Indications for Exercise Stress Testing
Dyspnea during exertion is a common complaint, and may indicate pulmonary or cardiac disease. The indications for an exercise stress test are simple. Anyone with unexplained dyspnea may benefit from a stress test. It will help to categorize the source of the dyspnea. The test should place the patient in 1of 5 categories.
A normal response to exercise includes:
- Heart rate (HR) increases linearly with O2 consumption (VO2) until predicted maximum heart rate is reached.
- Minute ventilation (VE) and CO2 production (VCO2) increases linearly as VO2 or work increases up to the anaerobic threshold. During anaerobic respiration VE and VCO2 increase faster than VO2.
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A sedentary response to a stress test does not imply physiologic dysfunction. It implies that the patient is out of shape.
- HR increases linearly with work, but at a higher rate than predicted.
- Maximum HR is reached without ECG abnormalities.
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- There is an increase in HR at each level of VO2 or work.
- Maximum HR is not reached
- Maximum O2 pulse is not reached.
- Systolic BP rises close to the predicted level.
- Anaerobic threshold will be reached early and could be due to hyperventilation.
- VE/VO2 >23-27 and is often elevated even during resting measurements.
- The ventilatory ceiling (VE) is less than predicted and reached at a lower VO2.
- O2 desaturation is common.
- Due to lung dysfunction, these patients tend to over-ventilate at every level of O2 consumption.