A Study of the 16-Segment Regional Wall Motion Scoring Index and Biplane Simpson's Rule for the Calculation of Left Ventricular Ejection Fraction: A Comparison with Cardiac Magnetic Resonance Imaging

Abstract

Accurate calculation of left ventricular ejection fraction (LVEF) is important for diagnostic, prognostic and therapeutic reasons. Cardiac magnetic resonance (CMR) is the reference standard for LVEF calculation, followed by real time three-dimensional echocardiography (RT3DE). Limited availability of CMR and RT3DE leaves Simpson's rule as the two-dimensional echocardiography (2DE) standard by which LVEF is calculated. We investigated the accuracy of the 16-Segment Regional Wall Motion Score Index (RWMSI) as an alternative method for calculating LVEF by 2DE and compared this to Simpson's rule and CMR. The 2D echocardiograms of 110 patients were studied (LVEF range: 7-74%); 57 of these underwent CMR. A RWMS was applied, based on the consensus opinion of two experienced cardiologists, to each of 16 American Heart Association myocardial segments (RWMSI: hyperkinesis = 3; normal regional contraction = 2; mild hypokinesis = 1.25; severe hypokinesis = 0.75; akinesis = 0; dyskinesis =-1). LVEF was calculated by: LVEF(%) =Σ(16segRWMS)/16×30. LVEF was calculated by Simpson's rule and CMR using standard methods. Results were correlated against CMR. Intertechnique agreement was examined. A P value of<0.05 was considered significant. RWMSI-LVEF correlated strongly with Biplane Simpson's rule (P< 0.001, r = 0.915). RWMSI-LVEF had a strong correlation to CMR (P < 0.001, r = 0.916); Simpson's rule-LVEF had a moderate correlation to CMR (P< 0.001, r = 0.647). In patients with LV dysfunction (EF < 55%), on linear regression analysis, RWMSI-LVEF had a better correlation with CMR than Simpson's rule. Further more Simpson's rule overestimated LVEF compared to CMR (mean difference: -6.12 ± 16.44, P = 0.002) whereas RWMSI did not (mean difference: 2.58 ± 14.80, P = NS). RWMSI-LVEF correlates strongly with CMR with good intertechnique agreement. In centers where CMR and RT3DE are not readily available, the use by experienced individuals, of the RWMSI for calculating LVEF may be a more simple, accurate, and reliable alternative to Simpson's rule.