Diagnosis of Coronary Artery Disease
Nowadays, there are two main methods to diagnose coronary artery disease.
1. Coronary Angiography (CAG) is the gold standard for identifying the blocked coronary arteries. This method provides the most accurate result.
- Proper treatment can be immediately performed by balloon angioplasty or percutaneous coronary intervention (PCI).
- It poses some risk for complications, e.g. dissection, because the catheter has to be inserted into an artery from a patient’s groin or arm or wrist to be carefully threaded to coronary arteries. However, such risk is very slight under the expert treatment of qualified doctors.
- It is quite costly.
- Patient needs to remain in hospital for 4-24 hours after the procedure.
1. Coronary Computed Tomographic Angiography (Coronary CTA)
CT technology has been rapidly evolving over the past several years. It now provides a high-resolution and high-contrast image of a small and beating organ such as the heart.
Patients undergoing a Coronary CTA scan receive an iodine-containing contrast dye as an intravenous solution to ensure the best images possible. During the examination, this usually takes about 10 minutes, x-rays pass through the body and are picked up by special detectors in the scanner.
- MDCT (Multi-Detector Computerized Tomography) procedure can be performed in a short time.
- Patient is not required to stay in hospital after the procedure.
- It delivers a high accuracy of over 90% in detecting coronary artery disease.
- It takes around 1-2 hours for image processing after the actual scan.
- Patient must have a regular heart rate and can hold the breath for about 10 seconds for each scanning with the newer generation of CT scanner. These requirements become unnecessary.
Who should undergo MDCT?
Patients who should undergo MDCT are:
1. Patients who have the following risk factors of coronary artery disease
- Heavy smoker
- People who have a history of coronary artery disease within their family
2. Patients who are suspected of having coronary artery disease
- Having chest pain
- Electrocardiogram (ECG) or exercise stress test (EST) cannot clearly identify the abnormalities.
3. Patients who have been treated for coronary artery disease by balloon angioplasty (PTCA) or percutaneous coronary intervention (PCI) or coronary artery bypass graft surgery (CABG), and need to see the result for further treatment.
Preparation for Examination
Preparation is similar to CT scanning of other parts of the body. Patients should not eat any food at least four hours before examination, except drinking water. However, before the procedure, they should not drink tea, coffee, and any beverages or medicines that stimulate the heartbeat rate.
Who should not undergo MDCT examination and injection of a contrast medium into veins?
Since patients are exposed to x-rays during the examination, those who are pregnant or suspect that they are should not undergo this examination.
Injection of a contrast medium into patients’ veins is required for the MDCT examination. Therefore, the patients with the following diseases or symptoms are not recommended for this test because they might be severely allergic to contrast medium or have acute renal failure.
1. Severe asthma
2. Renal disease with high creatinine level or chronic renal failure
3. A history of severe allergy to seafood or contrast medium from x-ray examination
However, if patients who have the above diseases or history need to be treated by this method, they are required to inform hospital personnel in advance.
Risk and Complications
1. Adverse event from a contrast medium can happen to some patients in the form of rashes, hives, swelling or respiratory symptoms. However, the chance is minimal.
2. Amount of x-ray radiation: The proper and safest amount of x-ray radiation is carefully exposed to each patient. The amount from this examination is in a range of 6-13 mSv, which is similar to the amount of natural radiation we would be exposed to over two or three years.
After the Examination
1. Drink plenty of water because the contrast medium is removed from the body via urine.
2. Patients may have allergy, such as rashes or hives, several hours after the injection of the contrast medium. However, the chance is minimal. If such symptoms occur, immediately see doctors.