MONDAY, May 12 (HealthDay News) -- Patients with Duchenne muscular dystrophy often suffer from heart failure, but Viagra might prevent or delay the onset of this condition, a new Canadian study finds.

In experiments with mice, researchers showed that Viagra (sildenafil) improved heart performance by preventing the breakdown of a compound called cGMP, which relaxes smooth muscle.

"Duchenne muscular dystrophy is a crippling disease that affects both skeletal muscle and cardiac muscle," said lead researcher Christine Des Rosiers, a professor of cardiology in the department of nutrition at the University of Montreal. "Currently, there is a need for the development of more effective treatment strategies for patients affected with this disease."

In their experiments, the researchers used mice bred to mimic Duchenne muscular dystrophy. Then the scientists gave the rodents doses of Viagra comparable to those taken by men for erectile dysfunction.

The researchers found that Viagra improved heart function in the mice by preventing the breakdown of cGMP.

In a further experiment, the researchers inserted a gene into the hearts of the mice that increased the production of cGMP. The result: The mice were able to maintain normal heart function.

The findings are published in this weeks issue of the Proceedings of the National Academy of Sciences.

"Our findings substantiate benefits for the dystrophic heart using a pharmacological approach, namely with sildenafil, which is safe, well-tolerated and currently available for clinical use," Des Rosiers said. "Hence, this could provide the basis for a new avenue for the treatment. Furthermore, the benefits of this therapeutic approach would be expected to extend beyond the heart to affected skeletal muscle and other tissues."

Dr. Valerie A. Cwik, medical director and vice president of research at the Muscular Dystrophy Association, said there's a need for new approaches to the treatment of heart failure in patients with Duchenne and other forms of muscular dystrophy.

"The findings presented by these authors are interesting and certainly have potential clinical implications for the various forms of dystrophinopathy [heart damage]," she said, adding that heart failure is a major cause of illness and death in late-stage Duchenne muscular dystrophy.

"At the present time, there is no consensus or standard of care for optimal management of the cardiac complications of dystrophinopathies, and further research in this area is clearly needed," Cwik said.

While Viagra hasn't been tested in humans to see if it benefits muscular dystrophy patients, it has been available for years and appears to be safe, Cwik noted.

More information

For more on muscular dystrophy, visit the Muscular Dystrophy Association.

SOURCES: Christine Des Rosiers, Ph.D., professor, department of nutrition, University of Montreal, Canada; Valerie A. Cwik, M.D., medical director and vice president, research, Muscular Dystrophy Association, Tucson, Ariz.; May 13-16, 2008, Proceedings of the National Academy of Sciences

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