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I./3.4.: Coronary angiography
Coronary angiography is the gold standard of the diagnostics of coronary heart disease. Contrast material is given to the coronaries through a thin catheter directed to the coronary orifice; so that the major epicardial coronary branch system is depicted with a sharp contour. A continuous moving X-ray recording is done on the examination; earlier it was made on conventional celluloid film stripes, now the data are already stored digitally. Recordings should be made from several projections. Reasonably, the left and right coronaries should be examined separately. Earlier the catheter of coronary angiography was inserted via the right femoral artery, in the recent years, in the possession of appropriate technical equipment and routine, it is performed through the radial artery what is much more comfortable for the patient and is associated with a significantly lower risk of a hemorrhage.
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The ratio of radial insertion is a quality parameter of the intervention centers, in up-to-date sites this is about 80%. In the remaining 20% the examination is not feasible through this way due to the gracile, tortuous or spastic radial or ulnar arteries. If neither the radial nor the femoral arteries can be used (the latter usually because of an occlusive arterial disease) on either sides, a brachial artery is used on one or another side. During coronary angiography the severe stenoses and occlusions can be detected. In patients with ST segment elevation myocardial infarction a definite complete, culprit coronary occlusion can be found in the decisive majority of cases. This develops on the base of a recent rupture of a plaque, it is markedly thrombotic, and correspondingly it often shows a filling with an incomplete shadow.
In patients with non-ST segment elevation acute coronary syndrome often not a complete occlusion of one branch, but severe stenoses of several branches can be observed, not infrequently the main trunk is also affected. If the determination of the culprit lesion (the directly etiologic lesion) is equivocal, the patient’s other clinical data may be helpful, including the ECG that may show the signs of an old infarction; the echocardiography that detects any wall motion disorder, akinesis, thinning of certain segments, as a definitive occurred old infarction. The examination may be associated with complications, but in case of an experienced site and experienced examiner, the rate of severe complications for a diagnostic coronary angiography is under 1 per mille. Complications may include a local hemorrhage (this can be avoided by using the radial artery), coronary dissection, occlusion, thrombus, possibly peripheral (brain, limb, mesenteric, renal) embolism, or contrast agent anaphylaxis (extremely rare!).
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A major amount of contrast media may cause further deterioration of the previously already impaired renal function; this can be prevented primarily by assuring the appropriate hydration of the patient. After the diagnostic coronary angiography, following the determination of the occlusion or stenosis to be dilated; the percutaneous coronary intervention (PCI) is started. For this, the diagnostic catheter should be replaced by a therapeutic guiding catheter, which has a larger diameter. Through the guiding catheter a thin PTCA (percutaneous transluminal coronary angioplasty) wire is directed to the chosen coronary branch, and then the necessary instruments (balloons, stents) can be led there attached to this wire. If a greater amount of thrombus is present, the thrombus could be aspired from the coronary with a special device, by this way much better flow is to be expected in the myocardial capillary system after the PCI.
At present already in more than 95% the coronary lumen can be fixed by stent implantation during PCI. Basically there are two types of stent. The conventional bare metal stents are associated a relatively high (10 to 15%) chance of restenosis, which is explicitly high in patients with diabetes mellitus, narrow vascular lumen or in case of an ostial localization. The prevention of it is made possible by the other type, the drug-eluting stent. These stents are coated with medicines and release various cytostatic agents for a few weeks (in an extremely low, only locally acting concentration) by which the proliferation of fibroblasts in the vascular wall, the cause of restenosis, is inhibited. Disadvantage of the drug-eluting stents that a part of the metal framework remains bare and therefore prolonged dual antiplatelet therapy is required; and in addition it is also essentially more expensive.
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