British scientists have discovered that the acute pain that accompanies many heart attacks could actually help a patient — and blocking it with morphine and other painkillers may worsen the victim’s chances of recovery and survival.
During a heart attack, when an artery is blocked by a blood clot, cardiac nerves signal pain. That helps to attract stem cells which repair the damaged heart and restore blood flow. Researchers atBristolUniversity found that when heart attack patients are given morphine, the drug not only blocks pain, it also blocks the stimulation of stem cell activity within the artery walls.
“This is a key finding,” said Jeremy Pearson, associate medical director of the British Heart Foundation (BHF), which co-funded the study with the European Union. “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. Obviously we want to ease pain, but not at the expense of long-term recovery.”
Researchers found that “Substance P” — a key molecule that drives the body’s pain sensation — is released by the heart during a heart attack. Substance P then calls stem cells to the site of the artery blockage from the bone marrow. These stem cells have the ability to restore some blood flow, bypass the blockage, and generate new blood vessels.
Professor Paolo Madeddu and his research team carried out their initial experiments on mice before going on to show that Substance P plays a role in stem-cell activity in humans after a heart attack.
“Our discovery shows that pain receptors are involved in repairing damaged blood vessels, through recruiting stem cells, and could point towards new ways to harness the body’s natural mechanisms of repair,” said Madeddu.
“Pain is a very complicated process,” said Dr Hélène Wilson, the BHF’s research adviser. “It’s not just the body’s way of warning you that something is wrong. When we feel pain, it can also be a sign that the body is doing what it can to fix the problem. As well as opening up exciting new avenues for new heart repair treatments, this discovery highlights the potential role of pain in our natural response to having a heart attack … It opens up the possibility that in the future we might be able to harness pain more effectively in the crucial window just after a heart attack, when there could be an opportunity to keep damage to a minimum.”
The study was published in the American Heart Association journal Circulation.