Coronary angiography is utilised to determine clinical presentations and stress induced reductions in coronary blood flow. The clinical applications of quantitative coronary arteriography are to predict restenosis after angioplasty as well as evaluating the natural history of coronary heart disease.
LIMITATIONS OF VISUAL CORONARY ARTERIOGRAPHY
The limitations of visual coronary arteriography are overcome with the use of quantitative coronary arteriography with the primary advantage of minimising observer influences and biases. In fact, it is estimated that in more than 35% of cases, errors in visual analysis from a coronary angiogram could occur. These errors could be due to the severity of the lesion or dependent on the vessel diameter.
A further limitation with visual coronary arteriography that it unable to differentiate between the narrowing and the functional significance of the stenosis. This is because the functional significance is determined by several features such as the length, shape and eccentricity of the lesion. The disparity between the physical assessment of the severity of the disease and the angiographic are brought about by the physical constraints and resultant flow characteristics.
An additional problem with visual coronary arteriography is that the 2-D projections of the vessels results in certain segments of the coronary vessel being distorted and qualitatively inaccurate. This could result in an incorrect finding and may warrant multiple angiographic projections. This is particularly important for the complex left coronary artery.
LIMITATIONS OF QUANTITATIVE CORONARY ANGIOGRAPHY (QCA)
Despite the benefits of computer-based quantitation which minimise observer variability, there are also significant limitations with this technique. A source of difficulty with quantitative coronary angiography is that some arterial side branches overlap with the regions of interest and this can produce inaccurate findings. Perhaps the most significant limitation of quantitative coronary angiograph is the lack of correlations with functional results.
RESTENOSIS AFTER ANGIOPLASTY
Following certain coronary procedures, QCA has been the standard technique for the study of restenosis. Studies have revealed the accuracy of QCA for post-stent assessment in most cases. Mechanisms of restenosis including angiographic risk factors and elastic recoil have been investigated using QCA. Further, QCA is used to evaluate pharmacologic therapies. In some studies, QCA has been used to determine the long term merits and therapeutic efficacy of a number of techniques and devices.