Left ventricular function in adults with muscular dystrophies: genotype-phenotype correlations

Left ventricular dysfunction (LVD) is a clinical manifestation of muscular dystrophy (MD) in adults and an important prognostic factor. However, there is a lack of recommendations concerning cardiac followup of these patients. The aim of this work was to evaluate the prevalence of systolic LVD in adults with MD.

The patients, referred from a Neuromuscular Diseases Unit, underwent clinical evaluation, ECG and transthoracic echocardiogram. Serum troponin I and NT-proBNP were also evaluated. Systolic LVD was defined by an ejection fraction of <0.45 and/or shortening fraction of <0.25.

During a one-year period, we evaluated 24 consecutive patients, 16 men, age 33 +/- 12 years (age at myopathy diagnosis 23 +/- 12 years). They had the following MD: dystrophinopathies--four patients (Duchenne: 1, Becker: 3); Steinert myotonic dystrophy--nine patients; limb-girdle myopathies--six patients; facioscapulohumeral (FSH) myopathies--four patients; and one dysferlinopathy (Miyoshi myopathy). The MD diagnosis, based on clinical and histological criteria, was genetically confirmed in 18 cases (75%). Five patients (20.8%) had thoracic pain, four (16.6%) dyspnea and one a history of syncope. ECG abnormalities were present in 14 cases (58.3%). Stolic LVD or left ventricular remodeling were present in six patients (25%): three with dystrophinopathies, one with limb-girdle myopathy, one with FSH dystrophy and one with myotonic dystrophy. Three patients (12.5%) were diagnosed with heart failure according to the European Society of Cardiology criteria. Three of the five patients with left ventricular dysfunction had elevation of NT-proBNP. One patient with Becker dystrophy had slight elevation of troponin I. In patients with systolic LVD or LV remodeling, the mutations identified were: deletion in intron 1 to exon 49 (one Duchenne MD patient) and deletions in exons 45 to 51 (two Becker MD patients) in the dystrophin gene; deletion of D4Z4 repeats in the DFS locus (4q35) (one patient with FSH MD); and 1300-1500 CTG triplet repeats in the DMPK gene (one patient with myotonic dystrophy).

These results, although preliminary, show that a high percentage of patients with genetically determined skeletal myopathies exhibit cardiac myocyte functional impairment, with severe LVD and heart failure, justifying periodic cardiovascular evaluation. In the future, phenotype-genotype correlations could help to determine the best cardiac surveillance in MD patients.