The study found that the likelihood of a heart attack occurring on a Monday was 13% greater than expected.
Doctors at the Belfast Health and Social Care Trust and the Royal College of Surgeons in Ireland analysed data from 10,528 patients across the island of Ireland – 7,112 in the Republic and 3,416 in Northern Ireland.
They had been admitted to the hospital between 2013 and 2018 with the most serious type of heart attack – an ST-segment elevation myocardial infarction (STEMI) which takes place when a major coronary artery is completely blocked.
The researchers found a spike in STEMI heart attacks at the start of the working week, with rates highest on a Monday.