Coronary CT angiography in the elderly

People over 75 years of age represent a specific group of patients for which the clinician is often in doubt about what to do, whether additional diagnostic workup is helpful or a primary medical approach would suffice. However, this patient population is less prone to the long-term effects of radiation burden or contrast medium-induced nephropathy, and therefore it may be especially worthwhile to use advanced imaging techniques such as contrast-enhanced CT in these patients. The following cases illustrate two common diagnostic problems, in which coronary CT angiography decided the clinical course.     

Mechanical aspects of CO2 angiography

The aim of this paper is to clarify some physical–mechanical aspects involved in the carbon dioxide angiography procedure (CO₂ angiography), with a particular attention to a possible damage of the vascular wall.CO₂ angiography is widely used on patients with iodine intolerance. The injection of a gaseous element, in most cases manually performed, requires a long training period. Automatic systems allow better control of the injection and the study of the mechanical behaviour of the gas.CO₂ injections have been studied by using manual and automatic systems. Pressures, flows and jet shapes have been monitored by using a cardiovascular mock. Photographic images of liquid and gaseous jet have been recorded in different conditions, and the vascular pressure rises during injection have been monitored.The shape of the liquid jet during the catheter washing phase is straight in the catheter direction and there is no jet during gas injection. Gas bubbles are suddenly formed at the catheter’s hole and move upwards: buoyancy is the only governing phenomenon and no bubbles fragmentation is detected. The pressure rise in the vessel depends on the injection pressure and volume and in some cases of manual injection it may double the basal vascular pressure values.CO₂ angiography is a powerful and safe procedure which diffusion will certainly increase, although some aspects related to gas injection and chamber filling are not jet well known. The use of an automatic system permits better results, shorter training period and limitation of vascular wall damage risk.     

Calcium scoring and contrast-enhanced CT angiography

Computed tomography (CT) technology has emerged as the most promising imaging modality for the noninvasive evaluation of the coronary circulation. Of the CT-based approaches, multidetector-row computed tomography (MDCT) and to a lesser extent electron beam computed tomography offer the potential of providing not only data on the spatial extent and burden of coronary calcium content, but also angiographic data, and plaque composition characteristics with the potential for prediction of susceptibility to future cardiovascular events. A number of studies have now confirmed that CT-based assessment of the presence and amount of coronary artery calcium provides incremental prognostic information over traditional risk factors in patients with coronary artery disease and can be employed to refine risk stratification in both asymptomatic and symptomatic subjects. With the advent of several recent advances in CT imaging, it is now possible to provide high resolution (sub-millimeter, isotropic voxels) images of the coronary arteries obtained rapidly with iodinated contrast injected peripherally. MDCT is currently the preferred modality for noninvasive contrast angiography of the coronary arteries by most groups, with a new generation of 64-slice scanners promising to further improve the results of this technique. MDCT-derived angiographic information in conjunction with coronary calcium scoring and plaque characterization has the potential of replacing invasive angiography, as it potentially could provide better global assessment of risk.