Twenty-three dogs were used for this study of cardiac mecanical efficiency. Seventeen point eight % (mean) of the artificially infarcted myocardium of the left ventricle were resected and sutured. The dogs were classified into two groups (5 effective, 5 noneffective). It was designated that the effective group showed no remarkable changes in left ventricular pressure (LVP), three hours after the infarctectomy in comparison with 30 minutes after infarctectomy, while the noneffective group showed a marked decrease. The datum in each experimental and operative stage was scored with the ratio to 100 % in control stage (intact stage). After infarctectomy, percentages to control values of stroke volume and stroke work were significantly lower than those of TTI and dp/dt/P50, which are generally admitted to be correlative to the myocardial oxygen consumption volume. This phenomenon was especially noted in the noneffective group. These facts would show that cardiac mechanical efficiencies differed in the two groups. Several parameters of the cardiac mechanical efficiency has been provided by the author. i) SW/TTI, ii) SW/(TTI-SV), [=(MEAOP-LVEDP)/TTI], (MEAOP: mean aortic pressure in ejection time, LVEDP: left ventricular enddiastolic pressure), iii) SW/(LVEDP-SV), [=(MEAOPLVEDP)/LVEDP], iv) ET(CI)･SW/(TTI-SV), [=ET(CI)･E(MEAOP-LVEDP)/TTI, (ET(CI): ejection time)]. The iv) parameter represents the ratio of impulse (force × time), which was calculated by using the cardiovascular formula of energy: Wp=P(t)-Q(t)dt in both the numerator and the denominator. SW=∮P(t)･△QAdt=△QA･∮P(t)dt=△QA･TTIAOP,∮P(t)･△Qvdt=△Qv･∮P(t)dt=△Qv･TTI(LVP), ∮P(t)･△QAdt/∮P(t)･△Qvdt=(△QA/△Qv)(TTI(AOP)/TTI(LVP)), (△QA: mean ejection volume, △QV: mean LV volume, during one beat). Therefore, assuming that △QA/△QV=K(constant): if an individual and physiological condition of heart, for instance, as the value of ejection fraction is constant, then, the iv) parameter represents the ratio of energy-the cardiac mechanical efficiency. Circulating blood volume had less influence upon these parameters of efficiency than upon SV and SW. When SV and SW showed significant depression after infarctectomy also in the effective group, these parameters of efficiency showed no remarkable change in the effective group, but these parameters of efficiency showed significant difference between the effective group and the noneffective group. Judging the results of the various data of parameters, it was considered that the hearts were overworking also in the effective group, and these cardiac mechanical efficiencies decreased in the noneffective group, moreover, the hearts of those group fell into decompensation. The prognosis was poor in the case in which cardiac mechanical efficiency decreased when cardiac work was relatively increased by infarctectomy, and suture; and the improvement of the efficiency for the heart would be necessary. Therefore parameter i), ii), iii) and iv) may be valuable indicators of the cardiac mechanical efficiency, as far as TTI correlates with myocardial oxygen consumption volume.
心(筋)機械効率 (Cardiac efficiency)
心筋梗塞切除術 (Myocardial infarctectomy)
心機能指標 (Cardiac function's parameter)