A bstractThe problems of applying mercury strain gauge venous occlusion plethysmography in quantitative measurements of high blood flow rates were studied in the extremities of humans and animals. The fast-acting ECG-controlled pneumatic Periflow system opens the possibility of measurements with reduced restriction of arterial inflow. In animal experiments the arterial inflow rate (about 0.25 vol%/min) during the arterial occlusion period was estimated by an indicator dilution technique. The accuracy of the perfusion rate estimation of a limb by plethysmography was tested in controlled perfused extremities of large dogs weighing about 60 kg. Strain gauges with different positions showed different—but for each filament quite proportional—relations to real values. The nonuniform venous capacities of the different segments of a limb, which have been shown by injections of a known volume and recording of pressure volume curves, may complicate blood flow measurements by volume displacements from low-compliance regions to high-compliance regions of the vein system. Estimations of the length resistance relation of mercury strain gauges agreed well with the theoretically expected function. If an inextensible part is inserted into the circumferential arrangement of the filament, a correcting calculation of volume changes is necessary.
The validity of the diastolic pressure time index (DPTI) as an estimate of myocardial 02 supply and tension time index (2TI) as an estimate of 02 demand has been examined in 10 closed-chest anesthetized dogs. We analyzed 158 steady states including maximal variation of hemodynamics and O 2 consumption. For each steady state 23 hemodynamic variables were calculated. Myocardial blood flow (MBF) was directly measured in the coronary sinus with a differential pressure catheter.Oxygen consumption (MVO2) was varied by application of catecholamines, atropine, negative and positive inotropic drugs and hypo-and hypervolemia. There was a close relationship between direct measurements of O 2 supply and 02 demand over a wide range of testing (r = 0.93), but there was no significant correlation between the ratio of DPTI/TI~I and the ratio of O2 supply/O2 demand (directly measured). With intact metabolic regulation of coronary blood flow there is no close correlation of mean diastolic aortic pressure to coronary blood flow (r = 0.45) over the entire tested range, which is one reason why the DPTI does not show a correlation to the direct measurement of O z supply (r = 0.34). The tension time index bears a close relationship to myocardial oxygen consumption only-under normal and moderate stimulation of inotropism (r = 0.96), but there is no significant correlation under high positive inotropic stimulation (r = 0.39). Our findings indicate that the ratio of DPTI/TTI should be interpreted with great care if it is generally used as an indicator of the adequacy of myocardial O2 supply. *) Supported by the Deutsche Forschungsgemeinschaft, SFB 89, Kardiologie, G6ttingen. T71
The measurement accuracy of clinically applicable methods for blood flow measurement in coronary sinus -- continuous local thermodilution (LTD), differential pressure (DP), ultrasonic Doppler (US) and the electromagnetic flow measurement method (EMF) -- was examined in 15 anaesthetized closed chest dogs with left ventricle weights between 150 and 200 g. The LTD, DP, US and the EMF were examined in each experiment in the two following arrangements. 1. In coronary sinus -- left jugular vein by-pass: This arrangement allowed four reference methods for measurement of coronary sinus blood flow (CBF). 2. In "clinical" position, without by-pass, which allowed two reference methods for CBF measurements. The results on the measurement accuracy of the LTD, DP and US are, depending on the measurement arrangement, contradictory. In the by-pass arrangement 1 there was observed a good agreement of the LTD, DP and US CBF values with the reference values. In the "clinical" position, without by-pass 2 the measurement accuracy of LTD was not sufficient for exact measurement of CBF and derived parameters. The examined velocity tip flow probes (US, DP) gave no correlation with the reference methods. US and DP are even for semiquantitative estimation of CBF unsuitable. The EMF tip flow probe was for the CBF measurement unsuitable, because of disturbance by the electrical activity of myocardium.
The DPTI/STTI ratio is applied to man, both in health and disease, for estimating the myocardial oxygen supply/ demand ratio. The physiological concept and the divergent values reported for the critical DPTI/STTI ratio led us to examine this index unter maximal variations of oxygen supply and demand. 247 steady states in 15 intact dogs with patent coronary arteries, including 89 points at maximal coronary vasodilatation were analyzed. Coronary blood flow was measured directly. Oxygen supply and demand were varied by use of an intra-aortic balloon catheter, hypo-and hypervolemia, inotropic stimulation, beta adrenergic blockade, cardiac pacing, hemodilution and Persantin® (dipyridamol). Adequate myocardial oxygen supply was evaluated by precordial ECG and cardiac performance. Our studies demonstrate that DPTI bears only a poor relationship to myocardial blood flow at maximal coronary vasodilatation (r = 0.60). The result for the STTI as an estimate of myocardial oxygen demand is even poorer (r = 0.53). A number of our values were far below the reported critical DPTI/STTI ratios without occurrence of subendocardial ischemia, depressed cardiac function or myocardial edema. Therefore, great caution is necessary if the DPTI/STTI ratio is applied in the treatment of patients with heart disease.
The DPTI/STTI ratio as an estimate of the myocardial 02 supply/demand ratio and the prediction of myocardial blood flow (MBF) by the diastolic pressure time index (DPTD and other indices have been examined in intact anesthetized dogs. We analyzed 89 steady states including maximal alterations of the variables determining DPTI and STI~I. Myocardial blood flow was directly measured in the coronary sinus with a differential pressure catheter. An experiments were carried out under maximal coronary dilation obtained by application of dipyridamol. Hemodynamics and MBF were varied by use of pressure loading, (3-stimulation and ~-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 02 supply were coronary venous 02 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 of MBF. A number of DPTI/STrI ratios fell far below the critical values *) Supported by the Deutsche Forschungsgemeinschaft, SFB 89, Kardiologie, GSttingen. 811
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