Abstract 13644: Novel Index Using Doppler Timing Intervals for Distinguishing “True” Severe Stenosis from “Pseudo-Severe” Stenosis in Low-Flow Low-Gradient Aortic Stenosis by Resting Transthoracic Echocardiography

Abstract

Background: Low-flow low-gradient aortic stenosis (AS) (LFLG AS: AVA<1.0cm2, LVEF<40%, mean gradient (MG)<30-40mmHg) remains a clinical dilemma, where aortic valve replacement (AVR) is indicated in “true” severe AS (TS) but not for “pseudo-severe” AS (PS). Low-dose dobutamine stress echocardiography (DSE) is recommended to stratify TS from PS. Acceleration (AT) and ejection times (ET) are angle- and relatively flow-independent Doppler indices of AS severity for prosthetic AVR assessment. We sought to determine if AT/ET can be used to distinguish TS from PS on resting echocardiography.

Methods: A retrospective analysis of all DSE for assessment of LFLG AS from July 2008 to May 2012 in a tertiary referral center was undertaken. DSE protocols were performed in accordance with current guidelines. TS with low-dose DSE was defined as a final AVA 40mmHg (with AVA20%). Averaged Doppler measurements from 3-5 beats were used for hemodynamic (MG, SVi, dimensionless index (DSI), and AVA) and timing (AT, ET, AT/ET ratio) calculations. Stroke work loss (SWL), valve resistance (VR) and projected AVA (pAVA) were extrapolated for comparison.

Results: Eleven TS and five PS patients by DSE-criteria were included (76±8yrs; 25% female). Baseline MG was higher in the TS group (TS 25.8±5.0 vs PS 18.4±4.5mmHg, P=0.02) but there were no differences in LVEF, SVi, DSI, and AVA. Significant differences were observed in baseline AT (TS 120.3±13.9 vs PS 94.7±6.2ms, P=0.0002) and AT/ET (TS 0.41±0.02 vs PS 0.32±0.03, P=0.0006) and this separation was preserved at peak-DSE (TS vs PS: AT 95.1±17.2 vs 71.4±14.3ms, P=0.01; AT/ET 0.38±0.04 vs 0.31±0.02, P=0.0002). The higher AT and AT/ET in TS paralleled differences in SWL (TS 19.0±4.6 vs PS 12.8±4.8%, P=0.04), VR (TS 198±44 vs PS 157±36dynes-s-cm-5, P=0.08), peak-DSE MG (TS 40.1±7.7 vs PS 22.0±7.6mmHg, P=0.002), peak-DSE AVA (TS 0.82±0.10 vs PS 1.23±0.25 cm2, P=0.018) and pAVA (TS 0.81±0.07 vs PS 1.12±0.14 cm2, P=0.007).

Conclusions: Resting AT and AT/ET appear to distinguish between TS and PS in LFLG AS as predicted by SWL, DSE and pAVA. This simple Doppler index may be a useful addition to the echocardiographic assessment of patients with LFLG AS.