Abstract 2252: Hemodynamic and Functional Assessment of Mechanical Aortic Valves Using Combined Echocardiography and Multidetector Computed Tomography
Introduction: Transthoracic echocardiography (TTE) can evaluate hemodynamics of mechanical aortic valve replacements (AVR), but may not be able to discriminate causes of suspected valve malfunction.
Hypothesis: Combined TTE and multidetector computed tomography (MDCT) may enhance hemodynamic and functional evaluation of AVR.
Methods: Retrospective assessment of 41 consecutive patients with AVR (27 bi-leaflet, 14 tilting-disc) and both TTE and 64-slice ECG-gated MDCT. Two cardiologists (TTE) and two radiologists (MDCT) independently, blindly evaluated studies. TTE measured cardiac index (CI), mean pressure gradient (MPG), effective orifice area (EOA), aortic insufficiency (AI), and sinotubular area (STA). Energy loss coefficient (ELCo) (correcting EOA for pressure recovery) was calculated: ELCo = (STA*EOA)/(STA-EOA). MDCT measured opening angles (OA), geometrical orifice area (GOA), and STA. Patients with elevated MPG (>15 mm Hg) were assessed for low EOA, low OA (>20° below specification), patient-prosthesis mismatch (PPM) (EOA/body surface area <0.85 cm2/m2), high CI (>4.0 L/min/m2), and AI.
Results: There was excellent correlation but a significant difference between the EOA and ELCo (r=0.97, p<0.001; 2.2 ± 0.8 vs. 3.1 ± 1.5 cm2, p<0.001). GOA was larger than and only moderately correlated with EOA (r=0.61, p<0.001; 3.6 ± 0.9 vs. 2.2 ± 0.8 cm2, p<0.001), with a smaller difference between GOA and ELCo (r=0.55, p<0.001; 3.6 ± 0.9 vs. 3.1 ± 1.5 cm2, p<0.001). Elevated MPG was observed in 16 patients, with a low EOA in 2 of these patients. Additional potential etiologies of elevated MPG included PPM in 8 patients and high CI in 4 patients; no patient had a low OA or > mild AI. Either PPM or high CI could be attributed to 12 of 16 patients with elevated gradients, while these were observed 7 of 27 patients with normal gradients (p=0.004).
Conclusion: MDCT is additive to the hemodynamic assessment from TTE, allowing for complete assessment of mechanical AVR hemodynamics and function, including detection of prosthesis OA, and enhances correction for pressure recovery using ELCo. Among patients with elevated gradient on TTE, MDCT allows further assessment to distinguish abnormal prosthesis function from other etiologies including PPM and pressure recovery.