Pain meds hinder heart attack recovery, British scientists say
Heart attack patients are routinely given morphine to ease the stabbing pain in the chest, which can be severe. But a new study from British researchers finds that giving pain medication to heart attack patients actually gets in the way of their recovery.
It turns out that the pain works as a signal to stem cells to begin repair on damaged heart cells, the scientists say in their new report, published in April issue of the American Heart Association’s journal, Circulation. And when morphine is used to relieve pain, it blocks the healing work of stem cells — slashing the chances of survival for heart attack victims.
The findings may also help explain why more heart attack patients given morphine have gone on to die, compared to those who weren’t given morphine. At the same time, it could also lead to new — and more effective — approaches to heart attack treatment.
The discovery has crucial implications on the treatment of heart attack and the long-term recovery of heart attack patients — say the Bristol University scientists who carried out the study. Their findings are results of both experiments in mice and early trials in humans.
A heart attack — called a myocardial infarction by doctors — occurs when blood flow to a part of your heart is blocked, often by a blood clot or by hardened arteries. The blockage cuts off the oxygen supply to the heart, causing cells to die and often wreaking permanent damage to the heart.
Symptoms include chest pain — like a belt tightening around your chest or an elephant sitting on it. And it turns out that this intense pain actually helps patients — pain signals from cardiac nerves help attract stem cells to repair the damaged heart tissue.
The routine treatment of heart attack patients involves being brought to the emergency room, where they are hooked up to a heart monitor, given oxygen to keep their hearts from working hard, punctured with an intravenous line (IV) for medicines and fluids to pass, given nitroglycerin — and finally, given morphine to help reduce chest pain. Morphine works by blocking pain-inducing substances.
But the Bristol University researchers found that morphine also blocks a substance that stimulates stem cell activity in artery walls.
During a heart attack, a key molecule in the body’s ability to sense pain — called Substance P — is released from nerve terminals in the heart, says Professor Paolo Madeddu, chairman of experimental cardiovascular medicine at Bristol University, who led the study.
Substance P signals stem cells from the bone marrow to mobilize at the site of the artery blockage. Like all stem cells, these bone-marrow stem cells have the ability to produce new blood vessels that can bypass whatever is blocking the flow of blood to the heart and restore some of the blood flow.
Dr. Madeddu and his team first carried out experiments on mice before going on to human trials. In all experiments, they found that Substance P plays a role in stem-cell mediated recovery after a heart attack.
“This is a key finding,” notes Dr. Jeremy Pearson, associate medical director of the British Heart Foundation (BHF), which — together with the European Union — funded Dr. Madeddu’s study.
“Other studies have indicated that morphine is associated with higher mortality in patients with acute coronary symptoms. This study provides further evidence that giving morphine to patients could have side effects and means we are going to think very carefully about its use in heart attack cases,” Dr. Pearson says. “Obviously we want to ease pain, but not at the expense of long-term recovery.”