A 67-year-old man comes to the emergency department due to lightheadedness and generalized weakness for the past 2 days. The patient has chronic stable angina with exertion. Over the past 2 days, he has also had occasional chest discomfort at rest. Medical history includes hypertension and asthma. The patient has no shortness of breath, cough, or peripheral edema. His only medications are aspirin and isosorbide dinitrate. Blood pressure is 105/66 mm Hg. ECG obtained in the emergency department is shown in the exhibit. Which of the following is the best next step in management of this patient?

Question

A 67-year-old man comes to the emergency department due to lightheadedness and generalized weakness for the past 2 days.  The patient has chronic stable angina with exertion.  Over the past 2 days, he has also had occasional chest discomfort at rest.  Medical history includes hypertension and asthma.  The patient has no shortness of breath, cough, or peripheral edema.  His only medications are aspirin and isosorbide dinitrate.  Blood pressure is 105/66 mm Hg.  ECG obtained in the emergency department is shown in the exhibit.  Which of the following is the best next step in management of this patient?

Quizplus · Accepted Answer

11ec25c8_d34f_298a_bc81_05deb4e6f5dd_MD0003_00 This patient's ECG reveals third-degree (complete) atrioventricular (AV) block, which involves a total lack of communication between the atria and the ventricles due to AV node dysfunction. It can result from ischemia, infiltrative disease (eg, sarcoidosis), infection (eg, Lyme disease), overdose of AV nodal blocking agents (eg, beta blockers), or age-related fibrosis of the conduction system. Because conduction signals from the atria cannot communicate with the ventricles, the intrinsic pacemaker of the His bundle or ventricles is triggered, resulting in a junctional or ventricular escape rhythm. On this patient's ECG (zoomed in on lead II), there is dissociation of P waves and QRS complexes, with P waves marching out at the intrinsic rate of the sinoatrial node (eg, ~85/min) and QRS complexes at the intrinsic rate of the His bundle or ventricles (eg, ~50/min). lead II ~50/min The slow ventricular rate in third-degree AV block leads to reduced cardiac output, which can cause dyspnea, fatigue, lightheadedness, syncope, or sometimes cardiac arrest. Angina can occur in patients with underlying coronary artery disease. Management requires cardiac pacing, which can be initially accomplished via transcutaneous or transvenous pacing, followed by definitive management with placement of a permanent pacemaker if no reversible causes (eg, reversible ischemia, excessive pharmacologic AV nodal blockade) are found. (Choices A, C, and E) Adenosine decreases conduction velocity in the AV node, which can lead to a transient AV block. Similarly, beta blockers (eg, metoprolol) and digoxin delay AV nodal conduction and can cause or worsen AV block. These drugs are all contraindicated in patients with advanced AV block. (Choice D) Fibrinolytic therapy can be used to treat an ST-segment elevation myocardial infarction. However, this patient has no ST-segment elevation on ECG, and his chest pain is most consistent with stable angina precipitated by third-degree AV block. Educational objective: Third-degree (complete) atrioventricular block involves dysfunction of the atrioventricular (AV) node, resulting in total lack of communication between the atria and the ventricles. On ECG, there is dissociation of P waves and QRS complexes, with P waves marching out at the intrinsic rate of the sinoatrial node and QRS complexes at the intrinsic rate of the His bundle or ventricles (escape rhythm). Management involves placement of a permanent pacemaker if no reversible causes of AV block are found. References: Complete heart block in late presentation of inferior STEMI successfully treated with percutaneous coronary intervention. (http://www.ncbi.nlm.nih.gov/pubmed/21891817) Temporary transvenous pacemaker placement in the emergency department. (http://www.ncbi.nlm.nih.gov/pubmed/17239740) Atrioventricular block in patients with thyroid dysfunction: prognosis after treatment with hormone supplementation or antithyroid medication. (http://www.ncbi.nlm.nih.gov/pubmed/22738687)

A 67-Year-Old Man Comes to the Emergency Department Due to Lightheadedness