How does a heart become damaged from a heart attack?A part of the muscle dies from lack of oxygen and blood to that area.
Is the damage from a heart attack always permanent?
Depends on the degree of the damage, but the damage is usually permanent because that part of the tissue dies. There may be some other tissue that is not dead but is not functioning properly, stunned myocardium, but with improved blood flow this part of the heart muscle may come back.
How can they tell if you had permanent damage after a heart attack?
There are non-invasive tests which can look at the heart and assess its function. These include an echo cardiogram, radionuclide studies or MRI to see how well the heart muscle is pumping.
Echo cardiogram is described in the hospitalization question.
Cardiac nuclear imaging allows assessment of heart function under induced stress (nuclear stress test). It involves injecting a small amount of a radioactive substance such as Thallium or Cardiology into the circulatory system and tracking it as it passes through the heart. The patient lies on a special table and a camera (gamma camera) which is able to see the radioactive isotope creates pictures as the isotope passes through the heart. When exercise is not possible, pharmacological agents such as dobutamine, adenosine, or dipyradimole (Persantine) are injected to induce stress.
The thallium (radioactive substance) mixes with the blood in the bloodstream and enters heart muscle cells. If a part of the heart muscle doesn't receive a normal blood supply, less than a normal amount of thallium will be seen. The first pictures are made shortly after the exercise test and show blood flow to the heart during exercise. The patient then lies quietly for 2-3 hours and another series of pictures is made. These show blood flow to the heart muscle during rest.
If the test is normal during both exercise and rest, then blood flow through the coronary arteries is normal. The coronary arteries supply blood to the heart muscle.
If the test shows that perfusion (blood flow) is normal during rest but not during exercise (a perfusion defect), then the heart isn't getting enough blood when it must work harder than normal. This may be due to a blockage in one or more coronary arteries.
If the test is abnormal during both exercise and rest, there's limited blood flow to that part of the heart at all times.
If no thallium is seen in some part of the heart muscle, the cells in this part of the heart are dead from a prior heart attack. (They have become scar tissue.)
Cardiovascular magnetic resonance imaging (CMRI) is an increasingly available diagnostic method. It uses powerful magnets to look inside the body. Computer-generated pictures can show the heart muscle, identify damage from a heart attack, diagnose certain congenital cardiovascular defects and evaluate disease of larger blood vessels such as the aorta. For cardiac imaging breath holding is frequently needed. Unlike radiographic imaging methods.
It's non-ionizing and has no known biological hazards.
It can produce high-resolution images of the heart's chambers and large vessels without the need for contrast agents.
It's intrinsically three-dimensional.
It produces images of cardiovascular structures without interference from adjacent bone or air.
It has high tissue contrast.
The disadvantages of the cardiac MRI are:
The technology is not as widely available.
Pacemakers/defibrillators are relative contraindications for MR imaging.
It is currently not suitable for claustrophobic individuals.
Motion during imaging results in significant image artifacts.
Technology is not suitable for portable (eg, bedside) studies.
How is pump function measured?
It is measured with an echocardiogram. In general the systolic function (how well the heart muscle squeezes and pushes out the blood and the diastolic function (how well the heart muscle relaxes) are measured. Pump function is measured by the ejection fraction which is the amount of blood pumped by the left ventricle (the largest chamber of the heart) divided by the amount of blood that the left ventricle contains.
What would be normal pump function?
Normal ejection fraction is more than 55% of the blood volume.
How low can you go before it would affect your life and how would you be affected by the reduced pump function?
Any decrease in the pump function below the normal level may impact a patient’s life. A reduced pump function may cause decreased energy level and a decreased exercise tolerance, increased fatigue, shortness of breath, and fluid accumulation in the legs and in the lungs. It also may disrupt normal sleep and cause increased somnolence during the day. Depression may also occur.
