Cardiac catheterization is a minimally invasive procedure in which a long, thin tube called a catheter is guided into the heart, usually through a blood vessel in the leg or arm. Once inside the heart, it can be used to diagnose a problem (diagnostic uses) or to treat a problem (therapeutic uses). This article deals with the diagnostic uses of cardiac catheters.

By gaining access to the beating heart, cardiac catheters allow a physician to check the internal blood pressure of the heart, assess blood supply, view the coronary arteries on the surface of the heart and (depending on where the catheter is placed) the aorta, monitor the electrical activity in the heart, and check the level of oxygen in the blood. It is also used to evaluate the ability of the pumping chambers to contract, as well as to assess the function of heart valves. Cardiac catheterization is one of the most accurate tests in the diagnosis of coronary artery disease, and over a million of them are done each year. 

During cardiac catheterization, the catheter is inserted through a very small cut made by the physician (in the groin, arm or wrist), then guided up through the blood vessel to the heart. The physician tracks the course of the catheter by watching it on a fluoroscope, an x-ray machine that displays the catheter and blood vessels in real time on a screen. A variety of measurements may be performed when the catheter is in place, and then the catheter is removed. After some recovery time, most patients are free to go home after about six hours. Results are available to the physician immediately.

Cardiac catheterization is a minimally invasive procedure in which a long, thin tube called a catheter is guided into the heart, most commonly passed through an artery in the groin. Once inside the heart, it can be used for diagnostic purposes to assess blood supply to the heart as well as the function of the heart's main pumping chamber (left ventricle). It can also be used to perform therapeutic interventions to correct a problem. This article deals with the diagnostic uses of cardiac catheters.

By gaining access to the beating heart, cardiac catheters can provide valuable information. Using a catheter, a physician can check the internal blood pressure of the heart, get a good look at the coronary arteries on the surface of the heart, and (depending on where the catheter is positioned) the aorta. Catheters are also used to monitor the electrical activity in the heart to diagnose arrhythmias and plan treatments.

During the cardiac catheterization, a physician inserts the catheter into a patient’s blood vessel (usually in the groin) and passes the tube toward the heart. Depending on where the catheter is placed, and which test is performed, the test can yield a wide range of information about the arteries connected to the heart and the structures of the heart itself. The procedure can help a physician identify narrowed or clogged arteries, evaluate the heart’s four valves, and assess for any congenital heart defects. Cardiac catheters can also be used to measure the blood pressure within the heart itself, or measure the amount of oxygen in the blood.

The cardiac catheterization may include four major components:

There are two basic reasons a cardiac catheterization might be done. The first reason is to gain critical information about the heart and major arteries before surgery, as well as to clearly see the source of the problem in the patient. This helps physicians plan any upcoming procedure. Specific examples include:

• Determining whether someone is a good candidate for surgery (e.g., a bypass surgery) or other procedures
  
  
• Detecting any other heart defects that may be present before doing surgery to correct a heart defect
  
  
• Getting a clear picture of a heart defect before surgically correcting it, or to determine whether surgery is necessary

The other basic reason cardiac catheterization would be done is to help make a diagnosis of a suspected cardiac problem, especially coronary artery disease. Other conditions that may be detected by cardiac catheterization include:

• Pulmonary hypertension. High blood pressure in the lungs, often due to cardiac abnormalities.
  
  
• Pulmonic valve stenosis. A condition when the pulmonic valve, which regulates blood flow from the right ventricle to the pulmonary arteries, is partially blocked.
  
  
• Pulmonary embolism. A condition when a blood clot has caused restricted blood flow inside the lungs.
  
  
• Congenital defects. Cardiac catheterization can be used to confirm certain heart defects present at birth, including tetralogy of Fallot, transposition of the great arteries, tricuspid regurgitation and ventricular septal defect, atrial septal defect. 
  
  
• Other heart valve problems. These may include stenosis (narrowing) or regurgitation of any of the heart valves.  

Cardiac catheterization is usually done after other tests have been performed. These tests include:

• Electrocardiogram (EKG). An EKG is a recording of the heart’s electrical activity as a graph on a moving strip of paper. The highly sensitive electrocardiograph machine helps detect heart irregularities, disease and damage by measuring the heart’s rhythms and electrical impulses.
  
  

• Echocardiogram of the heart. This test uses sound waves to visualize the structure and function of the heart. A moving image of the patient’s beating heart is displayed on a video monitor, where a physician can study the heart’s thickness, size and function. The image also shows the motion pattern and structure of the four heart valves, revealing any potential leakage regurgitation. During this test, a Doppler ultrasound may be done to evaluate blood flow through the heart valves.
  
  

  
  

• Exercise stress test. An EKG is performed while the patient exercises in a controlled manner on a treadmill or stationary bicycle at varied speeds and elevations. The reaction of the heart under exertion can be measured and evaluated. This test may be done in conjunction with an echocardiogram (as described above) or nuclear imaging (a nuclear stress test).
  
  
• Computed tomography scan, or CT scan. This test uses x-ray technology and multiple sensors to create very accurate, three-dimensional images of the heart. Advances in CT technology have made this an important diagnostic tool that, together with magnetic resonance imaging (see below), has reduced the need for cardiac catheterizations.

Physicians generally advise their patients to continue taking all medications except anticoagulants (e.g. warfarin). Generally, antiplatelet agents are continued. These medications interfere with normal blood clotting and may be reduced or discontinued at some point before the test. Diabetic patients who need additional guidance should ask their physician about any specific instructions. Finally, patients are encouraged to bring copies of any previous tests done by their primary physician, such as an electrocardiogram (EKG).

