1Your Heart & Valves

3.2Electrocardiography (ECG)

E
lectrocardiography (ECG) is a quick, simple, painless procedure in which electrical impulses flowing through the heart are amplified and recorded on a moving strip of paper. This record, the electrocardiogram (the ECG), provides information about the part of the heart that triggers each heartbeat (the pacemaker), the nerve conduction pathways of the heart, and the rate and rhythm of the heart.

An electrocardiogram (ECG) represents the electrical current moving through the heart during a heartbeat. The current's movement is divided into parts, and each part is given an alphabetic designation in the ECG.

Each heartbeat begins with an impulse from the heart's pacemaker (sinus or sinoatrial node). This impulse activates the upper chambers of the heart (atria). The P wave represents activation of the atria.

Next, the electrical current flows down to the lower chambers of the heart (ventricles). The QRS complex represents activation of the ventricles.

The electrical current then spreads back over the ventricles in the opposite direction. This activity is called the recovery wave, which is represented by the T wave.

Many kinds of abnormalities can be seen on an ECG. For example, the heart rhythm may be abnormal: too fast, too slow, or irregular. By reading an ECG, doctors can usually determine where in the heart the abnormal rhythm starts and can begin to determine its cause.

3.3Multiple-gated acquisition (MUGA) scan

The MUGA scan measures the heart's function and the flow of blood through it. The strongest chamber in the heart is the left ventricle, which serves as the main pump of blood through the body. The MUGA scan is the most accurate, non-invasive test available to assess the heart's ventricles.

MUGA is a nuclear heart scan, which means that it involves the use of a radioactive isotope that targets the heart and a radionuclide detector that traces the absorption of the radioactive isotope. The isotope is injected into a vein and absorbed by healthy tissue at a known rate during a certain time period. The radionuclide detector, in this case a gamma scintillation camera, picks up the gamma rays emitted by the isotope.

The MUGA scan is not dangerous. The technetium is completely gone from the body within a few days of the test. The scan itself exposes the patient to about the same amount of radiation as a chest x ray. The patient can resume normal activities immediately after the test.

Normal results

If the patient's heart is normal, the technetium will appear to be evenly distributed in the scans. In a stress MUGA, patients with normal hearts will exhibit an increase in ejection fraction or no change.

Abnormal results

An uneven distribution of technetium in the heart indicates that the patient has coronary artery disease, a cardiomyopathy, or blood shunting within the heart. Abnormalities in a resting MUGA usually indicate a heart attack, while those that occur during exercise usually indicate ischemia. In a stress MUGA, patients with coronary artery disease may exhibit a decrease in ejection fraction.

3.4Cardiac Catheterization (Cardiac Cath or Angiogram)

A catheter (inserted into your arm or leg) is guided to your heart, contrast dye is injected and x-rays of your coronary arteries, heart chambers, and heart valves are taken.

Additional tests, such as the exercise stress echocardiogram, radionuclide scans, and magnetic resonance imaging (MRI) may also be used.

4Valve Replacement and Repair

4.1Mechanical Valve Replacement

A

ortic Mitral

Mechanical valves are made totally of mechanical parts, which are non-reactive and tolerated well by the body. The bileaflet valve is used most often. It consists of two pyrolite (qualities similar to a diamond) carbon leaflets in a ring covered with polyester knit fabric.

Advantages:

Mechanical valves are very sturdy. They are designed to last a lifetime. Re-operations for mechanical failures or tissue in-growth are uncommon.

Drawbacks:

Due to the artificial material involved, patients who receive these valves will need to take a blood-thinner (anticoagulant) medication for the rest of their lives. Blood thinners are medications (such as warfarin or Coumadin) that delay the clotting action of the blood. They help prevent clots from forming on the valve prosthesis; such clots can cause a heart attack or stroke and disturb the valve function.

Bi Technology valve prosthesis. After the examination of 33 mechanical prostheses over 264 months (mean, 72 months), the overall causes of failure modes included paravalvular leak 15%, thrombosis 7%, tissue overgrowth 8%, degeneration or mechanical failure 43%, and endocarditis 19%.

No clear failure mode predominates with mechanical valve prostheses, although some designs have specific inherent limitations.

Tri Technology valve prosthesis has a high risk of structural failure; leaflet escape caused by a leaflet’s pivoting system fracture is usually fatal.

4.2Mitral valve repair

Mitral valve repair is the procedure of choice for most patients with mitral regurgitation (a leaky valve). When the leak is caused by mitral valve prolapse (degenerative mitral valve disease), a variety of repair techniques may be employed. Quadrangular resection is the technique used most frequently for posterior leaflet prolapse. Mitral valve repair is superior to replacement. If repair is not feasible, the subvalvular apparatus should be preserved. Early surgery before the development of severe symptoms and demonstrable left ventricular impairment is also needed to optimize outcome

C
hordal transfer to correct anterior leaflet prolapse. Posterior leaflet chordae are transferred to the unsupported free edge of the anterior leaflet. The posterior leaflet is repaired as after a quadrangular resection.

Gor-Tex chord for correction of anterior leaflet prolapse.

Chordae may be constructed from Gore-Tex sutures. A premeasured loop of Gore-Tex is affixed to the head of the papillary muscle with a pledgetted suture. The loop is then attached to the free edge of the unsupported anterior leaflet, providing support.

L
ong-term durability is excellent. The new chordae do not rupture or elongate.