CARDIAC-OUTPUT BY TRANSESOPHAGEAL ECHOCARDIOGRAPHY USING CONTINUOUS-WAVE DOPPLER ACROSS THE AORTIC-VALVE

Background: The use of transesophageal echocardiography for the determ ination of cardiac output (CO) has been limited to date. We assessed t he capability of aortic continuous-wave Doppler transesophageal echoca rdiography to determine CO (DCO) in a transgastric long-axis imaging p lane of the heart by comparing DCO to thermodilution CO (TCO). Methods : DCO was determined in 63 consecutive patients undergoing cardiac sur gery. Aortic valve area was obtained from the transverse short-axis vi ew of the valve assuming a triangular shape for the valve orifice. Str oke volume was calculated as the product of velocity-time integral and aortic valve area: stroke volume = velocity-time integral X aortic va lve area. DCO was calculated off-line, by multiplying stroke volume wi th heart rate: DCO = stroke volume X heart rate. Results: The aortic v alve orifice was easily imaged in all patients. Excellent-quality cont inuous-wave Doppler flow profiles were obtained in nearly all (62 of 6 3). A total of 109 DCO determinations were performed. Mean DCO was 4.3 5 +/- 1.18 1.min(-1) (range 2.02-7.42 1.min(-1)), and mean TCO was 4.4 1 +/- 1.17 1.min(-1) (range 2.24-8.94 1.min(-1)). Very high correlatio n and agreement were found between the two methods: DCO = 0.94 X TCO 0.19, r = 0.94, SEE (standard error of the estimate) = 0.41 1.min(-1) ; 95% confidence interval = 0.06 +/- 0.83 1.min(-1). Relative changes from pre- to postbypass CO (Delta) also showed a strong correlation (D elta DCO = 0.93 X Delta TCO + 5.4%, r = 0.82, SEE = 17.8%). For CO cha nges greater than 10%, Doppler was in accordance with thermodilution i n 43 of 45 measurements. DCO repeatability coefficient was 0.51 1.min( -1). Conclusions: Compared to thermodilution, continuous-wave Doppler measurements of blood flow velocity across the aortic valve in the tra nsesophageal echocardiographic transgastric view allow accurate CO det ermination.