Download Angiographic Procedures

Angiographic Procedures
ANGIOGRAPHIC PROCEDURES
Overview
As defined at the beginning of this chapter, angiography refers to radiologic
imaging of blood vessels after injection of a contrast medium. To visualize
these low-contrast structures, contrast media is injected by a catheter that is
placed in the vessel of interest. Positive contrast media are more commonly
used, but there are instances when use of negative contrast media is indicated.
Highly specialized imaging equipment is required for these procedures.
Angiography can be more specifically described as
follows:
•Arteriography: imaging of the arteries
•Venography: imaging of the veins
•Angiocardiography: imaging of the heart and
associated structures
•Lymphography: imaging of the lymphatic
vessels/nodes
THE ANGIOGRAPHY TEAM
Angiography is performed by a team of health professionals, including (1) a
radiologist (or other qualified angiographer), (2) a “scrub” nurse or
technologist who assists with sterile and catheterization procedures, and (3)
a radiologic technologist. Depending on the departmental protocol and the
specific situation, an additional physician, nurse, technologist, and/or
hemodynamic technologist also may be available to assist with the procedure.
CONSENT AND PREPROCEDURAL PATIENT CARE
A medical history should be obtained before the procedure is begun. This should
include questions intended to assess the patient's ability to tolerate the contrast
injection (e.g., allergy history, cardiac/pulmonary status, renal function). The patient
also will be interviewed regarding medication history and symptoms. Medication
history is important because some medications are anticoagulants and will cause
excessive bleeding during and after the procedure. Knowing the medication history
is also important when one is selecting the premedication. Previous laboratory
reports and other pertinent data are reviewed as well.
A detailed explanation of the procedure will be given to the patient, which is
important to ensure full understanding and cooperation. The explanation will
include possible risks and complications of the procedure, so that the patient is fully
informed before signing the consent
Solid food is withheld for approximately 8 hours before the procedure to reduce the
risk for aspiration. However, making sure that the patient is well hydrated is
important to reduce the risk for contrast-induced renal damage.
Premedication usually is given to patients before the procedure to help them relax.
The patient may be made more comfortable on the table by placing a sponge under
the knees to reduce strain on the back. Vital signs are obtained and recorded, and
pulse in the extremity distal to the selected puncture site is checked. The puncture
site is shaved, cleaned, and draped.
Continual communication and monitoring of the patient by the technologist and the
rest of the angiography team will greatly alleviate patient discomfort and fear.
VESSEL ACCESS FOR CONTRAST MEDIA INJECTION
To visualize the vessel(s) of interest, a catheter must be introduced into the patient's
vasculature, through which the contrast media will be injected. A commonly used
method for catheterization is the Seldinger technique. This technique was
developed by Dr. Sven Seldinger in the 1950s and remains popular today. It is a
percutaneous (through the skin) technique that can be used for arterial or venous
access.
Four vessels are typically considered for catheterization: (1)
femoral, (2) axillary, (3) brachial, and (4) radial. The
angiographer will make the selection based on the strong
presence of a pulse and the absence of vessel disease. The
femoral artery is the preferred site for an arterial puncture
because of its size and easily accessible location. It is
punctured just inferior to the inguinal ligament. If a femoral
artery puncture is contraindicated because of previous
surgical grafts, the presence of an aneurysm, or occlusive
vascular disease, the axillary, brachial, or radial artery may be
selected. The femoral vein would be the vessel of choice for
venous access.
SELDINGER TECHNIQUE
ANGIOGRAPHIC TRAY
A sterile tray contains the basic equipment
necessary for a Seldinger catheterization
of a femoral artery Basic sterile items
include the following:
1.Hemostats
2.Prep sponges and antiseptic solution
3.Scalpel blade
4.Syringe and needle for local anesthetic
5.Basins and medicine cup
6.Sterile drapes and towels
7.Band-Aids
8.Sterile image intensifier cover
CONTRAINDICATIONS
Contraindications for patients to experience angiography include contrast media
allergy, impaired renal function, blood-clotting disorders or taking
anticoagulant medication, and unstable cardiopulmonary/neurologic status.
