Spectrum of dysautonomia in mitral valvular prolapse

Symptoms suggesting altered autonomic regulation of cardiovascular function have been noted in some patients with mitral valvular prolapse (MVP) but may also occur in patients with other disorders. We evaluated cardiovascular responses to autonomic stimuli in 118 patients with symptoms of dysautonomia, 78 of whom had MVP, and 40 of whom did not, to determine if unique patterns of these responses distinguished patients in one symptomatic subgroup from another.

The responses of patients to standing, quantitated Valsalva maneuver, facial immersion in ice water, and administration of isoproterenol, phenylephrine, and tyramine were compared with those in 12 asymptomatic patients with MVP and 23 normal volunteers.

Constitutional, cardiovascular, and neuropsychiatric symptoms occurred with similar frequency in the two symptomatic patient groups. The most common pattern of abnormal responses in symptomatic patients with or without MVP was (1) an increased heart rate and elevated plasma norepinephrine levels while supine and then while standing quietly for five minutes, (2) an exaggerated increase in heart rate during phase II of Valsalva, (3) a diminished bradycardic response during phase IV of Valsalva, and (4) an exaggerated heart rate response to administration of isoproterenol. The increased heart rate during Valsalva, but not the exaggerated sensitivity to isoproterenol, was correlated with the magnitude of the chronotropic response to standing only in symptomatic patients with MVP. Exaggerated hypertensive overshoot during phase IV of Valsalva was observed in only a few symptomatic patients. No consistent pattern of these abnormalities, however, was noted in any of the patient subgroups. Hemodynamic responses to autonomic stimuli in asymptomatic MVP patients were generally indistinguishable from those observed in normal subjects.

These findings suggest that abnormal cardiovascular responses to autonomic stimuli may occur in any patient with symptoms of dysautonomia regardless of the presence or absence of MVP and that the pattern of these abnormal responses may be diverse. It is therefore important to characterize the pattern of altered autonomic regulation of cardiovascular function in each patient when considering mechanistic implications or making therapeutic decisions about these patients.