Familial risk of myocardial infarction with non-obstructive and obstructive coronary arteries: a nation-wide cohort study

AIMS: The familial risk among patients with myocardial infarction with non-obstructive coronary arteries (MINOCA) is unknown. Previous studies of family history in myocardial infarction (MI) have not made a distinction between MINOCA and MI due to coronary artery disease (MI-CAD), based on angiographic findings. We therefore sought to investigate familial risk of MI without and with obstructive coronary arteries. METHODS AND RESULTS: Register-based cohort study with a total of 15 462 MINOCA cases, 204 424 MI-CAD cases, 38 220 control subjects without MI, and with non-obstructive coronary arteries. First-degree relatives were identified in 1995-2020. Cox proportional hazard regression models were used to compare familial risk in MINOCA and MI-CAD with control subjects. During a mean follow-up of 8.1 ± 4.2 years, MINOCA occurred in 1.0% of first-degree relatives with MINOCA whereas MI-CAD occurred in 9.7% of first-degree relatives of MINOCA. The age- and sex-adjusted hazard ratio (HR) for a MINOCA relative experiencing MINOCA and MI-CAD, compared to control subjects, was 0.99 95% confidence interval (CI) 0.80-1.23 and 1.10 (95% CI 1.03-1.18), respectively. During a mean follow-up of 8.5 ± 4.8 years, MI-CAD occurred in 12.2% of first-degree relatives with MI-CAD with age- and sex-adjusted HR 1.43 (95% CI 1.37-1.49). CONCLUSION: No increased familial risk of MINOCA was observed for MINOCA patients whereas there was an increased familial risk for MI-CAD when compared to control subjects. These results may indicate that genetic factors and shared environmental factors within a family leading to CAD are important also for MINOCA, thus MI-CAD and MINOCA could share underlying mechanisms.