St-Elevation Myocardial Infarction With Complete Heart Block in the Setting of Vagally Mediated Coronary Vasospasm

ABSTRACT

Introduction: This case identifies vagal tone as a paradoxical cause of coronary artery spasm, coinciding with complete heart block. It will additionally identify proper management in these cases. Clinical Presentation A 53 year old male with a medical history of HIV not of ART, acute, infectious COVID-19 and late, latent syphilis admitted for malaise, found to have DLBCL. Following a routine blood draw the patient experienced acute chest and abdominal pain. Minutes later, while having a bowel movement he experienced syncope with heart rates in the 30s. EKG showed ST elevations in leads II, III, and aVF. Troponin-T was elevated to 0.15. Echocardiogram showed inferior wall hypokinesis. Coronary angiography showed non-obstructive right coronary disease. Cardiac MRI demonstrated no evidence of infiltrative disease or myocarditis. The patient experienced a similar episode the following morning, during blood draw, EKG and telemetry demonstrated complete heart block with ST elevations (image). This suggested vagal mediated AV block with coronary artery spasm (CAS). He was started on the anticholinergic hyoscyamine and amlodipine for vasodilation. Following initiation of therapy, the patient had no further episodes of chest pain or bradycardia. Discussion(s) While acetylcholine causes vasodilation via endothelial NO, interestingly, it can also lead to CAS. In the setting of vascular smooth muscle cell (VSMC) hyper-reactivity or high vagal tone, VSMC muscarinic receptors are activated leading to vasoconstriction. Vagal tone can cause both CAS with resulting STEMI as well as AV blockade resulting in high degree heart block (image). When ischemic symptoms are accompanied by AV block in the setting of high vagal tone, consider vagal mediated CAS. Calcium channel blockers such as amlodipine are used to manage CAS. When the suspected mechanism is vagal tone, management includes avoidance of precipitating factors and or anticholinergic premedication.