Non-Invasive Cardiac Tests
An electrocardiogram (ECG) records the electrical signals in your heart. Electrodes are placed on your chest and a recording of your heart rhythm is made. It is the most basic of the cardiac tests and allows detection of structural abnormalities of the heart and disorders of heart rhythm.
Exercise Treadmill Test
Exercise treadmill test allows us to assess the response of your heart to exercise. This is done by recording your electrocardiogram (ECG) while walking on a treadmill machine. We also monitor your symptoms and blood pressure (BP) during the test. This test is used to detect significant blockages of the heart arteries and is also used to assess for abnormalities of heart rhythm.
Ankle Brachial Pulse Wave Velocity/Pressure Index
The Ankle Brachial Index (ABI) is performed by measuring the systolic blood pressure from both brachial (arm) arteries and from both the dorsalis pedis and posterior tibial (foot) arteries. It is used to detect significant blockages of the leg arteries.
Pulse Wave Velocity (PWV) measures the speed at which the pulse travels through the artery (blood vessel). PWV is used to assess the stiffness of the artery. It can also be used to assess future risk of stroke and heart attack.
Carotid intima Media Thickness (CIMT)
The carotid arteries are found in the neck and supply blood to the brain. These arteries are large and lie just beneath the skin, allowing easy visualization through ultrasound scanning.
The intima and media are the layers that line the artery. With increasing age and with the presence of certain risk factors (such as high cholesterol, high blood pressure, smoking, obesity, diabetes) cholesterol become deposited in these layers. This increases the thickness of the inner layers which can lead to narrowings and even complete blockage. The thickening also leads to an increased risk of blood clots forming within the blood vessel.
Changes in the carotid artery reflect changes in other arteries found in various organs. It is presently not possible to easily see the heart arteries without more complex testing. The measure of carotid IMT is therefore an easy and safe way to find out the health of arteries throughout the body.
In multiple studies, carotid IMT has been shown to be a predictor for future heart attacks and stroke. An increase in thickness of just 0.1 mm actually increases risk for these illnesses by 11%. In particular, a thickness that is greater than 1 mm doubles the chance of developing a heart attack or stroke in the next 6 years.
Persons without known heart disease but have increased thickness would therefore benefit from aggressive treatment of risk factors to prevent the onset of both stroke and heart attacks.
Ultrasound is a safe imaging technique that uses no radiation. A person is asked to lie down and a colorless gel is applied to the neck. A scanner is applied with moderate pressure over the neck. The scanner is slowly brought up and down the neck to scan the entire length of the carotid artery. Thickness of the intima-media is measured and the flow rate of blood passing through the artery is also measured. The entire study usually takes less than 20 minutes.
Transthoracic Echocardiogram (2D Echo)
Transthoracic Echocardiogram (2D Echo) is an ultrasound machine with a probe specially designed to image the heart. It provides important information on the structure and function the heart. We can assess the chambers, valves, large blood vessels and pumping function of the heart.
Exercise and Dobutamine Stress Echocardiogram.
Persons with heart artery blockages may have minimal or no symptoms at rest. However, symptoms of underlying blockages may occur during stress. Stressing the heart can be done by exercise or by using medicines that stimulate the heart. During exercise, healthy heart arteries enlarge to accommodate increased blood flow. Narrowed arteries are unable to compensate for increased blood flow needed during exercise. This compromises blood flow to the heart muscle resulting in heart muscle being “starved” of oxygen.
A Stress Echocardiography test is conducted as an outpatient and does not require hospitalization.
A “resting” study is first performed with the person lying down. This provides a baseline examination, from which information regarding the size and function of the various chambers of the heart and structure and function of the valves may be obtained. Electrodes are attached to the chest and connected to wires to record the electrocardiogram (ECG).
A colourless gel is then applied to the chest and the Echo transducer is placed on top of it. The Cardiologist then makes recordings from different parts of the chest to obtain several views of the heart. The patient may be asked to move from the back to the left side. Instructions may also be given for the patient to breathe slowly of to hold their breath in order to obtain clear pictures of the heart.
Exercise is then initiated using a treadmill. In persons who are unable to complete a high level of exercise, stress to the heart is provided by medicines infused through an IV line inserted into the vein of an arm.
The initial stage is a warm-up phase and is done very slowly. The speed of the treadmill and slope is then increased every three minutes. The treadmill is stopped when the person exceeds 85% of the target heart rate (based upon person’s age). Exercise may be stopped earlier if the person develops symptoms such as chest discomfort, marked shortness of breath, weakness or dizziness. A Cardiologist would be in attendance throughout the test and the above problems are uncommon.
