Investigations - Heart

Heart investigations are performed in patients with blackouts when the history is suggestive of a blackout due to low blood pressure. Heart investigations can help determine what caused the blood pressure to drop and what can be done to prevent it recurring.

ECG – Electrocardiogram

An ECG is a test that should be performed on every patient who has had a blackout.
The ECG gives important information about the electrical activity of the heart.

It can indicate if there is an electrical disturbance of the heart which predisposes to blackouts or may indicate an underlying heart abnormality that can predispose to abnormal heart rhythms or obstruction to blood flow from the heart.

No preparation is required for this test.

ECHO – Echocardiogram

An Echocardiogram is a test that is commonly performed in patients who have blackouts.

This test is an ultrasound that looks at the structure and function of the heart.

It will indicate if there are any abnormalities of the heart which may predispose to blackouts.

No preparation is required for this test.

Exercise Stress Test

An exercise stress test is performed to assess the heart rate, blood pressure and electrocardiogram changes with exercise. It is usually performed on a treadmill but a bicycle is sometimes used.

This test can be helpful in assessing if there is evidence of heart artery blockages. It can also determine if there is an electrical disturbance of the heart, which occurs with exercise. The electrocardiogram changes of some conditions are more prominent after exercise also.

This test may be performed in conjunction with an ultrasound to assess the heart pumping function with exercise or with a nuclear scan to assess the heart pumping function and blood flow with exercise.

You should wear comfortable clothing and appropriate footwear for exercise for this test.

You may be asked to withhold some of your medications before the test. If the test is combined with a nuclear test you may be asked to exclude caffeine for 24-48 hours.

If you are unable to exercise on a bicycle or treadmill you should let the doctor know in advance.

Tilt test

A tilt test is performed to assess the heart rate and blood pressure changes in response to the upright posture. It can bring on a simple faint (Vasovagal/Neurocardiogenic/Neurally Mediated Syncope) in people who are predisposed to this type of faint.

The test involves lying on a table with straps placed over you to prevent you falling when the table is tilted. A drip may be inserted.

Once your heart rate and blood pressure have been observed lying flat you will be tilted with your head up. Your heart rate and blood pressure will be monitored. You will be asked to let the medical staff know about any symptoms. After the initial phase you may be given a medication by the drip or under your tongue that can make it more likely that you will faint if you are prone to fainting spells.

Preparation: You will be asked to fast for a period of time before the test and may be asked to stop some of your medications for a few days before the test.

As you may faint or feel light-headed after the test it is advised that you do not drive to the test and that you bring someone with you to take you home.

Coronary Angiogram

This is an invasive test performed to look for evidence of heart artery blockages.
People with heart artery blockages can blackout because the heart does not pump as effectively as normal, or they may experience a serious abnormal heart beat that can result in a blackout.
A coronary angiogram is usually performed if a blackout occurred during exercise, or in the course of the history or past history there is reason to suspect there may be heart artery blockages.
It is also performed to define heart artery blockages indicated by a stress test.

A coronary angiogram is usually performed as a day stay procedure and is associated with a small risk of serious complications. The test takes approximately 40 minutes and is performed in a cardiac catheterization laboratory (‘cath lab’). Dye is injected into the heart arteries via a narrow tube that is inserted in the leg and fed up to the heart. The tube is removed after the test and pressure applied to the groin.
Patients then must lie down for up to 4 hours after the test.

Preparation: You will usually be asked to fast for 6 hours before the test. Diabetic medications may need to be adjusted. Warfarin, a strong blood thinner is usually stopped for a few days before this procedure.

Holter Monitoring

A Holter monitor is a continuous 24-hour recording of the heart beat. Sticky dots on the chest have wires attached and the monitor is worn on a belt around the waist. The aim of cardiac monitoring in patients who are experiencing blackouts is to document the heart rhythm at the time of symptoms to find out if it is abnormal. Holter monitors are of limited use in the investigation of patients who are experiencing blackouts. They are only useful if the events are occurring every day, or if the monitor is being used to assess for evidence of asymptomatic abnormal heart beats that may help guide further investigation.

Preparation: No preparation is required. It is important to be aware that you will not be able to shower for 24-hours whilst the monitor is worn

Event Monitoring

An event monitor is similar to a Holter monitor but has less wires and is worn for a longer period of time – usually one to two weeks. The wires can be unhooked and the sticky dots removed to allow for showering and then reapplied once dry.
An event monitor records continuously but the information is not stored and is overwritten (hence the ‘loop’) unless the ECG is ‘frozen’ by the patient pressing a button at the time of symptoms.
Event monitors are helpful for patients who are experiencing weekly symptoms. These monitors have a high incidence of technical problems.

Preparation: No preparation required.

Implantable Loop Recorder

An Implantable Loop Recorder can be very helpful in determining if an abnormal heart rhythm is the cause of a person’s episodes of loss of consciousness.

It is implanted under the skin using a small incision after local anaesthetic has been injected.

Light sedation may also be given.

It has a battery life of 14 months and continually records the patient’s heart rhythm. If a blackout occurs the information in the recorder is frozen using an external activator.  The patient then contacts the doctor to have the information downloaded. The recorder will also record automatically if the heart goes too fast or too slow which can help capture the heart rhythm at the time of an episode even if the activator wasn’t used correctly or in time.

If no blackouts occur over the 14 month life of the recorder then the patient and their doctor must make a decision as to whether they wish to replace the device or not.

Cardiac Electrophysiology Study

This is an invasive test used to study the electrical system of the heart and to determine if a patients’ heart is prone to an abnormal fast or slow heart beat.

Although it can give information about  electrical disturbances that may result in an abnormal slow heart beat it is most commonly used when an abnormal fast heart beat is suspected as the cause of a blackout. Some abnormal fast heart beats can be cured during an electrophysiology study by a process called radiofrequency ablation.

Cardiac Electrophysiology Studies are performed in the Cardiac Catheterisation Laboratory (‘cath lab’). A tube is placed in the vein (and sometimes the artery) in the groin. Wires that can record electrical signals and also pace the heart are passed up to the heart.

These studies usually take 60-90 minutes. After the procedure the tube is removed from the groin and pressure applied. The patients will be asked to lie down for up to 4 hours after the procedure.

Preparation:
You will be asked to fast for 6 hours before the procedure.
You may be asked to stop some heart medications for a few days before the procedure.

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