Advanced Cardiac Imaging

Overview

A transthoracic echo is an ultrasound of the heart performed from outside the chest. A small probe is placed on the skin over the chest wall and uses sound waves to produce real-time images of the heart. No radiation is involved and the test is painless.

Purpose of test

This is the most commonly performed cardiac imaging test. It allows assessment of how well the heart muscle is pumping, the size and thickness of the heart chambers, and the function of all four heart valves. It is used to diagnose and monitor a wide range of heart conditions including heart failure, valve disease, and cardiomyopathy.

During the test

You will be asked to undress from the waist up and lie on a bed, usually on your left side. Gel is applied to the chest and the probe is moved across different positions to capture images from various angles. The test typically takes 30–45 minutes. No preparation is required.

Overview

A TOE is a specialised ultrasound of the heart in which a thin probe is passed through the mouth into the oesophagus (food pipe), which sits directly behind the heart. This allows much higher resolution images than a standard echo because there is no chest wall between the probe and the heart.

Purpose of test

A TOE is used when more detailed images are needed than a standard echo can provide. Common indications include assessment of heart valve disease, detection of blood clots in the heart before electrical cardioversion for atrial fibrillation, evaluation for infection on heart valves (endocarditis), and guidance during certain procedures such as mitral valve clipping and LAA closure. The high-resolution images obtained can also be reconstructed into detailed three-dimensional models of the heart valves, which is particularly valuable for characterising the anatomy of valve disease and guiding surgical or interventional planning.

During the test

You will need to fast for at least six hours beforehand. A sedative is given through a drip to keep you comfortable, and local anaesthetic spray is applied to the back of the throat. You will not be fully asleep but will be drowsy and relaxed. The probe is gently passed while you are sedated. The procedure takes approximately 20–30 minutes and you will need someone to drive you home afterward.

Overview

A stress echo combines a standard echocardiogram with a form of stress — either physical exercise on a treadmill, or a medication called dobutamine given through a drip if you are unable to exercise. Images of the heart are taken at rest and at peak stress.

Purpose of test

This test detects reduced blood supply to the heart muscle (coronary artery disease) that may not be apparent at rest — when part of the heart is underperfused during stress, it moves abnormally on the echo images. It is also used to assess valve conditions under physiological demand.

Stress echocardiography is also valuable for evaluating diastolic dysfunction — impaired relaxation of the heart muscle despite normal pumping function. This condition causes few symptoms at rest but produces significant breathlessness on exertion, as the stiff heart builds up pressure that is transmitted back to the lungs. Exercise echocardiography can detect this rise in filling pressures at peak stress, a pattern invisible on resting studies, and can explain otherwise unexplained exertional breathlessness.

During the test

You will need to fast for four hours beforehand and avoid caffeine on the day of the test. Sticky electrode patches are placed on your chest to monitor your heart rhythm throughout. If exercising, you will walk on a treadmill that gradually increases in speed and incline. If dobutamine is used, you will lie on a bed while the medication is infused and your heart rate is progressively increased. The test takes approximately 60–90 minutes in total.

Overview

A CT scanner is used for this test. The scanner machine is identical to that used for other applications (like abdominal or brain imaging) but scanning parameters and timing are adjusted to specifically image the heart. A cardiologist is also involved with supervising the scan. Most cardiac CT studies consist of two sequential parts: an initial non-contrast scan followed by a contrast-enhanced scan.

Purpose of test

This test assesses the anatomy of the heart and coronary arteries, detecting plaque (atherosclerosis) and the presence of significant narrowing. It is also essential for planning valve interventions.

The non-contrast scan generates a coronary artery calcium score — a numerical measure of calcified (older, hardened) plaque burden that can be compared against age- and gender-matched peers to quantify cardiovascular risk.

The contrast scan visualises non-calcified (soft) plaque — newer, lipid-rich deposits that are invisible without contrast and carry a higher risk of rupture. Contrast fills the vessel lumen, allowing the cardiologist to determine whether any plaque is causing significant obstruction. This level of detail is not possible without contrast injection.

During the test

Medications (metoprolol or ivabradine) may be given to you to be taken before the test to aid in lowering your heart rate (ideally 50–60 bpm). This is to reduce motion blurring and degradation of image quality that occurs with fast heart rates. An IV cannula will be inserted for injection of contrast dye. You may feel a warm sensation as the contrast dye is injected. This is needed to opacify the heart chambers and highlight the coronary arteries.

Overview

Nuclear cardiology studies use a small amount of a radioactive tracer injected into a vein to produce images showing blood flow through the heart muscle. The most advanced form of this is cardiac PET (positron emission tomography), which provides higher resolution images and more accurate measurements than conventional nuclear studies. John Fawkner Cardiology offers cardiac PET, which is available at only a small number of centres in Australia.

