Myotonic dystrophy (DM) is a multisystem disorder with autosomal dominant inheritance. Cardiac abnormalities may represent initial manifestations of DM even before neuromuscular involvement. Two such cases of DM are illustrated. A 14-year-old boy presents with exertional syncope and atrial flutter. After DC cardioversion, ECG demonstrated first degree atrioventricular block (AVB), left bundle branch block (LBBB). Electrophysiology study (EPS) revealed a HV interval of 79ms. A loop recorder is implanted. With further syncope, interrogation revealed paroxysmal atrial fibrillation and rapid tachycardia (ventricular rate 230bpm), with LVEF 35%, prompting insertion of a cardiac resynchronisation therapy defibrillator. Neurogenetic testing confirmed DM type 1, with CTG trinucleotide repeat expansion in DMPK gene. A 27-year-old male presents with rest syncope. Conduction disease (first degree AVB and HV interval (90ms)) was noted on ECG and EPS. Cardiac MRI revealed mild biventricular impairment. He developed recurrent broad complex tachyarrhythmias with LBBB morphology, consistent with bundle branch re-entry ventricular tachycardia (BBRVT), and underwent cardiac defibrillator implantation. Despite multiple appropriate shocks, non-compliance has delayed further treatment. Clinical features of DM are noted (frontal balding and myotonia) and neurogenetic testing is pending. Cardiac manifestations of DM include atrial/ventricular arrhythmias, conduction disease, cardiomyopathy and sudden cardiac death (SCD). The cardiac features can precede clinical diagnosis of DM. Furthermore, progression of conduction disease in DM is unpredictable, and VT (especially BBRVT) is common, so early invasive strategies are recommended. Awareness of this diagnosis is vital for timely management and prevention of SCD.