Cardiac CT Scan
From 1 July 2011, the federal government/Medicare will reimburse for Computed Tomography of the Coronary Arteries under certain conditions: If the procedure is performed on a minimum of a 64 slice (or equivalent) scanner, where the request is made by a specialist or consultant physician, and: a) the patient has stable symptoms consistent with coronary ischaemia, is at low to intermediate risk of coronary artery disease and would have been considered for coronary angiography; or b) the patient requires exclusion of coronary artery anomaly or fistula; or c) the patient will be undergoing non-coronary cardiac surgery (for example, aortic valve replacement surgery). These above items can only be claimed if the procedure and report were performed by a specialist or consultant physician recognised by the Conjoint Committee
Calcium score is a numerical value that quantifies the amount of calcium found along your coronary artery. Calcium deposited on the rim of the coronary artery is solely the result of coronary atherosclerosis, and NOT from ingesting calcium. A calcium score of 0 means there is no calcified coronary artery disease ( Unable to visualize Non calcified coronary disease ) . A high calcium score (more than 400) is very concerning for the high likelihood of established severe coronary artery disease, even if you are asymptomatic. Sometimes, a calcium score may be the only CT portion of the test required, especially among younger individuals, or for individuals who are planning to undergo very frequent (annual) testing, in order to reduce the amount of radiation exposure.
See a movie of a Rotating coronary tree and a Rotating heart. This test is one of the single most important advance in the development of non-invasive heart and coronary artery imaging. Multi-slice CT (MSCT) coronary angiogram allows doctors to determine if an individual has any coronary artery narrowing even before symptoms develop. Through an intravenous drip in the elbow, contrast dye is injected, and the person is asked to hold his/her breath for about 10 -15 seconds, and lie very still. After the CT scanner has obtained the X-ray images, the person is allowed to go home, a procedure which takes approximately 60 minutes. MSCT allows us to “look” into and through the heart and any structures that are within the heart. This include the sac around the heart (pericardium). Next, coronary arteries, their walls and contents (cholesterol plaques) are prominently and accurately quantified and measured. Hardened cholesterol plaques develop calcium, which can be quantified into a format (Calcium Score) to predict future cardiovascular events like heart attacks. Individuals at high risk for a heart attack, with risk factors such as diabetes, high blood pressure, high cholesterol, smoking, and family history of premature heart disease, will benefit from knowing if they harbour any (asymptomatic) coronary artery blockages.
If you believe you will benefit from having a CT coronary angiogram to check the status of your coronary arteries, you may obtain a request slip/form (see top) and discuss with your doctor about having the test performed.
Contra-indications to Cardiac CT
1.Atrial fibrillation, bigeminy, trigeminy, high-grade heart block.
2.Frequent atrial or ventricular ectopic beats.
3.Unable to hold breath or lie still for ~ 15-20 seconds.
4.Inability to control heart rate to less than 80 BPM (discuss first).
5.Renal impairment (Creatinine > 200 μmol/L – please discuss).
6.Anaphylactic reaction to contrast.
7.Morbid obesity (Please discuss if patient is over 150 kg).
8.(Atrial fibrillation is not a contra-indication if patient is undergoing scan for preparation prior to EP ablation procedure or biventricular pacemaker).
Patient preparation for Cardiac CT
Patients may need beta-blockers – routine target heart rate of < 60 BPM. Routine dose: Metoprolol 50mg PO 12 hours and 1 hour prior to exam. Verapamil 80 mg may be used for severe asthma, COPD.
Patients note the following:
• Usual food/fluids and routine medications for 4 hours prior.
• No heavy or regular exercise 24 hours pre-study.
• No Cialis, Viagra, or Levitra for 36 hours pre-study.
• No caffeine containing products for 12 hours pre-study.
• Omit Metformin for diabetics on the day of the procedure.
• Arrive early and in a calm and relaxed manner.
• The slower and more regular the heart beat, the better the images.