Noninvasive Regional Myocardial Perfusion with Radioactive Potassium: Study of Patients at Rest, with Exercise and during Angina Pectoris

Myocardial perfusion imaging after intravenously administered radioactive potassium (⁴³K) was used to delineate noninvasively areas of myocardial infarction and left ventricular regions that become transiently ischemic during angina pectoris. Forty-three subjects were studied at rest and during maximal treadmill exercise. In 12 normal subjects ⁴³K distribution was homogeneous both at rest and during exercise. In 13 of 15 patients with previous myocardial infarction studied at rest, regions of decreased radionuclide accumulation corresponded to the anatomic location of the infarct. In 16 of 19 patients with angina pectoris, regions of relatively decreased ⁴³K accumulation were identified when the tracer was administered during exercise, but were not present at rest. These zones of relative hypo-perfusion corresponded to regions supplied by angiographically demonstrable stenotic coronary arteries in all patients so studied. ⁴³K myocardial imaging thus provides a safe and simple noninvasive means of assessing regional myocardial perfusion at rest, with exercise and during angina pectoris. (N Engl J Med 288:809–812, 1973) ALTHOUGH coronary arteriography allows definition of the location and extent of obstruction in the coronary vascular tree, it provides only indirect information about blood flow across stenotic coronary arteries or perfusion of vascular beds distal to obstructed segments. Recently, methods have been developed to assess regional myocardial perfusion at the time of coronary arteriography by injecting radionuclides directly into the coronary arteries.^{1 2 3 4} The widespread clinical applicability of these technics is limited, however, by the need for cardiac catheterization and the inherent risk of repeated intracoronary injections. With current emphasis on an aggressive approach to the early recognition of coronary heart.