A Randomised Study of the Haemodynamic Changes Induced by Venodilatation and Arteriolar Dilatation Singly and Together in Left Ventricular Failure Complicating Acute Myocardial Infarction

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Abstract
A randomised between-group study of the immediate haemodynamic effects of venodilatation by intravenous isosorbide dinitrate infusion (50–200 μg/kg/h) and arteriolar dilatation by intravenous hydralazine bolus (0.15 mg/kg) given either in random sequence (Groups 1 and 2; n = 12) or simultaneously (Group 3; n = 6) was undertaken in 18 men with radiographic and haemodynamic evidence (left ventricular [LV] filling pressure greater than 20 mm Hg) of LV failure 6–19 h following acute myocardial infarction. Control measurements (1 h) preceded either two consecutive 90-min treatment periods (Groups 1 and 2) or a single 90-min period (Group 3). Given independently, both drugs reduced systemic arterial pressure and vascular resistance, whereas only isosorbide dinitrate reduced LV filling pressure and only hydralazine increased cardiac output and stroke volume. Isosorbide dinitrate/hydralazine in combination significantly reduced LV filling pressure, systolic and diastolic arterial pressure, and total systemic vascular resistance. Cardiac output, stroke volume, and heart rate were increased. In conclusion, combined arteriolar dilatation and venodilatation appears to be of greater haemodynamic benefit than either alone, if the fall in mean systemic pressure does not compromise peripheral perfusion.