Abstract 5773: Reduced Left Ventricular Vortex Formation Ability Despite Preserved Ejection Fraction in Low-Flow, Low-Gradient Severe Aortic Stenosis
Background and Aim: Low-flow, low-gradient (LFLG) severe aortic stenosis (AS) despite preserved left ventricular (LV) ejection fraction (EF) has been associated with more advanced stage of the disease, lower cardiac output (CO) and higher systemic afterload. We aim to characterize the LV performance determinants, including its vortex formation (VF) ability.
Methods: Echocardiography was performed in 61 consecutive patients with severe AS (aortic valve area index (AVAI) ≤ 0.6 cm2/m2) and preserved LVEF (≥ 50%). In addition to biplane LV measurements, AS severity indices and Tei index were measured. Hemodynamic indices (including systemic vascular resistance (SVR) and valvulo-arterial impedance (VAI)) were calculated. VF index (VFI) was obtained from 4 X (1-β)/πX α3 X LVEF where β is the fraction of total transmitral diastolic stroke volume (SVol) contributed by atrial contraction (assessed by time velocity integral of the mitral E and A waves) and α is the end diastolic volume (EDV)1/3 divided by mitral annular diameter during early diastole. Patients were categorized by their LV SVol index (SVI). LFLG group consisted of SVI < 45ml/m2.
Results: Mean VFI was 2.67±1.1; AVAI, 0.50±0.09 cm2/m2. Though AVAI was slightly lower in LFLG, dimensionless index and aortic valve resistance were similar and associated with no difference in LV mass and volume between the 2 groups. VFI was significantly reduced in the LFLG, 2.37±0.9 vs 3.12±1.3 (P=0.01), However other LV functional parameters including Tei index and LVEF were similar (Table⇓). LFLG was associated with higher SVR and VAI (Table⇓). In LFLG, the only significant correlates of VFI were SVR (r=0.38), VAI (0.37) and stroke work index (0.36); all Ps<0.05. VFI did not correlate to these parameters in the non-LFLG group.
Conclusion: In LFLG severe AS, increased afterload and suboptimal LV vortex formation ability contribute to lower CO/SV. VFI provides useful insights in understanding this relatively new entity.