Viagra, Pfizer's erectile dysfunction blockbuster, also has the potential to treat and prevent heart failure, US researchers have claimed.

A Johns Hopkins University team has shown that Viagra (sildenafil) does not just aid blow flow but also protects the heart from the effects of high blood pressure that can cause it to balloon and pump blood less efficiently. The scientists report what is believed to be the first direct, in vivo evidence that the drug amplifies the effects of a key heart-protective protein.

Their findings, to be published in the Journal of Clinical Investigation online, suggest that Viagra, which has been used by more than 35 million men worldwide since its introduction more than a decade ago, may find a new role in either treating or preventing heart failure due to chronic high blood pressure.
The cardiologists say their findings may explain why some doctors have already reported that impotent patients treated with Viagra have shown improved heart function.

The key, say the investigators led by David Kass, is Viagra's ability to boost the effect of a single protein, RGS2, newly identified in the latest study. RGS2 slows the body's slide towards heart failure in the presence of high blood pressure.

Mice genetically altered to have no RGS2 died rapidly - most within a week - when their blood pressure was artificially raised. Animals with the protein did not did die, but a third of them showed signs of heart failure. But a third group, animals with RGS2 that were treated with Viagra, suffered significantly fewer ill-effects than either of the other two groups.

"Sildenafil clearly prolongs the protective effects of RGS2 in mouse hearts," said Prof Kass. He added that by boosting "the protective effects of RGS2, researchers could develop new therapies or improve existing ones, including ACE inhibitors and possibly sildenafil, for people with heart failure".