PULSED WAVE DOPPLER MEASUREMENT OF CARDIAC-OUTPUT FROM THE RIGHT-VENTRICULAR OUTFLOW TRACT

Doppler ultrasound can be used to measure cardiac output (CO). Intraop erative Doppler cardiac output (DCO) by transesophageal echocardiograp hy (TEE) has been studied using blood flow velocity from the left vent ricular outflow tract (LVOT), the mitral valve (MV), and the main pulm onary artery (MPA). The purpose of this study was to compare DCO, meas ured from a relatively new TEE view of the right ventricular outflow t ract (RVOT), with thermodilution cardiac output (TDCO). We also compar ed changes in DCO from the RVOT to changes in TDCO. A 5.0/3.7 MHz mult iplane TEE probe was placed in 45 adult cardiac surgical patients unde rgoing general anesthesia. Patients were excluded if there was greater than mild tricuspid valve insufficiency. From the transgastric view, at approximately 110-140 degrees, the RVOT was imaged. DCO was calcula ted from 1) the time-velocity integral (TVI) using pulse wave (PW) Dop pler, 2) the area of the RVOT (measured in early systole using the dia meter (pi(D/2)(2)) of the RVOT at the level of the PW Doppler sample v olume), and 3) the heart rate. Simultaneous TDCO was performed by a se parate examiner. The RVOT was imaged satisfactorily in 84% of patients (38/45). The mean bias between DCO and TDCO was -0.01 L/min (2 SD +/- 0.45 L/min; n = 38). There was good correlation between DCO and TDCO (R(2) = 0.97). Changes in TDCO and changes in DCO were compared in 15 patients. The mean bias between changes in DCO and changes in TDCO was 0.04 L/min (2 SD +/- 0.66 L/min). Analysis of the changes in DCO and TDCO showed good correlation (R(2) = 0.96). We conclude that there is a good correlation between DCO measured from the RVOT and TDCO. This t echnique permits cardiac output measurement without the necessity of p lacing a pulmonary artery catheter, and it also provides a method of e valuating RVOT blood flow.