Cardiac Tests



Patient Perspective Paper 10

These notes are a patient’s view on the tests used on cardiac patients following a discussion at a meeting of the Oxford ICD Group led by Elaine Watson of JRH. You might like to refer to the various booklets on the subject and these are amongst the stock of information, which I bring to every meeting of the Group.

I must emphasise once again that notes such as these are very much my personal interpretation and I apologise but take no responsibility for any inaccuracy. If you are worried in any way concerning your own position, please consult your own doctor or consultant. Remember that you have an ICD which monitors you for certain conditions every second of every day, particularly for the very dangerous VF fibrillation.

Blood pressure. This is probably the first test you will have. High blood pressure is common for anyone over the age of 65 – probably an incidence of 6 out of very 10 people will have it. In short, high blood pressure makes you more likely to have a heart attack or stroke. There is no such thing as “normal” blood pressure (we are luckily all different) but for a heart patient it is suggested that a reading of less than 130/80 mmHg is acceptable. The higher figure denotes the systolic pressure when the beat or contraction in the heart forces the blood round the body and the lower reading is the diastolic pressure which is the lowest pressure that occurs when the heart is resting between heartbeats. There is no single cause of high blood pressure but an abnormal reading will flag up problems in your medical condition, how you live or what you eat.

If it is below 90/60, you may have a low blood pressure. This may be caused by a drug you are taking and therefore this is why blood pressure is always checked for those who are taking a lot of different drugs. Otherwise in most people there is no need for treatment just be careful when bending down or getting out of bed too quickly.

You may be asked to carry a monitor for 24 hours. The cuff round your arm inflates every hour or so and a monitor on your waist records your pressure.

Pulse. Your pulse is taken for 30 seconds. The AA believes that you can do this for yourself (Know your pulse). Any irregularities in your heart beat can be recognised. It is important to state that we all suffer irregular heart beats from time to time so, if you believe that it has happened to you, do test it for two more periods of 30 seconds.

Electrocardiogram (ECG). An ECG records the electrical activity of your heart . Electrodes are attached to your arms, legs and chest and these are connected to an ECG recording machine. This picks up the electrical signals from the heart and, by careful analysis of the result, abnormalities can be detected. This is probably the first test administered in any cardiac emergency by a GP or hospital A&E department.

Exercise Test. An ECG machine is connected to you whilst you are walking on a treadmill or using an exercise bike. The doctor will look at any changes in the ECG pattern to determine whether you have coronary heart disease (CHD) or how severe this might be. For instance the exercise might show that there are changes in the amount of oxygen supplied to your heart. Any levels of pain can be quickly ascertained as to whether these are originating from the condition of your heart. Those with an ICD already fitted are carefully monitored to ensure that the parameters of the ICD are not breached by the conditions of the test. It is also important to state that as you go through the test in order to reach about 85% of your maximum heart rate, you are very carefully monitored and the test is immediately stopped if you are in any danger.

24 hour ECG Recording. You are fitted with a machine (usually fitted round the waist with wires to your chest) to monitor your ECG for a full 24 hours. This will show up any episodes (such as palpitations) that occur only occasionally. You may be asked to keep a diary to note the times of any pain and what you were doing at the time.

Cardiac event recorder. If you have infrequent episodes of palpitations or collapse, the doctor might still need more information in order to treat you successfully: you may then be asked to have an event recorder. It might be something portable which you hold to your chest when you feel symptoms or it might be an implantable loop recorder (ILR) which is placed under your skin. The advantage of an ILR is it stores information from before the time you experience the symptom (e.g. before you collapse!)

Chest X-ray. A chest x-ray allows closer examination of the heart, lungs and chest wall. If you have shortness of breath, it can help doctors find out whether this is caused by a heart or lung condition.

Echocardiogram. This is a machine that uses sound waves (ultrasound) that echo against structures in your heart to build up detailed picture of your heart. It displays heart chambers and the major blood vessels. It is regularly used to assess people with disease in the heart valves and to assess any damage of the heart caused by a heart attack. It is useful to use with babies, as it is not traumatic in any way, to analyse any congenital heart defects.

Sometimes an echocardiogram can be taken from the gullet behind the heart using a small probe inserted into your stomach. Very occasionally an echo is taken under stress induced by exercise or a suitable drug to increase the heart rate whilst the test is being administered.

Coronary angiogram. This procedure, once rare, is now coming more common as a routine procedure to examine the condition of the arteries or the left ventricle. A catheter is inserted through your groin or your arm and the operator uses X-ray screening to position the catheter into the correct position in your body. A dye is then injected into you. This shows up all the coronary arteries on the X-ray screen so that the doctors can see whether there is any narrowing or are blockages in your arteries. A heart monitor checks your pulse and rhythms whilst this is being administered. See Patient Perpective – Angioplasty.

CT Scan. This uses a sophisticated type of X-ray and a dye but does not need the insertion of a catheter. A CT scanner is sometimes used to assess the amount of calcium in an artery as normal healthy arteries do not contain calcium. I am told that these tests are rarely used in our NHS.

Myocardial perfusion scan. You will be injected with a small amount of a radioactive isotope into your bloodstream. A large camera picks up the gamma rays sent out by the isotope as it passes through the heart. The test assesses the blood flow to the heart muscle and to determine what areas of it have decreased blood flow. This may be carried out in two parts, once at rest and then under the stress of exercise or a stimulation drug.

MRI Scan. You will lie in a short tunnel around which is a large magnet. You will be subjected to short bursts of magnetic fields and radio waves to allow images which can be analysed to show the structure of your heart and blood vessels. It is not routinely used to diagnose CHD but it can very useful to detect when the heart is working abnormally through a defect in the structure of the heart. An ICD has to be switched off, as it will be affected by the strong magnetic field.

Tilt table. This test is used for people who have had frequent episodes of fainting or collapsing. This may be particularly important if you are in a job where a collapse will put you and others in danger. You will be asked to lie on a special bed which will slowly be adjusted so that you move into an upright position whilst your blood pressure and heart rhythms are measured.

Electrophysiology Studies (EPS). A specialist heart rhythm cardiologist will insert flexible tubes (catheters) into a vein in your groin or neck area and with the aid of x-rays the catheters are moved into position in your heart. The electrode tip of the catheter stimulates your heart and picks up recordings of electrical activity from the specific areas being investigated. Extra beats are sometimes administered to find where any abnormal heart rhythm is coming from. If the problem is found immediately the cardiologist may decide to treat you immediately by using radio-frequency electrical energy to destroy the areas of the heart which are causing the abnormal rhythm: this treatment is called catheter ablation treatment.

Genetic testing. It is possible that inherited heart conditions (cardiomyopathy) are passed through families via genes. Members of a patient’s family are investigated using some of the tests mentioned above. Blood tests are sent to a specialist genetics laboratory to investigate DNA to find the possibility of altered genes. DNA tests administered to seemingly healthy people can raise complicated medical and ethical issues in families.

Risk. Any clinical test involves some risk. Obviously the possible benefits must be greater than the assessed risk for any test to be carried out. Some tests involve radioactive substances or the use of x-rays.

Medication monitoring. If you are using drugs, you will be given regular blood tests to determine whether any side-effects are taking you outside safe limits. I talk about some of these in the Perspective on Drugs (no 2).

References.
Geoff Shaw
GCS/24.05.10