From the Guidelines
A calcium coronary artery CT scan does not require dye, as it is used to detect and quantify calcium deposits in the coronary arteries without the need for contrast media. This is in contrast to a coronary CT angiogram, which does require intravenous injection of iodinated contrast media to visualize the inside of the coronary arteries, as stated in the American Heart Association's scientific statement on noninvasive coronary artery imaging 1. The use of contrast media in coronary CT angiography is necessary to evaluate the presence of coronary artery stenosis, but it also carries risks such as nephrotoxicity and anaphylactoid reactions.
The calcium scoring CT, on the other hand, is a quick and non-invasive test that uses computed tomography to measure the amount of calcified plaque in the coronary arteries. Key benefits of this test include:
- No need for injections or contrast media
- Simple procedure with no special preparation required
- Valuable screening tool for people with intermediate risk factors for heart disease
- Produces a score that reflects the total amount of calcium in the coronary arteries, with higher scores indicating greater risk of future cardiac events.
It is essential to note that while the evidence from 1 highlights the limitations of coronary CTA, including the need for contrast media, it does not apply to calcium coronary artery CT scans, which can be performed without dye.
From the Research
Calcium Coronary Artery CT Scan
- A calcium coronary artery CT scan can be performed with or without dye, depending on the specific protocol and equipment used 2, 3.
- Some studies have shown that contrast-enhanced CT scans can be used to measure coronary artery calcium scores, potentially eliminating the need for a separate non-contrast scan 2.
- However, other studies have found that non-contrast CT scans may be more accurate for detecting and quantifying coronary artery calcium 4.
- The use of dye in a coronary artery CT scan may affect the measurement of ionized calcium levels in the blood, with some contrast media causing a prolonged decrease in ionized calcium levels 5.
Detection and Quantification of Coronary Artery Calcium
- Non-contrast CT scans have been shown to be reliable for detecting and quantifying coronary artery calcium, with high sensitivity and specificity compared to dedicated calcium-scoring CT scans 4.
- Visual assessment of coronary artery calcium on non-contrast CT scans has also been found to be predictive of major adverse cardiac events, even among hospital inpatients 6.
- The Agatston score, which is a measure of coronary artery calcium, can be accurately measured from contrast-enhanced cardiac CT scans using a Hounsfield unit threshold of 320 2.
Clinical Implications
- Routine reporting of coronary artery calcium on all chest CT examinations, regardless of clinical indication and contrast material administration, may help identify patients with previously unknown coronary artery calcium who may benefit from preventive treatment 3.
- Incidental detection of coronary artery calcium on non-contrast CT scans may provide prognostic information that is independent of cardiovascular risk factors, and may help guide aggressive risk factor modification in high-risk patients 6.