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Cardiac tests in primary care - exercise testing

Over the coming months cardiologists Dr Clive Handler and Dr Gerry Coghlan will discuss eight commonly used tests in primary care. This week, exercise testing

Over the coming months cardiologists Dr Clive Handler and Dr Gerry Coghlan will discuss eight commonly used tests in primary care. This week, exercise testing

The purpose of exercise testing is to assess reversible myocardial ischaemia. The result provides both diagnostic and prognostic information. Patients are usually asked to sign a consent form, although the risk of death (one in 100,000), infarction or ventricular arrhythmia requiring treatment is very low. A profound vagal response is also uncommon and resolves quickly when the patient lies down or, if necessary, is given atropine.

The test

Patients are exercised on either a cycle or a treadmill. Many patients prefer a cycle. Only the resistance increases on a cycle, but the inclination and speed can increase on a treadmill, and patients may feel unsteady. Cycles take up less space, are quieter and, because there is less upper body movement, the ECG quality may be superior. But some patients find cycling difficult.

Although anti-anginal medication, including ß-blockers, may decrease the sensitivity of exercise testing, most cardiologists do not advise patients to stop taking these drugs before the test, because of logistics and the small risk of withdrawal symptoms.

Exercise endpoints

Patients are usually exercised to their maximum tolerance. The test is stopped if they cannot continue because of fatigue, breathlessness, claudication or dizziness, or if they develop angina, ST depression or important arrhythmias, or their heart rate or systolic blood pressure fail to increase appropriately. Patients then lie or sit down until they and their heart rate and BP have recovered and the ECG changes have resolved. Glyceryl trinitrate (GTN) may be given to patients who develop angina.

Value and limitations of the test

41209453The test is of most diagnostic use in patients at intermediate risk of CHD.

A ‘negative' result will probably be a false negative in a patient with a high probability of CHD, and a ‘positive' result will probably be a false positive in a patient with a low probability of CHD.

Exercise testing adds no diagnostic information about the likelihood of the presence of CHD in patients with previous MI, those with previous revascularisation and those with angina. However, it does provide prognostic information. It is commonly used to assess recurrent or new symptoms in patients who have had angioplasty or coronary artery surgery. An exercise test result that shows no ischaemic or haemodynamic abnormalities has a high negative predictive accuracy in a patient with a low risk of having CHD.

It provides an objective assessment of fitness and exercise capacity and is helpful in the evaluation of patients who complain of undiagnosed breathlessness.

It has a lower predictive accuracy in women, although the reason is not clear. The ST response to exercise is the hallmark of myocardial ischaemia, but this cannot be interpreted in patients with an abnormal ST segment at rest. This includes patients with bundle branch block and pre-excitation syndromes. Nevertheless, exercise tolerance, vulnerability to exercise-induced arrhythmia and symptoms can be evaluated.

Markers of a poor prognosis

Any of the following features suggest left ventricular impairment and/or significant coronary artery disease and therefore a poor prognosis:

• poor exercise time (less than 10 minutes)

• failure of the systolic blood pressure or heart rate to increase during exercise

• ischaemia (angina and/or ST depression) at a low heart rate and workload

• frequent ventricular ectopic beats or ventricular tachycardia

• ST elevation in Q-wave-bearing leads after infarction

• slow resolution of ST depression and heart rate after exercise.


Dr Clive Handler is consultant in pulmonary hypertension at the Royal Free Hospital, London

Dr Gerry Coghlan is consultant cardiologist at the National Pulmonary Hypertension Unit, Royal Free Hospital, London

This article is based on a chapter in Management of Cardiac Problems in Primary Care by Dr Clive Handler and Dr Gerry Coghlan, published by Radcliffe. Radcliffe Publishing is offering a 20% discount on this book to Pulse readers (usual price £29.95+p&p, offer price £23.96+p&p).

To claim, order via www.radcliffe-oxford.com or by telephone on 01235 528820. Please quote discount code ‘Pulse'. Offer expires 31 May 2009

Exercise testing is the most valuable test in patients with suspected CHD Advice for patients Advice for patients

- An exercise test or stress test is used to assess the blood supply to your heart muscle.
- It also tests your fitness and strength, the state of your heart muscle and your blood pressure response to exercise.
- It is used to test a variety of different conditions and is very useful and safe, in fact exercise tests can be carried out in patients within a day or two of a heart attack.
- You should wear a tracksuit or similar light, comfortable clothes and shoes.
- Men may need to have their chest hair shaved.
- Women should wear a comfortable bra and bring a loose-fitting shirt because electrode pads are stuck on the chest and connected to an ECG machine.
- You will exercise on either a cycle or a treadmill.
- Some cardiologists suggest you stop some of your tablets, such as ß-blockers, before the test, but others don't.
- Do your best during the test and let the technician or doctor know if you want to stop or if you get chest ache or tightness or breathlessness.
- During the test your ECG and blood pressure will be recorded.
- The cardiologist will see you in clinic or one of the team will see you after the test to explain the result and tell you whether any other tests are necessary.

indications

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