https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4242593/ In section "Genetics and long-term effects of caffeine" it goes a bit into details but here is relevant excerpt: "The finding of lower COMT activity with higher risk of myocardial infarction points to involvement of circulating catecholamines in caffeine’s effect on cardiovascular system, with the implication that slow-metabolizing individuals could be at increased risk due to decreased ability to handle the stress associated with caffeine-induced catecholamine response."

if you want to know more about caffeine in general this place sites all the studies: https://examine.com/supplements/caffeine/