[Intraoperative ejection fraction: estimation with Simpson's rule vs tissue Doppler imaging]

Transesophageal echocardiography is appropriate for intraoperative monitoring of hemodynamics. The parameter often estimated is ejection fraction (EF) by means of Simpson's rule. With the advent of tissue Doppler imaging and measurement of the systolic (S) wave, corresponding to the rate of myocardial perfusion during the systole, it is possible to estimate the EF more easily and rapidly during surgery.

To compare EF estimates obtained by Simpson's rule to those based on intraoperative tissue Doppler measurements of S-wave velocity (S').

Patients with chronic cardiovascular disease undergoing scheduled cardiac and noncardiac surgery were studied. Patients in nonsinus rhythm and with mitral valve disease were excluded. To apply Simpson's rule for calculating the EF, we measured end-diastolic volume in 4- and 2-chamber views. The group was divided into patients with normal (> or = 50%) and diminished (< or = 49%) ejection fraction. Tissue Doppler imaging of the mitral annulus was then used to measure S'. Ejection fraction was calculated according to the formula EF = 5.5 x S' + 8.

Ninety-two patients were studied; in 51 (55%) the EF was normal and in 41 (45%) it was reduced. In patients whose EF was < or = 49% according to Simpson's rule, the correlation between that measurement and EF based on tissue Doppler estimate of S' was good. The correlation was lower, however, in the group with normal EF (r=0.61; P>0.5).

EF is easy to estimate with tissue Doppler imaging and the procedure is reproducible. This approach is probably more useful in patients with left ventricular dysfunction.