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Exercise Stress Testing

There are several indications for a patient to undergo exercise stress testing:

 

1. Chest pain or shortness of breath on exertion:  Most causes of chest pain in children and adolescents are of a non-cardiac etiology. In fact, most causes may be attributable to musculoskeletal causes or asthma/reactive airway disease. However, certain cardiac causes (ie, coronary artery anomalies, Kawasaki disease - especially with coronary artery involvement, left ventricular outflow obstruction, hypertrophic cardiomyopathy) may either manifest themselves or are exacerbated by intense activity. Shortness of breath on exertion may also be an indication of exercise-induced asthma / reactive airway disease.

2. Asymptomatic Wolff-Parkinson-White syndrome:  exercise stress tests have been used at many centers as part of the "risk stratification" process of managing patients with asymptomatic Wolff-Parkinson-White syndrome. In essence, intense exercise may determine the extent to which signals from the sinus node are propagated along the "normal" conduction system (ie, SA node, AV node, bundle of His, Purkinje fibers) versus along the accessory pathway. If the patient no longer demonstrates evidence of ventricular pre-excitation during exercise, this suggests that his accessory pathway is "low-risk" for sudden cardiac death. 

3. Syncope on exertion:  syncope is a common presenting complaint, particularly amongst adolescent patients. Syncope on exertion, however, requires careful and thorough evaluation for arrhythmias or ischemic changes as the underlying etiology.

4. Evaluate the efficacy of beta-blockade:  some patients are placed on beta-blocking agents (ie, atenolol, propranolol, metoprolol, etc) for various cardiovascular conditions (ie, arrhythmias, hypertension, prophylaxis in Marfan syndrome, prophylaxis in long QT syndrome). Dosage of these medications are determined based upon the patient's weight. The patient's resultant heart rate provides some indication of the efficacy of the beta-blockade. However, in some patients, an exercise stress test will provide a more sensitive measure of the efficacy of beta-blockade. For example, a patient on a beta-blocker who is still able to attain a heart rate of more than 180 beats per minute on exertion may require an increase in the dose of his medication.

5. Atrial or Ventricular ectopy:  many patients may have premature beats that arise from either the top (atria) or bottom (ventricles) chambers of the heart. These are often benign, as long as they do not constitute a high percentage of the patient's overall heart-beat count and do not result in sustained arrhythmias. Exercise involves a strong adrenergic response and the production of several hormones that stimulate the heart's electrical conduction and heart muscle, resulting in an elevated heart rate and increased heart muscle contractility and blood pressure.   Some patients who continue to have premature beats during exercise may have a higher predisposition to develop an abnormal heart rhythm.

6. Evaluate exercise capacity in patients with underlying congenital heart disease: the physiology of patients with "hemodynamically significant" congenital heart disease is very unique and involves the re-distribution of blood through different chambers of the heart and/or the passage of blood through narrowed passageways. This phenomenon, therefore, may limit the adequate supply of blood to the heart and other organs during exercise, which requires higher demands than the usual resting state. Depending upon the specific underlying anomaly, this may result in either limited exercise capacity (fatigue, limited blood supply to the muscles, extremities, etc), or in ischemia (inability to provide adequate oxygenation to the heart).      

 

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Children's Heart Institute

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