Biological vs. mechanical aortic root replacement

Objectives: Although age and co-existing coronary disease are major determining factors when deciding valve choice (mechanical vs. biological) in simple aortic valve replacement, no studies have documented selection criterion for biological (BIO) vs. mechanical (MECH) aortic root prosthesis. Methods: Two hundred and twenty-one consecutive patients underwent elective aortic root replacement with either BIO (homograft, n=111, Freestyle®, n=25) or MECH composite grafts (n=85). Median age in BIO was 53 years and in MECH 54 years (P=NS). Groups were similar in gender, NYHA class and ejection fraction (BIO, EF=59% vs. MECH, EF=55%), but the need for concomitant coronary artery bypass grafting (CABG) did differ between groups (MECH=35% vs. BIO=17%, P=0.003). Mean follow-up was 42±28 months for mortality and 39±28 months for morbidity. Results: Full root replacement was performed in 213 patients (96%) and hemi-root in eight (4%). The most common underlying etiologies were annulo-aortic ectasia (n=82, 37%), calcified-degenerative (n=73, 33%) and bicuspid/congenital aortic valve disease (n=39, 18%). Operative mortality was 1.5% for BIO and 2.4% for MECH (P=0.5). By univariate analysis there was a trend towards greater 5-year survival in BIO (92.4% vs. 88.2%, P=0.068). By multivariate analysis, increasing age (HR=2.4, P=0.003), previous valve replacement (HR=4.7, P=0.024), concomitant CABG (HR=3.7, P=0.032), and perioperative stroke (HR=9.9, P=0.0005) were all independent predictors of late death. The 5-year freedom from valve-related complications was similar in both groups (BIO=93% vs. MECH=86%, P=0.5). Conclusions: Elective aortic root replacement is an exceedingly safe operation. At mean follow-up of 4 years, there is no meaningful difference in early or mid term valve-related results between BIO and MECH aortic root replacement. Continued evaluation for late valve-related complications in this cohort will be necessary to determine the advantages, if any, of one prosthesis over the other.