NONINVASIVE ASSESSMENT OF CORONARY STENOSES WITH MYOCARDIAL PERFUSION IMAGING DURING PHARMACOLOGIC CORONARY VASODILATATION .5. DETECTION OF 47-PERCENT DIAMETER CORONARY STENOSIS WITH INTRAVENOUS N-13 AMMONIA AND EMISSION-COMPUTED TOMOGRAPHY IN INTACT DOGS

To determine the minimal coronary lesions detectable with perfusion imaging, 16 stenoses of 43 to 66 percent diameter narrowing were applied to the left circumflex coronary artery of three chronically instrumented intact dogs. Orthogonal diastolic coronary arteriograms, obtained on cut film by triggering X-ray exposures from the electrocardiogram while injecting contrast medium through a chronically implanted coronary arterial catheter, were analyzed quantitatively by computer. Fifteen millicuries of nitrogen-13 ammonia was injected intravenously during resting conditions, and emission-computed tomography was performed without electrocardiographic gating. One hour later, after residual nitrogen-13 ammonia had decayed, 15 mg of intravenous dipyridamole was given followed by a second dose of intravenous nitrogen-13 ammonia and repeat performance of emission-computed tomography. The cross-sectional tomographs of the heart were of high quality and revealed in the images obtained with dipyridamole definite perfusion defects with coronary stenoses of 47 percent or greater diameter narrowing. Stenoses of 45 percent diameter narrowing or less did not produce perfusion defects. Quantitative perfusion abnormalities approximated the quantitative severity of stenoses. It is concluded that noninvasive myocardial emission-computed tomography with nitrogen-13 ammonia during dipyridamole-induced coronary vasodilatation detects mild coronary stenoses for purposes of potential medical intervention. © 1979.