JOURNAL OF THE LOUISIANA STATE MEDICAL SOCIETY
Figure 2. Twelve-lead electrocardiographic rhythm strip recorded during left carotid sinus massage shows a 3.6s sinus pause. Carotid sinus baroreceptors sense pressure.When it is low, afferent nerves signal the brainstem, which through efferent nerves stimulates the sympathetic nervous system and inhibits the parasympathetic nervous system causing vasoconstriction and an increase in heart rate. When the carotid sinus receptors signal the brainstem that the pressure is high, the efferent nerves inhibit the sympathetic nervous system and stimulate the parasympathetic nervous system causing vasodilatation and slowing of the heart rate.³ Carotid sinus massage sends a message that pressure is high. If this message is strong enough, it can result in such a marked slowing of heart rate and/or drop in blood pressure that syncope occurs.
The patient had two obvious potential causes of his syncopal episode. One was aortic stenosis. Syncope in patients with aortic stenosis, however, has usually occurred during or immediately after exercise and in patients withmore severe stenosis than was found in this patient. The patient clearly has a hypersensitive carotid sinus. His syncopal episode occurred when he was on a ladder attempting to cut some limbs, and he may well have been rotating and/or extending his neck. Although carotid sinus hypersensitivity has been found in many elderly patients with syncope of unknown cause, it has also been found in many patients who never had a syncopal episode.¹ Nevertheless, carotid sinus hypersensitivity seemed to be the most likely diagnosis in this patient, and the treatment for syncope due to carotid sinus hypersensitivity, an electronic cardiac pacemaker, has almost always had fewer complications than the treatment of syncope due to aortic stenosis, aortic valve replacement. Accordingly a dual chamber electronic pacemaker was implanted without difficulty, and the patient returned home.
REFERENCES
1. Hanna EB. Practical Cardiovascular Medicine . Oxford, UK: Wiley Blackwell;2017:488-498. 2. Lewis T. Observations upon ventricular hypertrophy with especial reference to preponderance of one or other chamber. Heart 1914;5:367-402. 3. Mohrman DE, Heller LJ. Cardiovascular Physiology , 4th edition. New York: McGraw-Hill;1997:151-173. Avaneesh Jakkoju, MD and Vishnupriya Kuchana, MD are fellows in the Section of Cardiology, Department of Medicine, Louisiana State University Health Sciences Center-New Orleans in New Orleans, Louisiana. Pramilla Subramaniam, MD and D. Luke Glancy, MD are professors in the Section of Cardiology, Department of Medicine, Louisiana State University Health Sciences Center-New Orleans in New Orleans, Louisiana.
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