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A hospitalized patient in their 80s became tachycardic. The patient initially presented with changes in mental status and generalized weakness, which were attributed to urinary tract infection. An electrocardiogram (ECG) showed a narrow-complex tachycardia with nonspecific ST-T wave changes (Figure, A). The patient was asymptomatic and denied having palpitations, chest pain, and shortness of breath; blood pressure was normal. The patient had a remote history of coronary artery disease. A left carotid sinus massage (CSM) was performed at the bedside (Figure, B).
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Carotid sinus massage was mentioned by Parry6 in 1799 as producing dizziness and slowing of the heart. The carotid sinus contains baroreceptors innervated by the carotid sinus nerve, a branch of the glossopharyngeal nerve. Increased pressure on the baroreceptors sends a signal to the solitary nucleus in the medulla of brainstem, which modulates the activity of the sympathetic and parasympathetic neurons in the medulla and pons. The end result is a reduction in blood pressure and slowing of the heart rate.
The ECG effects include sinus slowing; atrial conduction defects with changes in amplitude, duration, and morphology of the P wave; various degrees of AVB; asystole; and rarely, premature ventricular contractions. It is thought that right-sided CSM exerts more inhibitory effects on the sinus node compared with left-sided CSM, which slows conduction more so in the atrioventricular node.
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CME Disclosure Statement: Unless noted, all individuals in control of content reported no relevant financial relationships. If applicable, all relevant financial relationships have been mitigated.
Corresponding Author: Mazen M. Kawji, MD, Saint Margaret’s Health–Peru, 925 West St, Peru, IL 61354 (firstname.lastname@example.org).
Published Online: June 21, 2022. doi:10.1001/jamainternmed.2022.2078
Conflict of Interest Disclosures: None reported.
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