Purpose of test

These tests assess whether areas of the heart muscle are receiving adequate blood supply — both at rest and during stress. They are used to diagnose coronary artery disease, determine whether areas of muscle that appear weak are still alive (viability), and assess the severity of known disease to guide treatment decisions including bypass surgery or stenting.

During the test

A cannula is inserted for injection of the radioactive tracer. Stress is induced either with exercise or with a medication (adenosine or regadenoson) that dilates the coronary arteries. You will then lie still in a PET or gamma camera scanner while images are acquired — this is painless and takes approximately 15–30 minutes. The radioactive tracer leaves the body naturally within a few hours. You will need to fast beforehand and avoid caffeine for 24 hours prior to the test.

Overview

Cardiac MRI uses a powerful magnetic field and radio waves — not radiation — to produce highly detailed images of the heart. It is performed in a standard MRI scanner. A cardiologist with specialised training in cardiac MRI supervises and reports the study.

Purpose of test

CMR provides information that other imaging tests cannot. It is considered the gold standard for assessing the structure and function of the heart muscle, and is particularly valuable for diagnosing cardiomyopathies, myocarditis, cardiac sarcoidosis, amyloidosis, and congenital heart disease. It can also precisely measure heart chamber volumes and pumping function, and detect areas of scarring or inflammation within the heart muscle.

During the test

A cannula is inserted for injection of a contrast agent called gadolinium, which highlights areas of scarring or inflammation. The scan takes approximately 45–75 minutes. You will be asked to hold your breath briefly and repeatedly during the scan to reduce movement artefact. The scanner can be noisy — ear protection is provided. Most modern pacemakers and metallic implants are MRI-compatible, but please inform us of any devices or implants before your appointment so we can confirm safety in advance.

Overview

Direct current cardioversion (DCR) is a procedure used to restore a normal heart rhythm in patients with certain abnormal heart rhythms — most commonly atrial fibrillation (AF) or atrial flutter. A controlled electrical shock is delivered through adhesive pads placed on the chest, which briefly interrupts the abnormal electrical circuit and allows the heart's natural pacemaker to resume control. DCR is performed under a short general anaesthetic, so patients are fully asleep and unaware of the procedure.

Purpose of test

DCR is used to convert an abnormal heart rhythm back to normal sinus rhythm. It is often recommended when rate-controlling medications alone are insufficient, when symptoms such as breathlessness or palpitations are significantly affecting quality of life, or as part of a planned rhythm-control strategy. In patients with AF lasting more than 48 hours, anticoagulation (blood thinning medication) is required for a period before and after the procedure to reduce the risk of stroke.

During the procedure

You will need to fast for at least six hours beforehand. An intravenous cannula is inserted and a short-acting anaesthetic is given by an anaesthetist so you are asleep for the procedure. Adhesive electrode pads are applied to your chest and back, and a synchronised electrical shock is delivered — the entire procedure takes only a few minutes. You will wake up shortly afterward in the recovery area. Most patients are ready to go home within two to three hours, and you will need someone to drive you. Your cardiologist will discuss whether ongoing anticoagulation and rhythm-control medications are required following the procedure.

Overview

A bubble study is a specialised echocardiographic test that uses agitated saline as a contrast agent to detect abnormal communications between the chambers of the heart. It is typically performed as an extension of a standard transthoracic echocardiogram and requires no radiation or iodine-based contrast dye.

Purpose of test

The test is most commonly used to identify a patent foramen ovale (PFO) — a small opening between the right and left sides of the heart that is present in around one in four adults. In most people a PFO causes no problems, but in some it can allow small blood clots or air bubbles to bypass the lungs and enter the arterial circulation, potentially contributing to stroke or unexplained low blood oxygen levels (hypoxia). A bubble study is frequently requested as part of the investigation for cryptogenic (unexplained) stroke, transient ischaemic attack (TIA), or unexplained hypoxia.

During the test

An intravenous cannula is inserted into a vein in your arm. A small volume of your blood is drawn back and mixed with saline solution, then agitated briskly between two syringes to create a suspension of tiny microbubbles. This is injected rapidly into the vein while echocardiographic images of the heart are recorded. The bubbles appear as bright spots on the echo and are normally filtered out entirely by the lungs — if bubbles are seen crossing to the left side of the heart, this indicates a communication between the chambers. You will usually be asked to perform a brief Valsalva manoeuvre (bearing down as if straining) during the injection to increase right-sided heart pressures and improve the sensitivity of the test. The procedure takes approximately 10–15 minutes and is painless aside from the initial cannula insertion.