Computed tomography assessment of hemodynamic significance of coronary artery disease: CT perfusion, contrast gradients by coronary CTA, and fractional flow reserve review.

The need for functional estimation of the relevance of stenosis to guide appropriate treatment in coronary artery disease has recently been shown. Invasive coronary angiography (CA) with invasive measurement of the pressure gradient in patients with coronary stenoses becomes the method of choice for treatment decision-making in invasive cardiology. Coronary computed tomography angiography (CCTA) was established several years ago as a noninvasive alternative to invasive CA; it is used primarily to exclude coronary artery disease and has shown a very high negative predictive value in this regard. During the last several years, in an effort to obtain functional information, CCTA has received much attention. The rationale for this is that with the functional information provided by CT, the positive predictive value for "relevant" stenoses should be improved. In this article, the history and limitations of anatomic grading of coronary stenoses will be discussed. Furthermore, shifts in the treatment paradigm in modern cardiology will be introduced, as well as an overview of the currently used invasive methods to assess the "relevance" of stenosis. The current role and still-existing limitations of CCTA, as well as the systematic problems in comparing CA and CCTA, are addressed. As CCTA is a highly innovative technique, new innovations are currently under clinical evaluation, including myocardial perfusion imaging, attenuation gradient measurement, and assessment of fractional flow reserve with CT. This review article will mainly focus on the technical background of these techniques and the status of their clinical implementation and will attempt to provide some suppositions about the possible future role of these new innovations.