The Validity of the Total Myocardial Blood Flow Determination by Means of 113Xe in Regional Ischemia

Abstract

SummaryRegional MBF in the ischemic and healthy left ventricular myocardium was measured in 21 mongrel dogs by means of locally injected 133Xe and its washout one week after ligation of the left anterior descending coronary. Simultaneously the total MBF was calculated from the precordial washout determination of 133Xe injected into the left coronary artery. The 133Xe measurements were compared with the regional 86Rb uptake. The values of total MBF determination after left coronary artery injection did not diminish adequately to the size of the ischemic area; these values were usually higher as compared with the calculated mean MBF evaluated from the regional left ventricular blood flow and did not agree with regional MBF in the intact left ventricular myocardium. The difference of perfusion between the necrotic and the healthy left ventricular myocardium determined from the local 133Xe washout was higher in comparison to 86Rb uptake. The method of total MBF determination by means of precordially determined 133Xe washout injected into the coronary artery yields artificially higher values in cases with greater ischemic areas. This may be accounted for by a low initial radioactivity of the hypoperfused areas and their negligible contribution to the total radioactivity changes produced predominantly by the well perfused areas. The relatively low 86Rb uptake difference in the healthy and the necrotic left ventricular myocardium may be caused by affected extraction coefficients of 86Rb in the necrotic tissue.