RISKS/COMPLICATIONS
Angiographic procedures are not performed without always involving some level of
risk for the patient. Some of the most common risks and complications include the
following:
•Bleeding at the puncture site: this usually can be controlled by applying
compression
•Thrombus formation: a blood clot may form in a vessel and disrupt the flow to distal
parts
•Embolus formation: a piece of plaque may be dislodged from a vessel wall by the
catheter. A stroke or other vessel occlusion may result
•Dissection of a vessel: the catheter may tear the intima of a vessel
•Infection of puncture site: this is caused by contamination of the sterile field
•Contrast media reaction: this may be mild, moderate, or severe
POSTPROCEDURAL CARE
After the angiographic procedure has been completed, the catheter is removed
and compression is applied to the puncture site. The patient remains on bed rest
for a minimum of 4 hours, but the head of the bed/stretcher may be elevated
approximately 30°. During this time, the patient is monitored, and vital signs and
the peripheral pulse distal to the puncture site are regularly checked. The
extremity is also checked for warmth, color, and numbness to ensure that
circulation has not been disrupted. Oral fluids are given and analgesics are
provided if required.
Patients should be instructed on what to do if the puncture site spontaneously
begins to bleed: apply pressure and call for help.
AUTOMATIC ELECTROMECHANICAL CONTRAST MEDIUM INJECTOR
As contrast media is injected into the circulatory system, it is diluted by blood. The
contrast material must be injected with sufficient pressure to overcome the
patient's systemic arterial pressure and to maintain a bolus to minimize dilution
with blood. To maintain the flow rates necessary for angiography, an automatic
electromechanical injector is used. The flow rate is affected by many variables,
such as the viscosity of the contrast medium, the length and diameter of the
catheter, and injection pressure. Depending on these variables and the vessel to
be injected, the desired flow rate can be selected before injection.
CEREBRAL ANGIOGRAPHY
Purpose
Cerebral angiography is a radiologic study of the blood vessels of the brain.
The primary purpose of cerebral angiography is to provide a vascular “road map”
that will enable physicians to localize and diagnose pathology or other anomalies of
the brain and neck regions.
Pathologic Indications
Pathologic indications for cerebral angiography include the following:
•Vascular stenosis and occlusions
•Aneurysms
•Trauma
•Arteriovenous malformations
•Neoplastic disease
Catheterization
The femoral approach is preferred for the catheter insertion. The catheter is
advanced to the aortic arch, and the vessel to be imaged is selected. Vessels
commonly selected for cerebral angiography include the common carotid arteries,
internal carotid arteries, external carotid arteries, and vertebral arteries.
THORACIC ANGIOGRAPHY
Purpose
Thoracic angiography demonstrates the contour and integrity of the thoracic
vasculature. Thoracic aortography is an angiographic study of the ascending aorta,
the arch, the descending portion of the thoracic aorta, and the major branches.
Pulmonary arteriography is an angiographic study of the pulmonary vessels that
usually is done to investigate for pulmonary embolus. As was mentioned earlier,
pulmonary angiography is performed infrequently because of the availability of
alternative modalities.
Pathologic Indications
Pathologic indications for thoracic and pulmonary angiography include the following:
•Aneurysms
•Congenital abnormalities
•Vessel stenosis
•Embolus
•Trauma
Catheterization
The preferred puncture site for a thoracic aortogram is the femoral artery. The
catheter is advanced to the desired location in the thoracic aorta. Selective
procedures may be performed with the use of specially designed catheters to access
the vessel of interest.
Because of the location of the pulmonary artery, the femoral vein is the preferred
site for catheter insertion. The catheter is advanced along the venous structures,
into the inferior vena cava, through the right atrium of the heart into the right
ventricle, and into the pulmonary artery. Typically, both pulmonary arteries are
examined.
ANGIOCARDIOGRAPHY
Purpose
Angiocardiography refers specifically to radiologic imaging of the heart and
associated structures. Coronary arteriography typically is performed at the
same time to visualize the coronary arteries.
