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CLINICAL STUDIES

Diagnostic utility of mechanical, pharmacological and orthostatic stimulation of the carotid sinus in patients with unexplained syncope

Carlos A. Morillo, MD, Maria E. Camacho, MD, Mark A. Wood, MD, FACC^*, David M. Gilligan, MD, FACC and Kenneth A. Ellenbogen, MD, FACC^*

^* Department of Medicine, Medical College of Virginia, Virginia Commonwealth University, Richmond, Virgnia, USA
Hunter Holmes Mc Guire Veterans Affairs Medical Center, Richmond, Virgnia, USA
Department of Cardiology, Fundación Cardiovascular del Oriente Colombiano, Bucaramanga, Colombia

Manuscript received January 23, 1996; revised manuscript received May 12, 1999, accepted June 29, 1999.

Reprint requests and correspondence: Dr. Carlos A. Morillo, Department of Cardiology and Cardiovascular Sciences, Fundación Cardiovascular del Oriente, Colombiano Instituto del Corazón, Calle 155A, No. 23-58, Urbanización El Bosque, Floridablanca, Santander, Colombia

OBJECTIVES

The purpose of the present study was to systematically evaluate the diagnostic utility of mechanical, pharmacological and orthostatic stimulation of the carotid sinus in a consecutive series of patients with recurrent unexplained syncope.

BACKGROUND

Carotid sinus hypersensitivity (CSH) is an infrequently recognized cause of recurrent unexplained syncope usually diagnosed by carotid sinus massage (CSM) in the supine position. The diagnostic utility of systematic assessment of mechanical, pharmacological and orthostatic stimulation of the carotid sinus has not been clearly established.

METHODS

Eighty consecutive patients (63 ± 12 years) with a history of recurrent unexplained syncope (mean episodes: 6 ± 3); 30 age-matched controls (65 ± 14 years) and 16 patients (59 ± 12 years) with syncope not related to CSH were studied. Pharmacological stimulation of the carotid sinus was achieved by randomly administering bolus injections of nitroprusside and phenylephrine. Mechanical stimulation of the carotid sinus was performed by CSM applied for 5 s in the supine position and after 2 min at 60°. A 60° low-dose isoproterenol head-up tilt test (HUTT) was also performed for a total duration of 30 min.

RESULTS

Carotid sinus hypersensitivity was elicited by CSM in the supine position in seven (8.7%) patients, two (6.6%) controls and one (6.3%) patient with syncope unrelated to CSH, compared with 48 (60%) patients, two (6.6%) controls and one (6.3%) syncope unrelated to CSH patient after 60° HUTT, increasing the diagnostic yield by 51%. Baroreceptor gain was significantly reduced in the CSH group. Head-up tilt test was positive in 12 (25%) patients with CSH, two (6.6%) controls and two (12%) with documented syncope but not positive in any of the patients in which syncope remained unexplained. Diagnostic accuracy was enhanced by 38% (31% supine vs. 69% upright) when CSM was performed at 60°.

CONCLUSIONS

CSH was documented in 68% of patients, 8.7% in the supine position and 60% in the upright position. Sensitivity was increased by 51%, and diagnostic accuracy was enhanced by 38% by performing CSM in the upright position. Decreased baroreceptor gain was documented and may play a role in the pathophysiology of CSH.

Abbreviations and Acronyms   CSH = carotid sinus hypersensitivity   CSM = carotid sinus massage   ECG = electrocardiogram   HUTT = head-up tilt test   VF = ventricular fibrillation   VT = ventricular tachycardia

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