[Syndromes of autonomic dysfunction associated with orthostatic intolerance]

Stimulated by the wide-spread use of tilt table testing, disorders of autonomic function with orthostatic hypotension have recently gained attention by clinical cardiologists. At the same time, improved characterization of the underlying circulatory responses have led to a reclassification of these syndromes. In particular, three subgroups of chronic primary dysautonomia have been defined: pure autonomic dysfunction, multiple system atrophy, and the postural orthostatic tachycardia syndrome. On the other hand, acute dysautonomias represent a rare yet clinically sometimes dramatic form of autonomic disorders. Several diseases as well as enzymatic disorders, and pharmacological drugs may cause secondary dysautonomia. The clinical correlate of all these forms of dysautonomia is orthostatic hypotension and syncope. Thus, a careful history forms the basis of a successful diagnostic workup of the underlying cause of syncope. This review summarizes the current knowledge of autonomic disorders, their classification and diagnostic and therapeutic strategies.