We report an improvement in symptoms of heart failure, a reduced left ventricular dysfunction and induced reverse remodelling in one patient with Myotonic Dystrophy type 1, showing an early onset ventricular dysfunction secondary to a complete left bundle branch block (LBBB) who underwent cardioverter defibrillator CRT (ICD- CRT) implantation.

Myotonic dystrophy type 1 (MD1), is an autosomal dominant disorder associated with the presence of an abnormal expression CTG trinucleotide repeat on chromosome 19ql3.3. The phenotype is characterized by myotonia and muscle weakness, but multisystemic involvement is frequently associated. Cardiac involvement affects the conduction system in about 80% of cases and causes palpitations, lypotimia or syncope (1-4). Myocardial contractile function is less commonly impaired and heart failure (HF) often occurs late in the course of the disease as the final stage of cardiomyopathy (1, 2). Cardiac resynchronization therapy (CRT) is an innovative therapy that can relieve HF symptoms by improving the coordination of the heart's contractions (5). We report an improvement of symptoms of heart failure, ejection fraction and cardiac output values, and a decrease of left ventricular end diastolic diameter (LVEDD) in one patient with Myotonic Dystrophy type 1 showing an early onset of ventricular dysfunction secondary to complete left bundle branch block (LBBB), who underwent implantable cardioverter defibrillator CRT (ICD- CRT) implantation.

A 35-year-old woman with Myotonic Dystrophy type 1 was referred to our division for dyspnoea. The diagnosis of DM1 was previously made on the basis of the clinical features (frontal balding, bilateral temporal and masticatory muscle atrophy, distal weakness of all four limbs, and confirmed by molecular testing. On physical examination crackles at the basal fields of lungs were detected. Electrocardiogram (ECG) revealed sinus rhythm, left axis deviation, normal PR interval and complete left bundle-branch block with a QRS duration of 180 ms. Trans-thoracic echocardiography showed dilated cardiomyopathy, an ejection fraction (EF), calculated by the Simpson's biplane method, of 25% (n.v. > 55%) while Tissue Doppler echocardiography showed a significant intraventricular mechanical dyssynchrony. The electrophysiological study (EPS), performed using a non aggressive stimulation protocol, revealed a non sustained ventricular monomorphic tachycardia. In presence of overt ventricular dyssynchrony, complete LBBB, and inducible ventricular tachycardia, a biventricular ICD was implanted according to our clinical experience (6).

ICD-CRT can be a useful therapy in DM1 patients presenting with heart failure, cardiac dilatation with low EF, complete left bundle block and inducible ventricular tachy-arrhythmias because it improves left ventricular function, induces reverse remodelling and relieves symptoms of heart failure. It can be considered as a life-saving treatment, especially in patients at high-risk of inducible malignant ventricular arrhythmias, although the improvement in ejection fraction seems to not reduce the arrhythmic risk. Whether a biventricular ICD should be the first choice in the management of DM1 patients with early onset heart failure and complete left bundle-branch block needs further investigation.