Home > Encyclopedia of Nursing & Allied Health > Cardiac Catheterization

Definition

Cardiac catheterization (also called heart catheterization) is a diagnostic and occasionally therapeutic procedure that allows a comprehensive examination of the heart and surrounding blood vessels. It enables the physician to take angiograms, record blood flow, calculate cardiac output and vascular resistance, perform an endomyocardial biopsy, and evaluate the heart's electrical activity. Cardiac catheterization is performed by inserting one or more catheters (thin flexible tubes) through a peripheral blood vessel in the arm (antecubital artery or vein) or leg (femoral artery or vein) under x-ray guidance.

Purpose

Cardiac catheterization is most commonly performed to examine the coronary arteries, because heart attacks, angina, sudden death, and heart failure most often originate from disease in these arteries. Coronary artery disease is the first-ranked cause of death for both men and women in the United States. Cardiac catheterization with coronary angiography is recommended in patients with angina (especially unstable angina); suspected coronary artery disease; suspected silent ischemia and a family history of heart attack; ischemic cardiac myopathy; congestive heart failure; congenital heart disease; and pericardial disease. Catheterization is

also recommended for patients with suspected valvular disease, including aortic stenosis or regurgitation and mitral stenosis or regurgitation. In addition, the procedure may be performed after acute myocardial infarction; before major noncardiac surgery in patients at high risk for cardiac problems; before cardiac surgery in patients at risk for coronary artery disease; and before such interventional technologies and procedures as stents and percutaneous transluminal coronary angioplasty (PTCA).

Cardiac catheterization may reveal the presence of other conditions, including enlargement of the left ventricle; ventricular aneurysms (abnormal dilation of a blood vessel); narrowing of the aortic valve; insufficiency of the aortic or mitral valve; and septal defects that allow an abnormal flow of blood from one side of the heart to the other.

Symptoms and diagnoses that may be associated with the above conditions and may lead to cardiac catheterization include:

• chest pain characterized by prolonged heavy pressure or a squeezing pain
• abnormal results from a treadmill stress test
• myocardial infarction (heart attack)
• congenital heart defects
• valvular disease

Left- and right-side catheterization

Cardiac catheterization can be performed on either side of the heart to evaluate different functions. Testing the right side of the heart allows the physician to evaluate tricuspid and pulmonary valve function, in addition to measuring blood pressures and collecting blood samples from the right atrium, right ventricle, and pulmonary artery. Catheterization of the left side of the heart is performed to test the blood flow in the coronary arteries as well as the level of function of the mitral and aortic valves and left ventricle. The physician can assess the adequacy of blood supply through the coronary arteries, blood pressures, and blood flow throughout the chambers of the heart, collect blood samples, and take x rays of the heart's ventricles or arteries.

Coronary angiography

Coronary angiography, which is also known as coronary arteriography, is an imaging technique that involves injecting a dye into the vascular system to out- line the heart and coronary vessels. Angiography allows the visualization of any blockages, narrowing, or abnormalities in the coronary arteries. If these signs are visible, the cardiologist may assess the patient's readiness for coronary bypass surgery, or a less invasive approach such as dilation of a narrowed blood vessel by surgery or the use of a balloon (angioplasty). Because some interventions may be performed during cardiac catheterization, the procedure is considered therapeutic as well as diagnostic.

Outpatient catheterization

Cardiac catheterization is usually performed in a specially designed cardiac catheterization suite in a hospital, so that any procedural complications may be handled rapidly and effectively. Cardiac catheterization may also be performed on patients presenting to the emergency department with chest pain or chest injuries. The procedure may be performed on an outpatient basis, depending on the patient's pre- and post-catheterization condition. As of 2000, however, the American Heart Association (AHA) and the American College of Cardiology (ACC) issued a joint statement denying approval of the use of separate cardiac catheterization laboratories that are not part of a hospital, on the grounds that a small number of patients having the procedure on an outpatient basis will have unexpected reactions or complications.

Precautions

Contraindications

Cardiac catheterization is categorized as an invasive procedure that involves the heart, its valves, and coronary arteries, in addition to a large artery in the arm or leg. Cardiac catheterization is contraindicated for patients with the following conditions:

• A bleeding disorder, or anticoagulation treatment with Coumadin (sodium warfarin). These may affect bleeding and clotting during the catheterization procedure.
• Renal insufficiency or poor kidney functioning (especially in diabetic patients), which may worsen following angiography.
• Severe uncontrolled hypertension.
• Severe peripheral vascular disease that limits access to the arteries.
• Untreated active infections, severe anemia, electrolyte imbalances, or coexisting illnesses that may affect recovery or survival.
• Endocarditis (an inflammatory infection of the heart's lining that often affects the valves).

