Caffeine is a biologically active compound with stimulant and diuretic effects that is ingested throughout the world. Coffee is the primary source of caffeine, with 40 to 220 mg per cup of brewed coffee (vs 20-110 mg per cup of tea). The interest in caffeine’s effects on cardiovascular disease stems from its popularity in everyday consumption (more than half of Americans drink coffee daily) combined with its known actions as a central nervous system stimulant that may increase blood pressure. Thus, there is concern that it could increase risk of coronary heart disease events and of arrhythmias.
Kelly JP, Granger CB. More Evidence That Caffeine Consumption Appears to Be Safe in Patients With Heart Failure. JAMA Intern Med. Published online October 17, 2016. doi:10.1001/jamainternmed.2016.6381