A 78-year-old man is brought to the emergency department after experiencing 2 episodes of syncope. The first episode occurred yesterday while he sat reading a magazine after a heavy dinner. The second happened today in the bathroom after urination. The patient felt lightheaded and nauseated and had to sit down on the toilet seat before he briefly lost consciousness. He has never had similar episodes before, but he has experienced some lightheadedness during brisk uphill walking.
Over the last several days, the patient has had lower abdominal cramps accompanied by 2 episodes of diarrhea. He was diagnosed with aortic stenosis a year ago after a physical examination showed a murmur, but he refused to see a cardiologist for further evaluation. In the emergency department, he says that he feels "weak but okay."
His blood pressure is 124/60 mm Hg. Jugular venous pressure is estimated at 10 cm H₂O. There is a harsh 4/6 systolic mid-peaking murmur at the base of the heart that radiates to both carotids. The second heart sound is soft, and the carotid upstrokes are delayed after the first heart sound. His lungs are clear on auscultation. There is no peripheral edema.
An electrocardiogram is obtained in the emergency department.
Which of the following is the most likely cause of this patient's symptoms?

Question

Quizplus · Accepted Answer

This patient's syncope is most likely due to complete heart block, as seen on electrocardiogram. The arrows indicate P waves that have no relation to QRS complexes, confirming atrioventricular dissociation. Patients typically have dizziness, presyncope, or syncope (Stokes-Adams attacks). The bradycardia can exacerbate symptoms of existing heart failure and coronary artery disease. complete heart block electrocardiogram Treatment is first directed at reversible causes, such as medications (eg, beta blockers). Patients who are acutely symptomatic with a narrow QRS on ECG may be treated with atropine; those with a wide QRS may require temporary pacing. Stable, asymptomatic patients usually require a permanent pacemaker, preferably with dual-chamber pacing. (Choice B) Significant left main coronary disease may present with angina or dyspnea, either with exertion or at rest. This patient's stable clinical examination (eg, normal vital signs, no edema), lack of angina or dyspnea, and lack of ischemic changes on ECG make coronary disease less likely. (Choice C) Though this patient has severe aortic stenosis (eg, soft S2), syncope in aortic stenosis is typically associated with exertion. This patient's syncope has occurred during rest and he has ECG evidence of complete heart block. (Choice D) Vasovagal syncope (neurocardiogenic syncope) is usually associated with an identifiable trigger (eg, emotional upset, acute pain, micturition). It is characterized by a prodrome of warmth, diaphoresis, nausea and abdominal discomfort. Syncope is usually brief and frequently followed by emesis. In older patients and those with structural heart disease, it should be considered a diagnosis of exclusion after other etiologies are ruled out. (Choice E) Significant volume depletion can present with syncope and usually has associated tachycardia and hypotension. Although this patient did have diarrhea, his lack of hypotension or significant tachycardia makes this less likely. Educational objective: Complete heart block may present with syncope, especially in older patients or those with structural heart disease. Patients should be evaluated for reversible causes but usually require a permanent pacemaker. Acutely symptomatic patients may require atropine or temporary pacing depending on QRS width. __________ References: Suspected cardiac syncope in elderly patients: use of the 12-lead electrocardiogram to select patients for Holter monitoring. (http://www.ncbi.nlm.nih.gov/pubmed/11408724) Recurrent syncope due to complete atrioventricular block, a rare presenting symptom of otherwise silent coronary artery disease: successful treatment by PTCA. (http://www.ncbi.nlm.nih.gov/pubmed/9328714)

A 78-Year-Old Man Is Brought to the Emergency Department After