Tests
The goals of testing for heart disease are to distinguish between symptoms that are heart-related and those that are due to another condition. Testing is ordered to help determine which heart disease is present, to determine whether the disorder is acute or chronic, to monitor a cardiac event that is in progress – such as a heart attack, and to determine the severity and extent of the disease.
When a patient presents to the emergency room with acute coronary syndrome – a group of symptoms that suggest heart injury due to lack of blood flow – they are evaluated with a variety of laboratory blood tests and other tests. These are used to determine the cause of the pain and the severity of the condition. Since some treatments for a heart attack must be given within a short period of time to minimise heart damage, an accurate diagnosis must be quickly confirmed.
Heart disease that is causing few symptoms may be detected during a visit to the doctor for nonspecific symptoms such as fatigue. Doctors may order a variety of blood and other tests to investigate possible causes for the patient’s symptoms. Diagnosis of heart disease in these people may take time and patience.
Testing patients for existing heart disease is not the same as cardiac risk testing (which actually mostly determines risk of coronary heart disease). Cardiac risk testing is performed to screen asymptomatic people – to help determine their risk of developing coronary heart disease.
Laboratory Blood Tests
Cardiac biomarkers, proteins that are released when muscle cells are damaged, are frequently ordered when patients have symptoms of acute coronary syndrome, such as chest pain, pain in the jaw, neck, abdomen, back, or that radiates to the shoulder or arms, nausea, dyspnoea, and lightheadedness.
Tests include:
- Troponin - the most commonly ordered and cardiac-specific of the markers; will be elevated within a few hours of heart damage and remain elevated for up to two weeks
- CK-MB – one particular form of the enzyme creatine kinase that is found mostly in heart muscle and rises when there is damage to the heart muscle cells
- Myoglobin – a protein released into the blood when heart or other skeletal muscle is injured
- BNP or NT-proBNP – released by the body as a natural response to heart failure; increased levels of BNP, while not diagnostic for a heart attack, indicate an increased risk of cardiac problems in persons with acute coronary syndrome
Because BNP is also released by the heart when it is stretched, BNP is also measured in those who have swelling of the legs or abdomen, or shortness of breath, to see if heart failure may be present.
More general blood tests that may be ordered:
- Blood gases – performed to evaluate oxygen, carbon dioxide, and pH levels
- Electrolytes, kidney and liver function tests (E/LFTs) – a group of tests that evaluate organ function
- Full blood count (FBC) – looks at the body’s cells, checks for anaemia.
Other Evaluations
A range of other evaluations and tests are used to assess chest pain and other symptoms. These include:
- A medical history, including an evaluation of risk factors such as age, CAD, diabetes, and smoking
- A physical examination
- An electrocardiogram (ECG) – a test that looks at the heart’s electrical activity and rhythm
- Echocardiography – ultrasound imaging of the heart
Based on the findings of these tests, other procedures may be necessary, including:
- Stress testing
- Chest X-ray
- CT (Computerised tomography) scan
- Continuous ECG monitoring (sometimes also called Holter monitoring) – the patient wears a monitor that evaluates heart rhythm over a period of time
- MRI (Magnetic resonance imaging)
- PET (Positron emission tomography)
- Radionuclide imaging
- Cardiac catheterisation – in this procedure, a thin flexible tube is inserted into an artery in the leg and threaded up to the coronary arteries to evaluate blood flow and pressure in the heart and the status of the arteries in the heart
- Coronary angiography – X-rays of arteries using a radiopaque dye to help diagnose CAD; this procedure is performed during coronary catheterisation
- Tilt table test – ordered to evaluate syncope.
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