Cardiovascular System - DM1


  • DM1-related cardiac pathophysiology, although affecting all myocardial tissue, preferentially targets the cardiac conduction system. Conduction system defects are progressive and, while initially asymptomatic, increase the risk for symptomatic arrhythmias.

  • Pre-syncope, syncope, palpitations, dyspnea, chest pain or sudden death from cardiac arrest.

  • The development of a dilated, non-ischemic cardiomyopathy is an infrequent but recognized occurrence. Once a symptomatic dilated cardiomyopathy is present, progression is typically rapid, with congestive heart failure leading to death.


  • Palpitations, pre-syncope, syncope, dyspnea and chest pain.

  • Arrhythmias including sinus bradycardia, tachyarrhythmias, heart block, atrial fibrillation and flutter, and ventricular tachycardia. The most common tachyarrhythmias are atrial fibrillation and atrial flutter, which pose a risk of cardiogenic embolism and stroke.

  • Symptom change, abnormal cardiac imaging, abnormal ECG.


  • Discuss the following tests with your doctor:

    • Cardiac testing, including the 12-lead electrocardiogram (ECG), long-term ambulatory ECG monitoring, and an invasive electrophysiological study.

    • Imaging studies, including echocardiography, computerized tomography (CT), magnetic resonance (MR), and nuclear imaging can be used to assess the heart’s mechanical status, including left ventricular function.

    • Echocardiograph if abnormal ECG indicative of conduction disease or if other symptoms suggestive of heart failure are present.


  • Pacemakers can be implanted to treat symptomatic bradyarrhythmias or prophylactically in those at high risk for complete heart block.

  • Implantable cardioverter-defibrillators (ICDs) can be installed in those who have survived an episode of a ventricular tachyarrhythmia or, prophylactically, in those at high risk for a ventricular tachyarrhythmia.

  • Use of emergency medical alert devices.

  • Serial periodic clinical cardiology evaluations.

  • Ambulatory Holter ECG monitoring – either short-term (24-48 hours) or long-term (30 days or more) – to detect mechanisms of arrhythmias.

  • Mexiletine can provide relief for atrial fibrillation but because it is an anti-arrhythmic, a complete workup must be done first to rule out underlying structural or functional abnormalities that may complicate its use. Mexiletine-related monitoring should be conducted by a cardiologist experienced in the treatment of DM1.

  • Refer to:

    • A cardiology center experienced in care of DM1.

    • An anesthesia practitioner, separate from the operating physician, to provide procedural sedation and monitoring for electrophysiology studies and pacemaker or ICD implantation.