A 45-year-old man comes to the office after experiencing left-sided chest pain for a day. The pain is nonradiating and constant and increases with movement of the left hand. The patient has had no nausea, dyspnea, diaphoresis, lightheadedness, or syncope. He has a 25-pack-year smoking history. Vital signs are within normal limits. On examination, the pain is reproduced with palpation of the left-sided chest wall muscles. ECG reveals no significant ST-segment or T-wave abnormalities. The rhythm strip is shown in the exhibit. Which of the following is the best approach to this patient's ECG findings?

Question

A 45-year-old man comes to the office after experiencing left-sided chest pain for a day.  The pain is nonradiating and constant and increases with movement of the left hand.  The patient has had no nausea, dyspnea, diaphoresis, lightheadedness, or syncope.  He has a 25-pack-year smoking history.  Vital signs are within normal limits.  On examination, the pain is reproduced with palpation of the left-sided chest wall muscles.  ECG reveals no significant ST-segment or T-wave abnormalities.  The rhythm strip is shown in the exhibit.  Which of the following is the best approach to this patient's ECG findings?

Quizplus · Accepted Answer

11ec25c8_d34d_f108_bc81_91b3d03c4353_MD0003_00 This patient has chest pain that is most likely musculoskeletal in nature (eg, pain worse with arm movement, chest wall tender to palpation) rather than due to myocardial ischemia. ECG reveals normal sinus rhythm with no ischemic ST-segment or T-wave abnormalities, and an incidental finding of a prolonged PR interval (ie, >200 ms), consistent with first-degree atrioventricular (AV) block. prolonged PR interval ECG of first-degree AV block shows a QRS complex following every P wave, but the distance between the start of the P wave and the start of the QRS complex is longer than normal. This usually results from delayed conduction within the AV node, and affected patients are almost always asymptomatic. Causes include AV node structural variations, enhanced vagal tone (eg, highly trained athletes), and pharmacologic AV nodal blockade (eg, beta blockers). It can also occur in the setting of inferior wall myocardial ischemia and can rarely occur due to Lyme disease or infiltrative conduction disease (eg, sarcoidosis). In the absence of active myocardial ischemia or overt findings of systemic disease (eg, history of rash to suggest Lyme disease, cough and dyspnea to suggest sarcoidosis), first-degree AV block is a benign finding, and observation is most appropriate. (Choice A) 24-hour ECG monitoring (Holter monitoring) is used in patients with symptoms (eg, lightheadedness, syncope) suspected to be due to intermittent arrhythmia (eg, advanced AV block, paroxysmal supraventricular tachycardia); it is not indicated in asymptomatic patients. (Choice B) An electrophysiology study is indicated to identify the source of some supraventricular tachycardias (eg, atrial fibrillation, atrial flutter). It may sometimes be used to identify the level of blockade (eg, AV node vs His bundle) for advanced AV block, but it plays no role in the evaluation of first-degree AV block. (Choice D) Placement of a permanent pacemaker is typically indicated for advanced AV block (ie, Mobitz type II second-degree AV block, third-degree AV block); it is almost never indicated for first-degree AV block. (Choice E) Vagal maneuvers slow AV nodal conduction but have no effect on His bundle conduction; therefore, they may sometimes be helpful in determining the level of block in advanced AV block. However, they are of limited use for first-degree AV block. Educational objective: First-degree atrioventricular (AV) block results from delayed conduction through the AV node and is recognized on ECG by a prolonged PR interval (ie, >200 ms) with a QRS complex following each P wave. It is a benign finding and usually requires observation only. References: First degree atrioventricular block. (http://www.ncbi.nlm.nih.gov/pubmed/6373267) First degree heart block. (http://www.ncbi.nlm.nih.gov/pubmed/28846254) Atrioventricular block. (http://www.ncbi.nlm.nih.gov/pubmed/29083636)

A 45-Year-Old Man Comes to the Office After Experiencing Left-Sided