Radiation hazards

Cardiac catheterization involves radiation exposure for staff members as well as the patient. The patient's dose of radiation is minimized by using lead shielding in the form of blankets or pads over certain body parts and by choosing the appropriate dose during fluoroscopy. Staff members' exposure to radiation is monitored by the wearing of radiation badges that detect exposure and lead aprons that shield the body. The radiographic/fluoroscopic system may be equipped with movable lead shields that do not interfere with access to the patient and are placed between staff members and the source of radiation during the procedure.

Description

More than 1.5 million cardiac catheterizations are performed every year in the United States, primarily to diagnose or monitor heart disease.

Cardiac anatomy

The heart consists of four chambers separated by valves. The right side of the heart, which consists of the right atrium (upper chamber; sometimes called the right auricle) and the right ventricle (lower chamber), pumps blood to the lungs. The left side of the heart, which consists of the left atrium (or auricle) and the left ventricle, simultaneously pumps blood to the rest of the body. The right and left coronary arteries, which are the first vessels to branch off from the aorta, supply blood to the heart. The left anterior descending coronary artery supplies the front of the heart; the left circumflex coronary artery wraps around and supplies the left side and the back of the heart; and the right coronary artery supplies the back of the heart. There is, however, a considerable amount of variation in the anatomy of the coronary arteries.

Catheterization procedure

The patient lies on a table on his or her back during the catheterization procedure, connected to monitoring equipment, including an electrocardiography device. The insertion site is numbed with a local anesthetic, and access to the vein or artery is obtained using a needle. A sheath, a rubber tube that facilitates insertion of catheters and infusion of drugs, is placed in the puncture site. Under fluoroscopic guidance, a guidewire, which is a thin wire that guides the catheter insertion, is threaded through a brachial or femoral artery and up to the heart. The catheter, a flexible or preshaped tube approximately 32–43 inches (80–110 cm) long, is then inserted over the wire and threaded to the heart. The patient may experience pressure as the catheter is threaded into the heart. The contrast agent or dye used for imaging is then injected so that the physician can view the heart and surrounding vessels. The patient may experience a hot flushed feeling or slight nausea following injection of the contrast medium. Depending on the type of catheterization (left- or right-heart) and the area being imaged, different catheters with various shapes and ends are used.

The radiographic/fluoroscopic system has an x-ray subsystem and video system with viewing monitors that allow the physician to view the procedure in real time using fluoroscopy as well as taking still x rays for documentation purposes. Most newer systems use a digital angiography system that allows images to be recorded, manipulated, and stored digitally on a computer.

The procedure usually lasts about two or three hours. If further intervention is necessary, an angioplasty, stent implantation, or other procedure can be performed. At the end of the catherization, the catheter and sheath are removed, and the puncture site is closed using a sealing device or manual compression to stop the bleeding. One

commonly used sealing device is called Perclose, which allows the doctor to sew up the hole in the groin. Two other devices called AngioSeal and VasoSeal use collagen seals to close the holes in the femoral artery.

Preparation

Before undergoing cardiac catheterization, the patient may have had other noninvasive diagnostic tests, including an electrocardiogram (ECG), echocardiography, computed tomography (CT), magnetic resonance imaging (MRI), laboratory studies (e.g., blood work), and/or nuclear medicine cardiac imaging. The results of these noninvasive tests may have indicated a need for cardiac catheterization to confirm a suspected cardiac condition, further define the severity of a previously diagnosed condition, or establish the need for an interventional procedure (e.g., cardiac surgery).

Patients should give the physician or nurse a complete list of their regular medications, including aspirin and nonsteroidal anti-inflammatory drugs (NSAIDs), because they can affect blood clotting. Diabetics who are taking either metformin or insulin to control their diabetes should inform the physician, as these drugs may

Cardiac monitoring pressures and volumes
Pressure	Normal values
SOURCE: Pagana, K.D. and T.J. Pagana. Mosby's Diagnostic and Laboratory Test Reference. 3rd ed. St. Louis: Mosby, 1997.
Aortic artery pressure (routine blood pressure)	90–140/60–90 mm Hg
Central venous pressure	2–14 cm H2
End-diastolic left ventricular pressure	4–12 mm Hg
Pulmonary wedge pressure	Left atrial: 6–15 mm Hg
Pulmonary artery pressure	15–28/5–16 mm Hg
Systolic left ventricle pressure	90–140 mm Hg
Volumes
Cardiac index (CI)	2.8–4.2 L/min/m2 for a patient with 1.5m2 of body surface area
Cardiac output (CO)	3–6 L/min
Ejection fraction (EF)	0.67±0.07
End-diastolic volume (EDV)	50–90ml/m2
End-systolic volume (ESV)	25 ml/m2
Stroke volume (SV)	45±12 ml/m2

need to have their dosages changed before the procedure. Patients should also notify staff members of any allergies to shellfish containing iodine, iodine itself, or the dyes commonly used as contrast agents before cardiac catheterization.

