Cardiac repolarization evolves differently during the course of benign and disabling multiple sclerosis

Background: Cardiac repolarization is modulated by the autonomic nervous system. Even though multiple sclerosis associates with prolonged cardiac repolarization the physiology responsible for the phenomenon remains unknown. Objective: To study in longitudinal setting whether the patients with confirmed benign and disabling outcome of relapsing-remitting multiple sclerosis (RRMS) differ in regard to changes of cardiac repolarization. Methods: Total of 43 patients, 26% with benign (EDSS <= 2 at least 10y after onset symptom) and 74% with disabling (EDSS > 2 at least 10y after onset symptom) RRMS, having 12-lead electrocardiogram (ECG) recorded at the time of onset symptom (ECG1) and for follow-up (ECG2), were studied. Heart rate (HR) corrected QT intervals (QTc) reflecting cardiac repolarization were assessed. Results: The time interval between ECG1 and ECG2 showed no statistical difference between benign (7.8 +/- 4.8y) and disabling (10.2 +/- 5.6y; p=. 211) RRMS. Patients with benign and disabling RRMS showed similar values of HR (66 +/- 9 bpm vs 73 +/- 15 bpm; p=.146) and QTc (403 +/- 13 ms vs 408 +/- 19 ms; p=.450) at the time of ECG1. However, at the time of ECG2, HR was higher (79 +/- 14 bpm vs 65 +/- 10 bpm; p=.004) and QTc was longer (420 +/- 24 ms vs 400 +/- 15 ms; p=.012) in patients with disabling than benign RRMS. Correspondingly, HR increased (p=.063) and QTc prolonged (p=.014) during the disease course only in patients with disabling RRMS. Conclusions: Deterioration of cardiac autonomic regulation during the disease course associates with disabling but not with benign RRMS. Our findings suggest that assessment of cardiac autonomic regulation should be included in the evaluation of RRMS disease course. In addition, patients with disabling RRMS might be prone to unfavorable cardiovascular outcome also due to deterioration of autonomic nervous system.