Cardiac Output at Rest and during Exercise in Patients with Healed Myocardial Infarction.

Eight patients, five male and three female, ages 48 to 69, with documented healed myocardial infarction, were studied. Six were habitual smokers and two were nonsmokers. Each patient served as his own control. Some of the patients were studied in the fasting state and some after eating. The order of smoking and nonsmoking studies was randomly selected. Each patient smoked two standard-sized filter tip cigarettes within 10 minutes. All patients inhaled the smoke, although there was slight difficulty on this point in the two nonsmokers. Cardiac output, cardiac index, and stroke volume were measured at rest, in the supine position, by the dye-dilution technic with an indwelling Cournand brachial arterial needle, a Gilford densitometer, indocyanine green dye, and an Electronics for Medicine multichannel direct-writing recorder. Blood for these determinations was withdrawn at a constant rate with a Harvard infusion-withdrawal syringe. Calibrations were performed with the same densitometer setting and blood flow each time. Exercise was performed on a bicycle-ergometer set at 25 kilograms per watt, with the patient cycling for 3 minutes at 60 RPM, and the physiologic measurements were repeated. Each determination was performed in duplicate in six of the eight patients, and the average was calculated and re-