A 21-year-old man is seen in the clinic for a routine checkup. He is a cyclist and was asked by his trainer to see a physician due to a "slow heartbeat." The patient describes intense physical activity in preparation for tournaments and has no symptoms. Specifically, he has no chest pain, shortness of breath, lightheadedness, presyncope, or syncope. His family history is unremarkable. He does not take any medications or use performance-enhancing drugs. Blood pressure is 123/72 mm Hg and pulse is 46/min. No cardiac murmurs are heard in the supine or upright positions. There are no additional heart sounds. The lungs are clear on auscultation. Pulses are full and symmetric, and there is no peripheral edema. ECG shows sinus bradycardia at 48/min. The PR interval is prolonged at 250 msec, consistent with first-degree atrioventricular block. QRS complexes are normal with no repolarization abnormalities, and QTc interval duration is normal at 400 msec. Which of the following is the best next step in management of this patient?

Question

A 21-year-old man is seen in the clinic for a routine checkup.  He is a cyclist and was asked by his trainer to see a physician due to a "slow heartbeat."  The patient describes intense physical activity in preparation for tournaments and has no symptoms.  Specifically, he has no chest pain, shortness of breath, lightheadedness, presyncope, or syncope.  His family history is unremarkable.  He does not take any medications or use performance-enhancing drugs.  Blood pressure is 123/72 mm Hg and pulse is 46/min.  No cardiac murmurs are heard in the supine or upright positions.  There are no additional heart sounds.  The lungs are clear on auscultation.  Pulses are full and symmetric, and there is no peripheral edema.  ECG shows sinus bradycardia at 48/min.  The PR interval is prolonged at 250 msec, consistent with first-degree atrioventricular block.  QRS complexes are normal with no repolarization abnormalities, and QTc interval duration is normal at 400 msec.  Which of the following is the best next step in management of this patient?

Quizplus · Accepted Answer

Explanation: Sudden cardiac death (SCD) is the leading cause of mortality in young (age <35) athletes and most commonly results from ventricular arrhythmias triggered by intense exertion in the setting of undiagnosed structural heart disease (eg, hypertrophic cardiomyopathy, anomalous origin of a coronary artery, arrhythmogenic right ventricular cardiomyopathy). Less commonly, congenital conduction abnormalities (eg, long QT syndrome, Brugada syndrome) have been implicated. Nonetheless, not all cardiac abnormalities that may be present in young athletes are pathologic. Athletes participating in intense training have a heightened vagal tone that often results in resting bradycardia with or without first-degree atrioventricular block. In addition, these athletes can develop a responsive increase in left ventricular wall thickness that meets voltage criteria for left ventricular hypertrophy on ECG. These physiologic changes in heart rate and left ventricular size represent a nonpathologic condition commonly termed athlete's heart. Because the prevalence of conditions that increase the risk of SCD in young athletes is low, current guidelines aim to identify healthy individuals without creating a massive testing burden (eg, routine echocardiogram). This young athlete's condition is consistent with athlete's heart. He does not have any symptoms (eg, excessive dyspnea, chest pain, palpitations, lightheadedness, syncope), abnormal physical examination findings (eg, cardiac murmur), family history of SCD, or other abnormal ECG findings (eg, precordial T-wave inversions suggestive of arrhythmogenic right ventricular cardiomyopathy). He should be reassured without the need for additional cardiac evaluation. (Choice A) In patients with unexplained symptoms (eg, palpitations, syncope), 24-hour ECG monitoring is indicated to identify cardiac arrhythmia, but is not indicated in this young athlete with asymptomatic sinus bradycardia. (Choice B) Use of performance-enhancing drugs (eg, androgens) may increase the risk of SCD in young athletes. However, these drugs typically cause cardiac hypertrophy rather than bradycardia, and there is no reason to suspect their use in this patient. (Choice D) Echocardiogram should be performed in young athletes with unexplained symptoms, significant cardiac murmur, family history of SCD or inherited structural heart disease, or abnormal ECG findings not consistent with athlete's heart. (Choice E) Treadmill exercise testing is often used for risk stratification in patients with known structural heart disease, but it is not indicated in this patient. Educational objective: Athletes participating in intense training can develop nonpathologic cardiovascular changes, including resting sinus bradycardia with or without first-degree atrioventricular block and left ventricular hypertrophy detected on ECG. In the absence of other findings suggestive of underlying cardiac disease (eg, unexplained symptoms, cardiac murmur), these patients should be reassured without further cardiac testing. References: Twenty-four hour continuous ECG recordings in long-distance runners. (http://www.ncbi.nlm.nih.gov/pubmed/7083929) Electrocardiogram of the athlete: an analysis of 289 professional football players. (http://www.ncbi.nlm.nih.gov/pubmed/6231851)

A 21-Year-Old Man Is Seen in the Clinic for a Routine