Indirect ultrasound evaluation of left ventricular outflow tract diameter implications for heart failure and aortic stenosis severity assessment.

Abstract

Whereas dependency of left ventricular outflow tract diameter (LVOTD) from body surface area (BSA) has been established and a BSA-based LVOTD formula has been derived, the relationship between LVOTD and aortic root and LV dimensions has never been explored. This may have implications for evaluation of LV output in heart failure (HF) and aortic stenosis (AS) severity. A cohort of 540 HF patients who underwent transthoracic echocardiography was divided in a derivation and validation subgroup. In the derivation subgroup (N=340), independent determinants of LVOTD were analyzed to derive a regression equation, which was used for predicting LVOTD in the validation subgroup (N=200) and compared with the BSA-derived formula. LVOTD determinants in the derivation subgroup were sinuses of Valsalva diameter (SVD, beta=0.392, P<.001), BSA (beta=0.229, P<.001), LV end-diastolic diameter (LVEDD, beta=0.145, P=.001), and height (beta=0.125, P=.037). The regression equation for predicting LVOTD with the aforementioned variables (LVOTD=6.209+[0.201×SVD]+[1.802×BSA]+[0.03×LVEDD]+[0.025×Height]) did not differ from (P=.937) and was highly correlated with measured LVOTD (R=0.739, P<.001) in the validation group. Repeated analysis with LV end-diastolic volume instead of LVEDD and/or accounting for gender showed similar results, whereas BSA-derived LVOTD values were different from measured LVOTD (P<.001). Aortic root and LV dimensions affect LVOTD independently from anthropometric data and are included in a new comprehensive equation for predicting LVOTD. This should improve evaluation of LV output in HF and severity of AS when direct LVOTD measurement is difficult or impossible.