Reviewed by Dr Lim Chin Hock

Invasive Heart Tests

What does ‘invasive’ mean?

Sometimes, when other tests fail to yield a satisfactory diagnosis or provide a clear enough picture of health to your doctor, he may recommend invasive tests involving the insertion of catheters into the blood vessels of the heart to get a closer look at the coronary arteries or to stimulate and test the electrical system of the heart.

Blood Tests

The most common tests of all, blood tests are routinely ordered to help diagnose a wide variety of conditions. Blood tests are able to provide information on the existence and severity of CAD, if a heart attack has occurred and the extent of damage as well as to determine risks of future cardiac events and preventive steps to take.

Blood tests conducted specifically for heart diseases will often include cardiac enzymes (including troponin and creatine kinase), C-reactive protein (CRP), fibrinogen, homocysteine, lipoproteins (cholesterol), triglycerides, brain natriuretic peptide (BNP) and prothrombin and International Normalized Ratio (INR).

Cardiac Catheterization

Also known as Coronary Angiogram, Angiography or Arteriography, Cardiac Catheterization is one of the most useful and accurate way to diagnose heart disease and determine the ideal course of treatment.

Catheterization involves the insertion of a long, thin and flexible tube into your blood vessels or heart to determine how well your heart is working and the condition of your coronary arteries.

The doctor examines the inside of your heart’s blood vessels using special X-rays called angiograms. Dye visible by X-ray is injected into blood vessels using the catheter which may be inserted into various parts of your body (most commonly the arm or groin). A local anaesthetic is usually used such that it will numb the site of the insertion and you will remain conscious throughout the procedure.

While other non-invasive techniques are able to provide information on the heart conditions, some problems can only be detected with catheterization. Sometimes, your physician may request that you undergo catheterization after other tests to confirm the diagnosis.

Catheterization is often performed to obtain specific information relation to your heart functions. Left-heart catheterization is done to measure the pressure in the left ventricle to assess the severity of certain heart valve disease or congestive heart failure and cardiomyopathy, while Right-heart catheterization is normally done to evaluate the pressures and blood flow through the right heart chambers and lungs, particularly in people with heart failure and heart attacks.

As with all invasive procedures, there is a degree of risk involved and it is best to equip yourself with the necessary information and discuss them with your doctor.

Some of the risks associated with catheterization are bruising and infection at the puncture site, formation of bulge in the artery, blockage of the artery, numbness or tingling sensation at the site, bleeding or allergic reactions to contrast material used.

Rare but serious complications may also arise. Blockage of a coronary artery could cause a heart attack, irregular heart rhythms and cardiac arrest. Blood clot or tear of the inner lining from the aorta into the carotid artery may result in a stroke.

Complications in catheterization involving the arteries tend to be more severe than those in the veins as the arterial blood pressure is higher, increasing the likelihood of bruising and bleeding.

Carotid Angiography

Like cardiac angiography, carotid angiography is an imaging procedure that involves inserting a catheter into a blood vessel through the arm or groin, and guiding it to the carotid arteries with the aid of a special x-ray machine. Contrast dye is injected through the catheter so that x-ray movies of your carotid arteries (the arteries that supply your brain with oxygen-rich blood) are taken.

This procedure is carried out to detect if there is a narrowing or blockage in your carotid arteries and determine the next course of therapy for your condition.

Electrophysiology Study

For people with irregular heart rhythms, an EP study is useful to help doctors understand the cause of the disturbance and site of the disturbance by ‘reproducing’ the arrhythmia in a controlled setting.

Also involving a kind of catheterization technique, EP studies have electrode catheters inserted into your blood vessels and heart chamber to record impulses in different regions of the heart. By measuring how your heart conducts these impulses, the cardiologist is able to construct a ‘map’ of your heart’s electrical wiring system.

Based on the studies, your doctor will then be able to recommend an appropriate drug, pacemaker, implantable cardioconverter defibrillator, cardiac ablation or surgery for your condition.

Performed under local or general anaesthesia, an EP study will have several catheter electrodes inserted through the femoral vein in the groin into the heart where it will be stimulated with tiny impulses to trigger the symptom-causing arrhythmia. As the EP study also test out various treatment options for your condition, it can often become a lengthy procedure.

As with all other catheterization techniques, EP studies carries risks including bruising, bleeding, formation of blood clot or infection at site. Rare complications include perforation of the heart, tear at the lining of the blood vessel or stroke.

Sometimes, in the process of inducing the arrhythmia, severely abnormal heart rhythms may occur, including ventricular fibrillation where inadequate blood is being pumped to the body. Immediate defibrillation or even resuscitation is required in such circumstances.

You should find out what kind of equipments and expertise the EP laboratory possess and discuss all the risks and benefits of undergoing such a procedure with your doctor.

Intravascular Ultrasound (IVUS)

Usually performed along with cardiac catheterization, IVUS involves a miniature ultrasound probe (transducer) on the tip of a coronary catheter being threaded through the coronary arteries and with the use of high-frequency sound waves, produces detailed images of the interior walls of the arteries (from the inside).

Particularly useful in cases of complex narrowing (stenosis), as may occur in the aorta (coarctation) or pulmonary arteries.

IVUS is used to evaluate the disease present, its makeup and distribution as well as to help doctors to determine the need for further treatment.