Angiographic Procedures

ANGIOGRAPHIC PROCEDURESOverviewAs 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 TEAMAngiography 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 CAREA 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 INJECTIONTo 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 TRAYA sterile tray contains the basic equipment necessary for a Seldinger catheterization of a femoral artery Basic sterile items include the following:1.Hemostats2.Prep sponges and antiseptic solution3.Scalpel blade4.Syringe and needle for local anesthetic5.Basins and medicine cup6.Sterile drapes and towels7.Band-Aids8.Sterile image intensifier cover

CONTRAINDICATIONSContraindications 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/COMPLICATIONSAngiographic 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 CAREAfter 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 ANGIOGRAPHYPurposeCerebral 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 IndicationsPathologic indications for cerebral angiography include the following:•Vascular stenosis and occlusions•Aneurysms•Trauma•Arteriovenous malformations•Neoplastic disease

CatheterizationThe 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 ANGIOGRAPHYPurposeThoracic 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 IndicationsPathologic indications for thoracic and pulmonary angiography include the following:•Aneurysms•Congenital abnormalities•Vessel stenosis•Embolus•TraumaCatheterizationThe 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.

ANGIOCARDIOGRAPHYPurposeAngiocardiography 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

CatheterizationAs 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 ANGIOGRAPHYPurposeAbdominal 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 IndicationsPathologic indications for abdominal angiography include the following:•Aneurysm•Congenital abnormality•GI bleed•Stenosis or occlusion•TraumaCatheterizationFor 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 ANGIOGRAPHYPurposePeripheral 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 IndicationsPathologic indications for peripheral angiography include the following:•Atherosclerotic disease•Vessel occlusion and stenosis•Trauma•Neoplasm•Embolus and thrombus

CatheterizationThe 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.

LYMPHOGRAPHYPurposeLymphography 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 IndicationsPathologic 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