CATHETER
BASED CORONARY ANGIOGRAPHY
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| Plate 3-9 RIGHT CORONARY ARTERY: ARTERIOGRAPHIC VIEWS |
Until recently, diagnosis of human coronary atherosclerosis depended primarily on the physician’s ability to interpret the significance of chest pain described by patients who experience infinitely variable subjective responses to stress. Objective confirmation hinged on the recognition of transient or persistent electrocardiographic changes, which usually indicate the presence of myocardial ischemia, necrosis, or scar tissue replacement of functioning myocardium. Therefore the pres- ence of coronary atherosclerosis could be recognized in a patient only after the disease process had progressed to a point where arterial obstructions were so severe as to cause transient or permanent secondary changes in the myocardium (ischemia or infarction).
Selective cine
coronary arteriography provides a clinically useful approach to the precise
demonstration of the morphologic characteristics of the lumen of the human
coronary artery when used in combination with intravascular ultrasound (see
Plate 3-11). In the study of more than 10,500 patients representing all phases
of the natural history of coronary atherosclerosis, only nine deaths have been
attributable to this arteriographic procedure.
TECHNIQUE
With the
patient under local anesthesia, the right brachial artery is usually mobilized
in the right antecubital fossa immediately above its bifurcation. After
heparinizing the distal brachial artery and occluding flow, an 8-French woven
catheter 80 cm long, with a special tip that tapers to a 5-French diameter in
its distal 2 inches (5 cm), is passed retrograde from the right brachial
artery directly into the ascending aorta. The catheter tip is introduced
directly into one coronary orifice and then the other under direct vision,
using an image intensifier equipped with a closed-circuit television unit to
provide direct visualization during the procedure. Pressure measurements from
the catheter tip are recorded constantly to permit immediate recognition of
arterial occlusion by the catheter tip. The electrocardiogram also is monitored
constantly.
Multiple small
doses of radiopaque contrast are injected directly into the orifice of each
coronary artery, with the patient positioned in varying right and left anterior
oblique projections. Individual projections for each patient are selected based
on direct fluoroscopic visualization, to photograph all segments of each vessel
in a plane perpendicular to that of the x-ray beam. Usually, four to six arteriograms
of each artery are made, in varying RAO and LAO projections. On average, 4 to 6
mL of radiopaque contrast material is injected manually with a 10-mL syringe
for adequate opacification of individual coronary vessels. Positioning the
heart in multiple RAO and LAO projections is facilitated greatly by the use of
a movable camera. The passage of the contrast medium through all branches of
the coronary artery is digitally recorded (see Plates 3-9 and 3-10).
After each coronary
artery has been opacified effectively in the appropriate projections, the
catheter tip is passed across the aortic valve into the left ventricle.
Pressure measurements are recorded in the left ventricle. The LV cavity then is
opacified selectively with 20 to 30 mL of radiopaque contrast. Left ventriculography
is performed routinely in the RAO projection, clearly showing localized LV
aneurysms or areas of impaired contractility in the ventricular myocardium
caused by interstitial scar tissue replacement or grossly impaired myocardial
perfusion. Left ventriculography also permits the ready identification of
associated mitral or aortic valve lesions or severely impaired LV function
caused by generalized preexisting myocardial injury. The LAO ventriculogram
visualizes the ventricular septum and lateral LV wall.
On completion
of the procedure, the catheter is with-drawn and the brachial arteriotomy
closed by direct suture.
The Sones
technique is rarely used now in catheterization laboratories.
In contrast to
the Sones technique, the Judkins technique is done percutaneously with
preformed catheters from the femoral artery. Three catheters are required to
perform ventriculography and right and left coronary injections.
Ventriculography is usually performed with a “pigtail” catheter before
selective coronary angiography. As with the Sones technique, multiple
projections are used to identify coronary stenoses. Other catheters (e.g.,
multipurpose, Amplatz) are introduced percutaneously and often are used if the
coronary arteries cannot be engaged by the Judkins catheters.
Small catheters
can be used percutaneously for diagnostic coronary angiography, as well as
percutaneous coronary intervention (PCI), if blood flow to the hand is
adequate in the radial and ulnar arteries.
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| Plate 3-10 LEFT CORONARY ARTERY: ARTERIOGRAPHIC VIEWS |
Coronary
angiography can demonstrate distal vessels of the coronary artery as small as
100 to 200 microns in lumen diameter. Segmental variations in lumen diameter of
the major branches caused by atherosclerosis result in up to a 10% reduction in
diameter (minimal irregularities). More
advanced stenotic lesions can
limit myocardial perfusion and are visualized easily. Selective opacification
of the vessels allows precise delineation of the presence, sites of origin and
distribution of effective intercoronary collateral channels, which compensate
for severe stenotic or occlusive lesions. In patients with angiographically
normal vessels, coronary atherosclerosis may still be present, but myocardial
ischemia caused by epicardial vessel stenosis can be ruled out.
Coronary
arteriography is essential in selecting patients with coronary atherosclerosis
who may benefit from revascularization procedures to improve myocardial
perfusion, as well as objectively assessing results. Severe localized
obstructions in major proximal arteries are now removed by direct
angioplasty/stent or coronary artery bypass. More diffuse obstructive lesions
provide an objective basis for planning optimal medical therapy.
After
angioplasty or stent placement or postoperatively, repeated coronary
arteriograms and selective conduit angiograms permit long-term assessment of
the effectiveness of such revascularization procedures, as well as the evolving
disease process in the individual patient.
