For routine clinical evaluation of coronary angiograms, an experienced angiographer qualitatively estimates the degree of stenosis visually. Multiple views of the regions of interest are obtained over a range of projection angles to best define the three-dimensional geometry of the lesions. The result is generally reported as a percent reduction in lumen diameter (e.g., a 75% stenosis is a lesion that narrows the lumen diameter by approximately 75%). Quantitative coronary angiography can also be applied using algorithms based on computer image processing, although this method is generally cumbersome and is used almost exclusively as a research tool in clinical trials.
1Name the coronary arteries and their major branches as they are commonly identified by coronary angiography.
This drawing depicts right-dominant coronary anatomy:
LMC = left main coronary artery LAD = left anterior descending D = diagonal branch
S = septal perforator CX = circumflex RI = ramus intermedius OM = obtuse marginal
AC = atrial circumflex PL = posterolateral branch RCA = right coronary artery SA = sinus node branch RV = right ventricular branch AM = acute marginal branch PDA = posterior descending artery.
How do angiographers commonly categorize the severity of coronary artery stenoses?
A grading system of reduction in percent lumen diameter has been designed that incorporates the limitations of the qualitative nature of assessing the significance of coronary artery disease.
Coronary atherosclerosis is graded as absent (normal), intimal, 25%, 50%, 75%, 90%, 99% (subtotal occlusion), and 100% (occluded). A 75% reduction in luminal diameter is considered to be a significant‚ stenosis in that a lesion of this severity will affect that artery’s ability to increase coronary blood flow as needed during increased demand. The left main coronary artery is unique‚ in that a 50% stenosis is prognostically significant. Lesion characteristics such as presence of calcium, length of stenosis, location within the coronary artery tree, concentric vs. eccentric morphology, presence of an ulcerated plaque, and intraluminal thrombus are also important and should be described.
How does the degree of coronary artery stenosis affect coronary blood flow both at rest and with maximal vasodilatation?
Under resting conditions, progressive reduction of vessel luminal diameter does not reduce resting coronary blood flow until the vessel luminal diameter is approximately 90% stenosed. A normal distal coronary artery bed is able to dilate and increase coronary blood flow to about four to five times its resting value. This is a normal coronary flow reserve and can be achieved during maximal vasodilation, such as occurs with maximal exercise. A 50% reduction in luminal diameter will prevent a coronary vessel from achieving this normal four to five times increase in coronary blood flow during maximal vasodilation. For this reason, a 75% reduction in coronary luminal diameter is considered significant.‚
Additional procedures in the cardiac catheterization laboratory are applied to special patients. List several procedures and their indications.
Serial blood sampling to measure percent oxygenation at different points in the circulation.
a. Determination of cardiac output (Fick method)
b. Assessment of intracardiac shunting
Measurement of oxygen consumption.
a. Determination of pulmonary and systemic cardiac output by the Fick method.
Right ventricular endomyocardial biopsy
a. Monitoring of antirejection therapy in patients with heart or heart/lung transplantation
b. Diagnostic evaluation in cardiomyopathy or myocarditis
a. Treatment of cardiac tamponade
b. Diagnostic evaluation of pericardial effusion
a. Assessment of aortic valve competence
b. Assessment of suspected aortic dissection
c. Evaluation of aortic root dilatation
d. Localization of reverse saphenous vein bypass grafts
Coronary artery bypass angiography
a. Assessment of coronary artery bypass graft patency
Hemodynamic assessment during exercise or pharmacologic intervention
a. Assessment of valvular heart disease
b. Determination of reversibility‚ of pulmonary hypertension.