Cardiac Catheterization And Bypass Surgery

Anatomy

The heart is a muscular organ about the size of a clenched fist that lies in the chest beneath the sternum or breast bone. The function of the heart is to supply blood to the body. The heart is divided into four chambers, two upper chambers called the right and left atria and two lower chambers called the right and left ventricles (Figure 1)

Figure 1a - The heart viewed from in front showing the position of the right and left atria and ventricles.

Figure 1b - Diagram of the atria, ventricles and valves of the heart with the heart muscle relaxed (diastole). The yellow arrows show the direction of blood flow through the valves.

Figure 1c - Diagram of the heart during a contraction of the heart muscle (systole). The yellow arrows show the direction of blood flow through the valves.

The left ventricle of the heart pumps blood through the aortic valve into the aorta, the largest artery in the body, and then out through a network of arteries to the whole body. The valves control the direction of flow of blood through the heart. After passing through the tissues of the body, the blood collects into the veins and returns to the right atrium. Blood then passes through the tricuspid valve into the right ventricle. The right ventricle pumps the blood through the pulmonary valve into the arteries of the lung where the blood picks up oxygen. The oxygenated blood returns to the left atrium after which it passes through the mitral valve to the left ventricle and the cycle repeats. Like all tissues in the body, the heart requires oxygen filled blood in order to function. Blood goes to nourish the heart through the coronary arteries.

Pathology

Cardiac catheterization may be required when the valves of the heart, usually the tricuspid or mitral valves, become diseased and either leak or become narrowed.

The coronary arteries become narrow with the deposition of fatty or calcified material on the inside of the artery. This is called atherosclerosis. Once atherosclerosis has developed, there may be further narrowing of the coronary artery by formation of a blood clot. The combination of fatty deposit, calcification and blood clot prevents blood from getting through the artery causing a heart attack. (Figure 2)

[Karl Note:  Here you see one of the largest lies in medicine -- the fraud that "fatty deposits" are plaque and cause blockage of an artery.  The truth is that there are excessive amounts of calcium INSIDE individual living cells in the arteries, causing that cell to either die (calcified) or be sluggish -- making the artery rigid, and preventing flow of blood.  Remove the CALCIUM from INSIDE those cells (by reducing the bombardment by free radicals) and the cell comes back to healthy condition, ejects the excessive calcium, and blood flow increases.  Putting a stent into this area of blockage solves nothing on a permanent basis. The cells are still being damaged by free radicals, the cells are still accumulating excessive calcium INSIDE the cells, and the stent will fail on the edges, where the artery is still being damaged by free radicals.]

Figure 2

History and Exam

There may be a history of shortness of breath, ankle swelling, irregular heart beat or chest pain. Disease of the valves of the heart may be related to infectious childhood disease or other causes. Coronary artery disease is heightened by several risk factors. It is important for you and your physician to know these risk factors so that they can be modified or eliminated. Some of the factors are

• high blood pressure
• high blood cholesterol
• smoking, stress
• lack of exercise
• being overweight
• family history of heart disease

An examination of the heart may reveal enlargement, an irregular beat, or abnormal heart sounds. Examination of the lungs may show emphysema or water on the lungs. Swollen ankles or distended neck veins may suggest heart failure.

Tests

Prior to a cardiac catheterization, your doctor may run several tests including a chest X-ray, various blood tests, an electrocardiogram or EKG, and an exercise stress test with or without the administration a special isotope material called thallium.

The Procedure

Cardiac catheterization is usually a precursor to a surgical intervention such as:

• Angioplasty, a procedure usually carried out at the same time as the catheterization in which the narrowed coronary artery is dilated with a special balloon.
• Coronary artery stent, a procedure similar to angioplasty however a special metallic wire mesh called a stent is inserted to keep the artery from narrowing again,or
• Heart surgery varies depending on the problem determined by the cardiac catheterization. This may be surgery on one on the heart valves or surgery to bypass a blocked coronary artery.

