Contractile Filament Stress: Comparison of Different Disease States in Man
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Citation:The Ohio Journal of Science. v78, n5 (September, 1978), 259-266
Cardiac catheterization data on 39 patients was classified in 5 cardiovascular groups: normal, compensated volume overload, decompensated volume overload, compensated pressure overload, and congestive cardiomyopathy. Both the Lagrangian stress and contractile filament stress for the circumferential axis and the longitudinal axis were computed over a complete cardiac cycle. Contractile filament stress was 24% higher than Lagrangian stress in the circumferential direction, and 43% higher than Lagrangian stress in the longitudinal direction. The percent difference in stress between the contractile filament stress and Lagrangian stress was greatest for patients with pressure overload, and least for patients with compensated volume overload. No significant difference in calculated wall stress was noted between the normal group and the 4 pathological groups. Circumferential velocity of the contractile element occurring at peak stress was plotted as a function of peak contractile filament stress and patients with compensated pressure overload exhibited high values of both velocity and peak stress. Patients with congestive cardiomyopathy showed low values of both velocity and peak stress. Circumferential velocity of the contractile element occurring throughout the cardiac cycle was plotted as a function of both the instantaneous Lagrangian stress and the instantaneous contractile filament stress, resulting in 2 stress-velocity curves for each patient. The value of the maximum velocity extrapolated from either stress-velocity curve was approximately the same, but the maximum stress extrapolated from the contractile filament stress-velocity curve was significantly higher than the maximum stress extrapolated from the Lagrangian stressvelocity curve. The product of peak contractile filament stress in the circumferential direction times heart rate was a clinically useful index of myocardial oxygen consumption, and predicted a lower rate of oxygen consumption than did the product of peak developed stress times heart rate.
Author Institution: Department of Engineering and Department of Physiology, Wright State University
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