Simultaneous determination of the stroke volume and the left ventricular residual fraction with the fiberoptic- and thermodilution method

Abstract

Authors' synopsis Simultaneous measurements of the concentration of dye by a fiberoptic catheter and of the temperature by a thermistor catheter were obtained in dogs. No significant diference for cardiac output and stroke uolume was found. The slightly but significant higher residual.fraction by thermodilution than by Jiberoptic technique is caused by cold transfer between irentricular myocardium and caoity. It becomes evident after the jifth beat.Indicator dilution methods have been used t o measure ventricular volume for many years. The technique involves ventricular injection of a n indicator with measurement of its serial dilution immediately beyond the semilunar valves. Mainly cold or dye as indicators are employed (Holt, 1956;Liithy, 1962;Rapaport, Wiegand, and Bristow, 1962;Hugenholtz, Gamble, Monroe, and Polanyi, 1965; Krayenbuhl, 1969). To our knowledge n o comparison of the thermodilution versus the dye method with intravascular measurement at the same sensor site has yet been reported.Thermodilution is assumed to be complicated by heat exchange between blood and the heart wall because of temperature gradient (Rolett, Sherman, and Gorlin, 1964). The resultant cooling of the inner layers of the ventricular wall may serve as a storage of indicator which is then gradually released to the chamber as the blood temperature gradient is reversed. As a result the indicator decay slope may be prolonged.The present study was undertaken t o compare left ventricular residual fraction a n d stroke volume of simultaneously recorded aortic thermal and fiberoptic dye dilution curves and to estimate the error from heat transfer complicating the thermodilution method. For rapid sensing of the washout steps the thermistor and the fiberoptic catheters, both with similar time constants, were positioned together in the ascending aorta above the aortic valves. MethodsExperiments were carried out in five male mongrel dogs, ranging between 2 1 and 23 kg body weight. After premedication with z mg morphine sulphate/kg body weight, the animals were anaesthetized with 90 mg/kg body weight of a-chloralose. Heparin was given in a dose of 300 i.u./kg body weight. The animals were intubated with a cuffed endotracheal tube and ventilated with air by means of an Engstrom respirator at a rate of 20 c/min. Care was taken to maintain stable normal body temperature throughout the experiment.Catheters were positioned under fluoroscopic control in the following manner: through the

The thermodilution technique in on‐line computation of the left ventricular volumes on anaesthetized dogs

“…The present way of computing the stroke volume with a "dependent method" [26], using the same thermal dilution curve in cardiac output determination as in ejection fraction determination, minimizes the error induced by the beat-to-beat variation in forward stroke volume [4]. It has been further validated with the aid of the fiberoptic dye dilution method [15], which for its part has been shown to agree well with angiocardiographic [11,34,36] and Fick methods [4,36], as well as with measurements using an artificial model of the heart [ 131. Nevertheless, the determination of cardiac output from indicator dilution curves with indicator injected into the left ventricle, and obtaining recordings from the proximal aorta has been seriously criticized, mainly because of improper mixing and inadequate time response of the sampling system [5,6,8-10,221.…”

“…As a result, the temperature of the first stroke volume remains too low and the EDV as estimated by the first ejection method attains too great a value. This loss may, however, partially be compensated for during a few succeeding heart beats by a reverse thermal transfer into the blood [15,19], and hence the computed cardiac output and stroke volumes will be rectified. On the other hand, this cold return falsifies the determination of the residual fraction by the downslope method.…”

“…In early studies the downslope method gave considerably greater end-diastolic volumes than those obtained by artificial circulation models [7] or single-plane [6,8,9] or biplane [6,10] angiocardiography, and poor correlation with the reference methods. After the introduction of fiberoptic dye-dilution [ 111 and more advanced thermal dilution techniques [12], these methods have shown better agreement [13,14] as have also these two indicator dilution methods with each other [15]. The thermal dilution method [16] provides a safe means for repeated measurements of cardiac output and ventricular volumes in man [2] and animals [17].…”