Cardiovascular ImagingCoronary arteriography
X-ray examination of the coronary arteries after selective injection of iodinated contrast media. Precise depiction of the various coronary arterial segments without foreshortening or overlapping branches generally necessitates complex
multiplanar angulation in both the transaxial and craniocaudal planes. The views are named according to the position of the image intensifier relative to the patient (
Fig.1). For instance, the complex angulation of the image intensifier toward the head and left side of the subject is called the cranialleft anterior oblique view.
Technique
Selective coronary arteriography is performed using specially shaped catheters. The most frequently used catheters are the Judkins catheters for the right and left coronary arteries. These catheters are inserted percutaneously into the femoral artery employing the Seldinger technique. Another approach uses the Sones catheter inserted into the brachial artery through an arteriotomy. Iodinated contrast media is injected manually into the artery and cine filming is done during peak opacification and clearance of contrast media from the arteries. During the procedure the catheter is attached by a hydraulic line into a pressure transducer in order to continuously measure coronary arterial pressure.
Diagnostic features
Coronary arteriography depicts the anatomy of the coronary arterial system. An important anatomical variable is dominance of the right or left coronary artery. Dominance is determined by whether the right or circumflex coronary artery provides the posterior descending and posterolateral left ventricular branches. Right dominance is defined by these two branches originating from the right coronary artery (approximately 80% of humans). Left dominance is defined by these two branches arising from the circumflex coronary artery (approximately 10% of humans). Codominance is the pattern where the posterior descending originates from the right coronary artery and the postarterolateral branches from the circumflex artery.
The arteriogram can display a number of abnormalities including stenosis (Fig.2), thrombosis, aneurysm or ectasia, and spasm. The arteriogram is also used to guide coronary angioplasty and stent placement.
A haemodynamic stenosis is considered to be greater than 50% reduction in luminal diameter (75% reduction in cross-sectional area). Determination of the percentage stenosis is complicated in diffuse stenotic disease because a normal coronary arterial segment is not present which vitiates comparison with a normal coronary arterial diameter.
Coronary artery ectasia consists of diffuse or focal increase in diameter of a coronary artery. This is usually associated with decreased flow velocity in the ectatic vessel and a propensity to thrombosis in the region of slow blood flow.
Stenosis or occlusion which is indicative of spasm can be reversed by the administration of nitroglycerin and other vasodilators. Spasm may be spontaneously superimposed on a low or high grade stenosis or may occur in an apparently normal arterial segment. Coronary artery spasm can be provoked by administration of a vasoconstricting agent such as ergonovine.
After performance of angioplasty, coronary arteriography demonstrates the reduction in severity of stenosis and any injury to the arterial wall. Angioplasty may cause focal or extended coronary arterial dissection, or may induce thrombosis of the artery. Arteriography is also used to evaluate the arterial diameter and patency of the artery after placement of a stent. Also, see noninvasive imaging under coronary artery.
CBH