Increasingly, biological heart valves are being used preferentially to mechanical valves in surgical replacement procedures. New research at Sweden’s Karolinska Institutet might turn this preference on its head.
Aortic valve replacements have been carried out since the 1960s, and since those early days, the procedure has been repeatedly and significantly improved.
Today’s aortic valve replacement procedures can often be minimally invasive; around 280,000 aortic valves are replaced globally each year.
There are a number of reasons why a heart valve may need replacing. The most common of which is aortic stenosis, a narrowing of the aortic valve.
This narrowing restricts blood flow from the left ventricle to the aorta and increases the eventual risk of heart failure.
Aortic regurgitation is another of the most common reasons for valve replacement. In this case, the valve is leaky and allows blood to move back into the heart rather than exit and move through the body.
As with aortic stenosis, the excess work required to pump blood around the body can eventually lead to complications, including heart failure.
Surgeons completing modern valve replacement operations must choose between mechanical and biological valves, both of which have their own pros and cons.
Mechanical versions are constructed from sturdy man-made materials like carbon and titanium; these valves are stress tested for durability, and some are capable of remaining viable for an estimated 50,000 years.
Biological valves are made either from strong, flexible animal tissue or, rarely, human donor tissue. They are expected to last 10-20 years.
Biological heart valves are used in the majority of replacements and are generally considered, across all age groups, to be the best option.
Mechanical valves are much more durable, but they are also more likely to succumb to clotting problems. These clotting issues can lead to serious consequences. As such, patients with mechanical valves are required to take blood thinning medication, like warfarin, for the rest of their lives.
This clotting risk and lifelong medication is clearly not ideal for younger heart surgery candidates with decades left to live.
Whether mechanical or biological valves are preferable in relatively young patients is a question that has sparked lively debate among researchers and doctors.
New research, carried out by Dr. Ulrik Sartipy, associate professor at the Department of Molecular Medicine and Surgery at the Karolinska Institutet, looked at the mechanical-biological question in depth.
The study, reported in the European Heart Journal, followed 4,500 Swedish aortic valve replacement patients aged 50-69. The research team collated survival rates, incidents of stroke and re-operation rates.
Their investigation reconfirmed a previous study’s findings in relation to the reduced bleeding risks attributed to biological valves. However, the team’s other findings bucked the trend significantly.
Dr. Ulrik Sartipy says:
“We show that patients who had received a mechanical prosthesis had better survival rates than those who had received a biological prosthesis.”
Another of the study’s findings, which might help sway the pro-biological lobby, was that patients with a biological valve had a higher chance of needing further operations on the valve.
Additionally, stroke risk was found to be the same in both mechanical and biological valve replacements. Natalie Glaser, PhD student and part of the research team, says:
“Our research shows that mechanical valve prostheses should be the preferred option for young patients.”
The research certainly adds weight to the argument for using mechanical valves in younger patients. The debate, however, is likely to continue as weight is added to either side through further investigation.
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