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Mechanical or Tissue Valve for AVR and MVR
Study Questions:
How do long-term outcomes compare between patients undergoing mechanical versus tissue aortic valve replacement (AVR) or mitral valve replacement (MVR)?
Methods:
Long-term mortality and rates of reoperation, stroke, and bleeding were compared between inverse-probability-weighted cohorts of patients who underwent primary (isolated) AVR or MVR (with or without concomitant tricuspid valve repair, atrial fibrillation ablation, or coronary revascularization) with a mechanical or biologic prosthesis in California from 1996–2013. Baseline patient characteristics were derived from previous hospitalizations or from diagnoses coded as “present on admission” during the index hospitalization. Patients were stratified into different age groups on the basis of valve position (aortic vs. mitral valve).
Results:
Of 45,639 patients who underwent AVR during the study period, 9,942 (21.8%) were eligible for analysis; and of 38,431 patients who underwent MVR during the study period, 15,503 (40.3%) were eligible for analysis. From 1996–2013, the use of biologic prostheses increased substantially for both AVR (from 11.5% to 51.6%) and MVR (from 16.8% to 53.7%). Among patients who underwent AVR, a biologic prosthesis was associated with significantly higher 15-year mortality compared to a mechanical prosthesis among patients 45–54 years of age (30.6% vs. 26.4% at 15 years; hazard ratio [HR], 1.23; 95% confidence interval [CI], 1.02-1.48; p = 0.03), but not among patients 55–64 years of age. Among patients who underwent MVR, a biologic prosthesis was associated with significantly higher mortality compared to a mechanical prosthesis among patients 40–49 years of age (44.1% vs. 27.1%; HR, 1.88; 95% CI, 1.35-2.63; p < 0.001) and among those 50–69 years of age (50.0% vs. 45.3%; HR, 1.16; 95% CI, 1.04-1.30; p = 0.01). The incidence of reoperation was significantly higher among recipients of a biologic prosthesis than among recipients of a mechanical prosthesis. Patients who received mechanical valves had a higher cumulative incidence of bleeding and, in some age groups, stroke, compared to patients who underwent implantation of a biologic prosthesis.
Conclusions:
The authors concluded that a long-term mortality benefit associated with a mechanical prosthesis compared with a biologic prosthesis persisted until 70 years of age among patients undergoing MVR, and until 55 years of age among those undergoing AVR.
Perspective:
This is an important study that raises concern as to whether the increasing use of bioprostheses for AVR or MVR is associated with a compromise in all-cause mortality. Notably, the use of an administrative rather than a clinical database would be expected to lack important clinical details, including the etiology of valve disease, LV ejection fraction, valve size implanted, and medication and laboratory data. As expected, there were significant differences between groups of patients who underwent mechanical and tissue valve replacement; and inverse probability weighting cannot account for residual confounding caused by unmeasured variables, notably including potential bias introduced by biologic prostheses more likely used among frail patients. Although prospective, randomized trials for tissue versus mechanical valve replacement are not likely to be repeated, data such as these at least should be considered in the context of informed discussions with younger patients who are choosing between a mechanical and a tissue valve.
Keywords: Aortic Valve, Atrial Fibrillation, Biological Products, Bioprosthesis, Cardiac Surgical Procedures, Catheter Ablation, Heart Valve Diseases, Heart Valve Prosthesis, Hemorrhage, Mitral Valve, Myocardial Revascularization, Reoperation, Stroke, Stroke Volume, Tricuspid Valve
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