Research conducted at The University of Manchester has found that a drug used to treat erectile dysfunction can slow or even reverse the progression of heart failure in sheep.

The study, funded by The British Heart Foundation, represents a breakthrough in the treatment of heart disease, where five-year survival rates are lower than most common cancers.

The study of the drug Tadalafil (which is in the same class as Viagra) proves that it is biologically effective as a treatment for heart failure in sheep.

However, lead author Professor Andrew Trafford argues the effect is likely to also be shown in humans. The study has been published in the journal Scientific Reports.

Implications for patients

Heart failure is a life-threatening condition, occurring when the heart is too weak to pump enough blood to meet the body's needs.

It also causes a build-up of fluid that backs up into the lungs, resulting in breathlessness as well fluid retention, resulting in swelling of different parts of the body.

Most current treatments are ineffective.

“This discovery is an important advance in a devastating condition which causes misery for thousands of people across the UK and beyond,” said Professor Trafford.

“We do have limited evidence from human trials and epidemiological studies that show Tadalafil can be effective in treating heart failure.

“This study provides further confirmation, adds mechanistic details and demonstrates that Tadalafil could now be a possible therapy for heart failure.

“It’s entirely possible that some patients taking it for erectile dysfunction have also unwittingly enjoyed a protective effect on their heart.”

Sheep were used by the team as the physiology of their hearts is similar to humans

When the animals had heart failure - induced by pacemakers - which was sufficiently advanced to need treatment, the team administered the drug. Within a short period the progressive worsening of the heart failure was stopped and, importantly the drug reversed the effects of heart failure.

And the biological cause of breathlessness in heart failure – the inability of the heart to respond to adrenaline – was almost completely reversed.

The dose the sheep received was similar to the dose humans are given when being treated for erectile dysfunction.

Research findings

Tadalafil blocks an enzyme called Phosphodiesterase 5 (PDE5), which regulates how our tissue responds to hormones like adrenaline.

The research team found that in heart failure the drug altered the signalling cascade – a series of chemical reactions in the body – to restore the heart's ability to respond to adrenaline.

And that increases the ability of the heart to force blood around the body when working harder.

Professor Trafford added: “This is a widely-used and very safe drug with minimal side effects.

“However we would not advise the public to treat themselves with the drug and should always speak to their doctor if they have any concerns or questions.

“Tadalafil is only suitable as a treatment for systolic heart failure – when the heart is not able to pump properly – and there may be interactions with other drugs patients are taking.”