Asymptomatic myocardial infarction in a patient with myotonic dystrophy type 1

Abstract

Myotonic dystrophy type 1 (DM1) displays a wide range of cardiac manifestations, including conduction system disturbances, arrhythmias, and cardiomyopathy. As a result of progressive myocardial injury and fibrosis, patients with DM1 frequently show electrocardiogram (ECG) abnormalities which sometimes cannot be differentiated from myocardial ischemia. Even in DM1 cases with ECG findings indicative of coronary artery disease, coronary angiography and coronary computed tomography often demonstrate intact coronary arteries. In this article, we report a case of a 56-year-old DM1 patient with ST segment change on ECG, who was admitted to our hospital for further examination. Echocardiography revealed severe hypokinesis in the anteroseptal wall and left ventricular thrombus in the apex, suggesting the possibility of an old myocardial infarction in the left anterior descending artery (LAD) region. Coronary computed tomography angiography and coronary angiography demonstrated a severe stenosis suggestive of vulnerable plaque in the proximal part of LAD, although fractional flow reserve of the lesion did not indicate functional ischemia. A beta-blocker and a sodium-glucose cotransporter 2 inhibitor were introduced expecting a cardioprotective effect. One year after his discharge, the patient died of septic and cardiogenic shock triggered by aspiration pneumonia.

Learning objective: Although the prevalent cardiac manifestations of patients with myotonic dystrophy type 1 are conduction abnormalities and cardiomyopathy, the possibility of having coronary artery disease should be considered because they often have some atherosclerotic risk factors with their tendency toward metabolic abnormalities such as diabetes mellitus due to insulin resistance and dyslipidemia and with diagnostic difficulty due to asymptomatic or non-specific manifestations.

Keywords: Coronary artery disease; Myotonic dystrophy; Neuromuscular cardiomyopathy.

Fig. 1

12‑lead electrocardiogram. ST segment elevation and biphasic T waves in V2-V4 leads and left axis deviation were observed on the day of admission (b) not seen 3 years before admission (a).

Fig. 2

Transthoracic echocardiography showing left ventricle thrombus. Left ventricular thrombus of 11 × 10 mm was observed (a). Non-calcified plaque ((b): long arrows) in left anterior descending coronary artery is positively remodeled as compared with the normal coronary segment proximal to the lesion (short arrows). The diameter was 5.1 mm in normal segment (c) and 5.4 mm in the lesion (d). Remodeling index was 1.07.

Fig. 3

Coronary angiography. A proximal left anterior descending artery (LAD)#6 stenosis of 50%, LAD#7 of 50%, and LAD#8 diffuse obstruction of 75% were seen (a, b). No significant stenosis was found in the right coronary artery (c).