Stress exercise haemodynamic performance and opening reserve of a stented bovine pericardial aortic valve bioprosthesis.

OBJECTIVES

Despite unusual high rates of patient-prosthesis mismatch (PPM), excellent midterm clinical outcomes have been reported after surgical aortic valve replacement (SAVR) with the Avalus™ bioprosthetic valve (Medtronic). To elucidate this "PPM conundrum," the Avalus valve haemodynamics were assessed during exercise testing.

METHODS

Of the 148 patients who had undergone SAVR with the Avalus valve at our institution, 30 were randomly selected among those in whom stress test was deemed feasible and underwent a resting transthoracic echocardiography immediately followed by exercise echocardiography. Severe PPM was defined as indexed effective orifice area (iEOA) ≤ 0.65 cm2 /m2 and moderate PPM as iEOA > 0.65 and ≤ 0.85 cm2 /m2 . Measured PPM was determined with the use of the measured iEOA at rest or stress, while the estimated PPM was based on the estimated iEOA, derived from the mean EOA reported for each valve size in the manufacturer chart.

RESULTS

Measured EOA significantly increased from rest to peak exercise in all PPM groups (p < .05) and the rates of moderate and severe measured PPM decreased from 40% and 20% to 27% and 0%, respectively. The patients with low-flow state (flow < 250 ml/s) had significantly lower measured rest EOA (p = .03). On the basis of the estimated iEOA, there was no severe PPM and 19 patients had moderate PPM (63.3%), with a significantly lower opening reserve than the patients without estimated PPM (p = .04). The estimated iEOA was more reliably correlated to the measured iEOA at maximal stress than the measured iEOA at rest, especially in patients with a low-flow state.

CONCLUSIONS

This study supports the concept of an opening reserve of the Avalus valve to explain the PPM conundrum and promotes the use of exercise Doppler-echocardiography to complete the assessment of mismatch, especially in patients with a low-flow state. Published estimated EOA seems reliable to predict the haemodynamic performance of the Avalus valve, whether the flow conditions at rest.