It was apparent for some time that running on a treadmill with leads over the heart an “exercise ECG” was too inaccurate for diagnosing coronary artery disease, as it missed many cases of coronary artery disease. However invasive coronary angiography, where a tube is passed around to the heart, has a small risk of serious complications.
There was, therefore, a need for non-invasive tests to assess the coronary arteries. Four main tests have been developed-
1. Coronary CT Angiography
NICE recommend Coronary CT Angiography. However, it is not suitable for everyone and if there is substantial coronary calcification/ degeneration in the arteries, it will not give an accurate result. In general it is very accurate, and it will detect tiny amounts of coronary artery disease that the other tests will miss but that still need treatment.
The test is simple to perform-the patient lies in a scanner and whilst the scan is done and X-Ray contrast medium is injected into an intravenous drip in a vein in the arm. It is painless and takes about 30 minutes.
Coronary CT Angiogram of a very nice 56-year-old man who had experienced chest discomfort whilst playing golf. Following this scan he had coronary stenting to the severe narrowing and has had no chest discomfort since.
2. Myocardial Perfusion Scan
This involves injecting radio-isotope in into an intravenous drip in a vein in the arm. It is painless, 2 scans need to be done, one with the heart at rest and one with the heart working harder, each taking about 30 minutes.
A myocardial perfusion scan in an 80-year-old lady showing an area of the heart whose blood supply is compromised by a coronary narrowing.
Both of the above tests use some radiation which will increase the lifetime incidence of cancer by about 1/1000
3. Stress Echocardiogram
A stress echocardiogram is basically the same as an echocardiogram, except that images are taken during a period when the heart is made to work harder. The heart can be made to work harder “stressed” by either getting the patient to exercise or injecting a medication that stimulates it to work harder.
4. Cardiac MR Scan
The test is simple to perform-the patient lies in a scanner and whilst the scan is done a contrast medium and a medication to make the heart work harder is injected via an intravenous drip in a vein in the arm. It is painless and takes about 45 minutes.
Both the stress echocardiogram and MR scan do not use any radiation.