Myocardial Infarction in Experimental Hypertension in Rats: Mechanism of the Reduction in Blood Pressure

1. Haemodynamic changes during graded methoxamine infusion have been measured in 16 spontaneously hypertensive rats with healed myocardial infarction produced by left coronary artery ligation and in 15 hypertensive rats without infarction. 2. Arterial pressure of the hypertensive rats was reduced to levels within the normotensive range in animals with moderate and large myocardial infarctions. 3. The peripheral vascular response to methoxamine was similar in rats with and without infarction. 4. The reduction in blood pressure resulted from a combination of lower heart rate and inability to maintain stroke volume at hypertensive pressures.