A 21-year-old woman is evaluated for syncope. She has had recurrent episodes of syncope since her mid-teens. The first episode happened when she was having blood drawn for a test. She has also passed out several times while standing in a crowded church. The syncope is typically preceded by a feeling of warmth, lightheadedness, diaphoresis, and nausea. During one episode, the patient had a minor head injury and facial laceration. Her medical history is otherwise insignificant. She takes no medications and uses no illicit drugs. Blood pressure is 122/76 mm Hg supine and 125/80 mm Hg after 2 minutes of standing. Pulse is 72/min and regular. Physical examination is unremarkable. ECG shows normal sinus rhythm with no significant abnormalities. Long-term ECG monitoring is most likely to show which of the following immediately preceding and during the syncopal episode?

Question

A 21-year-old woman is evaluated for syncope.  She has had recurrent episodes of syncope since her mid-teens.  The first episode happened when she was having blood drawn for a test.  She has also passed out several times while standing in a crowded church.  The syncope is typically preceded by a feeling of warmth, lightheadedness, diaphoresis, and nausea.  During one episode, the patient had a minor head injury and facial laceration.  Her medical history is otherwise insignificant.  She takes no medications and uses no illicit drugs.  Blood pressure is 122/76 mm Hg supine and 125/80 mm Hg after 2 minutes of standing.  Pulse is 72/min and regular.  Physical examination is unremarkable.  ECG shows normal sinus rhythm with no significant abnormalities.  Long-term ECG monitoring is most likely to show which of the following immediately preceding and during the syncopal episode?

Quizplus · Accepted Answer

11ec25c8_d2f4_37d8_bc81_ff41b682c0f1_MD0003_00 Syncope is a quick-resolving loss of consciousness that results from transient cerebral hypoperfusion leading to loss of postural tone (eg, collapse). This patient is most likely experiencing vasovagal syncope (neurocardiogenic syncope), which occurs due to an alteration in autonomic drive. Most commonly, abrupt parasympathetic activation leads to a cardioinhibitory response that manifests as bradycardia with sinus arrest. Less commonly, decreased sympathetic drive leads to a vasodepressor response, resulting in peripheral vasodilation and abrupt hypotension. In both scenarios, cerebral perfusion suddenly decreases and syncope occurs. The episode resolves quickly (typically <1 minute) as cerebral perfusion is rapidly restored. Vasovagal syncope most commonly affects young patients and is often triggered by emotional stress (eg, fear of venipuncture) or prolonged standing. The diagnosis is usually clinical. A prodrome (eg, nausea, diaphoresis, pallor, lightheadedness) typically precedes vasovagal syncope and helps differentiate it from serious causes of syncope (eg, cardiogenic syncope). In addition, measurement of normal orthostatic blood pressure helps rule out orthostatic syncope. Isolated episodes of vasovagal syncope require no treatment other than reassurance. Recurrent episodes may warrant counseling to avoid common triggers as well as training in counterpressure techniques (eg, leg-crossing, hand grip) to try to avert a syncope episode once prodromal symptoms occur. (Choices A and E) Atrial arrhythmias (eg, atrial fibrillation, atrial flutter) with a rapid ventricular rate (eg, >150/min) and ventricular arrhythmias (eg, ventricular tachycardia) can cause cardiogenic syncope due to inadequate ventricular filling and loss of cardiac output. The syncope is typically sudden; patients may experience palpitations prior to the episode, but a prodrome of nausea and diaphoresis is not typical. (Choice C) Sinus tachycardia does not cause syncope. Patients often have sinus tachycardia as a reflex response after a syncope episode. (Choice D) Third-degree atrioventricular block can cause cardiogenic syncope but typically in patients with a history of heart disease (eg, myocardial infarction, systemic amyloidosis, Lyme carditis). It would be unusual in this young woman with no significant medical history. Varying degrees of atrioventricular block can occur as a cardioinhibitory response in vasovagal syncope; however, sinus bradycardia with sinus arrest is the typical finding on cardiac monitoring. Educational objective: Vasovagal syncope is typically preceded by a prodrome (eg, nausea, diaphoresis, pallor, lightheadedness) and usually occurs due to a cardioinhibitory response from increased parasympathetic activity. Cardiac monitoring immediately preceding the syncope typically shows sinus bradycardia and asystole due to sinus arrest. References: Guidelines for the diagnosis and management of syncope (version 2009). (http://www.ncbi.nlm.nih.gov/pubmed/19713422) Mechanism of syncope in patients with isolated syncope and in patients with tilt-positive syncope. (http://www.ncbi.nlm.nih.gov/pubmed/11551877)

A 21-Year-Old Woman Is Evaluated for Syncope