By Michael H. Crawford, MD
SOURCE: Chiang YP, et al. Survival and long-term outcomes following bioprosthetic vs mechanical aortic valve replacement in patients aged 50 to 69 years. JAMA 2014;312:1323-1329.
This article originally appeared in the November 2014 issue of Clinical Cardiology Alert.
Bioprosthetic aorta valves are recommended for those > 70 years of age because of their reduced durability compared to mechanical valves and mechanical prostheses, which are recommended for those < 60 years because bioprosthetic valves deteriorate more rapidly in younger individuals. Those between ages 60 and 70 represent a gray zone, yet this is a decade in which most valve surgery is done. Thus, these investigators from Mount Sinai Medical Center in New York performed a retrospective cohort analysis of primary, isolated aortic valve replacement in New York State over a recent 6-year period in patients aged 50-69 years. Patients with concomitant coronary or thoracic aortic surgery were excluded. The primary endpoint was all-cause mortality. Secondary endpoints included stroke, reoperation, and major bleeding. Follow-up was stopped at the end of 2012. Among the 4253 patients identified, 35% received bioprosthetic valves and 65% mechanical prostheses. Propensity score matching was done to adjust for differences in baseline characteristics and variations in practice between surgeons. This resulted in 1001 pairs of patients receiving the two valve types. There was no difference in 30-day mortality between the two groups (both 3%). Over a median follow-up of 11 years (range 0-17), there was no difference in survival. Actualized 15-year survival was 61% in the bioprosthetic group and 62% in the mechanical prosthesis group (HR mechanical vs bio 0.97; 95% CI, 0.83-1.14). Also, no difference in stroke rates were observed (8% bio vs 9% mechanical). Reoperation was significantly more common with bioprostheses (12% vs 7%). Major bleeding was more frequent with mechanical prostheses (7% bio vs 13% mechanical). The authors concluded that in patients aged 50-69 years there was no difference in 15-year survival with a bioprosthetic valve vs a mechanical prosthetic valve, but bioprosthetic valve patients had more reoperations and mechanical valve patients had more major bleeding. These findings suggest that bioprosthetic valves may be acceptable in patients aged 50-70 years.
The choice of a prosthetic valve type in the 50- to 70-year age range is always challenging, especially since people are living longer. Durability favors mechanical prostheses, but many patients balk at taking warfarin. In fact, as shown in this study, over the course of the study a shift toward bioprosthetic valves occurred. At the start of their study in 1997, 15% of patients had bioprosthetic valves. By 2012, it was 74%. Perhaps their cardiologists were saying what I have been saying: If your bioprosthesis deteriorates faster than you do, you will be able to have a percutaneous one put in. It is nice to see this study exhibit a relatively low 15-year reoperation rate for bioprostheses of 12%. The mortality for reoperation in this study was 9%, but some high-volume centers in New York had rates in the 2-5% range. Transaortic valve replacement mortality should be even lower in this group.
The current AHA/ACC guidelines recommend a mechanical valve for those < age 60, but these results would suggest that the bioprosthetic valve range can be extended to age ≤ 50 years, and this is what has been happening, at least in New York. The guideline recommendations are based on older randomized trials. Since then, prosthetic valve mortality and resistance to thrombosis have improved. It is unlikely that new randomized trials will be done, but I am comfortable going with this compelling data and patient desires to have bioprosthetic valves. The early successes of non-surgical valve replacement have also bolstered my confidence that this is a reasonable strategy.
Of course, there are limitations to this study. Not all potential confounders were accounted for in their model. Notably left out were important factors such as frailty, etiology of aortic valve disease, presence of other valve disease, extent of coronary artery disease, and left ventricular ejection fraction. Also, surgeons tend to put biological valves in sicker patients. In addition, they couldn’t account for patients who moved out of state and didn’t die. Despite these limitations, the study is in line with other smaller recent observational studies and with the trends in valve surgery and replacement today. Perhaps it’s time to update the guidelines.