Myocyte reorganization in hypertrophied and failing hearts.

Abstract

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 cardiomyopathy) heart were used in these studies. Myocardial peak twitch tension (mN.mm-2) was reduced in dilated cardiomyopathy (human) (25.9 +/- 3.9 vs 13.9 +/- 2.0, 37 degrees C), volume overload (human) (44.0 +/- 11.7 vs 19.9 +/- 3.7, 21 degrees C) and pressure overload (rabbit) (46.1 +/- 2.6 vs 41.7 +/- 5.0, 21 degrees 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-1) (TIH) were reduced in all of the experimental preparations (dilated cardiomyopathy, human, 37 degrees C: TDH, 3.39 +/- 0.59 vs 1.34 +/- 0.22; TIH 1.51 +/- 0.02 vs 0.16 +/- 0.03) (volume overload, human 21 degrees 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 degrees C: TDH, 6.60 +/- 0.75 vs 3.05 +/- 0.46; TIH, 1.00 +/- 0.17 vs 0.41 +/- 0.08).(ABSTRACT TRUNCATED AT 250 WORDS)