Cardiac stress testing is a medical technology used to study how the heart performs when the body needs more oxygen. During exercise on a treadmill or stationary bike, the heart beats faster and pumps more blood, which can reveal problems that may not appear at rest. Clinicians monitor electrical signals, blood pressure, symptoms, and sometimes heart images to look for signs of reduced blood flow.
This test matters because it helps detect coronary artery disease, guide treatment, and evaluate exercise tolerance.
Key Facts
- Heart rate response is estimated by maximum predicted heart rate = 220 - age in years.
- A common target for diagnostic exercise stress testing is about 85% of maximum predicted heart rate.
- Cardiac output increases during exercise according to Q = HR x SV, where Q is cardiac output, HR is heart rate, and SV is stroke volume.
- ECG electrodes measure voltage changes from heart muscle activity, often in millivolts, to track rhythm and ischemic changes.
- Stress testing can be exercise based or pharmacologic, using drugs that make the heart work harder or increase coronary blood flow.
- Stress imaging may use echocardiography, nuclear perfusion imaging, or cardiac MRI to compare blood flow and wall motion at rest and under load.
Vocabulary
- Electrocardiogram
- An electrocardiogram, or ECG, is a recording of the heart's electrical activity using electrodes placed on the skin.
- Ischemia
- Ischemia is a shortage of oxygen-rich blood reaching a tissue, often because an artery is narrowed or blocked.
- Coronary artery
- A coronary artery is a blood vessel that supplies oxygen-rich blood to the heart muscle.
- Pharmacologic stress test
- A pharmacologic stress test uses medicine to mimic the effects of exercise on the heart when a patient cannot safely exercise enough.
- Ejection fraction
- Ejection fraction is the percentage of blood in a ventricle that is pumped out with each heartbeat.
Common Mistakes to Avoid
- Confusing a stress test with a heart attack trigger, which is wrong because the test is controlled, monitored, and stopped if unsafe symptoms or ECG changes appear.
- Assuming a normal resting ECG rules out coronary artery disease, which is wrong because reduced blood flow may only become visible when the heart is under load.
- Ignoring medications such as beta blockers before interpreting results, which is wrong because some drugs lower heart rate and can prevent the patient from reaching the target stress level.
- Treating one abnormal ECG change as a complete diagnosis, which is wrong because clinicians interpret ECG, symptoms, blood pressure, workload, and imaging together.
Practice Questions
- 1 A 50-year-old patient has a maximum predicted heart rate of 220 - age. What is the maximum predicted heart rate, and what is 85% of that value?
- 2 During exercise, a patient's heart rate is 150 beats per minute and stroke volume is 90 mL per beat. Using Q = HR x SV, calculate cardiac output in mL per minute and in L per minute.
- 3 A patient cannot walk safely on a treadmill because of severe joint disease. Explain why a pharmacologic stress test with ECG and imaging can still provide useful information about coronary blood flow.