A study led by the University of Bristol, Bristol, England, has found that mechanical heart valves provide better long-term survival than biological heart valves in patients aged 50-70 years. The findings challenge current guidelines, which frequently favour biological heart valves in this age group.
Researchers noted that mechanical heart valves are generally recommended for patients under 50 years of age, while biological heart valves are preferred for those over 65 or 70 years of age. For patients in the intervening ages, the current guidelines leave the choice to the discretion of surgeons and patient preference.
Over the past two decades, there has been an increase in the use of biological over mechanical heart valve replacements. However, while short-term clinical outcomes are known to be the same, long-term outcomes are still being debated.
Current Guidelines Under Scrutiny
The study, published in the European Journal of Cardio-Thoracic Surgery, analysed data from 1708 patients (61% men) with a median age of 63 years. Of these, 1191 (69.7%) received a biological prosthesis. Short-term survival rates were similar but 13 years post-surgery, patients with mechanical heart valves had significantly better survival than those with biological heart valves. The researchers concluded that the study “underscores the need for a critical re-evaluation of prosthesis selection strategies in this age group.”
The results echo those of a recent US study, which found that aortic mechanical valves were associated with better 12-year survival than bioprosthetic valves in patients aged 60 years or younger.
The Decline of Mechanical Heart Valves
Prof Bernard Prendergast, consultant cardiologist at the Cleveland Clinic London, attributed the decline in mechanical heart valve use to the growing availability of transcatheter aortic valve implantation (TAVI) and patient concerns about the lifestyle implications of lifelong warfarin anticoagulation. These had contributed to “the demise of mechanical valve replacement,” he told Medscape News UK.
Prendergast, a UK representative on the task force that developed the 2021 European Society of Cardiology/European Association for Cardio-Thoracic Surgery Guidelines for the management of valvular heart disease, noted that current recommendations state that the choice between a mechanical prosthesis and a bioprosthesis “should be patient-centred and multifactorial,” based on patient characteristics and preferences. A mechanical prosthesis is recommended if there are no contraindications to long-term anticoagulation and in patients at risk for accelerated structural valve deterioration.
A bioprosthesis is preferred where anticoagulation is unsuitable due to adherence issues or contraindicated because of high bleeding risks, and in those patients whose life expectancy is lower than the presumed durability of the bioprosthesis. The guidelines also recommend a bioprosthesis if there is a need for reoperation after mechanical valve thrombosis, despite good long-term anticoagulant control.
The Bristol study gives “important” new data, Prendergast told us. It reminds us that long-term prosthetic valve durability and avoidance of the need for a second — or even third — procedure are important considerations when contemplating valve surgery in younger patients. This is especially so in an era of modern mechanical valve designs, which require low levels of anticoagulation and self-directed patient care, which allows home-based international normalised ratio monitoring and warfarin dose adjustment.
Call for Reassessment
Prof Gianni Angelini, senior study author and British Heart Foundation chair of cardiac surgery at the University of Bristol, said in a press release that the results have “implications for decision-making in surgical heart valve replacements for patients aged between 50 and 70 years old.” The evidence supporting better long-term survival in patients receiving a mechanical heart valve suggests the current trend favouring biological heart valves in this age bracket “should be urgently reconsidered,” he said. The survival benefit of mechanical heart valves was “especially clear in smaller-sized valves,” Angelini added.
Prof Enoch Akowuah, consultant cardiac surgeon at South Tees Hospitals NHS Foundation Trust, described the study as “timely.”
As life expectancy has increased, with current projected longevity for a 50-year-old of 37 years, lifetime management of patients undergoing tissue aortic valve replacement is critical. Practice varies widely across the United Kingdom but has changed rapidly in the past 5 years, he said, with more and more young patients receiving a tissue valve.
Need for Further Research
The Bristol study “suggests that this change in practice may lead to significant mortality in these young patients over time,” Akowuah told Medscape News UK. However, he noted that the study was retrospective and prone to biases. A well-powered randomised controlled trial with long-term follow-up is “urgently needed” to provide definitive evidence. Akowuah said that his team is currently planning such a study.
“The study is needed now because if this question about differences in survival between biological and mechanical valves is not answered, practice will change, with young patients having tissue valves (including TAVI), and the opportunity to determine if mechanical valves are in fact a better option for long-term survival in this younger patient cohort will be lost permanently,” Akowuah said.
Neither Prendergast nor Akowuah declared any conflicts of interest.
Dr Sheena Meredith is an established medical writer, editor, and consultant in healthcare communications, with extensive experience writing for medical professionals and the general public. She is qualified in medicine and in law and medical ethics.