Computed Tomography of the Heart: Treatment, Effects & Risks

Computed tomography of the heart (CT) is a well-established diagnostic imaging modality that is becoming increasingly important in the field of coronary heart disease due to the use of high-resolution scanners. Tomography is derived from the Greek words “tomós” meaning cut and “gáphein” meaning to write. It is a radiological procedure for the three-dimensional imaging of organic structures. To achieve optimal diagnostics, cooperation between cardiology, diagnostic radiology, and internal medicine intensive care is essential.

What is computed tomography of the heart?

Cardiac computed tomography produces cross-sectional images of cardiac anatomy and gives cardiologists the ability to assess atherosclerotic processes in the coronary arteries. The different types of tissues and organs are clearly visible on the CT image thanks to the contrast gradation used. Computed tomography is an important tool for many medical issues, including heart disease. Cardiac computed tomography produces cross-sectional images of the heart anatomy and enables the cardiologist to assess atherosclerotic processes in the coronary arteries. Coronary stenosis can be detected or ruled out, making invasive diagnosis by cardiac catheterization unnecessary. Physicians perform the examination using electron beam tomography and multi-slice spiral CT. The main applications for this diagnostic imaging technique are calcium score determination, CT angiography of coronary vessels, CT angiography of bypass vessels, and examinations of the aorta and pulmonary veins. Cardiac computed tomography is also recommended in the case of complaints directly attributable to the heart, such as acute chest pain without ECG changes and current-onset heart failure.

Function, Effect, and Objectives

Computed tomography of the heart places high demands on both physicians and technology. To obtain optimal images given the heart’s inherent motion, cardiologists use the most advanced “second generation dual score” devices on the market. In these innovative scanners, two X-ray tubes rotate around the patient lying on his back three times per second. In less than half a second, the patient’s heart is scanned and the electrical cardiosignal is recorded by means of an electrocardiogram (ECG). As a result, the scanner provides an image data set that shows an apparently stationary heart, eliminating artifacts due to cardiac motion. The calcium score is determined by a non-contrast CT scan, which is used to detect or exclude and quantify coronary calcification. The diagnosed value is known as the Agatston-equivalent score and provides an indication of the risk of myocardial infarction. Based on these examination values, cardiologists determine the therapy strategy for patients with cardiovascular risk factors. For assessment, physicians use nomograms (diagram) based on the examination of large patient collectives. Patients are at increased risk if the critical threshold or absolute value of 400, as determined by the nomograms, is exceeded. This high-risk constellation requires intensive therapy. CT angiography (X-ray examination of the vessels) is a rapid, high-resolution imaging of the coronary arteries. To perform this examination, the patient is injected with an iodine-containing contrast agent via a peripheral indwelling vein catheter. This is usually placed on the back of the hand or in the crook of the elbow. To lower the heart rate, the patient takes a beta blocker before the examination. The breath-holding period is ten seconds. This non-invasive examination is very close to the insertion of cardiac catheters, since the spatial resolution of the devices used is 0.33 mm, which is very close to the value of cardiac catheterization (0.3 mm). However, this method replaces cardiac catheterization only in the case of certain issues. Angiography, in contrast to calcium score determination, shows complete vessel contouring including soft plaque deposits in addition to calcification (calcium deposition in tissues). Through this imaging, cardiologists are able to exclude or detect coronary stenosis with high accuracy.Three-dimensional processing of the data provides an additional plastic demonstration of the findings obtained. Angiography of vessels assesses the cardiac situation of patients who have undergone surgical bypass surgery and, in contrast to angiography of coronary vessels, records a greater distance of the chest, since the outlets of the “bypass vessels” are located further away from the heart. Patients who are difficult to examine by cardiac catheterization or who are suspected of early occlusion are submitted to this cardiac computed tomography of the “bypass vessels”. Other areas of application include imaging diagnostics of the pulmonary veins after stent implantation and ablation to eliminate atrial fibrillation. Furthermore, this innovative technology is used in the field of coronary vein morphology (prior to CRT), pericardial diseases (pericarditis), myocardial function (heart muscle, heart wall), congenital heart diseases and diseases of the aorta (main artery). Follow-up imaging of stents in coronary vessels is possible. However, image quality depends on the location, size, and metal type of the stent. Cardiac CT is also useful for regular follow-up of patients after heart transplantation. Cardiac computed tomography also images the heart valves very accurately. For patients recommended for catheter-based replacement of the aortic valve, the cardiologist can use the CT scan to determine the correct size of the prosthesis before deployment.

Risks, side effects, and hazards

The indication for cardiac computed tomography must be made precisely because of the X-ray radiation that unfortunately cannot be avoided. Before the examination, the cardiologist checks the patient’s renal function (keratin levels, eGFR). In patients taking metform-containing drugs for diabetes mellitus (diabetes), an interaction with the contrast media cannot be ruled out. The attending physician may have to temporarily discontinue the medication to prevent kidney damage. Pregnancy and allergic reactions to the contrast media must be ruled out before any X-ray examination. In contrast to the previous technology, the new generation devices ensure reduced X-ray radiation. With this reduced risk, coronary CT is a recommendable alternative to cardiac catheterization, scintigraphy (nuclear medical examination) and stress MRI for certain questions. A major advantage of cardiac computed tomography is the nonexistent risk of an invasive procedure. Disadvantages are seen in the lack of possibility of direct intervention such as stent implantation and balloon dilation (balloon dilatation). Cardiologists are limited in their assessment of CT images in cases of severe calcification, arrhythmias, and implanted stents. If indicated, private but not public health insurers cover the cost of this self-pay service.