[Impact of both cardiac-CT and cardiac-MR on the assessment of coronary risk].

Today's definition of coronary artery disease (CAD) comprises two forms: obstructive and non-obstructive CAD. The 31-72% chance of a life-threatening event-like a myocardial infarction-with non-obstructive CAD is well documented in numerous studies. The objective in modern strategies of diagnosis and therapy should therefore be expedient identification of patients at high risk for coronary events, who will benefit from a customized therapy. Before initiating diagnostic procedures of CAD, a well defined strategy should be pursued. There are two possible primary objectives: ASSESSMENT OF THE INDIVIDUAL RISK FOR A CORONARY EVENT: Assessment of the individual "absolute" risk for a coronary event is not possible using single traditional risk factors. The individual risk can be estimated by integrating several of the traditional risk factors into a scoring system. These so-called risk scores (e.g. Framingham score and Procam score), however, have been associated with shortcomings: insufficient discrimination of high-risk from low-risk individuals. The calcium score has therefore become increasingly established; this Agatston score is independent of the traditional risk factors, so there is no correlation between Agatston and Procam scores. Today, the calcium score is considered the superior test for identifying individuals at high risk for a coronary event and its use is recommended by the European Society of Cardiology (ESC) guidelines for prevention of cardiovascular diseases. PROOF OR EXCLUSION OF A HEMODYNAMICALLY SIGNIFICANT CORONARY STENOSIS: Another concept is the definitive proof or exclusion of a hemodynamically "significant" coronary narrowing. The probability of an obstructive CAD is traditionally assessed by the type of chest pain, age, gender and stress-ECG. In patients with a low probability of an obstructive CAD, cardiac catheterization is not indicated, whereas in patients with a high probability of a hemodynamically significant coronary stenosis, an invasive strategy should be performed. Since non-invasive coronary angiography (CTA) with cardiac-CT has been shown to provide a high negative predictive value, CTA (with good imaging quality) is suitable for ruling out a significant obstructive CAD in the group at intermediate risk for an obstructive CAD. Another approach could be a functional test to initially prove a relevant, inducible myocardial ischemia: In a large cohort it was shown that patients will only prognostically benefit from revascularization procedures if the ischemic myocardial area is greater than 10%. Therefore, the assessment of the extent of myocardial ischemia is the domain of modern stress imaging tests. Stress-echocardiography and myocardial scintigraphy have almost the same sensitivity (74-80%, 84-90%, respectively) and specificity (84-89%, 77-86%, respectively), which are considerably higher than for stress-ECG. Cardiac MR is most suitable for the assessment of myocardial perfusion, because it traces the first pass dynamics of gadolinium at rest and during stress in reproducible slices at an acceptable spatial and a high temporal resolution without ionizing radiation. Whether the non-invasive coronary angiography with cardiac-CT and the Adenosin-perfusion imaging with cardiac-MR will completely replace diagnostic cardiac catheterization and stress-echocardiography as well as myocardial scintigraphy remains to be evaluated in further studies.