Cardiac fibrosis in myotonic dystrophy type 1; an early marker of cardiac involvement

Abstract

Purpose: In the inherited progressive neuromuscular disorder, myotonic dystrophy type 1 (MD1), cardiac involvement is frequently observed and may present with conduction disturbances, arrhythmia, heart failure and sudden cardiac death. Similar to other non-ischemic cardiomyopathies, cardiac fibrosis is frequently identified in autopsies from patients with MD1. Screening for cardiac involvement in MD1 is recommended, but optimal screening modalities are not clearly defined. We compared the presence of cardiac fibrosis on cardiac magnetic resonance imaging (CMRI) with the findings based on routine clinical screening. Methods: All patients were evaluated by physical examination, ECG, TTE, 48-hours Holter-monitoring and CMRI with late gadolinium enhancement. Results: In 27 patients with MD1 (15 males, mean (SD) age 47.1 years (13.7)) cardiac fibrosis on CMRI was found in 10/27 (37%, 7 males). None of the patients complained of dyspnoea, chest pain, dizziness or syncope. Patients with cardiac fibrosis did not differ in age from the remaining patients (median (range) age 57.2 years (21.1-78.7) vs. 45.9 years (23.2-59), p=0.24). Left ventricular mass was significantly higher in patients with cardiac fibrosis (median (range) 55 g/m2 (43-83) vs. 46 g/m2 (36-64), p=0.04) and there was a tendency towards larger left ventricular end diastolic volume (median (range) 86 ml/m2 (53-130) vs. 71 ml/m2 (57-103), p=0.097). These findings were independent of gender. There was no association between the presence of cardiac fibrosis and blood pressure (median (range) systolic blood pressure 125.5 mmHg (104-168) vs. 115.5 mmHg (97-135), p=0.25), maximum heart rate on Holter-monitoring (median (range) 125.5 bpm (91-192) vs. 120 bpm (100-162), p=0.88), or abnormalities in ECG (6/10 vs. 8/17, p=0.70), Holter- monitoring (4/10 vs. 4/17, p=0.42) or TTE (4/10 vs. 4/17, p=0.42). Conclusion: Patients with MD1 had a high prevalence of cardiac fibrosis assessed by CMRI. The CMRI-findings were not predicted by standard screening, including clinical evaluation, ECG, Holter-monitoring and TTE. CMRI might be a clinically valuable tool for early detection of cardiac involvement in MD1.