How to diagnose and manage bradycardia with normal blood pressure (BP) in an athletic patient?

Diagnosis and Management of Bradycardia in Athletic Patients with Normal Blood Pressure

Bradycardia in athletic patients with normal blood pressure is typically a physiological adaptation to training and rarely requires intervention unless symptomatic or associated with concerning features.

Defining Bradycardia in Athletes

• Bradycardia is defined as a heart rate <60 beats per minute, but in clinical practice, symptomatic bradycardia is generally <50 beats per minute 1
• In athletes, sinus bradycardia is common and represents a physiological adaptation to regular training 1
• Resting heart rates as low as 30 beats per minute can be normal in highly trained athletes, particularly those in endurance sports 1
• Elite athletes demonstrate bradycardia in 47.4% of cases, compared to 36% in advanced athletes and 21.3% in intermediate athletes 2

Initial Assessment

• Evaluate for signs and symptoms of poor perfusion that may be associated with bradycardia: altered mental status, ischemic chest discomfort, acute heart failure, hypotension, or shock 1
• Obtain a 12-lead ECG to confirm bradycardia and assess for other abnormalities 1
• Consider the athlete's age, gender, race, family history of cardiovascular disease/sudden death, and intensity/duration of physical exercise when interpreting ECG findings 1
• Assess chronotropic response to mild aerobic activity (running on spot, climbing stairs) to determine if heart rate increases appropriately 1

Distinguishing Physiological from Pathological Bradycardia

Physiological Bradycardia Features:

• Asymptomatic presentation 1
• Normal blood pressure 2
• Heart rate normalizes with exercise or increased sympathetic tone 1
• No concerning ECG findings beyond sinus bradycardia 1
• No family history of cardiac disease or sudden death 1

Concerning Features Requiring Further Evaluation:

• Profound sinus bradycardia (<30 beats/min) while awake 1
• First-degree AV block with PR interval ≥400 ms 1
• Mobitz Type II second-degree AV block or third-degree (complete) AV block 1
• Symptoms such as dizziness, syncope, or exercise intolerance 1
• Failure of heart rate to increase appropriately with exercise 1
• Family history of cardiac disease or sudden death 1

Diagnostic Approach

For Asymptomatic Athletes with Isolated Sinus Bradycardia:

• If heart rate ≥30 beats/min and increases appropriately with exercise, no further evaluation is needed 1
• ECG changes due to cardiac adaptation to physical exertion (Group 1 changes) should not cause alarm 1

For Athletes with Concerning Features:

• Exercise ECG testing to assess chronotropic response and evaluate for exercise-induced conduction abnormalities 1
• Echocardiography to evaluate for structural heart disease 1
• 24-hour Holter monitoring to assess for more severe bradycardia or pauses during daily activities 1
• Consider cardiac MRI if echocardiography is inconclusive or suggests structural abnormalities 1

Management

For Physiological Bradycardia:

• No treatment required; reassurance and education about normal athletic adaptations 1
• Annual follow-up with ECG for competitive athletes 1

For Symptomatic or Pathological Bradycardia:

• Identify and treat underlying causes 1
• For acute symptomatic bradycardia:
  • Maintain patent airway and assist breathing as necessary 1
  • Provide supplementary oxygen if hypoxemic 1
  • Establish IV access 1
  • Consider atropine 0.5 mg IV every 3-5 minutes (maximum 3 mg) for symptomatic bradycardia 3
  • For refractory cases, consider temporary pacing 1
• For chronic symptomatic bradycardia unrelated to athletic conditioning:
  • Consider permanent pacing if symptoms persist despite correction of reversible causes 4
  • Evaluate for discontinuation or dose reduction of medications that may contribute to bradycardia 4

Special Considerations

• Bradycardia in athletes is often attributed to high vagal tone, but recent evidence suggests intrinsic electrophysiological remodeling of the sinus and AV nodes may also play a role 5
• Veteran athletes (typically over age 50) may develop pathological symptomatic bradycardia requiring pacemaker therapy due to cumulative effects of exercise training and aging 5
• Bradycardia with normal blood pressure is generally benign in athletes, but the combination of hypotension with bradycardia requires immediate evaluation 6

Common Pitfalls to Avoid

• Overdiagnosis of pathology in athletes with physiological bradycardia 1
• Failure to recognize potentially serious conduction disorders that may present with bradycardia 1
• Attributing symptoms to athletic bradycardia without appropriate evaluation 1
• Overlooking medications or other reversible causes of bradycardia 4