Early Mortality After Aortic Valve Replacement With Mechanical Prosthetic vs Bioprosthetic Valves Among Medicare Beneficiaries: A Population-Based Cohort Study

Study Questions:

What is the incidence of early mortality after aortic valve replacement (AVR) among recipients of mechanical and bioprosthetic aortic valves?

Methods:

This was a retrospective analysis of patients 65 years or older in the Medicare databases who underwent AVR from July 1, 2006, through December 31, 2011. In the mixed-effects models adjusting for physician and hospital random effects, the investigators estimated odds ratios (ORs) of early mortality to compare mechanical versus bioprosthetic valves. The main outcome measures were early mortality measured as death on the date of surgery, death within 1-30 or 31-365 days after the date of surgery, death within 30 days after the date of hospital discharge, and operative mortality (death within 30 days after surgery or at discharge, whichever was longer).

Results:

Of the 66,453 Medicare beneficiaries who met inclusion criteria, 19,190 (28.88%) received a mechanical valve and 47,263 (71.12%) received a bioprosthetic valve. The risk for death on the date of surgery was 60% higher for recipients of mechanical valves than recipients of bioprosthetic valves (OR, 1.61; 95% confidence interval [CI], 1.27-2.04; p < 0.001; risk ratio [RR], 1.60). The risk difference decreased to 16% during the 30 days after the date of surgery (OR, 1.18; 95% CI, 1.09-1.28; p < 0.001]; RR, 1.16). They found no differences within 31-365 days after the date of surgery and within the 30 days after discharge. The risk for operative mortality was 19% higher for recipients of mechanical compared with bioprosthetic valves (OR, 1.21; 95% CI, 1.13-1.30; p < 0.001; RR, 1.19). The number needed to treat with mechanical valves to observe one additional death on the surgery date was 290; to observe one additional death within 30 days of surgery, 121. Consistent findings were observed in subgroup analyses of patients who underwent concurrent AVR and coronary artery bypass grafting (CABG), but not in the subgroup undergoing isolated AVR.

Conclusions:

The authors concluded that use of mechanical aortic valves was associated with a higher risk for death on the date of surgery and within the 30 days after surgery compared with bioprosthetic aortic valves among patients who underwent concurrent AVR and CABG.

Perspective:

This study reports that when compared with bioprosthetic aortic valves, mechanical aortic valves were associated with an increased risk for early death after concurrent AVR and CABG surgery in Medicare patients ages 65 years and older. The greatest risk existed on the date of surgery, when the adjusted RR for the mechanical valve cohort versus the bioprosthetic valve cohort was 1.60. However, no significant association between valve type and risk for death was observed in the immediate period after hospital discharge. Additional research is needed to identify the cause of this difference and potential ways to mitigate risk.

Clinical Topics: Cardiac Surgery, Invasive Cardiovascular Angiography and Intervention

Keywords: Outcome Assessment (Health Care), Heart Valve Prosthesis, Odds Ratio, Bioprosthesis, Confidence Intervals, Medicare, Coronary Artery Bypass


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