Around half of those who suffer an MI without knowing it are still alive 10 years later, a similar rate to those whose heart attack had been picked up by a scan such as an electrocardiogram or cardiovascular magnetic resonance (CMR).
A research team from the National Institutes of Health discovered the phenomenon of the undetected heart attack when they examined the health of 935 elderly patients living in a care home in Reykjavik, Iceland, who had an average age of 76. After undergoing a heart scan, the researchers discovered that 10 per cent had suffered a heart attack that a previous scan had already identified—and yet 17 per cent of the whole group had unwittingly had a heart attack that had never been diagnosed. "That means 63 per cent of the MIs identified by CMR were missed in routine medical care. Unrecognised MI may be more common than recognised MI," said study team leader Tushar Acharya.
Yet whether or not the heart attack had been diagnosed, the survival rate was roughly the same after 10 years, at 49 per cent for an unrecognised attack and 51 per cent for a diagnosed MI.
What is surprising about the similar mortality rates is that the patient whose heart attack hasn't been diagnosed will not have been prescribed the usual medications to prevent a further attack, such as statins, beta blockers or ACE (angiotensin converting enzyme) inhibitors. They would also have continued with a lifestyle that could have contributed to the attack in the first place, such as smoking, not exercising or an unhealthy diet, Dr Acharya said.