Cardiac catheterization is a more general term that is used to describe placing a
catheter in the heart; it includes studies in addition to radiologic imaging ones, such
as obtaining blood samples to measure oxygen saturation (oximetry) and
measuring hemodynamic pressures and gradients. Specialized physiologic
monitoring equipment is required for these sensitive measurements. For the
purposes of this text, the focus will be on the imaging aspect of cardiac
catheterization.
Pathologic Indications
•Coronary artery disease and angina
•Myocardial infarct
•Valvular disease
•Atypical chest pain
•Congenital heart anomaly
•Other heart and aorta pathology
Catheterization
As for other angiograms, the femoral artery is the preferred site for catheterization.
The catheter is advanced to the aorta and along its length into the left ventricle for the
left ventriculogram. A pigtail catheter is used because a large volume of contrast
media will be injected. For the coronary arteriogram, the catheter is changed and the
coronary artery is selected; both right and left coronary arteries are routinely
examined. Specially shaped catheters are designed to fit each of the coronary
arteries.
After injection of contrast media into the coronary arteries, the catheter is immediately
removed to prevent occluding the vessel.
Access to the right side of the heart is obtained by catheterizing the femoral vein and
advancing the catheter through the venous structures until the right side of the heart
is reached.
ABDOMINAL ANGIOGRAPHY
Purpose
Abdominal angiography demonstrates the contour and integrity of abdominal
vasculature. This means that the placement or displacement of abdominal vessels
being studied and possible obstructions or vessel tears (e.g., aneurysm ballooning)
will be demonstrated. Any displacement of vessels may indicate a space-occupying
lesion.
Aortography refers to an angiographic study of the aorta, and selective studies refer
to the catheterization of a specific vessel. Venacavography demonstrates the
superior and/or inferior vena cava.
Pathologic Indications
Pathologic indications for abdominal angiography include the following:
•Aneurysm
•Congenital abnormality
•GI bleed
•Stenosis or occlusion
•Trauma
Catheterization
For an aortogram, the aorta typically is accessed by the femoral artery. The type and
size of catheter required depend on the structure, but a pigtail catheter usually is used
because a larger amount of contrast, as is needed for an abdominal aortogram, will be
delivered.
Selective angiographic studies require the use of specially shaped catheters to
access the vessel of interest. Common selective studies performed include the celiac
artery, the renal arteries, and the superior and inferior mesenteric arteries, which are
selected when a GI bleed is investigated. A superselective study involves selecting a
branch of a vessel. A common example of this is selection of the hepatic or splenic
artery; these are two of the branches of the celiac artery.
Catheterization for venacavography is obtained by a femoral vein puncture. The
catheter then is advanced to the desired level.
PERIPHERAL ANGIOGRAPHY
Purpose
Peripheral angiography is a radiologic examination of the peripheral
vasculature after the injection of contrast media. Peripheral angiography may be
an arteriogram, in which case the injection is administered by a catheter in an
artery, or a venogram, in which the injection is placed into a vein of the extremity
being examined. It should be noted, however, that venograms now are rarely
performed because of the increased sensitivity of ultrasound (color duplex) to
demonstrate pathology; they will not be discussed further in this chapter.
Pathologic Indications
Pathologic indications for peripheral angiography include the
following:
•Atherosclerotic disease
•Vessel occlusion and stenosis
•Trauma
•Neoplasm
•Embolus and thrombus
Catheterization
The Seldinger technique is used to access the
femoral artery or an alternate injection site for a
peripheral arteriogram. For a lower limb
arteriogram, the catheter is advanced just
superior to the aortic bifurcation.
LYMPHOGRAPHY
Purpose
Lymphography is performed to visualize the lymph vessels and nodes.
Although CT has largely replaced lymphography in the assessment of nodes,
lymphography is indicated in certain situations.
Pathologic Indications
Pathologic indications for lymphography include the following:
•Assessment of the lymphatics in the staging of malignancies, especially cervical
and prostate cancers
•Assessment of Hodgkin's lymphoma
•Peripheral swelling