An echocardiogram, often called an “echo,” is a non-invasive medical test that uses high-frequency sound waves to create moving images of the heart. This ultrasound allows a detailed look at the organ’s structure and function in real-time. A standard echocardiogram does not directly visualize blockages within the coronary arteries because these small vessels are challenging to see clearly with ultrasound. Instead, the test assesses the consequences of potential blockages, looking for changes in heart muscle movement and pumping ability that suggest a lack of blood flow. This functional assessment helps physicians determine if a specialized test is necessary to confirm blocked arteries.
Understanding the Standard Echocardiogram
The standard echocardiogram, known as a transthoracic echocardiogram (TTE), is performed by placing a handheld device called a transducer on the chest after applying a gel. The transducer emits sound waves that bounce off the heart structures, generating live images on a monitor. This painless procedure offers a comprehensive view of the heart’s anatomy and mechanics.
The echo provides the heart’s pumping strength, quantified as the ejection fraction (EF). The EF is the percentage of blood the left ventricle pushes out with each beat. A normal EF is typically above 50 to 55 percent, and a lower number signals a problem with the heart muscle.
The echocardiogram also details the size and structure of the heart chambers and the thickness of the walls. It uses Doppler technology to measure blood flow, which is vital for evaluating the function of the heart valves. This establishes a baseline of heart health, used to detect deviations caused by chronic lack of blood supply.
Indirect Evidence of Coronary Artery Disease
While the echo cannot image the coronary arteries directly, it detects damage caused by blockages through “regional wall motion abnormalities.” The heart muscle is divided into segments, each supplied by a coronary artery. If a segment receives insufficient blood flow, its ability to contract and thicken during a heartbeat is impaired.
This localized weakness is visible as a wall motion abnormality, categorized as hypokinesis (reduced movement), akinesis (absence of movement), or dyskinesis (paradoxical outward movement). The location of this abnormal movement suggests which coronary artery is blocked; for example, an abnormality in the anterior wall often indicates a problem with the left anterior descending artery. These abnormalities are a sensitive marker for ischemia (lack of oxygen).
A reduced ejection fraction also serves as an indirect sign of chronic or past coronary artery disease. Global muscle weakness may result from extensive damage from a previous heart attack. The echo can detect persistent wall motion abnormalities in damaged tissue, which may represent scar tissue from an old blockage.
The Role of Stress Echocardiography
A resting echocardiogram might not reveal a moderate blockage because the heart receives enough blood flow while at rest. This limitation is overcome by a stress echocardiogram, which increases the heart’s workload to provoke symptoms of a blockage. Stress is induced by exercise (treadmill or bike) or by administering medication like dobutamine.
The technician captures images before the stress and immediately after the heart rate reaches a target maximum. If an artery is significantly blocked, the supplied muscle segment becomes starved of oxygen when demand increases. This oxygen deprivation manifests as a new or worsening wall motion abnormality visible only during or immediately following the stress, confirming a functionally significant blockage.
Tests for Direct Artery Visualization
When an echocardiogram or stress echo suggests a blockage, physicians need a definitive image of the arteries to confirm the location and severity. These tests provide a direct structural view.
One non-invasive option is Coronary Computed Tomography Angiography (CCTA), which uses a specialized CT scanner and an injected contrast dye to create detailed 3D images of the coronary arteries. CCTA directly visualizes plaque buildup within the artery walls, allowing precise measurement of any narrowing.
The definitive standard for imaging blocked arteries remains Cardiac Catheterization, also known as coronary angiography. This invasive procedure involves inserting a thin tube, called a catheter, into an artery (usually in the wrist or groin), and guiding it to the heart.
A contrast dye is then injected directly into the coronary arteries, and X-ray images show blood flow in real-time. This method provides the clearest outline of blockages and is used for both diagnosis and immediate intervention, such as performing an angioplasty or placing a stent. The echocardiogram serves as a valuable screening tool that guides the decision to proceed with these structural imaging tests.