Vasovagal syncope in heart transplant patients during dental surgery.

The pathogenesis of vasovagal syncope during emotional stress is controversial. Several authors have postulated that the vasodepressor response in humans may be initiated by C-fiber mechanoreceptors situated in the heart and connected via cardiac vagal afferents to the medullary center for cardiovascular control. It has been argued that heart transplant patients cannot show any vasovagal reaction because the donor heart is transplanted completely deprived of any vagal or sympathetic innervation. In this report, however, 3 episodes of vasovagal syncope are documented in 3 heart transplant patients undergoing periodontal surgery. During vasovagal syncope in each of these patients, a dramatic fall in systolic blood pressure (from 137 +/- 5 mmHg to 76 +/- 3.6 mmHg) was detected, but, in contrast to what is observable in normal subjects, the heart rate did not show any relevant change (from 96.7 +/- 4.5 beats per minute to 102.6 +/- 7.6 beats per minute). These unexpected findings emphasize the marginal role of the heart on the pathogenesis of the vasovagal syncope and underline the fact that a vasovagal reaction can develop even in the absence of the bradycardia that is the primary symptom usually reported in the literature.