Background:Extracranial vascular malformations affect vessel inflammation, clotting, and ischemia. However, the relationship between extracranial vascular malformations and myocardial infarction (MI) or stroke has not been fully elucidated. Limited studies have investigated the association between extracranial vascular malformations and cardiovascular diseases.Methods:A total of 48,701 patients with extracranial vascular malformations and a control cohort of 487,010 age- and sex-matched participants from the Korean National Health Insurance database were included. The incidence and risk of MI, ischemic stroke (IS), and hemorrhagic stroke (HS) between participants with extracranial vascular malformations and the control cohort was compared.Results:After adjusting for other cardiovascular disease risk factors, the adjusted hazard ratios (aHRs) for venous malformations, capillary malformations (CMs), arteriovenous malformations (AVMs), and lymphatic malformations in patients with acute MI were 1.25 (CI, 1.04 to 1.50), 1.41 (CI, 1.24 to 1.61), 1.68 (CI, 1.18 to 2.37), and 1.40 (CI, 1.31 to 1.48), respectively. For IS, the aHRs were 1.55 (CI, 1.35 to 1.77), 1.92 (CI, 1.74 to 2.11), 1.13 (CI, 0.78 to 1.64), and 1.51 (CI, 1.44 to 1.58), respectively. For HS, the aHRs were 1.51 (CI, 1.12 to 2.05), 5.63 (CI, 4.97 to 6.38), 2.93 (CI, 1.82 to 4.72), and 1.34 (CI, 1.20 to 1.50), respectively.Conclusions:Independent of cardiovascular risk factors, extracranial vascular malformations were associated with an increased risk of MI, IS, and HS. For patients with CMs and AVMs, intracerebral hemorrhage risk was particularly high, accounting for 563% and 293%, respectively. Therefore, even in patients with extracranial CMs or AVMs, performing diagnostic evaluations for cerebral AVMs and using measures to prevent intracerebral hemorrhage are crucial.CLINICAL QUESTION/LEVEL OF EVIDENCE:Risk, II.