A cardiac stress test is a diagnostic procedure used to evaluate how the heart functions under increased workload. The test assesses blood flow to the heart muscle when it is made to work harder and beat faster, either through physical activity or medication. Its purpose is to determine if the heart receives adequate oxygen and blood supply during periods of physical demand, which helps detect coronary artery disease or irregular heart rhythms. This non-invasive examination is a common tool for physicians to understand the heart’s capacity and to guide treatment plans.
Preparing for the Stress Test
Patients must follow specific instructions before a cardiac stress test to ensure accuracy and safety. Preparation involves managing medications, especially heart drugs like beta-blockers and calcium channel blockers. Since these medications affect heart rate and blood pressure responses, the physician may instruct the patient to temporarily stop taking them beforehand. All changes to a medication schedule must be made under the direct guidance of a doctor.
Dietary restrictions are standard preparation. Patients must avoid all food and beverages other than water for at least four hours before the test. This fasting prevents nausea during exertion and is often required for accurate imaging during nuclear stress tests. Patients must also strictly avoid caffeine and nicotine for a minimum of 12 to 24 hours prior to the procedure. These substances stimulate the heart and constrict blood vessels, which alters test results.
For physical comfort, patients should wear loose-fitting clothing and supportive athletic shoes, as most tests involve walking on a treadmill. If a pharmacological stress test is planned, transportation home may be necessary, as temporary drug side effects can make driving unsafe. Patients with diabetes should consult their physician about adjusting insulin or oral medication dosages. Bringing a light snack for consumption immediately after the test is also recommended, especially after fasting.
The Procedure Step-by-Step
The stress test begins with the initial setup and collection of baseline data while the patient is at rest. Technicians attach electrodes to the chest to continuously monitor the heart’s electrical activity via an electrocardiogram (ECG). A blood pressure cuff is placed on the arm, and the medical team records resting heart rate, blood pressure, and a baseline ECG tracing. This initial phase includes an explanation of the procedure and what symptoms to report, such as chest pain or dizziness.
For an exercise stress test, physical exertion involves walking on a treadmill or using a stationary bicycle. Intensity is gradually increased according to a standardized protocol. The goal is for the patient to reach a target heart rate, usually 85% of their age-predicted maximum heart rate, or until symptoms appear. Throughout the exercise, the medical team closely monitors the ECG for signs of ischemia (reduced blood flow) and the blood pressure response.
If a patient cannot exercise due to physical limitations, a pharmacological stress test uses medication to simulate exertion. An intravenous (IV) line is inserted, and a stress-inducing drug is administered to increase blood flow to the heart. Common agents dilate the coronary arteries to reveal areas of compromised blood flow:
- Adenosine
- Dipyridamole
- Regadenoson
- Dobutamine
Patients may experience temporary sensations from these medications, such as flushing, mild shortness of breath, or chest discomfort, but a healthcare professional manages any reactions.
Dobutamine increases heart rate and contractility similar to exercise. Vasodilator agents like dipyridamole and adenosine are generally avoided in patients with severe reactive airway disease or specific heart rhythm issues. After the stress agent is administered or peak exercise is achieved, a small amount of a radiotracer or contrast agent is injected to capture imaging of the heart at its maximum stress level.
The final part of the procedure is the recovery phase, where the patient gradually cools down or the effects of the medication are reversed. Monitoring of the heart rate, blood pressure, and ECG continues until they return to near-baseline levels. This period is important because abnormal responses, such as a delayed decrease in systolic blood pressure, can predict underlying heart conditions.
Understanding the Test Results and Follow-Up
The medical team analyzes data from the rest, stress, and recovery phases to determine the heart’s function. A “normal” or negative result suggests the patient achieved the target heart rate without significant ECG changes, chest pain, or an abnormal blood pressure response. A normal result indicates the heart muscle likely received adequate blood flow at peak stress, though it does not completely rule out the presence of some plaque.
An “abnormal” or positive result suggests the heart did not receive sufficient oxygenated blood during the stress (cardiac ischemia). This outcome is indicated by specific changes on the ECG, such as ST-segment depression, severe symptoms, or an inadequate blood pressure response. The degree of abnormality is often correlated with the likelihood and extent of coronary artery disease.
An abnormal result is not a definitive diagnosis, but it warrants further investigation, as false positives can occur. If the test is abnormal, the physician typically recommends additional, more specific imaging tests, such as a coronary CT angiography or a cardiac catheterization (angiography). Angiography provides a direct visual assessment of the coronary arteries to confirm the presence and severity of any blockages.
The follow-up plan for an abnormal finding may involve lifestyle changes, new medications to manage blood pressure or cholesterol, or a procedure like angioplasty and stent placement to restore blood flow. The physician reviews the final report with the patient to discuss the findings and outline the appropriate next steps for long-term heart health management. Most patients resume normal activities immediately after the test.