Heart failure is rare in Myotonic Dystrophy type 1 and often occurs late in the course of the disease. The clinical recognition of heart failure in muscular diseases is more difficult than in patients with a normal muscular function, as fatigue is inherent to the muscular weakness and exercise tolerance is already impaired by the muscular disease itself.
In DM1, the conduction system is always more extensively affected than the contractile myocardium and high degree AV blocks requiring pacemaker therapy are a well known complication of the disease. The typical ECG of DM1 patients depicts complete LBBB (5 to 25%) with first-degree AV block (20 to 40%). According to ESC 2007 Guidelines for Cardiac Pacing, permanent pacemaker implantation is indicated in DM1 patients with acquired third-degree or second-degree atrioventricular (AV) block (class I B). There is also a class II B indication for first-degree AV block in neuromuscular diseases, when a family history of sudden death is reported.
However, neither a clear consensus about biventricular pacing nor the usage of implantable cardiac defibrillator for patients with Myotonic Heart Disease exists.
Basing on the progressive deterioration of the left ventricular function, progression of AV conduction disturbances and occurrence of ventricular tachyarrhythmia, Said et al. (12
) hypothesized a role for biventricular ICD in DM1 patients who need a permanent pacemaker implantation. Kilic et al. (13
) described the first case of beneficial cardiac resynchronization in one DM1 patient with heart failure, complete LBBB and ventricular asynchrony, who was not implanted of an intracardiac defibrillator, because no serious life threatening ventricular arrhythmias were induced in the EPS.
In our patient, the early onset of heart failure could be related to the electromechanical delay caused by both intra- and inter-ventricular asynchrony, that leads to regional molecular changes in a non coordinate contracting myocardium and accelerates the progression of the heart failure. The spontaneous ventricular tachycardia, occurred in our patient at twelve months follow up, suggests that the improvement in ejection fraction may not reduce the arrhythmic risk in these patients.