The frequency and severity of cardiac involvement in myotonic dystrophy type 2 (DM2) : long-term outcomes

Background: Frequency and severity of cardiac involvement in DM2 are still controversial. The aims of our study were to determine the frequency and progression of cardiac and muscle involvement in a relatively large cohort of patients with DM2 throughout Italy and Germany and to provide long-term outcomes in this disorder. Methods: 104 DM2 and 117 DM1 patients underwent baseline and follow-up assessments of, ECG, 24 h Holter monitoring, 2D echocardiography and electrophysiological study (EPS) when appropriate, and manual muscle strength testing (mean follow-up: 7.4±4.1 for DM2 and 5.7±4 years for DM1). Results: Overall, 10% of DM2 patients vs 31% of DM1 patients had PR≥200 ms and 17% of DM2 patients vs 48% of DM1 patients had QRSD≥100 ms. Six patients with DM2 vs 28 patients with DM1 required PM/ICD implantations. DM2 patients were stronger than DM1 patients at baseline, but muscle strength worsened significantly over time (pb0.0001), just as in DM1, although at a slower annual rate. Conclusion: Our data demonstrate that the frequency and severity of cardiac involvement and of muscle weakness are reduced in DM2 compared to DM1 and that progression is slower and less severe. Nonetheless, careful cardiac evaluation is recommended in this patient population to identify patients at risk for potential major cardiac arrhythmias.