A 72-year-old man is brought to the emergency department after an episode of syncope during a family gathering. The patient was sitting in his chair after dinner and passed out briefly. There are no apparent injuries and no seizure-like activity was observed. His granddaughter says that he has had frequent episodes of dizziness in the last 2 weeks. These episodes are sometimes accompanied by confusion and are not related to physical activity or changes in position. The patient's other medical problems include coronary artery disease and hypertension. He does not use alcohol or tobacco. His medications include aspirin, lisinopril, atorvastatin, and isosorbide mononitrate. Blood pressure is 105/60 mm Hg and respirations are 14/min. The patient is fully alert and oriented. Examination reveals no neck bruits. Lung fields are clear, and no cardiac murmurs are heard. Neurologic examination is within normal limits. ECG is shown in the exhibit. Serum potassium is 4.1 mEq/L and serum creatinine is 1.1 mg/dL. Which of the following is the best next step in management of this patient?

Question

A 72-year-old man is brought to the emergency department after an episode of syncope during a family gathering.  The patient was sitting in his chair after dinner and passed out briefly.  There are no apparent injuries and no seizure-like activity was observed.  His granddaughter says that he has had frequent episodes of dizziness in the last 2 weeks.  These episodes are sometimes accompanied by confusion and are not related to physical activity or changes in position.  The patient's other medical problems include coronary artery disease and hypertension.  He does not use alcohol or tobacco.  His medications include aspirin, lisinopril, atorvastatin, and isosorbide mononitrate.  Blood pressure is 105/60 mm Hg and respirations are 14/min.  The patient is fully alert and oriented.  Examination reveals no neck bruits.  Lung fields are clear, and no cardiac murmurs are heard.  Neurologic examination is within normal limits.  ECG is shown in the exhibit.  Serum potassium is 4.1 mEq/L and serum creatinine is 1.1 mg/dL.  Which of the following is the best next step in management of this patient?

Quizplus · Accepted Answer

Explanation: This patient has bradycardia due to Mobitz type II second-degree atrioventricular (AV) block. Ischemia, electrolyte abnormalities, medications (eg, beta blockers, nondihydropyridine calcium channel blockers), infiltrative disease (eg, sarcoidosis), or age-related fibrosis can lead to impaired electrical conduction across the AV node. Patients may be asymptomatic or may have symptoms of poor cardiac output (eg, dyspnea, lightheadedness, syncope). The diagnosis of Mobitz type II AV block is made by ECG showing intermittent nonconducted P waves and a regular PR interval; it differs from Mobitz type I AV block, which shows nonconducted P waves following progressive elongation of the PR interval. ECG Unlike Mobitz type I AV block (usually asymptomatic and benign), Mobitz type II AV block has a high rate of progression to complete (third-degree) AV block and potentially devastating outcomes (eg, sudden cardiac death). Therefore, in the absence of a reversible cause (eg, pharmacologic AV nodal blockade, hyperkalemia, myocardial ischemia), Mobitz type II AV block necessitates the placement of a permanent pacemaker. (Choice B) This patient's ECG is diagnostic for Mobitz type II AV block. Although he should be closely monitored for progression to complete heart block until a pacemaker is placed, further diagnostic testing of his heart rhythm will not change the need for a pacemaker. (Choice C) Per advanced cardiac life support protocol, unstable patients (eg, those with hypotension, confusion, or chest pain) with Mobitz type II AV block or another bradycardia should be treated with intravenous atropine (0.5 mg every 3-5 minutes). However, atropine can sometimes worsen bradycardia due to Mobitz type II AV block and is not recommended in stable patients such as this one. (Choices D and E) Because Mobitz type II AV block often progresses to potentially fatal (complete) AV block, stress testing should not be performed without a pacemaker in place. If there is high suspicion for ischemia as a reversible cause, a temporary, rather than a permanent, pacemaker can be inserted prior to testing. Lack of chronotropic competence (an appropriate increase in heart rate with exertion) is expected in patients with advanced AV block, so testing for it is generally not useful. Educational objective: Mobitz type II second-degree atrioventricular block has a high rate of progression to complete (third-degree) atrioventricular block. In the absence of a reversible cause, all patients should undergo permanent pacemaker implantation. References: Second-degree atrioventricular block revisited. (http://www.ncbi.nlm.nih.gov/pubmed/23224264)

A 72-Year-Old Man Is Brought to the Emergency Department After