Electrophysiologic evaluation of the cardiac conduction system and its autonomic regulation in familial amyloid polyneuropathy.

A high incidence of cardiac conduction disturbances is a salient feature in familial amyloid polyneuropathy (FAP) and amyloid infiltration of the conduction system has been found. In patients with FAP autonomic nervous dysfunction involving gastrointestinal, urogenital and cardiovascular systems has been described. However, the present study is the first to evaluate the results of autonomic tests and pharmacologic intervention in the autonomic nervous regulation of the cardiac conduction system during an invasive electrophysiologic study. Seven patients with FAP and severe disturbances of the conduction system, evaluated concerning indications for pacemaker treatment, were studied; in 3 of them the parasympathetic regulation was found to be abolished. In 1 patient the observations indicated either vagal overactivity or denervation oversensitivity of the receptors. The function of the beta adrenoceptors was intact in all patients, but a disturbance of sympathetic innervation could not be excluded. Dysfunction of autonomic nervous regulation of the cardiac conduction system was thus found in 4 of 7 patients. However, most conduction abnormalities were irreversible, indicating amyloid infiltration of the conduction system as the predominant pathophysiologic mechanism, in accordance with the findings of pathoanatomic studies.