About the Investigations
Echocardiography
Cardiac interventional procedures
Electrophysiology studies & pacing
Nuclear Studies
General Cardiac Testing
Glossary of Terms
Transthorasic Echocardiography Transthoractic Echocardiography involves a safe, non-invasive ultrasound imaging procedure called an echocardiogram, sometimes referred to as an “Echo”. This procedure allows doctors to visualize the anatomy, structure, and function of the heart as it can show all four chambers of the heart, the heart valves, the blood vessels entering and leaving the heart, and the sack around the heart. It can lead to a quick diagnosis of heart valve problems or abnormal flow within the heart.
During an exam, a sonographer moves an ultrasound probe over the part of the body to be imaged. The probe functions as both a loudspeaker (to create the sounds) and a microphone (to record them). High-frequency sound waves reflect off internal structures (soft tissue, organs and blood flow), producing echoes that are processed into an image displayed on the ultrasound system monitor.
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Stress Echocardigoraphy
Stress Echocardiography is used to evaluate the function of the heart under conditions of stress to identify problems with the blood supply of the heart as occurs with narrowed arteries. Initially ultrasound imaging is performed to assess the heart function at rest. Then a treadmill stress test is performed to place the heart under stress. Immediately after the completion of this test further ultrasound imaging is performed to assess the function of the heart under stress conditions. This will identify areas that work poorly indicating inadequate blood flow and possible blockages of the coronary arteries. The test is referred to as a “Stress Echo”.
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Transoesophageal Echocardiography (TOE)
Transoesophageal echocardiography provides exceptionally high quality images of cardiac structures. The technique is important for the diagnosis of specific pathological conditions, such as diseases of the aorta, infections on heart valves and complex birth defects of the heart. The procedure is done in hospital as a day patient and involves patients having an intravenous drip and usually medications to relax. A long, flexible tube with an ultrasound probe on the tip is inserted into the oesophagus and the heart can then be viewed by ultrasound from the inside of the body. Observation is required for a short period of time after the test and the patient will need to be driven home.
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Cardiac Catheterisation (Coronary Angiography)
Cardiac catheterisation is an x-ray test that uses radiographic contract (dye) to visualise the coronary arteries and pinpoint the presence and severity of blockages and, more importantly to determine the best treatment available. If the test reveals blockages, the patient will be offered one of three treatment modalities: medications only, angioplasty or by-pass surgery.
The test is done as a day patient. The patient is usually mildly sedated but awake during the procedure. A local anaesthetic is used to numb the area (usually the right groin). Soft plastic tubes (catheters) are inserted into the artery and then advanced under x-ray guidance. The dye is injected into the heart chambers and coronaries and pictures are taken from different angles. This is one of the best tests available to find and visualise blockages.
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Percutaneous Transluminal Coronary Angioplasty (PTCA) or balloon angioplasty
The preparation for balloon angioplasty is similar to a routine cardiac catheterisation (see previous description) and is frequently performed at the same time of the initial catheterisation.
A thin plastic tube with a balloon at its end is placed at the level of the blockage and inflated for a few seconds to expand the artery. The balloon is then deflated and removed. The patient usually goes home the next day.
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Coronary Stents
A stent is a small screen in a tubular shape made out of stainless steel that holds the artery open. The procedure to put a stent in place is the same as that for a balloon angioplasty. After the blockage in the artery has been opened to some extent with a balloon, a second balloon with a small crimped stent is positioned at the place of the blockage and deployed. The expanded stent stays in the artery. The healing that occurs in the first 4-6 months will cover the stent, which then has become part of the artery wall. Stents have been shown to reduce the likelihood of re-blockages and are used in about 70-80% of angioplasties today. A stent may not be able to be used for a variety of reasons such as the artery being too small or the blockage being too far along the vessel or involving an important side branch. Patients are given medication after the procedure to prevent clotting.
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Electrophysiology Studies (EPS)
An Electrophysiology Study (EPS) tests the electrical system of the heart and is frequently used as part of the evaluation of patients with palpitations, blackouts and arrhythmias i.e. fast, slow or irregular beating of the heart. An EPS is a safe test which is usually performed as a day procedure in hospital with the patient under local anesthetic. A number of thin wires are threaded via the veins in the groin to the heart and positioned at various points in the heart chamber under x-ray guidance. The electrical activity of the heart is then measured to assess whether the conducting system is normal.
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Radio Frequency Ablation
After an initial EPS, a special catheter may be used to deliver radiofrequency to the precise area of the heart causing the abnormal heartbeat to stop the arrhythmia. This is called radio frequency ablation. This mode of therapy has a high rate of success, low incidence of complication and low recurrence.
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Cardioversion
When the heart becomes irregular (atrial fibrillation) or is too fast (tachycardia) it may need to be "re-set" electrically with the patient under general anesthetic and an electric shock is given to the heart. Although electrical cardioversion may be necessary on an emergency basis if patients are unstable with low blood pressure, it is usually performed electively as a day patient. Patients may need to stay in hospital for 1 to 2 days to monitor the heart rhythm if certain antiarrhythmic medications are used.
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Permanent Pacemaker Implantation
A pacemaker is an electronic device that prevents your heart from beating too slowly.
It consists of two parts: a generator (battery) and one or more electrodes (wires). The
electrodes carry electrical impulses from the generator to your heart and makes your
heart beat consistently.
