A 67-year-old man is brought to the emergency department after a syncopal episode. He lost consciousness while shopping in a mall. He has no nausea, diaphoresis, chest pain, or shortness of breath. The patient has had 2 episodes of lightheadedness over the past month but has not sought treatment. Other conditions include long-standing hypertension, which is treated with enalapril. Blood pressure is 135/90 mm Hg while supine and 130/85 mm Hg while standing; pulse is 64/min. ECG shows sinus rhythm with high voltage, prolonged PR interval, prolonged QRS-complex duration, normal QTc interval, and occasional premature ventricular contractions. Basic metabolic panel is unremarkable. Echocardiography reveals left ventricular hypertrophy and ejection fraction of 55%. Which of the following is the most likely cause of this patient's syncope?

Question

A 67-year-old man is brought to the emergency department after a syncopal episode.  He lost consciousness while shopping in a mall.  He has no nausea, diaphoresis, chest pain, or shortness of breath.  The patient has had 2 episodes of lightheadedness over the past month but has not sought treatment.  Other conditions include long-standing hypertension, which is treated with enalapril.  Blood pressure is 135/90 mm Hg while supine and 130/85 mm Hg while standing; pulse is 64/min.  ECG shows sinus rhythm with high voltage, prolonged PR interval, prolonged QRS-complex duration, normal QTc interval, and occasional premature ventricular contractions.  Basic metabolic panel is unremarkable.  Echocardiography reveals left ventricular hypertrophy and ejection fraction of 55%.  Which of the following is the most likely cause of this patient's syncope?

Quizplus · Accepted Answer

11ec25c8_d192_fa41_bc81_d7424f7b8b83_MD0003_00 Syncope refers to an abrupt and transient loss of consciousness with loss of postural tone, followed by a spontaneous and complete recovery. It is usually benign and self-limiting (eg, vasovagal syncope), but it can be the initial presenting symptom of a life-threatening disease process (eg, cardiac syncope). The cause of syncope can often be determined by careful history taking, physical examination, simple laboratory tests, and ECG. This patient has conduction system abnormalities, including prolonged PR interval and intraventricular conduction delay (prolonged QRS-complex duration), on initial ECG. This is suggestive of a bradyarrhythmia or high-grade atrioventricular block as the most likely cause of his syncopal episode. Atrioventricular block with associated bradyarrhythmia can be quite intermittent and is likely responsible for this patient's prior episodes of lightheadedness over the past month. The fact that his heart rate is currently normal does not exclude bradyarrhythmia due to the intermittent nature of the block in many patients. He should be referred for additional electrophysiologic testing and evaluation for pacemaker implantation. (Choice A) Postural hypotension due to autonomic dysfunction can cause presyncope and syncope. However, this patient's supine and standing blood pressures are not consistent with orthostatic hypotension (>20 mm Hg drop in systolic blood pressure with position change). (Choice C) Decreased myocardial contractility from conditions such as cardiomyopathy or ischemic heart disease predisposes to serious ventricular arrhythmias (eg, ventricular tachycardia), and paroxysmal ventricular tachycardia can cause syncope. However, the patient's normal left ventricular ejection fraction on echocardiography makes this less likely. (Choice D) This patient has no reported symptoms (eg, preceding aura, tonic-clonic movements, postictal phase) suggestive of a seizure. (Choice E) Premature ventricular beats are usually asymptomatic or can cause palpitations in some patients. Isolated premature ventricular beats in a patient with normal ejection fraction are not associated with syncope. (Choice F) Torsades de pointes is a polymorphic ventricular tachycardia that can be triggered by a prolonged QT interval. This patient has a normal QTc interval and electrolyte levels and takes no medications known to prolong the QTc interval. Educational objective: ECG is useful in identifying cardiac syncope and should be obtained in all patients with unexplained syncope. ECG findings suggesting an arrhythmia as the cause of syncope include sinus bradycardia, sinus pauses, atrioventricular block, and prolonged QTc interval. References: Syncope: epidemiology, etiology, and prognosis. (http://www.ncbi.nlm.nih.gov/pubmed/25538626) Guidelines for the diagnosis and management of syncope (version 2009). (http://www.ncbi.nlm.nih.gov/pubmed/19713422)

A 67-Year-Old Man Is Brought to the Emergency Department After