Faster time to peak tension and velocity of shortening in right versus left ventricular trabeculae and papillary muscles of dogs.

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Abstract
Some of the mechanical characteristics of papillary muscles and trabeculae (n = 14) isolated from the free wall of the right ventricle of dogs were compared to those obtained from the free wall of the left ventricle (n = 14). Peak total tension (7.2 +/- 1.6 versus 7.9 +/- 1.7 g/mm2, p = NS) and peak velocity of tension development (31 +/- 8 vs. 28 +/- 4 g/mm2/sec, p = NS) were similar in both groups of muscles. However, right ventricular muscles shortened faster over nearly all loading conditions, and during isometric contraction, their time to attain peak total tension was shorter (336 +/- 26 vs. 401 +/- 42 msec, p less than 0.005) than that of left ventricular muscles. Varying stimulation rates (6, 12, 24, and 36 stimuli/min), increasing calcium concentration from 2.54 to 6.35 mM or adding norepinephrine 50 microM, did not significantly alter these differences. There were no differences in myosin isozymes (V1, V2, or V3) between ventricles to explain these differences. These results indicate that important mechanical differences exist between right and left ventricular myocardium and that these differences should be considered when extrapolations are made from myocardium of one area of the heart to another.