7 Pediatric Exercise Testing
7.1 Exercise Test
7.1.1 Indications and Contraindications
Exercise tests in childhood are used primarily for detecting and evaluating cardiac arrhythmia and myocardial ischemia as well as for objectifying physical capacity. Blood pressure behavior can be assessed by simultaneously measuring blood pressure. Another aim of exercise testing is to investigate stress-related symptoms (e.g., shortness of breath) and verify the effectiveness of treatment for certain diseases (hypertension, arrhythmia, abnormal circulatory regulation). For some clinical questions, it can also be useful to monitor oxygen saturation by pulse oximetry.
Specific clinical questions for exercise testing for a few selected diseases are listed in Table 7.1.
Detection of subendocardial ischemia (ST depression), occurrence of arrhythmia during exercise
Caution: The gradient of an aortic stenosis increases during exercise, thus potentially insufficient increase in blood pressure
Increase of the arterial hypertension during exercise, increase of the gradient during exercise
Blood pressure behavior during exercise, check of effective medication
Rule of thumb for structurally unremarkable hearts—harmless extrasystoles disappear during exercise, malignant extrasystoles increase during exercise. Cardiomyopathies (hypertrophic cardiomyopathy, right ventricular arrhythmogenic cardiomyopathy) or catecholamine-induced ventricular tachycardia, for example, must then be excluded
Determination of maximum achievable heart rate. AV blocks resulting from high vagal tone disappear during exercise
Long QT syndrome
In long QT syndrome, a prolonged QTc interval is observed during exercise. T wave changes and ventricular extrasystoles should also be noted
Caution: Tachycardia can be induced by exercise
The disappearance of the delta wave during exercise is a sign of a relatively long refractory period of the accessory pathway (favorable prognosis)
Assessment of physical capacity. An increase in cyanosis during exercise is a sign of venovenous collaterals or a right-to-left shunt through an atrial tunnel window, tunnel leak, or the like
After coronary artery surgery (arterial switch operation, Ross procedure, ascending aortic replacement, correction of Bland–White–Garland syndrome), after Kawasaki syndrome
Evidence of myocardial ischemia (ST depression, AV block, ventricular extrasystoles) should be particularly noted
Exclusion of arrhythmia; possible sudden drop in blood pressure associated with cardioinhibitory syncopes
Reduced physical capacity
Objective assessment of capacity, exclusion of underlying causes
Monitoring rate adaptation (R function) of the pacemaker, which should lead to an adequate increase in the heart rate during exercise
Absolute contraindications for exercise testing are:
Acute myocardial infarction or unstable angina pectoris
Decompensated heart failure
Acute inflammatory heart disease
Acute lung embolism
Congestive lung disease
High-grade aortic stenosis (subvalvular, valvular, supravalvular), aortic coarctation, aortic arch interruption
Significant hypertrophic obstructive cardiomyopathy (HOCM)
Uncontrolled symptomatic arrhythmia
Special caution is required if there are pre-existing cardiac arrhythmias, arterial or pulmonary hypertension, or certain heart defects. Particular caution is recommended especially for mild to moderate forms of aortic stenosis, aortic coarctation, HOCM, or other stenosis of the left ventricular outflow tract where exercise testing is not entirely contraindicated, as the gradient can increase considerably during exercise.
Exercise testing is usually performed on a treadmill or bicycle ergometer. The treadmill more closely approaches naturally induced stress. However, because of the many possible movement artifacts using the treadmill ergometer, a bicycle ergometer is usually the preferred method for children, and is possible for children over the age of 5 who are at least 110 cm tall. However, especially in younger children, rapid fatigue of the thigh muscles in bicycle exercise testing means that maximum workload is not achieved.
Complete emergency equipment including a defibrillator and oxygen supply must be present at all times. The limb leads of the ECG are attached to the torso to reduce movement artifacts. Precordial leads must be used to detect ischemic changes. The total duration of exercise is usually under 15 minutes. The patients should not have fasted longer than 3 to 4 hours prior to the test.
Maximum cardiac workload is assumed when the maximum heart rate is reached.
Bicycle ergometer: maximum heart rate = 200 – age (years)
Treadmill ergometer: maximum heart rate = 220 – age (years)
The exercise test is begun after a warm-up period according to a step or ramp protocol. In the step protocol, the workload remains the same for 2 to 3 minutes and is then gradually increased. In the ramp protocol, the workload is increased continuously. The exercise test is followed by a recovery period. As a rule of thumb, healthy boys achieve an average maximum workload of 3 to 3.5 W/kg, healthy girls an average of around 2.5 to 3 W/kg.
In childhood, arrhythmia during exercise testing often does not occur until the recovery period or increases in this phase.
Below are some examples of test protocols for bicycle and treadmill exercise testing as recommended by the German Society of Pediatric Cardiology (step protocols).
Warm-up period: 2 min freewheel
Exercise period: start with 0.5 W/kg; increase by 0.5 W/kg every 2 min
Recovery period: 2 min freewheel
During all phases, a regular pedal rate of approximately 50 to 60/min should be maintained.
Resting period: 90 s
Exercise period: start with 2.5 km/h and a 0% incline, increase speed in increments of 0.5 km/h and incline by 3% (up to max. 21%) every 1.5 min
Recovery period: 2 km/h at a 0% incline.
The test is terminated at the latest when the maximum workload is reached (maximum heart rate, see above). The following are additional criteria for termination:
Absolute criteria for termination:
Signs of cardiac ischemia (ST segment changes ±3 mm in the ECG
Ventricular tachycardia longer than 30 s
Subjective fatigue and complaints (dizziness, ataxia, dyspnea)
Severe angina pectoris
Failure of monitoring equipment
Relative criteria for termination:
Signs of hypoperfusion (cyanosis)
Progressive drop in heart rate and/or blood pressure
Increase of systolic blood pressure over 220 mmHg and/or diastolic pressure over 110 mmHg
More than 10 mmHg drop in blood pressure without signs of myocardial ischemia
Occurrence of conduction disturbances (AV block II° or III°, bundle branch block)
Complex arrhythmia longer than 30 s
Increasing angina pectoris