Heart Imaging Tests Explained: Echo, CT, MRI & More

The heart can be looked at in several different ways, and each test answers a different question. An echocardiogram shows how the heart is pumping; a cardiac CT shows the arteries that supply it; a cardiac MRI shows the heart muscle in fine detail; and a stress test shows how the heart copes with exercise.

Your GP or cardiologist chooses the test based on your symptoms, your risk factors, and what they need to find out - so two people with chest pain might quite reasonably be sent for different scans.

This guide explains the common heart imaging tests in plain language so you know what to expect. It's general information only; your doctor is the right person to advise which test suits your situation.

An echocardiogram ("echo") is an ultrasound of the heart. A sonographer moves a small probe over your chest, using sound waves to create moving images of the heart in real time. There's no radiation, no needles for a standard echo, and it typically takes 30-45 minutes.

An echo shows:

• How strongly the heart muscle pumps (ejection fraction) • Whether the heart valves open and close properly • The size of the heart's chambers • Fluid around the heart and some congenital abnormalities

It's one of the most commonly ordered heart tests - used to investigate breathlessness, murmurs, palpitations, and suspected heart failure. Echocardiograms attract a Medicare rebate with a valid referral, and out-of-pocket costs vary by clinic, so it's worth comparing providers before booking.

Cardiac CT looks at the coronary arteries - the vessels that supply the heart muscle. There are two common types:

• Coronary artery calcium score: a quick, low-dose CT that measures calcified plaque in the artery walls. The result is a score that helps estimate your risk of future heart disease, often used to guide decisions about cholesterol treatment. No contrast dye is needed. • CT coronary angiogram (CTCA): a more detailed scan using contrast dye to show narrowings inside the arteries. Your heart rate may be slowed with medication beforehand to sharpen the images.

Medicare coverage differs between the two - calcium scores are often not rebated and are paid out of pocket (commonly in the range of roughly $100-$250), while CTCA attracts a rebate in certain circumstances. Your doctor can explain which applies to you. For preparation, costs, and what the scan is like, see our full CT angiogram guide.

Cardiac MRI uses magnets and radio waves - no radiation - to produce highly detailed images of the heart muscle, chambers, and surrounding structures. It's considered the gold standard for measuring heart size and pumping function precisely.

It's typically used for more specific questions: assessing cardiomyopathies (diseases of the heart muscle), inflammation such as myocarditis, scarring after a heart attack, congenital heart conditions, and some tumours. Gadolinium contrast is often used to highlight scar tissue.

The scan takes longer than most MRIs - often 45-60 minutes - and involves repeated breath-holds. Cardiac MRI is a specialised test performed at a smaller number of centres, usually on referral from a cardiologist, and Medicare rebates apply only in specific circumstances, so ask about costs when the test is arranged.

Some heart problems only show up when the heart is working hard, which is where stress testing comes in:

• Exercise stress test (stress ECG): you walk on a treadmill while your heart rhythm and blood pressure are monitored. • Stress echocardiogram: an echo performed before and immediately after exercise (or medication that mimics exercise), showing how the heart muscle moves under load. • Stress nuclear scan (myocardial perfusion scan): a small amount of radioactive tracer shows blood flow to the heart muscle at rest and under stress.

These tests help investigate chest pain and breathlessness and assess known coronary disease. They're done under supervision with resuscitation equipment on hand, and you may be asked to avoid caffeine and certain medications beforehand - the clinic will give you specific instructions.

All of these tests require a referral from your GP or a specialist, and some - particularly cardiac MRI and CT coronary angiograms - are commonly arranged through a cardiologist.

Costs vary widely. Broadly speaking, echocardiograms and standard stress tests are Medicare-rebated with a referral and are bulk-billed at some clinics; calcium score CTs are often an out-of-pocket cost; and cardiac MRI rebates depend on the clinical indication. Always ask the clinic for a quote for your specific test before booking.

You can use Radly to compare imaging clinics across Victoria, check bulk billing, prices, and opening hours, and find a provider that offers the heart test you've been referred for. If anything about your referral is unclear, your GP can talk you through why the test was chosen.