How Does A Heart Attack Damage the Heart

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.

Hospital: When to go and What to Expect(About Heart)

When should you take your self to the hospital if you think you are having a heart attack?

Timing is every thing 1. If you think you are having a heart attack, call 911 ASAP. Do not drive yourself to the hospital or have someone else drive you. Call 911 which is different than calling an ambulance. 

What can they do in the hospital to tell if you are having a heart attack?

An electrocardiogram (ECG or EKG) is a is a painless non-invasive test that measures the electrical activity of the heart. Finding out how long a wave takes to travel from one part of the heart to the next shows if the electrical activity is normal or slow, fast or irregular. It can be used to detect if damage has been done to the heart muscle and in what general area of the heart the damage may have occurred. It also detects the rate and rythym of the heart.

Blood tests are done to detect cardiac enzymes. The blood test most commonly used to confirm the existence of heart muscle damage is the creation  kinase (CK). A small fraction of the CK enzyme, CK-MB, is often measured as well. CK-MB shows an increase above normal in a person's blood test about six hours after the start of a heart attack. It reaches its peak level in about 18 hours and returns to normal in 24 to 36 hours.

Tests can measure the amount of other cardiac muscle proteins called troponins, specifically troponin T (cTnT) and troponin I (cTnI). These proteins control the mechanism which contracts or squeezes the heart muscle. Troponins specific to heart muscle can detect minor heart muscle injury ("microinfarction") not detected by CK-MB. Normally the level of these special heart enzymes in the blood is very low because these enzymes normally exist and stay inside the heart muscle cells. When the heart muscle is damaged, these enzymes are released into the blood stream. It increases significantly within several hours (on average four to six hours) of heart muscle damage. It peaks at 10 to 24 hours and can be detected for up to 10 to 14 days. Levels of these cardiac enzymes compared to normal help doctors determine if you have a heart attack underway and its severity.

Echo cardiogram is a painless non-invasive imaging study which allows real-time imaging of the heart. It can assess how well the heart is or is not pumping. It uses high-frequency sound waves (ultrasound) to create an image of the heart . The sound waves measure the speed and direction of blood flow as well as wall motion and thickness of the heart chambers. It is commonly used for the evaluation of cardiac anatomy and physiology. It is similar to an ultrasound that is performed on pregnant women.

Cardiac catheterization is an invasive procedure used to detect the blocked arteries. See the page on operations for details.

CT coronary angiogram is a newer imaging study which may be done in some centers as a screening test for chest pains that are more atypical.

Coronary CT angiography (CCTA) has a relatively low technical burden for both the operator and patient and is quick to perform. The scanning time to acquire a three-dimensional dataset of the entire heart can take as little as 15 seconds. There are two types of CT scanners used for CCTA: electron beam computed tomography (EBCT), and multi-detector row or multislice CT scanners (MDCT or MSCT). MDCT scanners are much more widely available than EBCT scanners; as a result, most CCTA procedures are currently performed with MDCT scanners. To facilitate scanning and optimize image quality, most patients undergoing CCTA with current MDCT equipment receive oral or intravenous beta blockers to slow the heart rate to less than 60 to 70 beats/min. Sublingual nitroglycerin is sometimes given immediately before the scan to achieve maximal vasodilation.

Radiation exposure DCT scanners typically have higher spatial but lower temporal resolution than EBCT, and they impart a higher effective radiation dose to the patient when used for CCTA. In comparison, the effective radiation dose is 0.04 to 0.06 mSv from a routine chest x-ray, 2.0 to 5.0 mSv from an average diagnostic x-ray coronary angiogram, and the average annual background radiation in the United States is approximately 3.6 mSv.

Limitations The following patient-related factors can interfere with the diagnostic quality of CCTA images: 
Heart rate greater than 60 or 70 beats/min.
Irregular heart rhythm (atrial fibrillation; frequent atrial or ventricular extra-systoles). 
Inability to sustain a breath hold for at least 15 to 20 seconds.
Severe coronary calcification or the presence of coronary artery stunts, since image reconstruction artifacts related to radio-dense material such as calcium or metal can obscure the coronary artery lumen. 
Small vessel caliber (eg, distal segments of the left circumflex, marginal branches, and left anterior descending); segments with a diameter less then 1.5 mm can usually not be assessed for steno-sis 


These technical and image quality problems may be overcome with improvements in future generations of CT scanners.

Injection of iodinated contrast medium is required for both EBCT and MDCT coronary angiography. Thus, CCTA is contraindicated in patients with a history of allergy to iodinated contrast medium and relatively contraindicated in patients at high risk for contrast nephropathy (eg, diabetics with a serum creatinine concentration above 2.0 mg/dL.

How long does a heart attack patient need to stay in the hospital?

It varies depending on how complicated the case may be. In general 3 days is the average stay for an uncomplicated heart attack.

Heart Attack Symptoms

What are the symptoms of a heart attack?

