Autonomic etiology of heart block in amyotrophic lateral sclerosis: a case report

The cardiovascular consequences related to amyotrophic lateral sclerosis are relatively underappreciated. The disease invokes a systematic degeneration of autonomic neurons leading to autonomic dysfunction. We therefore hypothesized that patients with amyotrophic lateral sclerosis may have a predilection to the development of cardiac conduction disorders.

A 65-year-old Caucasian man with advanced amyotrophic lateral sclerosis presented with progressive dyspnea and palpitations. A previous evaluation attributed his dyspnea to neuromuscular weakness and he underwent a pulmonary evaluation. Pulmonary function tests did not indicate a worsening from baseline. An electrocardiogram was obtained which demonstrated new third degree atrioventricular block. A previously obtained electrocardiogram indicated normal sinus rhythm. On echocardiogram, a structurally normal heart was observed without significant valvular disease. He was offered a permanent dual chamber pacemaker for definitive treatment, however, he declined.

We believe that his symptoms were probably attributable to atrioventricular block. Patients with advanced amyotrophic lateral sclerosis experience loss of heart rate variability and enhanced vasomotor responses. As patients progress later in the disease, sympathetic denervation and vagal predominance contribute to the development of atrioventricular block. We conducted a query using the Explorys database of patients with amyotrophic lateral sclerosis and heart block. The prevalence of heart block was estimated to be 25% higher in patients with the disease as compared to the general population. This is the first reported case that attempts to describe the relationship of atrioventricular block with amyotrophic lateral sclerosis.