Evaluation of Aortic wall Distensibility in Anesthetized Dogs : Effects of Diltiazem on Aortic Pressure-Diameter Relationship

To study the effect of diltiazem (Dz) on aortic (Ao) pressure-diameter (P-D) relation, external diameter (D) of the thoracic Ao (sonomicrometry) and Ao pressure (AoP : micromanometer) were measured in 10 anesthetized dogs. The P-D relation from the point of 80msec after the dicrotic notch of AoP (t80) to that of 20msec after the peak of the next R wave in ECG (t20) was obtained every 30msec intervals. Ao occlusion immediately following the release of IVC occlusion was performed both before and after Dz (0.03mg/kg/min, over 10 minutes). The P-D relation in the whole range of AoP described a sigmoid curve in both conditions, and was fitted reasonably by a cubic equation (P=aD^3+bD^2+cD+d : a, b, c, d=constants