Cardiac Electrophysiology Consultants of South Texas, P.A.

Medical Center Tower I
7950 Floyd Curl Drive
Suite 803
San Antonio, TX 78229
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General information about the heart for patients, their family members, and concerned laymen

Cardiac Catheterization Section Contents
Cardiac Catheterization
Cardiac catheterization is the general name for a group of procedures in which long, thin tubes (catheters) are placed in the heart and its adjacent blood vessels. The tubes may be hollow or solid. The hollow tubes allow measurement of pressures, injection of fluids such as X-ray dyes, and/or withdrawal of blood. The solid tubes contain wires, for recording electrical activity and/or for pacing the heart; or specialized instruments, such as jaws (bioptomes) that allow taking a tiny piece of heart muscle for laboratory study. When X-ray dye is injected into the heart or its adjacent blood vessels, the procedure can also be called angiography.

It is important to remember that catheterization and angiography merely look at problems. They don't fix them. Problems in the heart, when they can and should be fixed, are treated by angioplasty or cardiac surgery.

The general types of cardiac catheterization and angiography in adults are described in the following subsections.

Left heart and coronary angiography
Left heart and coronary angiography is a study of the left ventricle, which is the main pumping chamber of the heart, and of the arteries that supply oxygen and nutrients to the left ventricle (the coronary arteries). The study also yields some information about the aortic valve and the mitral valve. It is commonly used in a person who has had heart attack or who is at risk for having a heart attack.

This test requires that the catheters, which are hollow, be placed into an artery in the groin (femoral artery) or the arm (brachial artery) and then be moved to the arteries (which lie in the aorta just above the left ventricle) or into the left ventricle. After pressures are measured, X-ray dye is injected and moving pictures are recorded using X-ray imaging to show how the dye moves after injection.

Measurement of Pressures during Cardiac Catheterization
Pressures are measured in the left ventricle and in the aorta. The end-diastolic left ventricular pressure reflects the state of hydration of the patient, the diastolic function of the ventricle, and, indirectly, the systolic function of the ventricle. It is below normal when the patient is dehydrated. It is above normal when the patient has too much fluid in the blood stream (e.g., in renal failure before dialysis), has diastolic dysfunction (e.g., due to hypertension or restrictive cardiomyopathy), and/or has system dysfunction (e.g., due to myocardial infarction or stunning).

The difference in the pressures between the left ventricle and the aorta is the "gradient" across the aortic valve. (Rarely, the ventricular muscle below the aortic valve can also create a gradient. This occurs in a condition known as "idiopathic hypertrophic subaortic stenosis". We do not discuss this here.) If the gradient is very high, the person most likely has such a small opening of the valve (small "valve area") that he or she may need to have it replaced with an artificial valve. People who have or may have bad heart valves (and/or intracardiac shunts) usually have simultaneous left and right heart catheterization instead of simple left heart catheterization so that the valve area can be estimated more accurately.

Coronary and Cardiac Angiography
The process of taking pictures of the blood vessels using X-ray imaging and injections of X-ray dye is called "angiography". If there are no blockages in the coronary arteries, the dye flows smoothly from the opening of each artery through all the branches until the branches become too small to see. If there are partial blockages, they appear as irregularities in the column of dye that fills the artery. Complete blockages, or occlusions, result in dye not being able to flow along branches that otherwise would be seen.

When dye is injected briskly into the left ventricle ("left ventriculogram") (or any of the other cardiac chambers), it fills the chamber fully and then is ejected and replaced with ordinary blood that has no dye in it. The X-ray movies that are taken while the chamber is full of blood show how the walls of the chamber move, and whether there are abnormal masses within the chamber. In adult cardiology, the left ventricle is the chamber that is studied most often. Because heart attacks damage the left ventricle in different ways in different people, a ventriculogram is one good way to see what parts of a person's ventricle are damaged and how badly, and how good the overall pumping action (the "ejection fraction") is. Note that the left ventricular wall motion and ejection fraction can also be assessed noninvasively with echocardiography and with nuclear ventriculography.

