Measurement of aortic valve regurgitation after valve-sparing root replacement - a quantitative and intraoperative method

Abstract

Introduction Aortic valve regurgitation (AR) is a common type of aortic valve disease that affects the surrounding tissues of the heart. Surgery may be required in patients with acute or chronic AR, aortic root disease or ascending aortic dissection. A viable alternative to traditional aortic valve replacement that offers encouraging clinical outcomes is aortic valve-sparing root replacement (VSRR). However, reoperation due to recurrent or residual AR has a high incidence. Transesophageal echocardiography (TEE) is the gold standard for intraoperatively evaluating residual AR. Evaluation is performed after aortic declamping; therefore, a longer bypass time is inevitable when additional repair is required. Furthermore, quantification of AR with TEE can be challenging. Therefore, the need for an early and quantitative assessment method rises. The main objective of this study was to identify the relationship between the intraoperative and quantitative assessment of the repaired aortic valve and the post-declamping echocardiographic assessment after VSRR. Echocardiographic parameters were studied to find the optimal parameter to identify this relationship. Furthermore, variables that influence the amount of leakage in the quantitative and intraoperative assessment of the repaired valve were identified. Two in vitro experiments were performed to investigate the contribution of these variables to the leakage of sufficient and insufficient aortic valves.

Experiment 1 The effective regurgitant orifice area was the optimal parameter to obtain the relationship between echocardiographic and quantitative assessment. It was implemented in an experimental setup as the orifice area. In addition to this parameter, the contribution of the orifice shape, pressure and fluid viscosity to the leakage was examined using a custom representation of the ascending aorta and the aortic valve. The orifice area was shown to have the most significant contribution to the amount of leakage, followed by the pressure and shape of the orifice. These three variables will be assessed in a second experiment. The viscosity of the fluid did not influence the leakage. 

Experiment 2 In a second experiment, the contribution of different variables to sufficient and insufficient aortic valves was evaluated at different pressures. The experiment was carried out in three cardiac tissues, in which first the contributions to the baseline leakage of a sufficient valve were evaluated. Two methods were used to create insufficiency. The first involved a punch and the second applied a more physiological approach of leaflet manipulation. The graft water permeability and the anastomosis leakage determined the leakage in a sufficient aortic valve state. The leakage of an insufficient aortic valve was almost completely determined by the size of the insufficiency. Graft permeability and anastomosis leakage could be neglected in the insufficient valve state. The leakage of the punched valve was comparable to the expected regurgitant volume based on the echocardiographic guidelines for that area. Leaflet manipulation resulted in less leakage than expected.

Conclusion The contribution of several variables to the leakage of sufficient and insufficient aortic valves was investigated in two in vitro experiments. The results of this study show that the contributions of each of these variables could be quantified. As a result, the leakage of an insufficient aortic valve could be quantified in a static, pressurised in vitro setting. This is the first step in obtaining the relationship between the quantitative amount of leakage and echocardiography, to improve intraoperative assessment of the repaired aortic valve after VSRR.