Immediately after the treadmill, the person moves directly to the examination bed and lies on the left side, where the Echo examination is immediately repeated.
By comparing the rest images with the post-exercise images the Cardiologist would look for any abnormalities in how the heart muscle contracts in response to exercise. Normally, exercise would result in a significant increase in heart muscle contraction. Reduced heart muscle contraction during exercise indicates the presence of blockages in one or more heart arteries. Depending on the severity of the abnormalities detected, further evaluation by Coronary Angiography may be indicated.
There are no known adverse effects from the ultrasound used during Echo imaging. The risk of the stress test is similar to the risks involved in any strenuous form of exercise. A Cardiologist would be present throughout the test to manage any rare complications that may occur. These problems could potentially have occurred if the same person performed an equivalent level of exercise at home or in a gymnasium.
Stress Echocardiography is capable of diagnosing significant disease in more than 85% of persons with significant heart artery narrowing.
On the basis of currently available information, Stress Echocardiography may be considered as a reasonable test in the following situations:
- Persons with symptoms suggestive of coronary artery disease
- Persons with unclear or inconclusive ECG treadmill test
- Persons with known heart disease in order to evaluate progression of the disease
- To assess heart attack risk for persons who are about to undergo major surgery
- To assess persons with chronic severe heart valve abnormalities
Stress Echocardiography is an outpatient test and does not require hospitalization. The whole procedure takes approximately 90 minutes.
The following steps are required:
- Do not eat or drink for three hours prior to the procedure. This reduces the likelihood of nausea that may accompany strenuous exercise after a heavy meal. Diabetics, particularly those who use insulin, will need special instructions from their doctor.
- Specific heart medicines (e.g. beta-blockers) may need to be stopped one or two days prior to the test. Such instructions are generally provided when the test is scheduled.
- Wear comfortable clothing and shoes that are suitable for exercise.
Transesophageal Echocardiogram (TEE)
Transesophageal echocardiography is an essential tool for assessing valvular function and guiding surgical decision making during the perioperative period.
Transesophageal echocardiography (TEE) is a test that produces pictures of your heart. TEE uses high-frequency sound waves (ultrasound) to make detailed pictures of your heart and the arteries that lead to and from it. Unlike a standard echocardiogram, the echo transducer that produces the sound waves for TEE is attached to a thin tube that passes through your mouth, down your throat and into your esophagus. Because the esophagus is so close to the upper chambers of the heart, very clear images of those heart structures and valves can be obtained.
24 hour Ambulatory BP Monitoring
Ambulatory Blood Pressure Monitoring (ABPM) is when your blood pressure is measured as you move around, living your normal daily life. It is measured for up to 24 hours. A small digital blood pressure monitor is attached to a belt around your waist and connected to a cuff around your upper arm. It allows us to assess your blood pressure (BP) when you are away from the clinic and is more reflective of what your true BP is.
24 hour Holter Monitoring
24 hour Holter monitoring is for palpitations which occur every day. This device is hooked up to the patient’s chest for 24 hours and continuously records the ECG.
Trans-telephonic monitoring for palpitations which occur once in a few months. This device is usually a single ECG lead recorder that the patient brings home and uses it to record the ECG during the episode of palpitations. The recordings are then transmitted by the patient via a phone call to a cloud based software.
Ambulatory Heart Telemetry Monitoring
Ambulatory Heart Telemetry Monitoring is a battery-operated portable device that measures and records your heart’s electrical activity (ECG) continuously and remotely. It is wireless and is much more convenient to use than the holter monitor. Due to it’s ease of use, we can continuously record the heart rhythm for up to one week.
Signal Averaged Electrocardiogram (SAECG)
Signal Averaged Electrocardiogram (SAECG) is a special ECG technique in which multiple electrical signals from the heart are averaged to remove interference to reveal subtle abnormalities not visible in the conventional ECG. Presence of these abnormalities predict increased likelihood of potentially dangerous electrical heart rhythm abnormalities.
Cardiac resynchronization Study
This is essentially a comprehensive transthoracic echocardiogram (2D Echo) study in which additional information on movement of the walls of the heart is obtained. It is used to identify individuals with severe heart failure in spite of optimum medical therapy who may benefit from Cardiac Resynchronization Therapy (CRT-D).
Tilt Table Testing
This procedure is used to evaluate someone who presents with unexplained black outs/loss of consciousness. The patient is made to lie down horizontally strapped to a tilt table. The table is then tilted to a vertical position with continuous monitoring of his heart rate, blood pressure and ECG. If the patient blacks out, the test is terminated by immediately tilting the bed back to a horizontal position. This test is used to diagnose “vasovagal syncope” a reflex black out that tends to occur in young people.