Because cardiac catheterization is considered surgery, the patient will be instructed to fast for at least six hours prior to the procedure. A mild sedative may be administered about an hour before the procedure to help the patient relax. If the catheter is to be inserted through the groin, the area around the patient's groin will be shaved and cleansed with an antiseptic solution.

Aftercare

While cardiac catheterization may be performed on an outpatient basis, the patient requires close monitoring following the procedure; he or she may remain in the hospital for up to 24 hours. The patient will be instructed to rest in bed for at least eight hours immediately after the test. If the catheter was inserted into a vein or artery in the leg or groin area, the leg will be kept extended for four to six hours. If a vein or artery in the arm was used to insert the catheter, the arm will need to remain extended for a minimum of three hours.

Most doctors advise patients to avoid heavy lifting or vigorous exercise for several days after cardiac catheterization. Those whose occupation involves a high level of physical activity should ask the doctor when they can safely return to work. In most cases, a hard ridge will form over the incision site that diminishes as the site heals. A bluish discoloration under the skin often occurs at the point of insertion but usually fades within two weeks. The incision site may bleed during the first 24 hours following surgery. The patient may apply pressure to the site with a clean tissue or cloth for 10–15 minutes to stop the bleeding.

The patient should be instructed to call the doctor at once if tenderness, fever, shaking, or chills develop, which may indicate an infection. Other symptoms requiring medical attention include severe pain or discoloration in the leg, which may indicate that a blood vessel was damaged.

Complications

As with all invasive procedures, cardiac catheterization involves some risks. The most serious complications include stroke, myocardial infarction, and death resulting from clotting or rupture in one of the coronary or cerebral vessels. Other complications include cardiac arrhythmias, pericardial tamponade, vessel injury, and renal failure. The most common complications resulting from cardiac catheterization are vascular-related, including external bleeding at the arterial puncture site, hematomas, and pseudoaneurysms.

The patient may be given anticoagulant medications to lower the risk of developing an arterial blood clot (thrombosis) or of blood clots forming and traveling through the body (embolization).

The risk of complications from cardiac catheterization is higher in patients over the age of 60; those who have severe heart failure; or those with advanced valvular disease.

Allergic reactions related to the contrast agent (dye) and anesthetics may occur in some patients during cardiac catheterization. Allergic reactions may range from minor hives and swelling to severe shock. Patients with allergies to seafood or penicillin are at a higher risk of allergic reaction; giving antihistamines prior to the procedure may reduce the occurrence of allergic reactions to contrast agents.

Results

Normal findings from a cardiac catheterization will indicate no abnormalities in the size or configuration of the heart chamber, the motion or thickness of its walls, the direction of blood flow, or motion of the valves. Smooth and regular outlines on the x ray indicate normal structure of the coronary arteries.

The measurement of intracardiac pressures, or the pressure in the heart's chambers and vessels, is an essential part of the catheterization procedure. Pressure readings that are higher than normal are significant for a

patient's overall diagnosis. Pressure readings that are lower, other than those resulting from shock, are usually not significant.

The ejection fraction is also determined by performing a cardiac catheterization. The ejection fraction is a comparison of the quantity of blood ejected from the heart's left ventricle during its contraction phase with the quantity of blood remaining at the end of the left ventri cle's relaxation phase. The cardiologist will look for a normal ejection fraction reading of 60–70%.

Abnormal results are obtained by viewing the still and live motion x rays during cardiac catheterization for evidence of coronary artery disease, poor heart function, disease of the heart valves, and septal defects.

The most prominent sign of coronary artery disease is narrowing or blockage (stenosis) in the coronary arteries, with narrowing greater than 50% considered significant. A clear indication for intervention by angioplasty or surgery is a finding of significant narrowing of the left main coronary artery and/or blockage or severe narrowing in the high left anterior descending coronary artery.

