A 72-year-old man comes to the clinic due to episodic lightheadedness. The episodes typically occur in the morning when the patient adjusts his shirt collar or tightens his tie and he briefly feels like he is going to pass out. The patient had a thyroidectomy 5 years ago for a large benign tumor. He also has hypertension and takes amlodipine. Blood pressure is 135/78 mm Hg and pulse is 78/min. Physical examination reveals no heart murmurs or carotid bruits. ECG shows normal sinus rhythm. The patient is given an ambulatory ECG monitoring device. During symptomatic episodes, the device is most likely to show which of the following?

Question

A 72-year-old man comes to the clinic due to episodic lightheadedness.  The episodes typically occur in the morning when the patient adjusts his shirt collar or tightens his tie and he briefly feels like he is going to pass out.  The patient had a thyroidectomy 5 years ago for a large benign tumor.  He also has hypertension and takes amlodipine.  Blood pressure is 135/78 mm Hg and pulse is 78/min.  Physical examination reveals no heart murmurs or carotid bruits.  ECG shows normal sinus rhythm.  The patient is given an ambulatory ECG monitoring device.  During symptomatic episodes, the device is most likely to show which of the following?

Quizplus · Accepted Answer

This patient with episodes of presyncope (eg, lightheadedness, feeling of impending loss of consciousness) that occur when he adjusts his shirt collar or necktie most likely has carotid sinus hypersensitivity (CSH). The condition results from overly sensitive carotid baroreceptors that stimulate an excessive vasovagal response to tactile stimulation. CSH is most commonly seen in elderly men; underlying carotid atherosclerotic disease and prior neck surgery (eg, thyroidectomy) are risk factors. The baroreceptor response in CSH mimics the normal response to increased blood pressure but is more exaggerated; increased parasympathetic output leads to a prolonged sinus pause (eg, 3-5 seconds) and decreased sympathetic outflow causes marked peripheral vasodilation. The resulting delay in ventricular contraction and decreased systemic vascular resistance leads to a profound reduction in blood pressure and transient loss of cerebral perfusion that manifests as presyncope or syncope. (Choices A, C, and E) Intermittent tachyarrhythmias, including atrial fibrillation with rapid ventricular response, paroxysmal supraventricular tachycardia (eg, atrioventricular nodal reentrant tachycardia), and ventricular tachycardia, can cause syncope due to loss of cardiac output and reduced cerebral perfusion (of the 3 tachyarrhythmias, ventricular tachycardia is most concerning). However, CSH is more likely in this patient with symptoms associated with tactile stimulation of the carotid sinus. (Choice B) Advanced atrioventricular block (ie, complete heart block, Mobitz type II second-degree heart block) can cause presyncope or syncope but is also less likely than CSH in this patient with symptoms associated with tactile stimulation of the carotid sinus. Educational objective: Carotid sinus hypersensitivity is most commonly seen in elderly men and involves an exaggerated vasovagal response to tactile stimulation of carotid sinus baroreceptors (eg, adjusting a shirt collar or necktie). The resulting increase in parasympathetic output leads to a prolonged sinus pause that contributes to the excessive drop in blood pressure, leading to transient loss of cerebral perfusion that manifests as presyncope (eg, lightheadedness) or syncope. __________ References: Carotid sinus syndrome: progress in understanding and management. (http://www.ncbi.nlm.nih.gov/pubmed/25405171)

A 72-Year-Old Man Comes to the Clinic Due to Episodic