Evidence-based application of cardiac magnetic resonance and cardiac computed tomography for primary diagnosis of stable coronary artery disease with special attention to disease management programs and the German National Medical Care Guidelines

摘要

BACKGROUND AND PURPOSE: Despite all the progress made in diagnosis and treatment, cardiovascular diseases remain the no. 1 cause of death worldwide. In 2005, 27.9% of males and 24.1% of females (eight times more than for mammary carcinoma) in Germany died of coronary artery disease (CAD). Although mortality rates following acute myocardial infarction have considerably dropped, morbidity has increased--people are getting older, but they are getting older sick. The resulting need for reduction of CAD morbidity can only be achieved by truly early detection of patients at high coronary risk before occurrence of a coronary event. Modern imaging techniques like cardiac magnetic resonance (MR) and cardiac computed tomography (CT) are being increasingly utilized. The goal of this review is the practical application of evidence-based recommendations by relevantly and cost-effectively implementing cardiac MR and cardiac CT with special attention to current national and international guidelines and recommendations. THE PATIENT WITH STABLE CHEST PAIN: The primary objective here is to ascertain if the described symptoms can be attributed to a stenosing CAD with inducible myocardial ischemia or if they are effected by extracardial sources. As always, patients' history, examination findings and the stress ECG play the major roles. The conventional approach prescribes that an abnormal resting ECG compromising the interpretation of a stress ECG, should immediately be followed by an imaging ischemia diagnosis technique, like stress echocardiography, myocardial scintigraphy or cardiac MR (recommendation I B). This also holds true when a stress ECG is assessable and the probability of a stenosing CAD is between 10% and 90% (recommendation I B or "appropriate"). Alternatively, "modern" procedures allow imaging ischemia diagnosis to be replaced by noninvasive coronary angiography using a CTA (recommendation IIa B). If the image quality by CTA is assessable (free of artifacts and no disruptive calcified plaques) and no coronary stenosis can be found, the coronary diagnosis process may at this point be terminated, avoiding superfluous cardiac catheterizations. If the CTA shows the possibility of a higher-grade coronary stenosis, a cardiac catheterization examination with stand-by PCI (percutaneous coronary intervention) can be performed. THE ASYMPTOMATIC PREVENTION PATIENT: The prim ary objective in cardiovascular primary prevention is the avoidance of a first myocardial infarction and/or a first stroke. Current guidelines for prevention of cardiovascular diseases recommend administration of acetylsalicylic acid (ASA) and a statin when risk>20%/10 years (recommendation I A). The coronary calcium score has a strong predictive power which is independent of conventional risk factors and thus offers the most relevant information in addition to Framingham, PROCAM or ESC scores regarding coronary risk. For patients initially showing "intermediate" coronary risk (10-20%), guidelines suggest the determination of the coronary calcium score, which leads to better risk assessment and to identification of patients needing more aggressive lipid lowering (recommendation IIb B). Thus, the cardiac CT, on the one hand, aims the intense risk reduction needed in primary prevention to the high-risk patients, on the other hand, it avoids "superfluous" cardiac catheterizations, unnecessary statin therapies and potentially harmful ASA administrations. However, the proof of coronary calcium must not be confused with the presence of coronary artery stenoses: a positive calcium score in an asymptomatic person does not by itself indicate the need for a cardiac catheterization.