A 46-year-old man experiences syncope while getting out of bed. The patient has been feeling weak during the past several days and has had dyspnea and chest discomfort. He believes the symptoms are due to a respiratory infection 2 weeks ago, but he did not see a doctor at that time. Medical history includes hypertension that is controlled with lisinopril. Family history includes coronary artery disease. ECG rhythm strip is shown in the exhibit. Which of the following is the most appropriate treatment for this patient?

Question

A 46-year-old man experiences syncope while getting out of bed.  The patient has been feeling weak during the past several days and has had dyspnea and chest discomfort.  He believes the symptoms are due to a respiratory infection 2 weeks ago, but he did not see a doctor at that time.  Medical history includes hypertension that is controlled with lisinopril.  Family history includes coronary artery disease.  ECG rhythm strip is shown in the exhibit.  Which of the following is the most appropriate treatment for this patient?

Quizplus · Accepted Answer

11ec25c8_d361_2afd_bc81_bd2e4e9a6fd0_MD0003_00 IVC = inferior vena cava; JVD = jugular venous distension; LV = left ventricular; SBP = systolic blood pressure. This patient's ECG rhythm strip shows normal sinus rhythm; close inspection reveals that the height of the QRS complexes alternates with each cycle (noticeable in precordial lead V1), a finding known as electrical alternans. Electrical alternans is a specific but poorly sensitive (often not present) finding for pericardial effusion with cardiac tamponade; it results from the heart changing position within the fluid-filled pericardial sac with each heartbeat. Low-voltage QRS complexes (eg, <10 mm in precordial leads), as seen in this patient, are a moderately sensitive and moderately specific finding for cardiac tamponade that results from attenuation of cardiac electrical signals by fluid within the pericardial sac. alternates Viral infection is a common cause of acute pericarditis, which can be complicated by pericardial effusion. This patient has likely experienced slow accumulation of fluid within the pericardial sac, leading to progressive symptoms of weakness, dyspnea, and chest discomfort. Eventually, the fluid compresses the relatively low-pressure right-sided heart chambers and restricts diastolic filling, leading to subacute tamponade. With the right-sided heart chambers unable to fill, less blood is delivered to the left side of the heart and cardiac output drops, leading to hypotension and associated symptoms (eg, lightheadedness, syncope). Treatment requires emergency pericardiocentesis to relieve pericardial pressure and restore blood flow through the chambers of the heart. (Choice A) Adenosine briefly slows conduction through the atrioventricular node and is used to help identify and treat supraventricular tachycardias, particularly atrioventricular nodal reentrant tachycardia. atrioventricular nodal reentrant tachycardia (Choice B) Amiodarone has wide-ranging antiarrhythmic effects and can be used to treat arrhythmias, including atrial fibrillation (ie, rhythm control strategy) and monomorphic ventricular tachycardia. monomorphic ventricular tachycardia (Choices C and E) Atrial fibrillation is commonly treated with a combination of anticoagulation (eg, heparin infusion) to lower the risk of arterial thromboembolism and an atrioventricular node conduction inhibitor (eg, metoprolol) to slow the heart rate (ie, rate control strategy). Atrial fibrillation (Choice D) Intravenous magnesium sulfate is used to treat torsade de pointes, a polymorphic ventricular tachycardia typically resulting from excessive prolongation of the QT interval. torsade de pointes (Choice G) Synchronized cardioversion is used for acute conversion of some cardiac arrhythmias (eg, atrial flutter, atrial fibrillation, stable monomorphic ventricular tachycardia) back to normal sinus rhythm. Educational objective: Electrical alternans is a specific but poorly sensitive finding for pericardial effusion with cardiac tamponade; it results from the heart changing position within the fluid-filled pericardial sac with each heartbeat. Tamponade is treated with emergency pericardiocentesis to relieve pericardial pressure. References: Cardiac tamponade. (http://www.ncbi.nlm.nih.gov/pubmed/21716107) A systematic approach to evaluation of pericardial effusion and cardiac tamponade. (http://www.ncbi.nlm.nih.gov/pubmed/21808166)

A 46-Year-Old Man Experiences Syncope While Getting Out of Bed