INTRAOPERATIVE VALIDATION OF MITRAL INFLOW DETERMINATION BY TRANSESOPHAGEAL ECHOCARDIOGRAPHY - COMPARISON OF SINGLE-PLANE, BIPLANE AND THERMODILUTION TECHNIQUES

Objectives. This study investigated the accuracy of mitral inflow quan tification using biplane transesophageal echocardiography. Background. Mitral stroke volume can be reliably quantified by transthoracic Dopp ler echocardiography, but previous studies involving monoplane transes ophageal echocardiography have yielded mixed results. Methods. Thirty patients without mitral regurgitation were prospectively examined imme diately before cardiovascular surgery. Mitral annulus diameter was mea sured in the transverse (d(1)) and longitudinal views (d(2)) by biplan e transesophageal echocardiography. Assuming an elliptic shape, the an nular area was calculated as pi d(1)d(2)/4; area was also calculated f rom single-plane data assuming a circular annular shape as pi d(2)/4. The time-velocity integral of mitral annular Doppler velocity was then multiplied by annular area to yield stroke volume. These data were co mpared with simultaneous thermodilution measurements by linear regress ion. Results. Good correlations were observed between thermodilution ( x) and Doppler (y) measurements of stroke volume (SV) (r = 0.86, p < 0 .01, Delta SV [y-x] = 2.64 +/- 9.86 ml for single four-chamber view; r = 0.77, p < 0.01, Delta SV = 1.82 +/- 12.59 ml for two-chamber view; r = 0.94, p < 0.001, Delta SV = 1.78 +/- 5.90 ml for biplane measureme nts) with similar data for cardiac output (r = 0.82, r = 0.74 and r = 0.92, respectively). The biplane measurements were most accurate and h ad less variability in individual patients (p < 0.05). This finding wa s supported by a numerical model that demonstrated (for an ellipse of eccentricity 1.5:1) that even maximal misalignment of biplane diameter s yielded only 8% area overestimation, whereas single-plane calculatio ns assuming a circular shape produced a variation in area of 225%. Con clusions. This study validates the accuracy of measurements of mitral inflow using biplane transesophageal echocardiography with potential a pplication for quantification of valvular regurgitation in the operati ng room. The results are further generalizable, indicating that orthog onal biplane measurements are both necessary and sufficient to ensure accuracy in area calculation for any elliptic structure.