A 28-year-old competitive cyclist presents for routine cardiac evaluation. His 12-lead ECG shows the pattern marked **A** in the diagram—progressive PR prolongation over consecutive beats followed by a dropped QRS complex, with the cycle repeating. His heart rate is 42 bpm at rest, and he is completely asymptomatic. Exercise stress testing shows normalization of the rhythm. Which of the following is the most appropriate next step in management?
A. Observation with reassurance; no treatment required
B. Urgent coronary angiography to rule out inferior wall ischemia
C. Immediate permanent pacemaker implantation
D. Initiation of beta-blocker therapy to stabilize AV conduction
Explanation
Why "Observation with reassurance; no treatment required" is right
The pattern marked A—progressive PR prolongation followed by a dropped QRS in a group-beating pattern—is pathognomonic for Mobitz Type I (Wenckebach) second-degree AV block. In an asymptomatic athlete with high vagal tone at rest and normalization with exercise, this is a benign, nodal phenomenon. Per the 2018 ACC/AHA/HRS Bradycardia Guidelines, asymptomatic Mobitz I requires no treatment, only observation and reassurance. The block is intranodal, reversible, and carries an excellent prognosis in the absence of structural heart disease.
Why each distractor is wrong
Immediate permanent pacemaker implantation: Pacemakers are reserved for symptomatic Mobitz I (Class IIa indication per 2018 ACC/AHA/HRS guidelines). This asymptomatic athlete does not meet criteria; unnecessary device implantation increases morbidity and limits athletic participation.
Initiation of beta-blocker therapy to stabilize AV conduction: Beta-blockers would worsen nodal conduction and are contraindicated. The block is already vagally mediated; further AV-nodal suppression is harmful and unnecessary.
Urgent coronary angiography to rule out inferior wall ischemia: While inferior MI is a recognized cause of Wenckebach, the clinical context (young athlete, asymptomatic, resolution with exercise, no chest pain or ECG ischemic changes) makes acute ischemia extremely unlikely. Angiography is not indicated.
High-YieldNEET PG
Asymptomatic Mobitz I in athletes = benign vagal phenomenon = observation only; Wenckebach resolves with exercise and atropine (nodal block), whereas Mobitz II worsens with these maneuvers (infranodal block).
ACC/AHA/HRS Bradycardia Guidelines 2018
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