Sequential Circulatory Changes following Acute Myocardial Infarction in Man

After informed consent, 12 men with documented acute myocardial infarction had hemodynamic studies performed within 18 hours after onset of symptoms. These were repeated on the second day, at 3-5 weeks, and at 3-5 months in the 10 who survived. One half of the patients were “uncomplicated” and significant differences with the “complicated” patients were seen in pulmonary artery pressure, mean arterial pressure on the first day, acute phase stroke volume and cardiac index, and the total blood volume within 48 hours. The optimal heart rate at each stage was determined by atrial pacing and was found to be 110 ± 10 beats/min. Abnormalities in pH, blood gases, and circulation time were related to the cardiac index. Control groups with and without coronary artery disease were studied prior to angiography to obtain information regarding preinfarction circulatory status, and significant impairment of the ejection fraction was noted even in angina patients without prior infarction. The sequential circulatory changes and possible compensatory mechanisms available were discussed.