in the overall contractile performance. We present a review of our previous work relating the alterations in myocardial force, work, power and relaxation, that lead to changes in overall ventricular performance, to changes in the actin-myosin cross-bridge cycle characteristics along with the degree of activation and inactivation (calcium cycling). Tissues from hypertrophied rabbit and failing human (volume overload, dilated car-diomyopathy) heart were used in these studies. Myocardial peak twitch tension (mN.mm–2) was reduced in dilated car-diomyopathy (human) (25.9 ± 3.9 vs 13.9 ± 2.0, 37°C), volume overload (human) (44.0 ±11.7 vs 19.9 ± 3.7, 21°C) and pressure overload (rabbit) (461 ± 2.6 vs 41.7 ± 50, 21°C). We used myothermal and mechanical data to analyse the average cross-bridge force time integral and the amount of calcium cycled per gram per beat. Tension-dependent heat (mJ.g–1) (TDH) (cross-bridge cycling) and tension-independent heat (mJ.g") (T1H) were reduced in all of the experimental preparations (dilatedcardiomyopathy, human, 377°C: TDH, 3.39 ± 0.59 vs 1.34 ± 0.22; TIH, 0.51 ± 0.02 vs 0.16 ± 0.03) (volume overload, human 21"C: TDH, 7.23 ± 2.22 vs 1.92 ± 0.25; TIH, 0.75 ± 0.19 vs 0.39 ± 0.04) (pressure overload, rabbit, 21"C: TDH, 6.60 ± 0.75 vs 305 ± 0.46; TIH, 1.00 ± 0.17 vs 0.41 ± 0.08). The cross-bridge force-time integral (pNs, pico Newton seconds) was increased in all experimental preparations (dilated cardiomyopathy, 138%; volume overload, 175%; pressure overload, 253%), while in each of the experimental preparations, the amount of calcium cycled (nmoles.beat-g) is reduced (expressed as % control) (dilated cardiomyopathy, 36%; volume overload, 53%; pressure overload, 46%). The decrease in power observed in these hearts and the inadequate cardiac output in the failing hearts are attributed to these documented changes in the contractile and excitation contraction coupling systems

Key Words: Cross-bridge cycling • calcium cycling • failing and non-failing human hearts • pressure overload rabbit hearts • myothermal analysis • mechanical analysis


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