The person undergoing left heart catheterization feels a stinging and some burning as the numbing medicine ("local anesthetic") is injected into the skin, and sometimes some temporary deep pain as the introducer (through which the catheters are passed into the artery) is placed in the artery. Usually, people cannot feel the catheters moving inside the arteries or in the heart. The person may feel some fluttering as the catheter is positioned within the heart itself, may feel anginal pain when dye is injected into the coronary arteries, and will almost certainly feel a hot flash as dye is injected rapidly into the left ventricle during the ventriculogram. Sometimes people feel nauseated for a minute or two after the ventriculogram, but this is unusual.

The risks of left heart catheterization are moderate, and arise from four principal steps: insertion of the catheter into the artery, positioning of the catheter(s) in the heart, leaving the catheter(s) in the heart for minutes at a time, and use of X-ray dye. The risks include bleeding and/or obstruction of the artery, puncture of the heart with a catheter, dislodgement of atherosclerotic plaques from the aorta, dissection of the aorta or a coronary artery with the catheter, and development of blood clots (thrombi) on the catheter. There are other rare risks also. These risks can cause death, myocardial infarction, and stroke. The catastrophic risks occur in about 1 of 500 cases.

More minor risks can create the need for emergency surgical repair, usually of the arterial puncture. This level of risk occurs in about 1 of 100 cases. The X-ray dye is usually well tolerated. It can cause allergic reactions and can damage the kidneys. Although kidney failure is unusual and is often reversible, it can lead to permanent renal failure requiring dialysis in people whose kidneys are not working well before the procedure. The newer and much more costly "non-ionic" dyes, which have fewer side effects than the older "ionic" dyes, do not seem to have a lower risk of causing kidney failure.

As with any many procedure that is not free of risk, it should be performed only when its estimated benefit exceeds the estimated risks.

Right heart catheterization
Right heart catheterization consists of placing a long, thin tube ("catheter") into the heart through a vein in the arm, the shoulder, the neck, or the groin. (The veins are the brachial, subclavian, internal jugular, and femoral veins, respectively.) This procedure allows measurement of the rate of blood flow ("cardiac output") and the pressure gradient across the tricuspid and pulmonic valves, and the pressures in the right atrium, right ventricle, pulmonary artery, and the left atrium (via the indirect "pulmonary capillary wedge pressure"). When pacemaker electrodes or a bioptome are placed in the heart instead of hollow catheters, the procedures are called cardiac electrophysiology studies and cardiac endocardial biopsy, respectively.

There are several reasons for performing right heart catheterization:

  • When a person has an enlarged heart for which there is no other explanation, sometimes there is a "hole in the heart" (an intracardiac shunt due to an atrial septal defect or an ventricular septal defect). These can be diagnosed by echocardiography, but the gold standard is cardiac catheterization. The concept behind the use of catheterization is that blood on the right side of the heart, which is on its way to the lungs, should have relatively little oxygen. Blood on the left side of the heart, which comes from the lungs, should have a lot of oxygen. The amount of oxygen in the blood should not change much from place to place on either side of the heart. By measuring oxygen saturations at various places on both sides of the heart, abnormal changes in the oxygen content can be detected. If there is a left-to-right shunt (the more common type in adults), there will be an increase in oxygen content starting at the shunt and continuing into the lungs. In the case of a right-to-left shunt, there will be a decrease in oxygen content starting at the level of the shunt and continuing into the aorta.
  • Pressures measured on the right side of the heart are also useful for estimating the risks and benefits of surgery to repair intracardiac shunts and valves, and for transplanting hearts.
The risks of right heart catheterization are small, and arise from two principal steps: insertion of the catheter into the vein, particularly when the vein is in the shoulder or the neck, and positioning of the catheter in the heart. The risks include pneumothorax and myocardial puncture with pericardial effusion and tamponnade. There are also the general risks of placing foreign items in the body, which include bleeding, infection, and blood clots. Because the procedure is not free of risk, it should be performed only when its estimated benefit exceeds the estimated risks.
Left and Right heart catheterization
Right heart catheterization allows measurement of the rate of blood flow ("cardiac output"), the pressure gradient across the tricuspid and pulmonic valves, and the pressures in the right atrium, right ventricle, pulmonary artery, and the left atrium (via the indirect "pulmonary capillary wedge pressure"). Left heart catheterization allows measurement of the pressure lgradient across the aortic valve. Simultaneous right and left heart catheterization allows measurement of the pressure gradient across the mitral valve, and oxygen saturations (which measure the amount of oxygen in sample of blood taken from various parts of the heart and great vessels) can be measured simultaneously both sides of the heart.

