Acute symptomatic sinus bradycardia in a woman treated with pulse dose steroids for multiple sclerosis: a case report

INTRODUCTION Sinus bradycardia has been reported after administration of pulse dose steroids, although most cases have occurred in children and are asymptomatic. We report a case of acute symptomatic sinus bradycardia due to pulse dose steroids in a woman with multiple sclerosis. Interestingly, this patient also suffered from inappropriate sinus tachycardia due to autonomic involvement of multiple sclerosis. CASE PRESENTATION A 48-year-old Caucasian woman with multiple sclerosis and chronic palpitations due to inappropriate sinus tachycardia was prescribed a 5-day course of intravenous methylprednisolone for treatment of an acute flare. Immediately following the fourth dose of intravenous methylprednisolone, she developed dyspnea, chest heaviness, and lightheadedness. She was referred to the emergency department where an electrocardiogram showed marked sinus bradycardia (40 beats per minute). Initial laboratory test results, including a complete blood count, basic metabolic profile and cardiac biomarkers, were normal. She was admitted for observation on telemetry monitoring. Her heart rate gradually increased and her symptoms resolved. Her outpatient dose of atenolol, taken for symptomatic inappropriate sinus tachycardia, was resumed. CONCLUSIONS Our patient's acute symptoms were attributed to symptomatic sinus bradycardia due to pulse dose steroid treatment. Although several theories have been suggested to explain this phenomenon, the exact mechanism still remains unknown. It does not warrant any specific treatment, as it is a self-limiting side effect that resolves after discontinuing steroid infusion. Young patients who are free of any active cardiac conditions can safely be administered pulse dose steroids without monitoring. However, older patients with active cardiac conditions should have heart rate and blood pressure monitoring during infusion. Our patient also suffered from inappropriate sinus tachycardia, a manifestation of autonomic involvement of multiple sclerosis that has not been previously described. This case has implications for the pathogenesis and treatment of dysautonomia in patients with multiple sclerosis.