The classic symptom is a crushing left sided or mid-sternal chest pain which may be triggered or exacerbated by exertion, but it may also occur at rest. The pain may be localized or it may radiate to the left arm, elbow, the back, the jaw or ear lobes.

However, the symptoms may be more atypical and present as shortness of breath, dizziness, sweating, or just isolated arm, jaw, or back pain. There may also be anxiety, nervousness or feeling of impending doom.

According to a study in the 1998 issue of Archives of Internal Medicine1, “knowledge of the complex constellation of heart attack symptoms is deficient in the US population.”

When describing the chest pain to your doctor make note of the following characteristics:
Quality of the pain — Is the pain a squeezing, tightness, pressure, sharp, stabbing, constriction, burning, fullness in the chest, band-like sensation, knot in the center of the chest, heaviness on chest (elephant sitting on chest), or like a bra that is too tight.

Location of the pain — Is the pain in the center of the chest, on the right or on the left. Is it in the upper abdomen. Is the pain focal and can the location be pinpointed with one finger or is it vague and throughout the chest. In some cases, the discomfort cannot be described, but the patient places a fist in the center of the chest, known as the "Levine sign."

Radiation of pain — Is the pain localized or does it shoot to other sites such as to the neck, throat, lower jaw, teeth (feeling like a toothache), or the shoulders, shoulder blades or arms. Sometimes, pain is felt in the wrists or in fingers.

Timing of the pain — Does the pain come on gradually and get worse over time. How long does it last, a few seconds or minutes, 15 minutes or longer, or a few days.

Things that make the pain better or worse — Is the pain triggered by or worsened by activities that increase physical exertion, such as walking up stairs, sexual intercourse, or raking leaves. Does the pain get worse with deep breaths or with pushing on the area. Does the pain improve with rest or with antacids.


Do men and women experience different things when having a heart attack?

Yes, the symptoms in women may be more atypical2. It may present as abdominal pain or a vague malaise or weakness. It also may present as more of a prickly sensation in the chest rather than the classic sensation of an elephant sitting on the chest.

According to one study presented in the American Heart Journal3 men were significantly less likely to complain of neck pain, back pain, jaw pain and nausea than women.

How can you tell the difference between a heart attack and heart burn?

It can be difficult to tell the difference between a heart attack and heart burn. The most common non-cardiac cause of ER visits for chest pain is heart burn. If it’s a first time for a chest pain you should contact your doctor. In general, heart burn tends to occur after meals and not with exertion. It is often relieved by burping or by medications such as Tums or Pepcid. Heart burn also may leave a sour or bitter taste in the back of the mouth.

Are they any chest pains that are normal or should be ignored?

A first chest pain should never be ignored. In general if a chest pain is aggravated by a change in body position such as twisting or turning or by pushing on it then it may indicate a muscular source for the pain.

Are there things that you might experience weeks or months before a heart attack that are really warning signs if you paid attention to them?

The symptoms may be vague and some patients recall after the heart attack that they may have had milder chest pain or shortness of breath with exertion or just some general fatigue. It should be noted than in a small percentage of patients the first symptoms are the last symptoms. If you are feeling ANY chest pain, especially chest pain with physical exertion, then it should be brought to your doctor’s attention.

What kinds of things should put you on alert that you could be at an increased risk for a heart attack?

Increased weight and obesity, high cholesterol or blood pressure, smoking now or in the past, family history of heart disease, lack of physical activity, presence of diabetes, increasing age, males over 50, and females post menopause.

What exactly is happening in your heart that causes a heart attack?
All organs and tissues in the body require the oxygen and nutrients carried in the blood to function properly. The heart pumps oxygen and nutrient-rich blood through a huge network of arteries throughout the body, which includes vessels that supply blood to the heart itself. The heart receives nourishment via a specific set of arteries. Problems begin when one of these arteries becomes blocked or blood flow to that part of the heart is interrupted and deprives the heart of oxygen.

A heart attack occurs when a fatty plaque (deposits of fat-like substances) in the lining of the blood vessels supplying the heart ruptures. A blood clot (thrombus) can form on the plaque, which can partially or completely block the artery. This blockage slows or blocks blood flow to the area of heart muscle fed by that artery. If this continues for more than 15 minutes, the muscle can become damaged or infarcted (that is, the tissue in that area dies). This can kill or disable someone, depending on how much heart muscle is damaged. The medical term for heart attack is myocardial infarction. A heart attack is also sometimes called a coronary thrombosis or coronary occlusion. As plaque in the heart arteries builds up and the narrowing causes decreased blood flow pain in the heart can result. This pain may be called angina and represents a symptom of heart disease rather than a heart attack itself.

Does it matter how long a heart attack continues before you seek medical help?

Yes, it is essential to seek treatment early. The first 1-2 hours are critical in the successful treatment of a heart attack. The longer you wait the more damage may occur to the heart muscle.