Increased ejection fraction produced by a long-term subhypertensive infusion of norepinephrine in the conscious dog

Five mongrel dogs with chronically implanted catheters in the left atrium, mid-thoracic aorta, and right atrium were continuously infused with subhypertensive doses of norepinephrine for 3 months. Left ventricular cineangiography, determinations of aortic pressure, and cardiac output were performed in the conscious dog. After 3 months of continuous norepinephrine infusion, stroke volume increased from 38 +/- 3.0 to 67 +/- 8.0 ml. (p less than .01), the left ventricular end-diastolic volume increased from 72 +/- 6.4 to 89 +/- 12.9 ml. (p less than .05), and the ejection fraction increased from 52 +/- 3.6 to 76 +/- 3.6% (p less than .005). We postulate that norepinephrine results in an increased myocardial function by producing physiological myocardial hypertrophy.