Cardiovascular Investigation Unit - Services

Holter monitor

Also known as an ambulatory ECG monitor, a Holter monitor records your heart rhythms for an entire 24 or 48 hour period. Wires from electrodes on your chest go to a battery-operated recording device carried in your pocket or worn on a belt or shoulder strap. While you are wearing the monitor, you will keep a diary of your activities and symptoms. Your doctor will compare the diary with the electrical recordings to help determine what triggers your symptoms.

When an extended period of monitoring is required, more specialized equipment called an "Event Recorder" can be used. This mode of monitoring is especially useful for patients who have very infrequent symptoms.

Risk factors

There are no risk factors associated with holter monitoring.

What to expect before the test

There is no need for fasting or any other special preparation. Take all your prescribed medications as usual and record them in the diary provided. Wear loose fitting clothes when coming to the hospital.

What to expect during the test

Surface electrodes will be placed on the upper chest (pictured above). The electrodes will be connected to a recorder (the size of a small cassette player,), which will be strapped around your waist. You will wear it continuously for 24/48 hours as requested by your physician. Please do not remove the electrodes on your own during the recording.

You will be asked to keep a diary to record all your activities and any symptom with the exact time of their occurrence. It is a good idea to synchronize your watch with the timer on the recorder. Please carry out all your activities as usual except for bathing.

You will be advised to return to the hospital at a given time to have the recorder removed for analysis.

What to expect after the test

After the prescribed testing period is over, the recorded results are analyzed. Depending on the results, further testing or treatment (e.g., taking medications called antiarrhythmics) may be advised.

Follow up

No follow-up is required after holter monitoring.

Stress test

If your heart problems occur most often during exercise, your doctor may ask you to walk on a treadmill or ride a stationary bike during an ECG. This is called a stress test and it is used to assess the response of your heart to increased demand for blood.

If you have a medical condition that makes it difficult for you to walk, medication may be injected to stimulate your heart.

Risk factors

A stress test is very safe. Some patients may experience chest pain during the test. The risk of heart attack or abnormal heartbeat is extremely low.

A doctor is present (either physically in the lab or in the vicinity) during the test to ensure your safety.

What to expect before the test

Some preparation may be required on your part before you come in for the stress test.

You may be asked to stop certain medications a day before the test. Please confirm this with your doctor.
On the day of the test, have a light meal before the test.

Please bring comfortable shoes (preferably running shoes) and wear loose fitting clothes. Male patients may need to shave the chest so that ECG electrodes can be attached.

If you have a fever or are feeling unwell, please inform the staff so that the doctor can assess you before the test.

What to expect during the test

Once you start walking on the treadmill, your blood pressure, heart rate, general condition and ECG will be monitored continuously. After every three minutes, the speed and slope of the treadmill will be increased.

You will be encouraged to exercise for as long as you can and the test will continue until you reach a desired heart rate or cannot exercise any more (usually 10-15 minutes).

What to expect after the test

After the test, you will be asked to rest while your blood pressure and ECG are recorded. A cardiologist analyzes all the recordings and the results are made available in a few days. A stress test is valuable in providing the following information:

  • Heart rate: Normally, heart rate can be measured by checking your pulse. However, an ECG may be helpful if your pulse is difficult to feel or too fast or too irregular to count accurately.
  • Heart rhythm: An ECG can help your doctor identify an unusually fast heartbeat (tachycardia), unusually slow heartbeat (bradycardia) or other irregular heart rhythms (arrhythmias).
  • Heart attack: An ECG can often show evidence of a previous heart attack or one that is in progress. The patterns on the ECG may indicate which part of your heart has been damaged, as well as the general extent of the damage.
  • Inadequate blood and oxygen supply to the heart: An ECG can often help your doctor determine whether chest pain is caused by reduced blood flow to the heart muscle.
  • Structural abnormalities: An ECG can provide clues about enlargement or inflammation of the heart, congenital abnormalities and various other heart problems.

Follow up

No follow-up is necessary after a stress test.

Electrocardiogram (ECG/EKG)

An electrocardiogram - also called an ECG or EKG - is a simple test that provides valuable information about your heart's health.

Each beat of your heart is initiated by an electrical impulse generated from special cells in the right upper chamber of your heart. An electrocardiogram records these electrical signals as they travel through your heart. Your doctor can look for patterns between these heartbeats and rhythms to diagnose various heart conditions.

