Researchers at the University of Alberta have shown that Viagra, the popular drug prescribed for erectile dysfunction, can improve heart function and potentially save the lives of people with specific heart problems.
Viagra's unexpected benefit has led the U of A researchers to encourage doctors to consider the drug when a patient has a failing right ventricle of the heart, a dire condition for which there are currently no treatments available.
The research will appear next week in Circulation, a journal of the American Heart Association.
"There are a number of medical conditions in both children and adults for which there is a need to boost the performance of the right ventricle, and this drug can be clinically and immediately relevant to help these patients," said Dr. Jayan Nagendran, a cardiac surgery resident at the U of A and the first author of the paper.
"Sometimes the right ventricle can fail rapidly and even result in death, like in lung transplant surgery, for example. In such a case, Viagra may increase the right ventricle's performance and save the patient." Nagendran added.
"We have a number of drugs and therapies available to treat the left ventricle of the heart to prevent it from failing or to treat it after it has failed, but we don't have anything for the right ventricle. The phosphodiesterase type 5 inhibitors, which include Viagra, Cialis and Levitra, may offer some important benefits in this case," said Dr. Evangelos Michelakis, a U of A cardiologist, the Canada Research Chair in Pulmonary Hypertension and the senior author of the paper.
In a healthy person, phosphodiesterase type 5 constricts arteries in two places in the body, the lungs and the penis. In the lungs, it prevents excessively low blood pressure. In the penis, it prevents excessive engorgement.
However, undue phosphodiesterase type 5 can constrict these arteries too much and cause problems, as it does in the case of pulmonary hypertension, where lung arteries constrict and put a strain on the right ventricle of the heart. Phosphodiesterase type 5 inhibitors allow the arteries to relax so that blood can flow more easily.
In 2002, a U of A research team led by Michelakis published the first evidence that Viagra may improve pulmonary hypertension in humans. This work was later conformed by larger trials and Viagra sold under the name Revatio, is now approved all over the world for pulmonary hypertension.