Reviewed by Dr Lim Chin Hock

Non-invasive cardiac tests

There are numerous tests to diagnose heart disease. The choice of which (and how many) tests to perform depends on factors such as a patient's risk factors, history of heart problems, current symptoms and the doctor's interpretation of these factors.

Simple tests are usually ordered first and the more complicated ones if needed.

Most of these preliminary tests are non-invasive, meaning they do not involve inserting instruments or fluids into the body. Those that do are called invasive tests.

Electrocardiogram (ECG/ EKG)

One of the most common cardiac tests, an electrocardiogram often referred to as an ECG or EKG, is a harmless and non-painful test that measures the electrical activity of the heartbeat. 

Using 12-15 sticky electrodes patches attached to various parts of your body, they can pick up tiny electrical currents that go through your body. Each heartbeat sends an electrical impulse through the heart that causes the muscle to squeeze and pump blood from the heart.

The normal timing of the top and lower chambers of the heart will be reflected on an ECG. All the activities of the heart’s right and left atria, chambers and ventricles are measured by the waves (PQRST) waves that are created.

An ECG is typically ordered to detect rhythm disturbances, heart attack or other structural abnormalities.

Ambulatory Electrocardiography

Also known as Holter monitoring, ambulatory ECG refers to the monitoring and measurement of your heart’s activities as you go about your daily activities. The purpose of this constant monitoring is to detect abnormalities that are intermittently presented by sleep-related problems or caused by emotion or stress.

There are two usual types of recording devices. Continuous recorders, which are used for 24-48 hours and Intermittent recorders, which can be used up to months to provide brief, intermittent recordings.

Other than the inconvenience of keeping the device on you, there is hardly any pain or risk involved.

Exercise Stress Test

An exercise ECG test is sometimes called a treadmill test as it requires the patient to walk on a treadmill or pedal a stationary bicycle while an ECG is being performed.

Subjecting the patient to this additional exercise allows doctors to find out how the heart handles the extra workload demanded of it. It is easier to detect if there is adequate circulation and other abnormalities related to insufficient blood and oxygen supply when the heart rates are increased. Certain rhythm abnormalities are also triggered by exercise, which makes it a good test for such conditions. Sometime your cardiologist may order this test to follow your progress after a cardiac event.

This test is often conducted with a medical professional who will monitor your heart rate, breathing, blood pressure, electrocardiogram, and how tired you feel at various phases. Because there is very little risk, it is a suitable test to help to determine the level of exercise that is suitable for you.

Echocardiography

This procedure which allows doctors to ‘look’ at your heart by using diagnostic ultrasound waves  to create an image (echocardiogram) that is displayed and recorded on a video or screen.

It makes use of a probe that is moved over your chest area and is a painless and convenient test that reduces the need for surgery or other risky procedures.

It is generally recommended if you have:

·         A heart murmur

·         A previous heart attack

·         Rheumatic fever

·         Chest pains

·         Other congenital heart defects

There are several types of echocardiographic techniques and echocardiograms that enable doctors to accurately visualize and measure the following:

• Heart size and shape
• Pumping abilities
• Any damage to the heart muscle
• Valve damage
• Structural abnormalities
• Blood pressure in lung arteries

Nuclear Scanning

Involving several techniques, nuclear scans are able to produce images that can show the features of your heart’s functions such as the pumping ability of the ventricles, blood flow to the myocardium and lungs as well as the heart chamber size.

Nuclear scans allow images to be produced when a tiny amount of radioactive materials (radionuclide) that is introduced into the body radiates outwards and captured on cameras.

This test is rather similar to the exercise stress test, except doctors will give you a small amount of a radioactive substance (known as a Tracer), just before the end of the exercise part of the test.

While it may sound intimidating to be injecting radioactive substances into your body, the actual amounts of radiation that you will be exposed to in these tests are very low and doses are determined at a safe level. Other than pregnant women, these tests are very beneficial in helping doctors obtain crucial information about your heart health.

Chest X-ray

Although it does not show the inside of the heart, it is still an important and basic test in the screening of heart disease. The Chest X-ray is able to show the size and shape of your heart, the presence of calcium deposits as well as your lung condition.

Standing against the plate containing an X-ray film, you be exposed to a small beam of X-rays as it passes through the chest and makes an image on special photographic film when the machine is switched on for a fraction of a second. 

Usually, both the front and side view are taken. The X-ray film takes about 10 minutes to develop.

Many people worry about radiation risks associated with X-rays. Although there is a small amount of X-ray emitted, the risk of harm is very low and is outweighed by the benefits that the image produces. Pregnant women, however, should inform their doctors or technicians to minimize any exposure to the unborn foetus.

Other Radiographic and Tomography tests

Featuring a wide array of computer imaging (tomography) and X-ray machines to create pictures of the internal structure of the heart and chest, these non-invasive tests are able to provide doctors with a lot of information based on the clarity of the images produced.

Some common radiographic tests include:

• Calcium Score Screening Heart Scan
• Cardiac Computed Tomography (also known as CT scan or CAT)
• Coronary Computed Tomography Angiography
• Magnetic Resonance Imaging (MRI)
• Cardiac Positron Emission Tomography
• Single Photon Emission Computed Tomography (SPECT)
• Digital Cardiac/Subtraction Angiography