Assessment of aortic valve stenosis severity - A new index based on the energy loss concept

Background-Fluid energy loss across stenotic aortic valves is influenced by factors other than the valve effective orifice area (EOA), We propose a ne w index that will provide a more accurate estimate of this energy loss. Methods nad Results-An experimental model was designed to measure EOA and e nergy loss in 2 fixed stenoses and 7 bioprosthetic valves for different flo w rates and 2 different aortic sizes (25 and 38 mm). The results showed tha t the relationship between EOA and energy loss is influenced by both flow r ate and aortic cross-sectional area (AA) and that the energy loss is system atically higher (15+/-2%) in the large aorta. The coefficient (EOAXA(A))/(A (A)-EOA) accurately predicted the energy loss in all situations (r(2)=0.98) . This coefficient is more closely related to the increase in left ventricu lar workload than EGA. To account for varying flow rates, the coefficient w as indexed for body surface area in a retrospective study of 138 patients w ith moderate or severe aortic stenosis, The energy loss index measured by D oppler echocardiography was superior to the EOA in predicting the end point s, which were defined as death or aortic valve replacement. An energy loss index less than or equal to 0.52 cm(2)/m(2) was the best predictor of adver se outcomes (positive predictive value of 67%). Conclusions-This new energy loss index has the potential to reflect the sev erity of aortic stenosis better than EGA. Further prospective studies are n ecessary to establish the relevance of this index in terms of clinical outc omes.