A finding of impaired wall motion is an additional indicator of coronary artery disease, an aneurysm, an enlarged heart, or a congenital heart problem. Using an ejection fraction test that measures wall motion, cardiologists regard an ejection fraction reading under 35% as increasing the risk of complications while also decreasing the possibility of a successful long- or short-term out- come from surgery.

Detecting the difference in pressure above and below the heart valve can verify the presence of valvular disease. The greater the narrowing, the higher the difference in pressure.

To confirm the presence of septal defects, measurements are taken of the oxygen content on both the left and right sides of the heart. The right heart pumps unoxygenated blood to the lungs, and the left heart pumps blood containing oxygen from the lungs to the rest of the body. Elevated oxygen levels on the right side indicate the presence of a left-to-right atrial or ventricular shunt. Low oxygen levels on the left side indicate the presence of a right-to-left shunt.

Health care team roles

A cardiac catheterization team consists of a physician (e.g., interventional cardiologist), a nurse, a circulating nurse, and a radiologic technologist. Nurses assist the physician and monitor the patient during the procedure. Because clinical laboratory equipment may be used during the procedure to monitor certain parameters (e.g., blood coagulation time), nursing or other staff should be familiar with the operation of laboratory devices used in the cardiac catheterization suite. The radiologic tech- nologist assists the physician with the operation of the xray and fluoroscopy equipment during the procedure and oversees any image processing, printing, and/or storage needs. The radiologic technologist may work with a medical physicist to monitor radiation safety protocols for the patient and staff.

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KEY TERMS

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Aneurysm—An abnormal dilatation of a blood vessel, usually an artery. It may be caused by a congenital defect or weakness in the vessel's wall.

Angiography—A procedure that allows x-ray examination of the heart and coronary arteries following injection of a radiopaque substance (often referred to as a dye or contrast agent).

Angioplasty—A procedure in which a balloon catheter is used to mechanically dilate the affected area of a diseased artery and enlarge the constricted or narrowed segment. It is an alternative to vascular surgery.

Aortic valve—The valve between the heart's left ventricle and ascending aorta that prevents regurgitation of blood back into the left ventricle.

Arrhythmia—A variation in the normal rhythm of the heartbeat.

Catheter—A flexible or preshaped curved tube, usually made of plastic, used to evacuate fluids from or inject fluids into the body. In cardiac catheterization, a long, fine catheter is inserted through a blood vessel directly into the chambers of the heart.

Computed tomography (CT)—A diagnostic imaging procedure that uses x rays to produce cross-sectional images of the anatomy. It may be performed prior to cardiac catheterization.

Coronary bypass surgery—A surgical procedure that places a shunt to allow blood to travel from the aorta to a branch of the coronary artery at a point below an obstruction.

Echocardiography—An ultrasound examination of the heart that may be performed prior to cardiac catheterization.

Fluoroscopy—A diagnostic imaging procedure that uses x-rays and contrast agents to visualize anatomy and motion in real time.

Hematoma—An accumulation of clotted blood that may occur in the tissue around the catheter insertion site following cardiac catheterization.

Ischemia—A localized deficiency in the blood supply, usually caused either by vasoconstriction or by obstacles to the arterial blood flow.

Magnetic resonance imaging (MRI)—A diagnostic imaging procedure that uses a magnetic field to produce anatomical images. It may be performed prior to cardiac catheterization.

Mitral valve—The bicuspid valve that lies between the left atrium and left ventricle of the heart. "Bicuspid" means that the valve has two flaps.

Percutaneous transluminal coronary angioplasty (PTCA)—A cardiac intervention in which an artery blocked by plaque is dilated, using a balloon catheter to flatten the plaque and open the vessel. It is also called balloon angioplasty.

Pericardial tamponade—The collection of blood in the sac surrounding the heart that causes compression. Tamponade is a possible complication of cardiac catheterization

Pseudoaneurysm—A dilation of a blood vessel that resembles an aneurysm. Pseudoaneurysms may occur as a complication of cardiac catheterization.

Pulmonary valve—The heart valve that separates the right ventricle and the opening into the pulmonary artery.

Septum—The muscular wall that separates the two sides of the heart. An opening in the septum that allows blood to flow from one side to the other is called a septal defect.

Shunt—A passageway (or an artificially created passageway) that diverts blood flow from one main route to another.

Stent—A small tubelike device made of stainless steel or other material, used to hold open a blocked artery.

Tricuspid valve—The right atrioventricular valve of the heart. It has three flaps, whereas the mitral valve has only two.

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Jennifer E. Sisk, M.A.