VIAGRA blunts effects of stress on the human heart
sildenafil citrate (Viagra), a drug used to treat erectile dysfunction (ED) in millions of men, reduces the stimulatory effects of hormonal stress on the heart by half, according to results of a new study by researchers at the University Johns Hopkins.
While sildenafil is more widely known for helping genital blood vessels expand to maintain an erection and thought, more recently, as a treatment for pulmonary hypertension, has been to have little direct effect on the human heart.
In the heart, blunts sildenafil beating reinforced heart caused by stress induced chemically, thus reducing the excess amount of blood and the force used to pump the body, according to lead author of the study and cardiologist David Kass, MD, professor at Johns Hopkins university School of Medicine and its Institute of the heart.
"Sildenafil effectively puts un'freno'en chemical stimulation of the heart," says Kass.
Researchers from appearing in the journal Circulation online Oct. 24, are believed to be the first confirmation in humans that sildenafil has a direct effect on the heart. Previous research by Kass and his team showed that sildenafil had such effects in mice, blocking the short-term effects of hormonal stress on the heart. Related studies by the group also showed that sildenafil prevents and reverses the effects long term chronic heart of high blood pressure.
Moreover, Kass adds, the latest Hopkins findings confirm that sildenafil helps the heart function monitoring only when the heart is under duress, but has little impact under normal conditions.
Another research Kass and his team published earlier this year in the journal Nature Medicine showed that, in mice, sildenafil could reverse the negative effects on heart muscle weakened by heart failure and enlargement, a condition known as hypertrophy. "But we had no firm evidence as to whether or how this therapy might work in the human heart. Our latest research provides firm evidence this drug does have an important impact on the heart. "
Thirty-five healthy men and women with an average age of 30 and no previous signs of coronary artery disease, participated in the six-month study. Within a period of three hours, each participant received two separate injections dobutamine (5 micrograms per kilogram of five minutes), a synthetic, adrenaline-like chemical that increases heart rate and pumping force.
Between injections, the study participants were randomly assigned to a group that was treated with sildenafil (100 milligrams taken orally) or a group given placebo sugar pill. All participants were given the second dobutamine injection to see what effects sildenafil or placebo had on the heart.
Measurements of heart function were made before and after each injection. This included blood readings, electrocardiograms and echocardiograms pressure and blood samples to confirm relatively equal levels of sildenafil and other enzymes.
The results showed that each dobutamine injection stimulates the function of the heart, increased heart rate and strength of each beat of the heart to pump blood throughout the body.
"This stimulation is similar to the way the nervous system normally increases heart function when activated by emotional stress or exercise or diseases such as heart failure," Kass added.
After the first injection of dobutamine, the force of contraction of the heart increased by 150 percent in both groups. In the placebo group, this increase is repeated after the second injection. However, in the group treated with sildenafil, increased heart rate was reduced by 50 percent, resulting in a smaller increase in blood flow and blood pressure generated by the heart in response to chemical stimulation.
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