groin is infiltrated with a 1% to 2% lidocaine solution. Most patients
require conscious sedation and this varies with the preference of the
artery is felt by the fingertips, and a needle is directed towards it
through a tiny hole, created with the tip of a scalpel. A thin-walled
needle is used for this purpose.
When pulsatile blood flow is noted, a curved tip guide wire is then
introduced into the needle and guided to the ascending aorta with intermittent
use of fluoroscopy.
vascular access sheath is advanced over the guide-wire and placed in
the artery. The size of the sheath is dictated by the catheters that
will be employed in the case. Thus, a 6 French (F) sheath is used when
one anticipates the use of 6F catheters. Remember that 1 mm = 3F. Thus
a 6F system has an outer diameter of 6/3 = 2 mm.
Through the sheath, and over a guide-wire, a pre formed (Judkin,
Amplatz or other) or multipurpose catheter is inserted and guided
towards the ostium of the coronary artery under fluoroscopic guidance.
The type of selected catheter is based upon operator preference and
may be modified on the basis of the patient's coronary artery anatomy.
The preformed left and right Judkin's catheters are most commonly
employed to selectively engage the right and left coronary arteries.
engaging the ostium of each coronary artery, the cardiologist confirms
that the pressure is not damped by a significant ostial narrowing
or because the catheter tip is against the wall of the artery. Forceful
injection in the latter situation can create a coronary artery dissection
when contrast is pushed into the subintimal portion of the artery.
Under fluoroscopy, 1 - 2 ml of contrast
is injected to confirm appropriate positioning of the catheter tip.
Cineangiographic recordings are then made during the injection of
approximately 5 to 9 ml of contrast.
Throughout the procedure, the cardiologist constantly monitors the
patient's pressure and EKG. Angios obtained during injection
of the contrast is viewed on a second monitor (to the left of the
cardiologist in the picture above).
Pressures within the aorta and the left ventricle are also measured
during the procedure. Blood samples may be drawn to assess their oxygen
content, if needed in select cases.
The tip of a pigtail (or multipurpose) catheter is advanced retrograde
across the aortic valve and placed within the left ventricle. Left ventricular
(LV) systolic and end-diastolic pressures (LVEDP) are measured and contrast
is injected with the use of a power injector. However, hand-injection
may be occasionally employed in hemodynamically unstable patients or in
an attempt to conserve the contrast volume in a patient with renal insufficiency.
LV angiography is performed to visualize its size, assess the ejection
fraction and look for segmental wall motion abnormalities. The patient
is asked to momentarily hold his or her breath during the injection of
the contrast to get the diaphragm out of the way. Frequently, the patient
experiences a very warm feeling or "hot flash" during the injection.
This lasts less than half a minute. Following angiography, LV pressure
is re-measured to reassess the response of LV function to the contrast.
Pressures are also recorded as the catheter tip is withdrawn from the
LV to the aorta. A significant systolic pressure gradient across the LV
outflow tract is seen in patients with hypertrophic obstructive cardiomyopathy,
and a gradient across the aortic valve is seen in cases of aortic stenosis.