An echocardiogram uses sound waves to create moving images of the heart’s chambers, valves, and walls, providing a view of the organ’s function at rest. A stress echocardiogram builds upon this non-invasive ultrasound technology by adding controlled physical or pharmaceutical demand. The purpose is to observe how the heart muscle and coronary blood flow behave when the heart rate and blood pressure are significantly increased. This diagnostic tool uncovers functional issues that may not be apparent while the heart is beating at a normal, resting pace.
Defining the Diagnostic Tool
The core objective of a stress echocardiogram is to assess the performance of the heart muscle and the blood vessels supplying it under high demand. During intense physical activity or pharmaceutical stimulation, a healthy coronary artery system can increase blood flow to match the heart muscle’s greater need for oxygen. If a coronary artery is significantly narrowed, however, this increased demand creates a mismatch between oxygen supply and demand, a condition known as myocardial ischemia.
The test looks specifically for changes in the heart muscle’s movement, which is a direct sign of insufficient blood flow. When a part of the heart muscle does not receive enough oxygen-rich blood, it begins to contract weakly or abnormally, a phenomenon called a wall motion abnormality. This test is often used when a patient presents with unexplained chest pain or shortness of breath, or when evaluating the extent of known coronary artery disease.
Preparing for the Procedure
Patient preparation is specific and greatly impacts the accuracy of the test results. Patients are typically instructed to fast for at least two to four hours before the procedure. This reduces the risk of nausea during the physical exertion or pharmacological stress phase of the test.
Patients must avoid all forms of caffeine and nicotine for a full 24 hours before the appointment, as these substances interfere with the heart rate response. Medication adjustments are routinely required, especially stopping certain heart medications like beta-blockers or calcium channel blockers. These drugs slow the heart rate and may prevent the patient from reaching the necessary target heart rate, so a physician will provide explicit instructions on when to temporarily discontinue them. Comfortable clothing and footwear suitable for walking on a treadmill are also recommended.
Step-by-Step Procedure
The stress echocardiogram procedure is carefully orchestrated in three distinct phases, beginning with the acquisition of baseline images. The patient is fitted with electrodes on the chest to continuously monitor the heart’s electrical activity (ECG), and a blood pressure cuff is secured to the arm. Lying on the side, a sonographer uses an ultrasound probe to capture initial two-dimensional images of the heart at rest.
The second phase involves introducing the stressor, which is determined by the patient’s physical ability. For patients who can exercise, a treadmill or stationary bicycle is used, with the speed and incline gradually increasing every few minutes according to a set protocol. The goal is to safely increase the heart rate to a target level, typically 85% of the maximum predicted for the patient’s age.
If a patient is unable to exercise due to physical limitations, a pharmacological approach is used, most commonly involving the drug Dobutamine delivered through an intravenous line. Dobutamine is a medication that mimics the effects of exercise by increasing the heart rate and the force of its contractions, simulating a state of physical demand. Throughout both the exercise and pharmacological stress phases, the patient’s ECG, blood pressure, and symptoms are closely monitored by the medical staff.
The third and most time-sensitive phase is the immediate post-stress imaging. As soon as the patient reaches the target heart rate or peak effect of the medication, the stressor is stopped, and the patient is quickly moved back to the examination bed. The sonographer must capture a second set of high-quality echocardiogram images within 60 to 90 seconds, before the heart rate rapidly returns to its resting state. Monitoring continues until the heart rate and blood pressure have returned to baseline levels.
Understanding the Findings
The interpretation of the stress echocardiogram relies on a side-by-side comparison of the heart images taken at rest and those taken at peak stress. A physician, typically a cardiologist, examines the movement and thickening of all segments of the heart muscle. In a healthy heart, the response to stress is increased contractility, meaning all segments of the left ventricle pump more vigorously than they did at rest.
An abnormal result, or a positive test, is characterized by the development of new or worsening regional wall motion abnormalities (RWMA) during stress. This lack of normal movement or thickening in a specific area indicates that the corresponding part of the heart muscle is not receiving adequate blood flow, which points toward a blockage or narrowing in one of the coronary arteries. The location and extent of these wall motion abnormalities help the physician determine which coronary artery is likely affected and the severity of the underlying disease.
A normal, or negative, result shows that all segments of the heart wall moved normally and demonstrated augmented function at peak stress, suggesting the coronary arteries are providing sufficient blood supply. The information gathered from the test is a detailed functional assessment that helps guide future treatment and management decisions for heart health.