Degree of external force to the left ventricle determines hemodynamic response to nitroprusside in failing hearts: comparison with the response to dobutamine

Insights into the mechanism of the nitroprusside-induced increase in cardiac output in failing hearts: an attempt at its prediction with Doppler echocardiography

Increased left ventricular (LV) diastolic pressure is consistently decreased by the administration of nitroprusside; however, nitroprusside-induced changes in cardiac output (CO) vary among patients with failing hearts. Although the variation has been considered to be related to interindividual inhomogeneity of LV diastolic performance, nitroprusside-induced changes in CO are not predictable before drug administration in individual subjects. We attempted to clarify whether nitroprusside-induced changes in CO may be predicted by analysis of the mitral flow velocity pattern in failing hearts. LV diastolic pressure was increased by the combination of the decrease in LV function and the volume expansion, and 15 conditions with LV end-diastolic pressure (EDP) > or =15 mm Hg were obtained in 8 dogs. In each condition, pulsed Doppler mitral flow velocity patterns were recorded simultaneously with hemodynamic variables before and during intravenous nitroprusside infusion. After nitroprusside administration, LV systolic pressure and LVEDP decreased in all dogs, and CO increased in eight conditions but decreased in seven conditions. CO was more likely to increase with administration of nitroprusside, and its change was greater in the conditions in which deceleration time of the early diastolic filling wave before nitroprusside infusion was longer (r = 0.56, p<0.05, n = 15). Better correlation was obtained with multiple-regression analysis, using the deceleration time and peak filling velocity at atrial contraction (r = 0.67, p<0.05, n = 15). The deceleration time correlated with LV dynamic compliance (r = 0.66, p<0.01, n = 30). Analysis of mitral flow velocity patterns may be useful in predicting nitroprusside-induced changes in CO in failing hearts.

Role of basal release of nitric oxide in the presence of acute left ventricular dysfunction: comparative study with normal condition

The basal release of nitric oxide (NO) plays an important role in the regulation of vascular circulation in the presence of acute left ventricular dysfunction. It is not clear, however, whether the role is as important in the presence of acute left ventricular dysfunction as it is in the normal condition. In addition, the effects of flow rate on the role of basal NO have not been clarified in the presence of acute left ventricular dysfunction. This in vivo study was attempted to compare the contribution of the basal release of NO to the regulation of vascular circulation and the effects of a mechanically reduced basal flow rate on the contribution of basally released NO between the normal condition and acute left ventricular dysfunction. In eight anesthetized dogs, the responses of femoral artery blood flow to NG-monomethyl-L-arginine (L-NMMA, 10(-5)M) were observed with and without a reduction in basal flow. The same observation was performed after the production of acute left ventricular dysfunction by coronary microembolization. Without the reduction in basal flow, the L-NMMA-induced decrease in femoral artery flow was significantly larger in acute left ventricular dysfunction than in the normal condition (-40 +/- 12% vs-17 +/- 6%, P < .01). Under the reduction in basal flow, there was no significant change in flow during the infusion of L-NMMA in the normal condition and only a small decrease in acute left ventricular dysfunction. There was no significant difference in the L-NMMA-induced changes in flow between these conditions. The contribution of basally released NO to the regulation of vascular circulation is larger in the presence of acute left ventricular dysfunction than in the normal condition; however, the role of basal NO is reduced with a decrease in basal flow rate.