Broughton A, Korner P I
Am J Physiol. 1983 Jul;245(1):H33-41. doi: 10.1152/ajpheart.1983.245.1.H33.
We studied three isovolumic indexes of contractility, i.e., dP/dtmax, dP/dtDP40, and (dP/dt)/TPmax, in normal dogs and in a matched group of chronically hypertensive dogs with left ventricular hypertrophy (LVH) [DP40, developed LV pressure of 40 mmHg; TP, total LV pressure above atmospheric]. The LVH was moderate in degree with the LV-to-body weight ratio 50% greater than in normal dogs. The experiments were performed under pentobarbital with open chest, autonomic blockade, and independent control of mean left atrial pressure (LAP) and mean aortic pressure (MAP). We found that dP/dtmax provided the most consistent comparison of inotropic state in the two groups under both basal conditions and with norepinephrine (NE). The other indexes occurred too early in systole to reflect complete LV activation, particularly during the infusion with NE. Under controlled conditions basal dP/dtmax of LVH dogs was 1.28 times the value of normal dogs, with the increase accounted for by the amplifier effect of the increase in LV mass. But with moderate lowering of aortic pressure, inotropic state was more easily compromised in LVH than in normal dogs. With steady-state stimulation by infusing increasing amounts of NE, dP/dtmax rose by 10 times basal in both LVH and normal dogs at maximum stimulation. The absolute value of the index was 1.31 times higher in the LVH group, with the amplifier effect thus the same as under basal conditions. The results suggest that basal and maximal inotropic states are normal in LVH under optimum loading conditions.
我们研究了正常犬以及一组与之匹配的患有左心室肥厚（LVH）的慢性高血压犬的三个等容收缩力指标，即dp/dtmax、dp/dtDP40和(dp/dt)/TPmax [DP40，左心室压力升至40 mmHg时的压力变化；TP，左心室高于大气压的总压力]。LVH程度为中度，左心室与体重之比比正常犬大50%。实验在戊巴比妥麻醉下进行，开胸，自主神经阻断，并独立控制平均左心房压力（LAP）和平均主动脉压力（MAP）。我们发现，在基础状态和使用去甲肾上腺素（NE）时，dp/dtmax能最一致地比较两组的心肌收缩状态。其他指标在收缩期出现过早，无法反映左心室的完全激活，尤其是在输注NE期间。在受控条件下，LVH犬的基础dp/dtmax是正常犬的1.28倍，增加的部分是由左心室质量增加的放大效应导致的。但是，随着主动脉压力适度降低，LVH犬的心肌收缩状态比正常犬更容易受损。通过输注递增剂量的NE进行稳态刺激时，在最大刺激下，LVH犬和正常犬的dp/dtmax均比基础值升高了10倍。该指标的绝对值在LVH组中高1.31倍，因此放大效应与基础条件下相同。结果表明，在最佳负荷条件下，LVH的基础和最大心肌收缩状态是正常的。
