A case of doxazosin-induced acute coronary syndrome in a patient with myocardial bridging

Introduction

Myocardial bridging (MB) is an anatomical variation characterized by narrowing during systole of some of the epicardial coronary arterial segments running in the myocardium. It can be encountered in 0.5% to 16% of routine coronary angiographies [1]. Although it is considered as a benign anomaly, it may lead to such complications as myocardial ischemia, acute coronary syndromes, coronary spasm, exercise-induced dysrhythmias such as supraventricular tachycardia, ventricular tachycardia, syncope, or even sudden death [2].
In this report, we present a previously unreported case of a 51-year-old man with doxazosin-induced acute coronary syndrome, who was diagnosed with myocardial bridging overlying the left anterior descending artery.

Case report

A 51-year-old man was admitted to the coronary intensive care unit due to chest pain and syncope without any prodromal symptoms after taking the first doxazosin dose. Blood pressure was 100/60 mm Hg and heart rate was 100 bpm at initial evaluation. He had had hypertension for over ten years. He was on losartan. The electrocardiogram showed sinus rhythm with biphasic T wave on precordial derivations and negative T wave in leads DI and aVL (Figure 1 A). High-sensitivity troponin T level was elevated (42 ng/l, 0–14 ng/l). Kidney function tests were normal. A transthoracic echocardiogram showed left ventricular ejection fraction of 60% with normal wall motion, left ventricular hypertrophy, and diastolic dysfunction. Coronary angiography revealed that myocardial bridging was confined to the left anterior descending artery (LAD) with severe systolic compression (90%) (Figures 1 B, C). Other coronary arteries were normal. Doxazosin was discontinued. The patient was initially treated with metoprolol and aspirin. Myocardial perfusion scintigraphy was found to be normal under -blocker treatment. The protocol was performed at rest and during exercise, with 99mTc sestamibi. Cardiac enzyme level was decreased at follow-up. The patient was discharged with -blocker and acetylsalicylic acid. He has been followed up without any symptoms for 1 month.

Discussion

Coronary arteries that tunnel through the myocardium are seen in as many as 40% to 80% of cases on autopsy; however, functional MB is less commonly observed on angiography (0.5% to 16.0%) [1]. Although it is considered as a benign anomaly, it may lead to such complications as myocardial ischemia, acute coronary syndromes,...


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