Aortic valve replacement in middle-aged patients: Is the increased use of bioprostheses justified?

Photographer Ulf Sirborn, Karolinska Institutet.

Aortic valve replacement (AVR) is the standard treatment option for severe aortic valve disease and is performed in approximately 280,000 patients worldwide each year [1]. The aortic valve can be replaced by either a mechanical valve prosthesis or a bioprosthesis. Mechanical valves have an unlimited durability but require the use of lifelong anticoagulant treatment with warfarin. Bioprostheses, on the other hand, do not require warfarin treatment, but have a limited durability. Therefore, mechanical valves are usually recommended to young and healthy patients, whereas bioprostheses are recommended to older patients with a limited life expectancy. Prosthetic valve choice in middle-aged patients (50–70 years) has been widely debated over the last decades, and the scientific evidence for optimal valve choice is limited. In this age group, the risk of reoperation with a bioprosthesis has to be balanced against the risk of bleeding complications that comes with a mechanical valve prosthesis and its mandatory warfarin treatment. Also, the younger the patient, the faster the degeneration of the bioprosthetic valve [2,3].

During the last decade, bioprostheses are increasingly used in all age groups [4], even though there is no convincing scientific evidence to support this. The increased use of bioprostheses can be explained by the fact that bioprostheses used today have a good durability [2,3] and transcutaneous aortic valve implantation with a valve-in-valve approach has emerged as a possible treatment alternative to reoperation [5]. Also, many patients want to avoid the lifelong use of warfarin and therefore prefer a bioprosthesis.

The European Society of Cardiology states in their guidelines [6] that a bioprosthesis is recommended in patients above 65 years of age and a mechanical valve prosthesis is recommended in patients below 60 years of age. Between 60 and 65 years of age, both valve types are considered acceptable options. According to the current guidelines from the American Heart Association/American College of Cardiology [7], a bioprosthesis is recommended in patients above 70 years of age and a mechanical valve prosthesis is recommended in patients below 60 years of age. Between 60 and 70 years of age, both valve types are considered reasonable options.

Contemporary studies evaluating morbidity and mortality after AVR with a mechanical valve versus a bioprosthesis in middle-aged patients have shown contradictory results. Some previous studies found that patients in this age group who received a mechanical valve had a better survival [8,9] whereas others did not find a survival difference between patients with a mechanical valve and a bioprosthesis [10,11].

Chiang et al. [10] performed a cohort study including 4253 patients aged 50–69 years that underwent primary, isolated AVR in New York State between 1997 and 2004. They compared long-term survival, the rate of stroke, aortic valve reoperation, and major bleeding events according to prosthesis type in 1001 propensity score-matched pairs. They found no difference in survival between the groups; 15-year survival was 61% in the bioprosthetic group and 62% in the mechanical valve group (hazard ratio (HR) 0.97, 95% confidence interval (CI) 0.83–1.14). There was no difference in the rate of stroke between the two groups, but the rate of aortic valve reoperation was higher in patients who received a bioprosthesis, and the rate of major bleeding was higher in patients who received a mechanical valve prosthesis. They suggested that current guidelines recommending either a mechanical or a biological valve prosthesis between 60 and 70 years of age could be extended to include patients aged 50–59 years. They concluded that both valve types are reasonable options in patients down to 50 years of age.

Stassano et al. reported the only contemporary randomized clinical trial and included 310 patients aged 55–70 years who underwent AVR with a mechanical or a biological valve prosthesis at two centers in Italy between 1995 and 2003 [12]. The primary outcomes were long-term survival, structural valve deterioration, and reoperation. Major adverse prosthesis-related events including thromboembolism, bleeding, endocarditis, and non-structural dysfunction were the secondary end points. They found no difference in survival between the groups. Patients with bioprostheses had a higher risk of reoperation, but no other differences in the rate of major adverse prosthesis-related events were found. However, the mean age was 64 years in both groups, and it is not clear how many of the patients that were below 60 years of age. Also, it should be noted that only 28% (310/1120) of eligible patients were included in the study which may affect the generalizability of the results.

In a nationwide population-based cohort study, Glaser et al. [8] included all patients (n = 4545) aged 50–69 years that underwent primary, isolated AVR and received either a mechanical or biological valve prosthesis in Sweden between 1997 and 2013. In 1099 propensity score-matched pairs, they found that patients who received a mechanical valve prosthesis had a better long-term survival than patients who received a bioprosthesis. The 15-year survival was 59% in the mechanical valve group compared to 50% in the bioprosthetic group (HR 1.34, 95% CI 1.09–1.66). In a subgroup analysis, patients aged 50–59 years who received a mechanical valve prosthesis had a significantly higher long-term survival than patients who received a bioprosthesis. However, in patients aged 60–69 years, no difference in survival was found between the groups. Similarly to the study performed by Chiang et al. [10], there was no difference in the rate of stroke between the groups, and patients who received a bioprosthesis had a higher risk of aortic valve reoperation and a lower risk of major bleeding. The better long-term survival with mechanical valve prostheses seen in the study by Glaser et al. [8] is in contrast with the results reported by Chiang et al. [10], and Stassano et al. [12], but is consistent with current guidelines.

In conclusion, the optimal valve choice in middle-aged patients undergoing AVR remains controversial because large randomized clinical trials are lacking. Results from observational studies are conflicting. After summarizing the available literature, it is our opinion that there is no sufficient scientific support to justify the increased use of bioprosthesis in middle-aged patients. As stated in current guidelines, each patient should be individually and carefully assessed and factors other than age, such as life expectancy and comorbidities, should be given a higher value than age when advising middle-aged patients regarding aortic prosthetic valve choice.

Financial & competing interests disclosure

The authors have no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties.