Ludbrook P A, Byrne J D, Kurnik P B, McKnight R C
Circulation. 1977 Dec;56(6):937-43. doi: 10.1161/01.cir.56.6.937.
To clarify the mechanisms of afterload reduction on left ventricular diastolic function, the influence of nitroglycerin upon ventricular diastolic pressure-volume relations was studied in 22 patients during catheterization. After nitroglycerin, average ventricular systolic pressure declined by 25 mm Hg (18%) and end-diastolic pressure by 7 mm Hg (28%) (P less than 0.005). End-systolic and diastolic ventricular volumes decreased by 37% and 23% respectively (P less than 0.005). Although peak negative dP/dt fell by 22% (P less than 0.0005), "T", an index of the time course of isovolumic diastolic ventricular relaxation, was insignificantly changed. Diastolic pressure-volume curves were significantly displaced downward and leftward without significant change in slope, suggesting that a family of pressure-volume curves for each ventricle with similar slope but positions depend upon immediate loading conditions. Absence of change in slope or of "T" suggests that this displacement may be mediated indirectly, perhaps by relaxation of extracardiac constraints to ventricular distensibility. Accordingly, improvement in ventricular function by vasodilators may be partly due to downward displacement of the pressure-volume relation, with associated reduction of wall tension and myocardial oxygen consumption.
为阐明后负荷降低对左心室舒张功能的作用机制，在22例患者心导管检查期间研究了硝酸甘油对心室舒张压力-容积关系的影响。应用硝酸甘油后，平均心室收缩压下降25 mmHg（18%），舒张末期压力下降7 mmHg（28%）（P<0.005）。收缩末期和舒张末期心室容积分别减少37%和23%（P<0.005）。虽然最大负dP/dt下降了22%（P<0.0005），但等容舒张期心室舒张时间过程的指标“T”无明显变化。舒张压力-容积曲线显著向下和向左移位，斜率无明显改变，提示每个心室的一族压力-容积曲线斜率相似但位置取决于即刻的负荷状态。斜率或“T”无变化提示这种移位可能是间接介导的，或许是通过心外对心室扩张性的限制因素的舒张。因此，血管扩张剂改善心室功能可能部分归因于压力-容积关系的向下移位，以及随之而来的壁张力和心肌氧耗的降低。
