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Neutral, isotonic Na 24 Cl solution was injected into the left ventricular wall of open-chest dogs. The disappearance of local radioactivity was recorded. Individual injections that exceeded 5 mm 3 retarded Na clearance. The rate of Na clearance from individual deposits did not measure coronary flow in absolute terms; however, when one hemodynamic parameter was suddenly changed 50–200 sec after the injection of a radioactive deposit, the changed Na clearance slope reflected directional variations of coronary flow. In ischemic regions of self-perfused hearts, elevation of aortic pressure that was paralleled by increased left ventricular and central coronary pressures did not always result in more rapid Na clearance. Submitted on November 24, 1961
Salisbury et al. (Tue,) studied this question.