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CLINICAL STUDIES: SYNCOPE

Provocation of neurocardiogenic syncope by clomipramine administration during the head-up tilt test in vasovagal syndrome

George N. Theodorakis, MD^*, Manolis Markianos, MD, Elias Zarvalis, MD^*, Efthimios G. Livanis, MD^*, Panagiota Flevari, MD^* and Dimitrios Th Kremastinos, MD^*

^* Onassis Cardiac Surgery Center, Second Department of Cardiology, Eginition Hospital, Athens University Medical School, Athens, Greece
Laboratory of Neurochemistry, Eginition Hospital, Athens University Medical School, Athens, Greece

Manuscript received September 28, 1999; revised manuscript received January 21, 2000, accepted March 27, 2000.

Reprint requests and correspondence: Dr. George N. Theodorakis, Onassis Cardiac Surgery Center, 356 Sygrou Avenue, 17674 Athens, Greece
elbee{at}ath.forthnet.gr

OBJECTIVES

We sought to test the hypothesis that activation of the serotonergic system in patients with vasovagal syndrome during the head-up tilt test provokes syncope.

BACKGROUND

Central serotonergic activation participates in the pathogenesis of neurocardiogenic syncope. Drugs increasing serotonin (5-HT) in the central nervous system have not been tested as drug challenges during the head-up tilt test with clomipramine (Clom-HUT).

METHODS

The serotonergic re-uptake inhibitor clomipramine was infused (5 mg in 5 min) at the start of Clom-HUT in 55 patients (mean age 40 ± 17 years) with a positive history of recurrent neurocardiogenic syncope and in 22 healthy control subjects (mean age 46 ± 15 years). Blood samples were taken at 0, 5, 10 and 20 min for estimation of plasma prolactin and cortisol as neuroendocrine indicators of central serotonergic responsitivity. All subjects had been previously tested with a basic 60° head-up tilt test (B-HUT) for 30 min, and if negative, isoproterenol infusion was given at the end of the test.

RESULTS

Twenty-nine (53%) of the 55 patients and none of the 22 control subjects had a positive result in the B-HUT. With Clom-HUT, the proportion of patients who experienced a positive response increased to 80% (n = 44), although this happened to only one control subject. Prolactin and cortisol plasma levels increased significantly in the positive Clom-HUT patient group only.

CONCLUSIONS

The results indicate an increased responsitivity of the central serotonergic neural system in subjects with vasovagal syndrome, the activation of which leads to sympathetic withdrawal. The use of clomipramine infusion with the tilt test seems to considerably improve its diagnostic value.

Abbreviations and Acronyms   B-HUT = basic head-up tilt   Clom-HUT = head-up tilt test with clomipramine   ECG = electrocardiographic   5-HT = serotonin

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