Abstract
The Ross procedure consists of replacing a diseased aortic valve with the patient’s own pulmonary valve and root. In some instances, patients develop pulmonary autograft dilatation and regurgitation, requiring re-operation. It has been suggested that bicuspid aortic valves are associated with autograft dilatation, which has led some to contraindicate the Ross procedure in this patient population. However, bicuspid aortic valves are very prevalent in the age group that would benefit the most from this procedure. The aim of this study was to compare the biomechanical properties of aortas (Ao) and pulmonary arteries (PA) according to aortic valve phenotype (tricuspid, bicuspid and unicuspid), in patients undergoing the Ross procedure. At the time of surgery, segments of anterior aortic and PA wall (1x1cm) were obtained and categorized according to phenotype, from 27 patients undergoing the Ross procedure. The segments were subjected to displacement-controlled biaxial stretch testing within 8 hours of surgery, at 37 degrees Celsius in a physiological solution. Tissue stiffness (elastic modulus) at an engineering strain of 60% was evaluated in the longitudinal and circumferential axes. Fourteen patients were male (52%) and mean age was 47±13 years. Aortic valve phenotype was bicuspid in 17 patients (63%), unicuspid in 7 patients (26%) and tricuspid in 3 patients (11%). Surgical indication was aortic stenosis in 19 patients (70%), mixed disease in 5 patients (19%), aortic regurgitation in 2 patients (7%) and endocarditis in 1 patient (4%). When comparing PAs from patients with different aortic valve phenotypes, there were no significant differences in PA thickness (p=0.57), circumferential elastic modulus (p=0.7) and longitudinal elastic modulus (p=0.47). Comparisons between Ao and PA within each valve phenotype group showed no differences between Ao and PA longitudinal elastic moduli in unicuspid and bicuspid patients (p=0.11 and p=0.14, respectively). Similarly, circumferential elastic modulus between Ao and PA was similar in the unicuspid population (p=0.44). In contrast, PAs from the bicuspid population were significantly less stiff in the circumferential axis than their respective Ao (0.10±0.06 MPa vs 0.17±0.06 MPa, p=0.01). Despite the small sample size, current findings suggest that the biomechanical properties of PAs obtained from patients undergoing the Ross procedure are independent of aortic valve phenotype. These findings suggest that changes in autograft dimensions in the long term are not related to the intrinsic biomechanical properties of PAs. Further analyses are warranted to correlate these findings with histological sections and to determine their clinical significance.
Published Version
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