Viagra compounds found to shrink abnormally large hearts

WASHINGTON - Compounds related to Viagra, already in clinical trials to prevent heart failure, may also counter the disease in a different way, says a new study.

The results hold promise for the design of a new drug class and for its potential use in combination with Viagra or beta blockers.

In heart failure, which affects about 5.7 million Americans, the heart gradually loses the ability to pump with enough force to supply the body with blood.

One reason for lost pumping strength is the mass death of heart muscle cells seen in many heart attacks. Fewer remaining muscle cells must then push around the same amount of blood, and hard working muscles grow.

Unlike the healthy bulging of an athlete’s bicep, abnormal muscle growth (pathogenic hypertrophy) in diseased hearts thickens chamber walls, slows the heartbeat and causes potentially fatal arrhythmias (erratic beats) and heart failure as well.

Recent efforts to reverse hypertrophy included a clinical trial, sponsored by Viagra manufacturer Pfizer, and the National Heart, Lung, and Blood Institute (NHLBI), where they looked at whether Viagra (sildenafil) can treat moderate heart failure and reduce hypertrophy.

Along with increasing blood flow in arteries, Viagra interferes with phosphodiesterases (PDEs), the enzymes that break down the messenger molecule called cyclic guanosine monophosphate (cGMP), which would otherwise restrain heart muscle cell growth.

“Our results suggest that a PDE1a inhibitor alone can shut down abnormal cardiac growth, and when combined with Viagra or beta blockers, may do so in more than one way,” said Chen Yan, associate professor cardiology, University of Rochester Medical Centre (URMC) and study co-author, says a Rochester release.

Yan’s lab is focused on revealing the role of various PDE enzymes in atherosclerosis and hypertension as well as in heart failure.