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.

1. Normal
2. Sedentary
3. Cardiac
4. Pulmonary
5. Mixed

Objectives

Indications

Types

Protocols

Procedure

Termination

Contraindications

Quiz

 

 

 

 

 

 

 

 

 

 

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.

O2 pulse indicates the rate of O2 consumption by the body during exercise. O2 pulse is calculated as VO2/HR. It is less than predicted since HR is increased at every level of O2 consumed. VO2/kg at maximum exercise is less than predicted. VE increases linearly with work, but at a higher rate than predicted (VE/VO2 > 23-27).

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A cardiac limitation to a stress test implies a problem with the circulatory system.

• There is an abnormal relationship between HR and VO_2, HR is increased at every level of O₂ consumption.
• ECG changes; ventricular arrhythmias and ST segment depression are common. Persistence of these ECG changes after the test is terminated may represent multiple coronary artery vessel occlusion.
• Anaerobic threshold usually is not reached before the test is terminated, as demonstrated by graphic above.
• O₂ pulse is decreased due to decreased stroke volume.
• Normally, systolic blood pressure (BP) increases due to increased cardiac output. An abnormal response is a faster rise in systolic BP than predicted.
• Diastolic pressure normally changes very little. An abnormal response would be an increase in diastolic pressure.
• A significant drop in diastolic BP and little or no change in systolic BP indicates cardiac output is not increasing with exercise and testing should be terminated.
• VO₂ max may be low.
• The patient’s maximum predicted VE will not be reached.

A pulmonary limitation implies that the problem lies with the respiratory system.

• 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 (V_E) 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.