Intraoperative transesophageal echocardiography using a quantitative dynamic loading test for the evaluation of ischemic mitral regurgitation.

BACKGROUND

Intraoperative transesophageal echocardiography may underestimate ischemic mitral regurgitation (MR) as a result of the unloading effect of general anesthesia on the left ventricle (LV). An intraoperative loading test could prove useful to avoid underestimation of ischemic MR.

METHODS

We prospectively studied 30 patients with ischemic MR referred for coronary artery bypass, mitral valve surgery, or both. Transthoracic echocardiography was performed 1.6 +/- 1.6 days preoperatively, and intraoperative transesophageal echocardiography after induction of general anesthesia before and after LV loading. Preload was adjusted using fluids (if pulmonary occlusion pressure < 15 mm Hg), and the afterload increased using intravenous phenylephrine aiming at systolic blood pressure of 160 mm Hg. MR severity was estimated using color Doppler, pulmonary venous flow, and the proximal isovelocity surface area method.

RESULTS

Preoperative median MR grade was 2 (interquartile range 1-3), effective regurgitant orifice area was 0.16 +/- 0.17 cm2, and regurgitant volume was 23 +/- 23 mL. Intraoperative MR grade decreased to 1.5 (1-2.25), effective regurgitant orifice area to 0.13 +/- 0.16 cm2, and regurgitant volume to 21 +/- 26 mL (P = .02, P = .06, and P = .18). After LV loading, MR grade increased to 3 (1-4), effective regurgitant orifice area to 0.21 +/- 0.24 cm2, and regurgitant volume to 39 +/- 38 mL (P < or = .005). All patients with preoperative +3 MR or greater had +3 MR or greater after loading whereas most patients with +1 MR had +1 MR. Of the 11 patients with preoperative +2 MR, 6 had +3 and 2 had +4 MR.

CONCLUSIONS

A quantitative loading test with fluids and phenylephrine is useful to avoid underestimation of ischemic MR by intraoperative transesophageal echocardiography, and may detect significant MR in some patients who had unloaded LVs and nonsignificant MR during their preoperative assessment.