[Analysis of factors influencing the accuracy of ejection fraction measurement based on the thermal washout technic--investigation in a model heart].
Evaluation of ejection fraction and ventricular volume is more difficult in the right side of the heart than in the left side. Thermal washout method in the right ventricle with the aid of a rapid response thermistor made it possible in the clinical practice, but its accuracy is uncertain. We attempted to elucidate what factors could influence the accuracy of the measurement of the right ventricular ejection fractions in a model circuit and artificial heart equipped with two one-way valves. Findings are as follow: 1) By ventricular injection of the cold water it is possible to evaluate the ejection fractions more accurately than by atrial injection. The latter technique measured the ejection fraction 8.4% lower than the actual values. 2) The first ejection fraction measured will be the most accurate among the serially obtained ejection fractions using a thermal washout curve. 3) When the ejection fraction is high, the ejection fractions calculated from the later part of a thermal washout curve will be falsely low. 4) When the cold water is injected through the catheter running in the circuit, the effect of the catheter cooling could not be neglected and ejection fraction will be measured falsely low. The temperature change is so small in the later part of the descending limb of the thermal washout curve, that the effect of catheter cooling and ventricular cooling will be exaggerated and the calculation of the temperature change will be measured falsely high. This seems to be the cause of our findings in this research.(ABSTRACT TRUNCATED AT 250 WORDS)
Imai
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T
Katoh
K
K
Kani
H
H
Fujita
T
T
Ohno
K
K
Nakayama
T
T
Shioya
S
S
D006358:Hot Temperature; D006801:Humans; D007201:Indicator Dilution Techniques; D008955:Models, Cardiovascular; D013318:Stroke Volume