myotonic dystrophy ( md ) is an inherited disorder transmitted in an autosomal dominant fashion.1 ) in md , cardiac complications are the second most common cause of death in up to 30% of patients.2 ) the cardiac involvement in patients with md is usually characterized by arrhythmias , mainly due to conduction system abnormalities and an increased risk of sudden death . however , the occurrence of clinical myocardial disease appears to be rare , with only occasional reports of cardiomyopathy , and little is known about the clinical course as it relates to involvement of the myocardium.3 ) a 48-year - old male patient with a 10-year history of md was referred for evaluation of an abnormal electrocardiogram ( ekg ) . md was confirmed by rectus femoralis muscle biopsy that showed atrophy and degenerated fibers with internal nuclei , consistent with a myotonic myopathy ( fig . the patient had four uncles who all died because of myopathic disease before 50 years of age . he had premature balding and had a characteristically thin face , hand myotonia , and bilateral weakness of the lower extremities . an initial 12-lead ekg showed first - degree atrioventricular block ( pr interval , 220 msec ) and intraventricular conduction delay ( qrs duration , 142 msec ) ( fig . . the serum creatine kinase was mildly elevated , but the creatine kinase - mb isoenzyme and troponin t levels were normal . however , an inappropriate heart rate ( 83/min ) response with suspicious atrioventricular block at stage 4 was observed on the exercise treadmill test . initial transthoracic echocardiography ( tte ) demonstrated hypokinesia of the inferior wall with mild left ventricular systolic dysfunction ( ejection fraction , 45% ) . there were no signs of ischemic disease by coronary angiography ; there was no fat infiltration or fibrosis demonstrated on cardiac mri ( fig . 1d ) , and more aggravated regional wall motion abnormalities ( hypokinesia of the anterolateral and inferior walls ) were shown on tte ( ejection fraction , 40% ) with dyspnea on exertion new york heart association . a permanent pacemaker insertion was considered to prevent sudden death based on american college of cardiology / american heart association guidelines . while cardiac involvement ( ci ) in md is usually characterized by arrhythmias ( conduction abnormalities and tachyarrhythmias ) , myocardial damage with symptoms of heart failure is rare because ci is mainly due to selective degeneration of the infra - nodal conduction system.3 - 5 ) on histologic evaluation , ci in md involves interstitial myocardial fibrosis and fatty infiltration.6 ) interestingly , in the case described herein , there were no significant arrhythmias on ekg , no fibro - lipomatous changes , and no evidence of myocardial ischemia on cardiac mri . however , the initial and follow - up ekgs showed decreased left ventricular systolic function and extended regional wall motion abnormalities . therefore , serial ekgs may be a more useful imaging tool than ct or mri for earlier detection of myocardial involvement in asymptomatic patients with md . in primary md patients , cardiac involvement is the second most common cause of death.2 ) atrioventricular block and ventricular tachyarrhythmia are considered to be the main cause of sudden death in patients with md.7 ) several studies have recommended that holter monitoring should be performed on a regular basis.8)9 ) recent pacing guidelines have recognized that asymptomatic conduction abnormalities in md may warrant special consideration for pacing.10 ) in the present case , the patient showed non - specific findings on initial holter monitoring , but treadmill testing showed a significant arrhythmia and an inappropriate heart rate . we therefore suggest that comprehensive evaluation with treadmill testing and an ekg may be beneficial for patients with primary md , even when asymptomatic , to identify non - ischemic cardiomyopathy in an effort to determine the appropriate time for pacemaker insertion and prevention of life - threatening complications .
in patients with myotonic dystrophy ( md ) , impairment of the conduction system is a common and progressive finding . 
 however , only a few cases of md with cardiomyopathy have been reported . 
 herein we report a case of md with progressive non - ischemic cardiomyopathy and severe electrocardiographic abnormalities .