Correspondence

Neurocardiogenic Syncope

N Engl J Med 1993; 329:1966-1967December 23, 1993

Article

To the Editor:

The Images in Clinical Medicine in the July 1 issue1 intrigued me. I am uncertain whether the hemodynamic reaction shown represents syncope mediated by the neurocardiogenic (Bezold-Jarisch) reflex or carotid-sinus hypersensitivity with only a vasodepressor component. Generally, bradycardia is expected in neurocardiogenic syncope, which is thought to be mediated by vagal afferent and efferent fibers2,3. Conversely, carotid-sinus hypersensitivity mediated by glossopharyngeal afferent fibers occurs without bradycardia in a pure vasodepressor reaction4. Given the patient's history of metastatic cancer of the neck, carotid-sinus hypersensitivity seems to be a strong candidate for having produced the illustrated hemodynamic reaction. I am interested in the results of carotid-massage testing in this patient and the authors' interpretation of the reflex arcs involved in the patient's syncopal episode.

Stephen E. Piwinski, M.D.
John Peter Smith Hospital, Fort Worth, TX 76104

4 References

1. 1

   Osswald S, Trouton TG. Neurocardiogenic (vasodepressor) syncope. N Engl J Med 1993;329:30-30
   Full Text | Web of Science | Medline

2. 2

   Sra JS, Jazayeri MR, Avitall B, et al. Comparison of cardiac pacing with drug therapy in the treatment of neurocardiogenic (vasovagal) syncope with bradycardia or asystole. N Engl J Med 1993;328:1085-1090
   Full Text | Web of Science | Medline

3. 3

   Linzer M. Syncope: 1991. Am J Med 1991;90:1-5
   CrossRef | Web of Science | Medline

4. 4

   Taylor AA, Mitchell JR. Laboratory evaluation of autonomic nervous system function. In: Laragh, JH, Brenner BM, eds. Hypertension: pathophysiology, diagnosis, and management. Vol. 2. New York: Raven Press, 1990:1461-78.
   

Author/Editor Response

The authors reply:

To the Editor: Dr. Piwinski has made a reasonable suggestion that glossopharyngeal-nerve involvement and carotid-sinus hypersensitivity might have had a role in triggering clinical syncope in our patient1. Furthermore, the patient was initially treated with carbamazepine, which relieved her neuralgia but did not prevent recurrent syncope. However, there are several features that are not adequately explained by the occurrence of classic carotid hypersensitivity alone. First, palpation of the patient's neck did not induce syncope, whereas head-up tilt testing in the absence of carotid-sinus irritation did reproducibly induce her syncope. Second, her frequent syncopal episodes were completely abolished by treatment with disopyramide, a drug that is thought to inhibit cardiac mechanoreceptors (C fibers) in neurocardiogenic syncope by means of its negative inotropic properties2. This property of disopyramide in unlikely to be effective in the management of carotid hypersensitivity.

On the basis of the current understanding,3 the afferent limb of the reflex arc in neurocardiogenic syncope may be quite variable, whereas the uniformity of the efferent response suggests the involvement of a final common pathway4,5. This concept is supported by the clinical observation that multiple stimuli, such as pain, fear, psychological stress, use of vasodilators, inferior myocardial ischemia, and gastrointestinal hemorrhage, have the potential to trigger a uniform vasodepressor response4,5. This suggests that mechanisms in addition to abnormal afferent parasympathetic activity, such as lowering of the central nervous system threshold for activation of the efferent autonomic response, may have a pivotal role in people susceptible to neurocardiogenic syncope.

Stefan Osswald, M.D.
Thomas G. Trouton, M.D.
Brian A. McGovern, M.D.
Massachusetts General Hospital, Boston, MA 02114

5 References

1. 1

   Wallin BG, Westerberg CE, Sundlof G. Syncope induced by glossopharyngeal neuralgia: sympathetic outflow of muscle. Neurology 1984;34:522-524
   Web of Science | Medline

2. 2

   Milstein S, Buetikofer J, Dunningan A, Benditt DG, Gornick C, Reyes WJ. Usefulness of disopyramide for prevention of upright tilt-induced hypotension-bradycardia. Am J Cardiol 1990;65:1339-1344
   CrossRef | Web of Science | Medline

3. 3

   Abboud FM. Neurocardiogenic syncope. N Engl J Med 1993;328:1117-1120
   Full Text | Web of Science | Medline

4. 4

   Benditt DG, Remole S, Bailin S, Dunnigan A, Asso A, Milstein S. Tilt table testing for evaluation of neurally-mediated (cardioneurogenic) syncope: rationale and proposed protocols. Pacing Clin Electrophysiol 1991;14:1528-1537
   CrossRef | Web of Science | Medline

5. 5

   Rea RF, Thames MD. Neural control mechanism and vasovagal syncope. J Cardiovasc Electrophysiol 1993;4:587-595
   CrossRef | Web of Science | Medline