These additional pieces of information are important for several reasons.

  • When a valve is suspected of being too tight, it is useful clinically to estimate the "valve area", which is the size of the opening in the valve when it is opened as far as it will go. The valve area cannot be estimated from only the gradient because the gradient depends on the area of the opened valve, the heart rate, and the rate of blood flow across the valve (the "cardiac output").

    It is important to note that valve areas can also be estimated by echocardiography, which can be performed with much less risk than can cardiac catheterization. The final decision as to whether echocardiography can replace cardiac catheterization in a person who may need valve replacement surgery should be made by the surgeon who would replace the valve. If echocardiography estimates the valve as being not too bad, the final decision should be made by the senior cardiologist on the case. The reasons behind these rules of thumb are (1) echocardiography can be wrong in its estimates of valve gradients, (2) catheterization carries a small but definite of risk of morbidity and mortality, and (3) valve replacement surgery (even if the valve still turns out at surgery not to need replacement) carries a larger risk of morbidity and mortality.

  • This procedure can detect and estimate the size of "holes in the heart" (an intracardiac shunts); and to estimate the risks and benefits of surgery to repair intracardiac shunts and valves, and for transplanting hearts. The methodology is described above.
The risks of left and right heart catheterization are about the same as the individual risks of these procedures.
Cardiac Biopsy
A "biopsy" is a small piece of tissue that is removed from the body to diagnose illnesses. Cardiac biopsy is performed mostly in people who have had heart transplants in order to see whether the body is rejecting the new heart. It is sometimes performed in people who have unusual symptoms to see whether they might have rare diseases such as viral myocarditis or cardiac amyloidosis.

A "cardiac biopsy" is the removal of a small piece of heart tissue (myocardium) using a small pincer-like device called a "bioptome". The tissue is usually removed from the "interventricular septum", the thick part of the heart that divides the right ventricle from the left ventricle. The biopsy process starts with placing the bioptome into a large vein, usually the right internal jugular vein in the neck or the right femoral vein in the groin. Using X-ray ("fluoroscopy") to make sure the bioptome goes where it supposed to go, the bioptome tip is positioned in the right ventricle against the septum. Its jaws are opened, the tip is pushed gently against the septum, and the jaws are then closed around a bit of muscle about the size of a few grains of rice. The bioptome is then removed from the body, and the piece of tissue is removed from the bioptome using sterile technique. The process is repeated until about three to five satisfactory pieces of heart muscle are removed.

The person having the procedure will feel some burning in the skin before the numbing medicine ("local anesthetic") takes effect. There is sometimes some deep pain briefly as the introducer (through which the bioptome is place into the vein) is itself placed in the vein. There may be some "fluttering" in the chest as the bioptome is moved around, and a "tugging" feeling as the bioptome is pulled back with a sample in its jaws. Otherwise, people don't feel much during the procedure except when the table is hard to lie upon.

The risks of the procedure are those of introducing a needle into a large vein (bleeding, infection, blood clot, puncture of the lung or a nearby artery when the needle goes into the shoulder or neck), and the risk of making a hole in the heart with the bioptome. The last risk is quite small, but there is always the possibility of emergency heart surgery if a large hole is made that won't close on its own.

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