A heart scan is a broad, non-invasive diagnostic tool used to create detailed images of the heart, its blood vessels, and surrounding structures. Since the term “heart scan” encompasses several distinct imaging technologies, the specific focus and information gathered can vary widely. These scans provide a comprehensive look at the heart’s anatomy and function, helping to detect potential issues early.
The Primary Purpose of Cardiac Scans
Cardiac scans are ordered for multiple reasons centered on assessing cardiovascular health and determining future risk. For individuals without symptoms, these scans serve as a screening tool to assess the long-term risk of heart disease. They can detect the early accumulation of plaque in the coronary arteries before it causes noticeable problems.
When a patient experiences symptoms such as chest pain or shortness of breath, a scan is used for definitive diagnosis. Physicians use the detailed images to identify underlying conditions like coronary artery disease, structural defects in the heart, or damage to the heart muscle. For patients undergoing treatment, heart scans help monitor the effectiveness of medications or procedures, providing objective data on whether the condition is improving, stable, or worsening.
Categorizing Common Heart Scans
Cardiac CT and Coronary Artery Calcium (CAC) Scoring
A specialized Computed Tomography (CT) scan is used for Coronary Artery Calcium (CAC) scoring. This rapid, non-invasive method uses X-rays to look for calcified plaque in the coronary arteries. The presence of calcium indicates atherosclerosis, or hardening of the arteries, and produces a numerical Agatston score quantifying the extent of calcification.
Cardiac CT Angiography (CCTA) involves injecting a contrast dye to visualize blood vessels in greater detail. CCTA shows both calcified and soft, non-calcified plaque, providing a complete picture of any narrowing or blockages within the coronary arteries. These CT scans are useful for risk stratification in asymptomatic individuals and for diagnosing coronary artery disease.
Cardiac MRI
Cardiac Magnetic Resonance Imaging (MRI) uses strong magnetic fields and radio waves to generate detailed, three-dimensional images of the heart’s soft tissues. Unlike CT scans, MRI does not use ionizing radiation. This technology provides excellent visualization of the heart muscle, allowing physicians to assess its viability, detect scar tissue from a prior heart attack, or identify inflammation.
Cardiac MRI is the standard for accurately measuring the size of the heart chambers and evaluating overall function, including how effectively the ventricles pump blood. It is useful for diagnosing conditions affecting the heart muscle, such as cardiomyopathies, and for assessing complex congenital heart defects.
Echocardiogram
An echocardiogram, or “echo,” is an ultrasound test that uses high-frequency sound waves to create moving pictures of the heart in real-time. It visualizes the heart’s structure and function without using radiation. It allows for a dynamic assessment of the heart valves, showing how they open and close, and measures the speed and direction of blood flow using Doppler technology.
The echo provides immediate information on the heart’s pumping capacity, often expressed as the ejection fraction. It is commonly used to diagnose valve disorders, assess the aftermath of a heart attack, and identify fluid buildup around the heart.
Nuclear Stress Tests
A nuclear stress test, also known as myocardial perfusion imaging (MPI), evaluates blood flow to the heart muscle during rest and physical or chemical stress. A small radioactive tracer is injected into the bloodstream, and a specialized camera tracks its movement through the heart. If a coronary artery is narrowed, areas of the heart muscle may show reduced tracer uptake during the stress phase compared to the rest phase. This difference points to reduced blood flow, helping diagnose the presence and severity of coronary artery disease.
Preparing for and Undergoing the Scan
Preparation for a heart scan is generally straightforward, though it varies depending on the specific test. Patients are advised to wear comfortable clothing and remove all metal objects, such as jewelry, which can interfere with the imaging equipment. For most scans, an electrocardiogram (ECG) is performed first, requiring small electrode patches on the chest to monitor the heart’s rhythm.
For many CT and nuclear scans, patients must avoid caffeine and nicotine for several hours before the procedure, as these substances can increase the heart rate. Tests involving contrast agents or pharmacological stress may require fasting. During the scan, the patient lies on a movable table and may be asked to hold their breath briefly to capture clear pictures. The entire process is non-invasive and often takes less than an hour for a typical CT calcium score.
Understanding Scan Results
The results of a heart scan are translated into data and images that a physician interprets to determine risk and guide treatment decisions. For a Coronary Artery Calcium (CAC) scan, the Agatston score is the primary metric. A score of zero indicates no detectable calcified plaque and a very low risk of a cardiac event.
The scoring system is:
- A score between 1 and 99 suggests minimal plaque.
- A score of 100 to 300 indicates moderate plaque deposits and a higher risk over the next three to five years.
- Scores greater than 300 signify extensive disease and an elevated risk.
Echocardiogram and Cardiac MRI results focus on the heart’s mechanical performance, specifically the ejection fraction (EF), which is the percentage of blood pumped out of the left ventricle with each beat. A normal EF is generally between 50% and 70%; a lower number suggests impaired pumping function. Both technologies also identify structural abnormalities, such as thickening of the heart walls, issues with valve function, or scar tissue in the heart muscle. Physicians use these combined findings for risk stratification, leading to personalized recommendations that may include lifestyle changes, medication adjustments, or further diagnostic procedures.