New research suggests that the erectile dysfunction drug Viagra could be a safe and effective treatment for heart disease.

Phosphodiesterase-5 inhibitor (PDE5i), the main ingredient in Viagra, blocks the enzyme PDE5; this enzyme works to prevent the relaxation of smooth muscle tissue, BioMed Central reported.

In past animal studies, the cardioprotective effects of PDE5i have been unclear, but researchers from Sapienza University of Rome looked at its effects in humans for the first time. Researchers carried out a meta-analysis of randomized controlled trials by looking at articles published between January 2004 and May 2014 from the MEDLINE, EMBASE, Cochrane Library and SCOPUS databases. The analysis encompassed 1,622 patients from mixed populations who were treated with either PDE5i or a placebo.

The study suggests PDE5i prevented the heart from increasing in size in patients suffering from ventricular hypertrophy, which causes the muscles of the left ventricle to thicken. Viagra proved to improve heart conditions in all of the patients without causing heightened blood pressure.

"We found that the main ingredient in Viagra can be used as an effective, safe treatment for several patients with heart disease. Large clinical trials are now urgently needed to build on these encouraging findings," said lead author of the study, Andrea Isidori.

Researchers concluded the medication could be safely administered to men who suffered from heart muscles thickening, and even certain types of early heart failure.

Since the majority of the participants in the recent trials were men, researchers suggested a larger study should be conducted that looks at "sex-specific long-term responses."

The study marks the first parallel analysis of the effects of the inhibitor on the shape and size of heart muscles, as well as its performance. The findings were published October 19 in the journal BMC Medicine.