COVID-19
and the Heart

COVID-19 has proven to be far more than a respiratory disease. While the world initially focused on pneumonia and lung damage, mounting evidence revealed that SARS-CoV-2 could trigger severe complications throughout the body including the cardiovascular system.

Our research team set out to quantify this risk using Sweden's unique registry data, analyzing all confirmed COVID-19 cases in the country during the first wave of the pandemic. What we found was striking: COVID-19 infection dramatically increases the risk of heart attacks and strokes, particularly in the first weeks following diagnosis.

This study, published in The Lancet in August 2021, represents one of the largest and most comprehensive analyses of COVID-19's cardiovascular impact, drawing on data from over 86,000 patients.

The Swedish Advantage

Sweden's comprehensive registry system provided a unique opportunity to study COVID-19's cardiovascular effects at a population level. Every Swedish resident has a personal identification number that allows researchers to link data across multiple national registers, creating a detailed picture of health outcomes.

We could access inpatient records dating back to 1987, outpatient data from 1997, and cause of death records, all linked to confirmed COVID-19 diagnoses from the Swedish Public Health Agency. This allowed us to identify cardiovascular events with high precision and track patients over time.

What We Measured

The study examined two major cardiovascular outcomes: acute myocardial infarction (heart attack) and ischaemic stroke. We used two complementary statistical methods to ensure our findings were robust.

The self-controlled case series method compared each patient's risk during the weeks following COVID-19 to their own baseline risk, controlling for individual differences. The matched cohort study compared COVID-19 patients to similar individuals from the general population who hadn't been infected.

A Critical Time Window

Our data revealed a clear temporal pattern. The risk of cardiovascular events was highest immediately following COVID-19 diagnosis, with an 8-fold increase in heart attack risk during the first week when including the day of diagnosis.

This elevated risk gradually declined over the following weeks but remained significantly above baseline even 3-4 weeks after infection. The pattern was consistent for both heart attacks and strokes, suggesting a shared underlying mechanism.

The findings held true even among patients who weren't hospitalized for COVID-19, indicating that even milder infections carry cardiovascular risk. This has important implications for how we monitor and protect all COVID-19 patients, not just those with severe respiratory disease.