The Covid-19 Pandemic and the Incidence of Acute Myocardial Infarction. DOI: 10.1056/NEJMc2015630.

During the Covid-19 pandemic, multiple observational studies have suggested a decrease in the number of patients presenting to hospitals with acute myocardial infarction (MI). Authors of a recent analysis published in NEJM examined data from Kaiser Permanente Nothern California, a large integrated US health care system. They examined weekly incidence rates of hospitalisation for acute myocardial infarction (both ST-segment elevation myocardial infarction, STEMI and non–ST-segment elevation myocardial infarction, NSTEMI) before and after the first reported death from Covid-19 in Northern California on March 4, 2020. The weekly rates of hospitalisation for acute MI decreased by 48% during the Covid-19 pandemic. The incidence rate of 4.1 per 100,000 person-weeks from prior to the outbreak dropped to 2.1 per 100,000 person-weeks during the outbreak (incidence rate ratio, 0.52; 95% confidence interval [CI], 0.40 to 0.68; P<0.001). Decreases were similar among patients with NSTEMI and those with STEMI. The reduction seen in the comparison of the Covid-19 period with the pre–Covid-19 period in 2020 was similar to the decrease seen in the comparison of the Covid-19 period in 2020 with the same weekly periods in 2019.

The same reduction in patients presenting with heart attacks occurred in the UK. Many units poised for a large influx of patients stood idle despite expecting more heart attacks during the COVID-19 pandemic. Respiratory infections usually increase the risk of heart attacks, which is why vulnerable people are offered flu vaccines. Stress, anxiety and depression, more likely during the outbreak, would be expected to lead to more heart attacks. The Coronavirus itself is also known to have an adverse effect on the heart.

The most concerning - but sadly the most likely - explanation for empty cardiology wards is that people were simply too scared to seek medical help due to concerns about catching the virus in the hospital. The public information campaign may have been too successful in persuading people to stay at home no matter what. It is of course possible that some triggers for heart attacks, such as work-related stress, have reduced in the time of furloughing and economic inactivity, but the magnitude of observed changes makes this less likely.

Eugene Braunwald’s axiom ‘time is muscle’ remains true in MI treatment even in the era of a viral pandemic. A late or no treatment of heart attack dramatically increases the risk of complications including heart failure and death; nasty collateral damage of the COVID-19. The message to patients is clear: If you’re ever in doubt or suspicious, don’t delay in calling 999. Very efficient treatments, including primary PCI (percutaneous coronary intervention, 'stent'), are available. A heart attack is a medical emergency, and every second counts.