Immediately before the test, patients will be asked various questions about their medical history. Patients are urged to discuss any history they may have had of blood clotting disorders or an allergic reaction to any of the following:

Cardiac catheterization may be performed as either an inpatient or outpatient procedure (sometimes referred to as an ambulatory cardiac catheterization). However, the American Heart Association and the American College of Cardiology stress that this test should be done in a hospital’s catheterization laboratory to be sure that appropriate resources are available should problems arise.

On the day of the procedure, the patient is taken to a cool and sterile catheterization laboratory that, to a patient, may resemble an operating room with its many monitoring devices, video display equipment and x-ray cameras. A nurse or physician will explain what is going to happen and the patient is encouraged to ask any questions that he or she may have.

Once the patient is made comfortable, the physician inserts an intravenous (I.V.) line into the patient’s wrist or arm. The I.V. allows the physician to give the patient a sedative and other necessary medications during the procedure. Small devices will be taped to the patient’s body, which allow the physician to monitor heart rate and rhythm.

The physician usually uses the groin/upper thigh area (the femoral artery) as the place where the catheter will enter the body on its way to the heart, but some physicians may choose to use the elbow or wrist. Whichever area is chosen will be cleaned, shaved, swabbed with germ-killing solution and numbed (with a local anesthetic). The catheter is then fed through the artery in that area (e.g., the femoral artery in the groin/upper thigh) and up into the heart. There may be some minor discomfort during this period. However, patients should let someone know if they are feeling any pain.

The physician will position the catheter in the left ventricle of the heart (although some physicians may choose to begin with the coronary arteries). When the catheter is correctly positioned in the left ventricle (and, if measuring the right heart pressure, another catheter is placed in the pulmonary artery), blood pressure measurements will be taken. Blood samples may also be taken. While the catheter is still in place in the left ventricle, a left ventriculogram may be performed to gain a clear picture of the left ventricle’s structure and functioning. To perform the ventriculogram, a special dye (contrast medium) is injected through the catheter and into the left ventricle. The injection of the dye may cause brief, normal experiences such as the following:

Following the left ventriculogram, a coronary angiogram is usually performed. The physician positions a different catheter in the coronary arteries and completes the coronary angiogram.

In some cases, an aortogram is also necessary. This part of the catheterization gives a clear image of the aorta (the main artery carrying oxygen-rich blood from the heart to the rest of the body). Following these procedures, the cardiac catheterization is complete. The entire test may take between 20 minutes and an hour depending upon factors such as physician experience.

Once the procedure is completed, the patient will be moved to a cardiac recovery room. They may feel groggy from the sedative. The catheter insertion site may be bruised and sore.

If the groin area was used as the point of catheter insertion, then patients will be instructed to lie in bed with legs out straight. The physician may choose to use one of two techniques for removing the sheath that was placed at the initiation of the procedure. The traditional technique is to wait until the effects of the anticoagulant have passed (four to six hours) and then to apply pressure while removing the sheath from the femoral artery. It is common to use a hemostatic device that allows the placement of a stitch or plug in the artery wall. This allows patients to get up out of bed within 2 hours after catheterization.

If the wrist or arm was used as the point of catheter insertion, then the patient does not need to stay in bed and can be discharged in two hours. In either case, the sedative will have worn off before discharge. Throughout the post-catheterization monitoring, the point of catheter entrance will be checked for bleeding, swelling or inflammation. Patients are encouraged to drink plenty of extra fluids during this period of rest to help flush the dye from their body. Results should be available within a matter of hours.

Patients are given instructions from the medical staff regarding the following:

The actual movement of the catheter should be painless and the risk of complications during this procedure is below 1 percent for the most serious complications. Although rare, these risks include:

Patients are encouraged to talk with their cardiologist about all aspects of this test, including complications, alternatives, risks and benefits. Both physicians and the American Heart Association strongly recommend that cardiac catheterization be performed in a hospital’s catheterization lab, where emergency equipment and trained personnel are close by, if necessary.

People are encouraged to speak with their physician if they have any questions or concerns about this very common and minimally invasive technique.

Magnetic resonance angiogram (MRA) has reached a very sophisticated level, such that blood flow through the coronary (heart) arteries can be viewed without the use of a cardiac catheterization. Instead, the noninvasive MRA scan is used to take three-dimensional images of the heart and blood flow, so the physician can detect any damage to the vessel walls.

The test takes less time than a cardiac catheterization, requires no recovery period and does not entail the same risks as a more invasive procedure. The MRA has already shown benefit in evaluating large blood vessels (e.g., the carotid arteries leading to the brain or the femoral arteries in the leg). It is also seeing increased use in diagnosing stenosis (narrowing) of the renal (kidney) arteries.

As this technology becomes more widely available, MRAs may become the preferred alternative to cardiac catheterization.

Preparing questions in advance can help patients have more meaningful discussions with their physicians regarding their conditions. Patients may wish to ask their doctor the following questions about cardiac catheterization:

1. How can cardiac catheterization help with my diagnosis?
   
   
2. Will I feel pain or discomfort during the test?
   
   
3. Do I need to alter my diet or stop taking any medications prior to the test?
   
   
4. What test results do you expect to see?
   
   
5. How will I find out the test results?
   
   
6. What follow-up tests may be necessary?
   
   
7. Who should I contact if I have questions about my test results?
   
   
8. Should I bring the results of previous tests with me to the test?
   
   
9. Will I be able to drive myself home after the test?
   
   
10. Will the test affect my pregnancy in any way?