From the Guidelines
When performing a CT scan of the heart, the constraint used is typically electrocardiogram (ECG) gating, which synchronizes the scan with the patient's heartbeat to minimize motion artifacts and provide clear images of the heart and great vessels. This technique is crucial for accurately assessing intracardiac anatomy, postoperative complications, and calculating cardiac output, shunt flow, and ventricular volumes 1. The use of ECG gating allows for the acquisition of high-quality images with low radiation doses, making it a valuable tool for patients with congenital heart disease (CHD) or other cardiac conditions.
The constraint of ECG gating is used in conjunction with other techniques, such as variable pitch and low-kilovolt scanning, to reduce radiation exposure and improve image quality 1. Additionally, the use of contrast media, such as low-osmolality agents, can help to enhance the visualization of the heart and great vessels, while minimizing the risk of adverse effects 1.
In terms of patient preparation, some studies have shown that lowering the heart rate to 60 beats per minute or less through the use of β-receptor blocking agents can help to decrease motion artifacts and improve image quality 1. However, this may not be necessary for all patients, particularly those undergoing scans on newer, higher-resolution CT scanners.
Overall, the constraint of ECG gating, combined with other techniques and patient preparation strategies, allows for the acquisition of high-quality images of the heart and great vessels, which is essential for accurately diagnosing and managing cardiac conditions.
Key points to consider when using CT scans to image the heart include:
- The use of ECG gating to minimize motion artifacts and improve image quality
- The importance of patient preparation, including the use of β-receptor blocking agents to lower heart rate if necessary
- The selection of appropriate scan protocols, including variable pitch and low-kilovolt scanning, to reduce radiation exposure and improve image quality
- The use of contrast media, such as low-osmolality agents, to enhance visualization of the heart and great vessels while minimizing the risk of adverse effects.
From the Research
Constraint in CT Scan for Heart Imaging
- The constraint in CT scan for heart imaging refers to the need to minimize the amount of contrast media used while still obtaining high-quality images 2.
- This is particularly important in patients with chronic kidney disease (CKD) or those at risk of contrast-induced nephropathy (CIN) 3, 4.
- The use of isoosmolar contrast media (IOCM) versus low-osmolar contrast media (LOCM) has been studied, with some research suggesting that IOCM may not be associated with a significant benefit in preventing CIN 4.
Imaging the Heart with CT Scan
- Coronary computed tomography angiography (CCTA) is a non-invasive testing modality for coronary angiography that uses CT scans to image the heart 5, 2, 6.
- CCTA has been shown to have high sensitivity and specificity for detecting obstructive coronary artery disease, even in patients with advanced kidney disease 5.
- The technique involves injecting a contrast agent into the bloodstream, which highlights the coronary arteries and allows for visualization of any blockages or stenosis 2, 6.
- Advances in cardiac CT contrast injection and acquisition protocols have improved the quality and safety of heart imaging with CT scans 2, 6.