Athletic Heart Syndrome

By admin On Nov 28, 2023

Ovid: 5-Minute Sports Medicine Consult, The

Justin Wright

Basics

Description

A benign condition consisting of physiologic adaptations to the increased cardiac workload of exercise. Its primary features are biventricular hypertrophy and bradycardia associated with normal systolic and diastolic function.
Many characteristics overlap with serious pathologic conditions. This makes the differentiation challenging and of paramount importance.
Synonym(s): Athlete's heart; Physiologic cardiac hypertrophy

Epidemiology

These changes are almost universal in highly trained athletes.
Often mistaken for pathologic conditions

Risk Factors

Chronic endurance exercise
Genetic predisposition

Etiology

Changes in cardiac structure vary based on type of exercise (1).
Dimensions of athlete's heart rarely exceed upper limits of normal
Dynamic exercise (eg, distance running):
- Increased heart rate and stroke volume
- Adaptive responses in the heart due to volume overload and increased systolic BP
- Increase in left ventricular end-diastolic diameter with proportional increases in septal and free-wall thickness to normalize wall stress
Static exercise (eg, weight lifting, bodybuilding):
- Marked increased peripheral resistance with smaller increases in heart rate and cardiac output
- Increase in septal and free-wall thickness without increase in left ventricular end-diastolic diameter
Combined exercise (eg, cycling, rowing):
- Extreme volume load and extreme pressure load
- Largest increases in left ventricular end-diastolic diameter and septal and free-wall thickness

Diagnosis

History

Used to differentiate benign physiologic change from pathologic conditions
History of chest pain, dizziness, or syncope associated with exercise may be suggestive of pathology.
Inquire about heart disease risk factors, including HTN, hyperlipidemia, tobacco use, and family history of sudden cardiac death.
History of previously identified murmur should be investigated.

Physical Exam

Decreased body fat and increased muscle mass (generally very physically fit)
Pulse slow and often irregular (sinus bradycardia or bradycardia with 1st- and 2nd-degree blocks)
Grade 1 or 2 midsystolic murmurs (benign functional ejection murmur resolves with Valsalva maneuver)
3rd and 4th heart sounds very common (benign filling sounds)
BP typically remains normal.
Laterally displaced left ventricular impulse

Diagnostic Tests & Interpretation

Imaging

Electrocardiography (2)[B]:
- Rhythm:
  - Sinus bradycardia of 40–55 beats/min while at rest
  - Sinus pauses of more than 2 sec due to increased vagal tone
  - Wandering atrial pacemaker, found only in dynamic athletes
- Atrioventricular block:
  - 1st-degree atrioventricular block present only at rest; P-R interval normalizes with exercise
  - 2nd-degree atrioventricular block present only at rest; Mobitz I (Wenckebach block) common in marathon runners
  - Higher-grade atrioventricular blocks (Mobitz II, 3rd-degree) rare in athletes; may be indicative of underlying heart disease
- Voltage:
  - Left ventricular hypertrophy
  - Right ventricular hypertrophy, common in dynamic athletes, but rarely seen in sedentary controls and static athletes
- Repolarization:
  - S-T segment elevation with peaked T waves, normalizes with exertion
  - S-T segment depression with depressed J points, rarely found in athletes
  - T-wave inversion in lateral leads associated with interventricular septal hypertrophy in static athletes (can be normal finding in dynamic athletes)
Chest radiography (2)[C]:
- Heart is globular in appearance, particularly in endurance athletes.
- Cardiomegaly (cardiothoracic ratio >0.50)
Echocardiography:
- Biventricular hypertrophy
- Left ventricular wall thickness >13 mm uncommon in highly trained athletes; values >15 mm indicative of hypertrophic cardiomyopathy (3)
- Dynamic athletes: Left and right ventricular dilation with left, right ventricular and septal hypertrophy (eccentric hypertrophy)
- Static athletes: Left ventricular and septal hypertrophy with either decrease or no change in left ventricle chamber size (concentric hypertrophy); similar changes occur with chronic HTN (2)[B]
Cardiac magnetic resonance (1,3)[B]:
- Precise assessment of chamber size, myocardial mass, systolic function
- Capable of measuring both ventricles
- Useful in differentiating athlete's heart from hypertrophic cardiomyopathy and arrhythmogenic right ventricular cardiomyopathy (ARVC)

P.37

Diagnostic Procedures/Surgery

Detraining leads to a decrease in wall thickness and a reversal of electrocardiographic abnormalities (2,3)[B]:

Reversal happens over several weeks.
- Can be used to differentiate from hypertrophic cardiomyopathy if other methods are unrevealing

Differential Diagnosis

Hypertensive cardiac hypertrophy
Hypertrophic cardiomyopathy
Dilated cardiomyopathy
ARVC

Ongoing Care

Follow-Up Recommendations

Many of the physiologic adaptations observed in athletic heart syndrome resolve when exercise is stopped.
Because the adaptations that occur in the resistive or static athlete are similar to those caused by chronic HTN, the long-term effects could be damaging. Therefore, these individuals should be encouraged to incorporate dynamic components to their weight-lifting routine.
Patients with overlapping features of athletic heart and a pathologic process (ie, exertional symptoms or family history) should be evaluated by a cardiologist prior to being allowed to return to sport or exercise.

References

1. La Gerche A, Taylor AJ, Prior DL. Athlete's heart: The potential for multimodality imaging to address the critical remaining questions. JACC Cardiovasc Imaging. 2009;2:350–363.

2. Rich BS, Havens SA. The athletic heart syndrome. Curr Sports Med Rep. 2004;3:84–88.

3. Lauschke J, Maisch B. Athlete's heart or hypertrophic cardiomyopathy? Clin Res Cardiol. 2009;98:80–88.

Additional Reading

Pluim BM, et al. The athlete's heart. A meta-analysis of cardiac structure and function. Circulation. 2000;101:336–344.

Maron BJ. Sudden death in young athletes. New Engl J Med. 2003;349:1064–1075.

Codes

ICD9

429.3 Cardiomegaly