ABSTRACT
Background. 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.
Methods. 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.
Results. LVOTD determinants in the derivation subgroup were
sinuses of Valsalva diameter (SVD, beta=0.392, P<0.001), BSA
(beta=0.229, P<0.001), LV end-diastolic diameter (LVEDD,
beta=0.145, P=0.001), and height (beta=0.125, P=0.037). The regression
equation for predicting LVOTD with the aforementioned variables
(LVOTD=6.209+[0.201xSVD]+[1.802xBSA]+[0.03xLVEDD]+[0.025xHeight])
did not differ from (P=0.937) and was highly correlated with measured
LVOTD (R=0.739, P<0.001) 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<0.001).
Conclusion. 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, avoiding use of LVOT
velocity-time integral alone, which can be misleading, especially when
LV cavity and aortic root dimensions are abnormal.