Influence of Reduction of Preload and Afterload by Nitroglycerin on Left Ventricular Diastolic Pressure-Volume Relations and Relaxation in Man
Influence of Reduction of Preload and Afterload by Nitroglycerin on Left Ventricular Diastolic Pressure-Volume Relations and Relaxation in Man
复制标题
硝酸甘油降低前负荷和后负荷对人左心室舒张压-容积关系和舒张的影响
作者：
P. Ludbrook;J. Byrne;P. Kurnik;R. C. McKnight
为探讨后负荷减少对左室舒张功能的影响机制，观察了22例患者留置导尿管时硝酸甘油对左室舒张压-容量关系的影响。服用硝酸甘油后，平均心室收缩压下降了25毫米汞(18%)，舒张末压下降了7毫米汞(28%)(P<；0.005)。收缩末期和舒张期心室容量分别减少37%和23%(P<；0.005)。尽管负峰值dp/dt下降了22%(P<；0.0005)，但反映等容舒张期心室舒张期时间进程的指标“T”却没有显著变化。舒张压-容量曲线明显向下和向左移动，斜率没有明显变化，这表明每个具有相似斜率但位置取决于即刻负荷条件的心室的一系列压力-容量曲线。斜率或“T”没有变化表明这种移位可能是间接调节的，可能是通过放松心外对心室扩张性的限制。因此，血管扩张剂对心功能的改善可能部分是由于压力-容量关系的下移，伴随着室壁张力和心肌耗氧量的减少。
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%percnt;) and end-diastolic pressure by 7 mm Hg (28%percnt;) (P < 0.005). End-systolic and diastolic ventricular volumes decreased by 37%percnt; and 23%percnt; respectively (P < 0.005). Although peak negative dP/dt fell by 22%percnt; (P < 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.