VALIDITY OF CARDIAC-OUTPUT MEASUREMENT BY THE THERMODILUTION METHOD IN THE PRESENCE OF ACUTE TRICUSPID REGURGITATION

Evaluation of patients with acute tricuspid insufficiency may include assessment of cardiac output by the thermodilution method. Tle accurac y of estimates of thermodilution-derived cardiac output in the presenc e of tricuspid insufficiency has been questioned. This study was desig ned to determine the validity of the thermodilution technique in a can ine model of acute reversible tricuspid insufficiency. Cardiac output as measured by thermodilution and electromagnetic flowmeter was compar ed at two grades of regurgitation. The relationship between these two methods (thermodilution/electromagnetic) changed significantly from a regression slope of 1.01 +/- 0.18 (mean +/- standard deviation) during control conditions to a slope of 0.86 +/- 0.23 (p < 0.02) during seve re regurgitation. No significant change was observed between control a nd mild regurgitation or between the initial control value and a contr ol measurement repeated after tricuspid insufficiency was reversed at the termination of the study. This study shows that in a canine model of severe acute tricuspid regurgitation the thermodilution method unde restimates cardiac output by an amount that is proportional to the lev el of cardiac output and to the grade of regurgitation.