Heart disease is the leading cause of death in the United States, killing more than 600,000 Americans each year, and more than 5 million Americans are diagnosed with heart valve disease each year.

Heart valve disease can occur in any single valve or a combination of the four valves, but diseases of the aortic and mitral valves are the most common. Replacement of diseased valves with prosthetic heart valves reduces the morbidity and mortality associated with native valvular disease, but it comes at the expense of complications related to the implanted prosthetic device.

Worldwide, approximately 280,000 people undergo aortic valve replacement surgery each year. Although mechanical prostheses are more durable, the patients need to take blood-thinning drugs for the rest of their lives. Biological valve prostheses are normally made from cow or pig tissue.

In a new study out of Sweden, researchers found a mechanical valve prosthesis had a better survival record than a biological valve prosthesis. The finding can be highly significant because the use of biological valve prostheses has increased in all age groups in recent years.

In this latest registry study, the researchers examined Swedish patients in the 50-to-69 age group who had had an aortic valve replacement. Of the 4,545 patients, 60 percent had received mechanical valves and 40 percent bioprostheses. In 1,099 propensity score-matched patient pairs, 16 percent had died in the mechanical valve group and 20 percent in the bioprosthetic group; mean follow-up 6.6 years.

Survival was higher in the mechanical than in the bioprosthetic group (5-, 10- and 15-year survival at 92, 79 and 59 percent vs. 89, 75 and 50 percent). There was no difference in stroke, but the risk for aortic valve re-operation was higher and for major bleeding lower in patients who had received bioprostheses than in those with mechanical valves.

According to Dr. Ulrick Sartipy, associate professor at the Department of Molecular Medicine and Surgery at Karolinska Institutet and cardiac surgeon at Karolinska University Hospital's Department of Cardiothoracic Surgery, patients who had received a mechanical prosthesis had better survival rates than those who had received a biological prosthesis.

These results are important because the trend in recent years has been toward a greater use of biological valve prostheses in relatively young patients, partly because these patients don't have to take blood thinners. This research shows mechanical valve prostheses should be the preferred option for young patients.