If you do not wish to follow through with any of these surgical procedures, you may not wish to undergo the cardiac catheterization.

Usually the catheterization is performed as an outpatient and you return home the same day. Prior to catheterization, medication is given for relaxation. A needle is inserted into a vein for the any necessary intravenous medication. In the cardiac catheterization laboratory or cath lab, sticky electrodes are applied for an EKG. The needle insertion site, usually in the groin, is antiseptically cleansed and local anesthetic injected at the site.

Left heart catheterization is used to investigate the coronary arteries. A special needle is inserted into an artery at the injection site through which a flexible wire is inserted. The needle is removed and a catheter sheath is slipped over the wire and into the artery. The wire is removed, a catheter inserted through the sheath into the artery and manipulated under fluoroscopic control into a coronary artery. An iodine containing fluid (contrast dye) is injected into the coronary artery under pressure to obtain the coronary angiogram.

When a significant blood clot is seen on coronary angiography, your doctor may treat you with thrombolytic therapy. Thrombolytic drugs dissolve clots. Intravenous thrombolytic therapy is given into a vein while intracoronary therapy is given directly into the narrowed coronary artery."

Occasionally, the findings at the time of catheterization necessitate immediate angioplasty, stent or coronary artery bypass surgery.

Right heart catheterization is used to study the valves and chambers of the heart. The special needle is inserted into a groin vein. In a manner similar to that described above for coronary artery catheterization, a catheter is inserted into the vein and manipulated under fluoroscopic control toward the heart and into the right atrium. The contrast dye is injected and shows up on rapid sequence X-ray movies and outlines the interior of the heart, the atria and ventricles. The pressures in the chambers of the heart are measured and blood samples may be taken from the catheter to measure the level of oxygen in the various heart chambers.

Additional Procedures

While still on the angiographic table, your doctor may choose to unblock your narrowed coronary artery by carrying out a coronary angioplasty.

Select image below to view animation
A special catheter is used that contains a balloon at its tip. The balloon is positioned in the middle of the blockage in the coronary artery and inflated with a dye solution that can be seen under the flouroscope. This helps your doctor determine when the block is reduced. When the balloon is inflated in the coronary artery, you may feel a pressure in your chest similar to the anginal pain that you may have had	Your doctor may choose to insert a stent in the dilated coronary artery. A stent is a specially designed metal mesh that is introduced on a balloon that can be selectively pressurized. The stent is positioned in the middle of the blockage and the balloon inflated. This forces the stent open against the wall of the artery. The stent is designed to remain open after the balloon is deflated and the catheter removed

Complications

Most complications of cardiac catheterization are minor such as:

• Groin hematoma
• Transient cardiac arrhythmia
• Transient low or high blood pressure

More significant complications such as:

• Heart attack
• Large groin hematoma
• Loss of pulse to the limb
• Stroke
• Perforation of the wall of the heart
• Allergic reaction to the contrast dye can occur. If you are allergic to iodine or have a previous history of allergy to intravenous contrast dye for previous medical tests, it is important to tell your doctor before the procedure

The chance of a serious complication including the necessity of immediate cardiac surgery increases if coronary angioplasty or stenting is necessary. For this reason, these procedures are carried out only in hospitals with heart surgery capability.

After catheterization

After the catheterization, you will be observed so as to be sure that you do not develop a collection of blood or hematoma at the needle insertion site. A small hematoma at the needle site is not unusual and of little significance. The pulse, temperature and feeling in the arm or leg may also be checked. Should you notice swelling at the needle site or feel pain, cold or numbness in the arm or leg, it is important that you contact the nurse immediately.

Though during catheterization, your doctor may get a preliminary idea of your problem, a final determination is made after your doctor reviews the X-ray films, movies and other data taken during the catheterization. Later your doctor will review with you the findings of the catheterization and make a recommendation for further care such as a change in medication or heart surgery for correction of a valvular defect or coronary artery bypass surgery.

see Coronary Artery Surgery