An electrocardiogram is a painless way to diagnose many common types of heart disease. Your doctor may use an ECG to detect irregular heart rhythm, structural abnormalities in your heart, or problems with the supply of blood and oxygen to your heart. An ECG can also confirm if you are having a heart attack or if you have had a heart attack in the past.

Risk factors

An electrocardiogram is a safe procedure. There may be minor discomfort when the electrodes are removed. Rarely, a reaction to the electrodes may cause redness or swelling of the skin. During a stress test, the exercise or medication may trigger heart distress - not the ECG.

What to expect before the ECG

No preparation is required. However, avoid exercising immediately before an electrocardiogram. Physical activity, such as climbing stairs, may increase your heart rate.

What to expect during the ECG

A standard ECG takes only a few minutes. Various electrodes, often 12 to 15, will be attached to your arms, legs and chest. The electrodes are sticky patches applied with a gel. The gel helps detect and conduct the electrical currents of your heart.

You can breathe normally during the electrocardiogram. Make sure you are warm and ready to lie still. Moving, talking or shivering may distort the test results.

What to expect after the ECG

If your electrocardiogram is normal, no further testing is needed. Your doctor may need a repeat ECG or other diagnostic tests if the results are inconclusive or concerning. Treatment depends on what is causing your signs and symptoms.

Follow up

No follow-up is necessary after an electrocardiogram.


An echocardiogram, more simply called an “echo”, is an ultrasound examination of the heart. Ultrasound images are generated when harmless high frequency sound waves are used through a probe.  The echocardiogram is considered a painless, non-invasive test.  The test is performed by a qualified, registered cardiac sonographer. The echocardiogram assesses heart anatomy, function and blood flow to help rule out heart, valve or congenital disease.

Risk factors

There are no complications related to this test and everyone can have this test.

What to expect 

A complete echo could last from 30 minutes to 1 hour in length. While the sonographer scans your heart, you may see moving images and hear sounds of blood flow. There is no special preparation required for an echocardiogram. Do not discontinue any medications for this procedure unless your doctor has specified otherwise

Occasionally, due the limitations of ultrasound, the echo images may not be of a quality to accurately assess heart function. In these cases, the sonographer may suggest using a contrast agent such as Definity. An intravenous (IV) site would have to be established for the injection. The use of Definity will add approximately 10 minutes to the exam. Definity is very safe compared to other invasive contrast testing modalities. 

Another contrast that may be used during an echo is called Saline Bubble contrast. This very safe test is used to rule out if a patient has a hole in their heart. This contrast is injected intravenously to see if any bubbles cross over from one side of the heart to the other.

What to expect during the test

You will be asked to remove your clothing from the waist up. Women can wear a gown during the test. The sonographer will attach electrodes to your chest with tape. ECG lead wires will then be attached to these electrodes..

The sonographer will put an ultrasound gel onto a microphone-like device called a transducer, which sends and receives the harmless ultrasound waves between your body and the machine. The sonographer collects images of your heart by moving the transducer around on your chest, stomach, and neck. At certain key locations or "views", he or she will take recordings of your heart.

During a recording, you may be asked to change your position and to hold your breath. This allows the sonographer to get the best pictures. Sometimes, the sonographer may push the transducer more firmly against your skin. Please let him or her know if this becomes uncomfortable.

The imaging will take about 30 to 45 minutes. During the exam, the sonographer will take various measurements on the computer screen of the size, function and blood flow of the heart.

An echocardiogram exam usually includes a Doppler recording of the blood movement or flow within the heart. Doppler examinations often also include an audio signal of the blood flow, which can be heard and seen.

What to expect after the test

Once the test is completed, the ultrasound images are safely downloaded to be interpreted by specially trained echo cardiologists at London Health Sciences Centre. A written report is generated and immediately faxed to the referring doctor and or family physician. This process could take up to 1 week in length. At no time will the sonographer inform the patient of any findings from the exam.

Going home

You can go home immediately after the test. There is no recovery or rehabilitation stage.

Follow up

Your referring or family doctor will contact you with the result. Usually, you will be contacted only if there is a problem with the results, unless otherwise stated by your doctor.