Advances in cardiac imaging open big window into the heart

What it is: A test to determine the heart rhythm by measuring the electric signals flowing through the heart. Small adhesive electrodes are placed on the arms, legs, and chest and connected to a recording device, which displays the electrical signals that make your heart beat.

What it shows: Irregular heartbeats or abnormal rhythms (arrhythmias), signs of previous heart damage or heart attacks.

When you might need it: EKGs are often conducted during a routine exam to establish the heart rhythm and screen for previous heart damage. They are also used during stress tests to study the heart during exercise. An EKG may also be recommended for younger patients who have an elevated family risk of heart disease. An EKG is typically the first test used to diagnose a heart attack in an emergency situation because it produces accurate results quickly and can detect a heart attack in progress.

What it is: A cornerstone of imaging technology, an echocardiogram – also called transthoracic echocardiogram (TTE) – uses sound waves to create moving pictures of your heart’s chambers, valves, and walls. An “echo” utilizes the same safe technology that is used to see a baby during pregnancy. Small electrode patches are attached to your chest to simultaneously detect the heart rhythm while a sonographer moves a transducer back and forth along the chest to record the ultrasound pictures.

What it shows: Changes in heart size; pumping strength; damage to the heart muscle; valve problems; and congenital heart defects. It can determine the presence of weak heart function or damaged valves and can be done several times over the course of years to measure the effectiveness of treatments.

When you might need it: If you have symptoms such as chest pain or shortness of breath. It can also evaluate damage after a heart attack, heart failure, and valve disease.

Echocardiograms are very versatile, and we apply them in multiple ways, such as:

• Stress echocardiography (“stress echo”) measures how well the heart pumps before and after exercise during a cardiac stress test.
• 3D echocardiography (“3D echo”) produces highly detailed images to help assess heart valves and other structures.
• A transesophageal echocardiogram (TEE) involves a small tube with an ultrasound sensor at the tip that is passed down the throat to provide unobstructed views of the heart chambers to look for blood clots or infections in hard-to-see areas.

What it is: A stress test that uses a small amount of radioactive material (called a radiotracer) injected through an IV to determine how well blood flows through the heart arteries and ultimately into the heart muscle. A nuclear camera takes a picture of your heart at rest and after activity.

What it shows: A detailed look at blood flowing to the heart muscle to screen for any significant blockages in the heart arteries. Nuclear stress tests can also show scars from previous heart attacks.

When you might need it: When you have new or worsening chest pain to determine if you have significant blockages in one of the heart arteries.

What it is: Cardiac computed tomography (CT) combines X-rays and computer technology to create detailed, cross-sectional views of the heart, allowing direct views of the heart arteries. You lie on your back with your head and feet outside the scanner, and an X-ray rotates around your body to obtain the images.

What it shows: Levels of cholesterol plaques in the arteries. A CT scan can measure a patient’s coronary artery calcium (CAC) score.

When you might need it: If your primary care doctor or cardiologist suspects you have significant heart artery blockages. Cardiac CT can also detect congenital heart disease, or problems present at birth.

CT angiography, which combines a CT scan with contrast “dye” given through an IV, will allow doctors to see blockages or narrowing in your heart arteries. CT angiography can also be done in combination with scans of the aorta to assess problems in its structure or size.

What it is: Cardiac magnetic resonance imaging (MRI) uses powerful magnets – not radiation – to create precise still and moving pictures of the heart and surrounding blood vessels. The patient is placed on a table that slides into a tube about the length of the body and is open at both ends. MRIs do not require radiation, but patients with metal implants, such as a pacemaker or defibrillator, will need screening to ensure they can safely receive this type of test.

What it shows: Excellent views of the heart’s size and structure, including evidence of scarring from previous heart attacks or active inflammation due to a variety of conditions. It can also reveal valve disorders and enlarged arteries known as aneurysms, and is very helpful in diagnosing rare disorders such as cardiac amyloidosis and sarcoidosis.

When you might need it: Your doctor might recommend a cardiac MRI if he/she is searching for causes of a weak heart pump known as cardiomyopathy, which can lead to heart failure. Cardiac MRI can also be used to detect heart valve disease, pericardial disease (which affects the outside lining of the heart) and congenital heart disease. Finally, it’s also an effective evaluation tool after a heart attack.

What it is: Positron emission tomography (PET) is a nuclear heart scan that uses a small amount of a radioactive tracer injected via an IV to create detailed 3D images of the heart.

What it shows: Whether areas of the heart muscle are scarred from previous heart attacks as well as areas of active inflammation from diseases such as sarcoidosis.

When you might need it: Heart PET scans can be used to diagnose coronary artery disease and associated damaged muscle from a heart attack. At UT Southwestern, we use it primarily to diagnose active inflammation in a rare but important disease known as cardiac sarcoidosis.