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Implantable Cardio-Defibrilator (ICD)
An ICD is an electronic device that prevents your heart from beating too quickly. This fast heart beat usually arises from an abnormal heart rhythm called a ‘tachyarrhythmia’. The ICD consists of two parts: a generator (battery) and one or more electrodes (wires).
In a life threatening situation, these electrodes can correct fast heart rhythms by carrying electrical impulses or even an electrical shock from the generator to your heart. Modern ICD devices can also act as a standard pacemaker to stop your heart beating too slowly.
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Nuclear Studies (Nuclear myocardial perfusion studies)
A nuclear “perfusion” study examines the blood flow to the heart muscle. It is performed on an outpatient basis and is quite safe, and rarely attended by complications or side effects.
This test uses an IV injection of a small amount of a radioactive substance called an “isotope” which is eliminated from the body in one or two days. A special camera (gamma camera) is used to take pictures of the heart at "rest" and after exercise on the treadmill (sometimes on two different days).
If the patient cannot exercise, a "chemical stress test" will be used. This involves the use of an IV medication (instead of exercise) that increases the blood flow to the heart.
If there is a blockage in one or more of the arteries, there will be a "spot" or "defect". The size, number and degree of "darkness" of these spots will correlate with the number, location, and severity of the coronary artery disease. This test is frequently used to evaluate patients with chest pain or after an angioplasty to detect re-blockage of the dilated artery and after coronary by-pass surgery to assess the integrity and function of the by-pass grafts done.
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Electrocardiography (ECG)
An Electrocardiagram (ECG) is a record of the electrical activity of the heart. During this test, electrodes are placed on each arm and leg and at 6 points on the chest. If the ECG is abnormal, it may suggest different types of heart problems. The ECG can provide important information about the heart rhythm, a previous heart attack, increased wall thickness of the ventricles, signs of insufficient oxygen delivery to the heart muscle or an ongoing heart attack, and problems with conduction of the electrical signals from one part of the heart to another. A normal ECG does not exclude heart disease.
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Exercise Stress Test
A treadmill exercise test is basically continuous ECG monitoring during physical exertion with close attention to the blood pressure and heart rate. Its major use is to detect coronary artery disease (blockages in the coronary arteries). It is frequently used as part of the evaluation of patients with chest pain and arrhythmia (irregular heartbeats). It also provides assessment of the exercise capacity, circulation to the legs, and blood pressure response to exercise.
Firstly an ECG is recorded at rest and then the patient exercises on the treadmill at increasing speed and slope. One of the end-points of the exercise test is to achieve at least 85% of the age-predicted maximum heart rate. If a patient has a significant narrowing in the coronary arteries, the exercise may elicit chest discomfort (angina pectoris) or changes in the ECG. Although the regular treadmill test is extremely useful, it can occasionally miss coronary artery disease and is used in combination with other testing.
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Holter Monitor
A Holter Monitor is used to measure a patient’s electrical activity of the heart. It records a continuous electrocardiogram (ECG) during their everyday routine to detect abnormal heart rhythm. Five electrodes are attached to the patient’s chest, which are connected to leads and plug into the holter monitor recorder (about the size of a Walkman). The recorder is worn outside the patient’s clothing on a belt or shoulder strap for up to 24 hours.
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Ambulatory Blood Pressure Monitor
Ambulatory Blood Pressure (ABP) monitors are small, lightweight battery-powered units designed to take blood pressure and heart rate measurements for 24 hours. The monitors are carried in pouches that are strapped and/or belted to the side. Blood pressure and heart rate measurements are taken using a blood pressure cuff attached to the arm. Readings are automatically taken half hourly through the day and hourly at night.
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GLOSSARY OF TERMS
Angina
This term refers to midsternal, anterior chest pain due to a partially blocked coronary artery. It is often felt as a chest pressure like an elephant sitting on one’s chest, spreading to the inner aspect of the upper arm, neck and upper mid back. It can last anywhere from 5 to 10 or more minutes.
Hypertension
Systolic blood pressure persistently over 140mmHg, and diastolic blood pressure repeatedly over 90mmHg constitute hypertension. Theoretically, hypertension could result from an increase in cardiac output or in total peripheral resistance (caused by abnormally reduced arteriolar radius), or both. There are two types of hypertension: essential with no known cause and secondary resulting from an identifiable disease or condition.
Hyperlipidaemia
Cholesterol, is a major risk factor for coronary heart disease. A high level of cholesterol is referred to as hyperlipidaemia. Cholesterol is made up of HDLs - the protective cholesterol because it transports lipid out of the arterial wall; LDL referred to as the bad cholesterol and triglycerides which appear to increase risk factor further when LDL count is high. A normal cholesterol level is lower than 5.5mmol/L but in patients with known coronary disease their cholesterol should be less than 4mmol/L.
Heart Failure
The heart produces inadequate cardiac output and blood pressure to sustain the body’s requirements. Left ventricular failure and right ventricular failure may occur independently, or together as congestive cardiac failure.
Arrhythmias (irregular heartbeats)
An arrhythmia is an abnormal heart rate or rhythm. Normal cardiac rhythm originates from impulses generated within the sinus node, hence normal heart rhythm is called a sinus rhythm. When electrical activation of the heart begins in places other than that controlling the sinus rhythm it is known as a cardiac arrhythmia. An arrhythmia can be fast, slow or irregular beating of the heart.
Murmurs
Abnormal heart sound. Murmurs appear to result from vibrations set up by turbulent blood flow often through the heart valves. The following features of a murmur should be noted: its timing in the cardiac cycle, its location and radiation, its intensity and its quality.
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