Right ventricular function computed by thermodilution and ventriculography. A comparison of methods.

Abstract

Right ventricular ejection fractions have been difficult to estimate clinically. It has been recently suggested that right ventricular ejection fractions can be calculated by thermodilution techniques with a fast-response thermistor and computer. These studies were performed to compare right ventricular ejection fractions obtained from thermodilution and biplane ventriculography. Ten pigs were instrumented with a right ventricular angiographic, thermodilution, and systemic arterial catheter. Right ventricular ejection fractions were determined by thermodilution and ventriculography at four times: (1) baseline, (2) infusion of isoporterenol (5 micrograms/min), (3) 50% of baseline mean arterial pressure produced by hemorrhage, and (4) reinfusion of isoproterenol during hypovolemia. A significant correlation existed between thermodilution and ventriculographic ejection fractions (r = 0.74, p = 0.004). However, during hypovolemia, thermodilution measurements of right ventricular ejection fraction were significantly lower than ventriculographic measurements (p less than 0.05). To determine if the position of the thermistor had a significant effect on thermodilution computations, right ventricular ejection fractions were computed by thermodilution in 10 additional pigs by means of a jugular and femoral insertion, as well as by ventriculography in each pig. Femoral insertion resulted in a greater distance from pulmonic valve to thermistor as compared with jugular placement (p = 0.005). Right ventricular ejection fractions obtained from femoral placement were significantly less than those obtained by jugular insertion (p = 0.008) and ventriculography (p = 0.006). There was no significant difference between jugular and ventriculographic ejection fractions (p = 0.35). Results from these studies demonstrates that thermodilution right ventricular ejection fraction measurements are strongly correlated to ventriculographic methods over a wide hemodynamic range and that improved accuracy is obtained when the pulmonic valve to thermistor distance is minimized. Thus thermodilution may provide a simple and repeatable means to monitor right ventricular function in the critical care setting.