PREDICTION OF MYOCARDIAL BLOOD-FLOW BY DPTI AND PREDICTION OF THE ADEQUACY OF MYOCARDIAL-O2 SUPPLY BY THE DPTI-STTI RATIO UNDER MAXIMAL CORONARY DILATION

The DPTI/STTI ratio as an estimate of the myocardial O2 supply/demand ratio and the prediction of myocardial blood flow (MBF) by the diastolic pressure time index (DPTI) and other indices have been examined in intact anesthetized dogs. We analyzed 89 steady states including maximal alterations of the variables determining DPTI and STTI. Myocardial blood flow was directly measured in the coronary sinus with a differential pressure catheter. All experiments were carried out under maximal coronary dilation obtained by application of dipyridamol. Hemodynamics and MBF were varied by use of pressure loading, β-stimulation and β-blockade, hypo- and hypervolemia, electrical stimulation and hemodilution. Hemodynamic variations included clinically significant situations such as tachycardiac heart failure based on exhausted coronary vascular reserve and severe anemia. Parameters of sufficient myocardial O2 supply were coronary venous O2 saturation, precordial Ecg, hemodynamic evaluation of myocardial performance, result of autopsy and determination of the wet and dry weight ratio. All tested parameters show a poor correlation for prediction of MBF. Correlation coefficient for DPTI is r=0.60. Using the primary data of Buckberg (1) we obtained similar results for the correlation of DPTI to subendocardial blood flow measured with microspheres (r=0.65). The highest r (0.66) was found in our data for the difference between mean diastolic aortic pressure and mean left ventricular diastolic pressure without regard to diastolic duration. Therefore, in contrast to theoretical expectation, diastolic duration is not a practically important determinant and of MBF. A number of DPTI/STTI ratios fell far below the critical values reported in the literature, but they were never associated with the occurrence of subendocardial ischemia, infarction, depressed cardiac performance or myocardial edema © 1979 Dr. Dietrich Steinkopff Verlag.