Regional Myocardial Blood Flow

nary artery disease has provided an intense stimulus for expansion of our present knowledge of the coronary circulation. In the experimental animal laboratory, the electromagnetic flowmeter has proved to be an excellent tool by which one can study dynamic aspects of the coronary circulation. A flowmeter is clearly unsuitable for human investigation; therefore, the search for a simple method of analyzing myocardial blood flow has intensified. Over 20 years ago, Eckenhoff et al.' described a method based upon the principle that an inert gas, nitrous oxide (N20), diffuses across the capillary membrane proportional to the rate of coronary blood flow. Coronary venous sampling at regular intervals provides a time-concentration curve that permits calculation of myocardial blood flow according to the Fick principle. Myocardial blood flow is expressed as ml/ 100 g of tissue