Myocardial Infarction Daisy Carmona Biology 2401
What is a myocardial infarction? • A myocardial infarction is commonly known as heart attack. • A heart attack is the death of part of the heart muscle due to its sudden loss of blood supply. • most heart attacks occur when an unstable, atherosclerotic plaque lesion, filled with cholesterol and fat, suddenly breaks apart, thus forming an open wound within the artery wall. Blood platelets and clotting proteins rush to the wound and form a clot — called a thrombus. The clot can enlarge in a matter of moments, causing obstruction of blood flow to the heart with resultant angina (chest pain). If the blood flow becomes completely obstructed, a heart attack ensues. • Many people confuse heart attacks with a stroke. But, a stroke or brain attack occurs when a blood clot blocks a blood vessel or artery, or when a blood vessel breaks, interrupting blood flow to an area of the brain, and it has nothing to do with the heart.
What are the causes of a heart attack? • In his book, The McDoughall Program for a Healthy Heart , author John McDoughall, MD, outlines the following key elements that can lead to a heart attack: • The presence of high total cholesterol and LDL cholesterol • The initial injury to the lining of the artery wall • The formation of unstable, cholesterol–filled, fat–filled plaques • The rupture of the plaque • The formation of a clot over the open plaque • The clot closing off blood flow to the heart or brain (or other major organ), causing a heart attack or stroke. • At a recent conference on the Mind-Body Connection (Friends Connection, Mar,00, Moorestown, NJ) that it is his observation that many heart attacks can be traced back to a very stressful life event that occurred about four to seven days prior.
A complete blockage of a coronary artery by a blood clot. A coronary artery is an artery that supplies blood (along with essential nutrients) to the heart muscle. Death of the heart muscle often causes chest pain and electrical instability of the heart muscle tissue. Permanent brain damage and death can occur unless oxygenated blood flow is restored within five minutes. The loss of blood supply Orderly transmission of electrical signals in the heart is important for the regular beating (pumping) of the heart. Electrical instability of the heart causes ventricular fibrillation (chaotic electrical disturbance). A heart undergoing ventricular fibrillation simply quivers, and cannot pump or deliver oxygenated blood to the brain. Cause and Effect
Healthy Coronary Artery smooth muscle is red, and connective (supporting) tissue is black (elastic) or blue (collagen). Coronary Artery with stable plaque Coronary Artery
Coronary Artery (cont.) Rupture of plaque in the coronary artery
Tests that prevent heart attacks Angioplasty (Percutaneous Transluminal Angioplasty) – • PURPOSE-PTCA is a non-surgical procedure that relieves narrowing and obstruction of the arteries to the muscle of the heart (coronary arteries). This allows more blood and oxygen to be delivered to the heart muscle. • PROCEDURE- PTCA is accomplished with a small balloon catheter inserted into an artery in the groin or arm, and advanced to the narrowing in the coronary artery. The balloon is then inflated to enlarge the narrowing in the artery. When successful, PTCA can relieve chest pain of angina, improve the prognosis of patients with unstable angina, and minimize or stop a heart attack without having the patient undergo open heart coronary artery bypass graft (CABG) surgery. • Electrocardiogram (ECG or EKG)- • PURPOSE- The electrocardiogram (ECG or EKG) is a noninvasive test that is used to reflect underlying heart conditions by measuring the electrical activity of the heart. • PROCEDURE- By positioning leads (electrical sensing devices) on the body in standardized locations, information about many heart conditions can be learned by looking for characteristic patterns on the ECG.
Implantable Cardiac Defibrillators PURPOSE-The ICD is capable of monitoring the heart rhythm. When the heart is beating normally, the device remains inactive. If the heart develops a life-threatening tachycardia, the ICD delivers an electrical "shock(s)" to the heart to terminate the abnormal rhythm and return the heart rhythm to normal. PROCEDURE- A local anesthetic is injected under the skin over the area where the ICD will be placed, usually in the right or left upper chest near the collarbone. The lead is then inserted into a vein located in the upper chest near the collarbone. The tip of the lead is placed on the inner wall of the heart with the visual guidance of x-rays. If there is more than one lead, the process is repeated. The other end of the lead (or leads) is connected to the defibrillator unit, which is then inserted under the skin at the incision site. Because there are no nerve endings inside the blood vessels and the heart, the patient usually does not feel the placement of the lead(s). Test (cont.) Homocysteine- • PURPOSE-testing for homocysteine blood levels is conducted because elevated levels of homocysteine in the blood are believed to cause narrowing and hardening of the arteries. This narrowing leads to diminished blood flow through the affected arteries. Elevated levels of homocysteine in the blood also increase the tendency to excessive blood clotting. Blood clots inside the arteries further diminish the flow of blood. The resultant lack of blood supply to the heart muscles causes heart attacks, and the lack of blood supply to the brain causes strokes. • PROCEDURE- Blood testing
Tests (cont.) Coronary Artery Bypass Graft- • PURPOSE- CABG surgery creates new routes around narrowed and blocked arteries, allowing sufficient blood flow to deliver oxygen and nutrients to the heart muscles. • PROCEDURE- The cardiac surgeon makes an incision down the middle of the chest and then saws through the breastbone (sternum). This procedure is called a median (middle) sternotomy (cutting of the sternum). The heart is cooled with iced salt water, while a preservative solution is injected into the heart arteries. This process minimizes damage caused by reduced blood flow during surgery and is called "cardioplegia." Before bypass surgery can take place, a cardiopulmonary bypass must be established. Plastic tubes are placed in the right atrium to channel venous blood out of the body for passage through a plastic sheeting (membrane oxygenator) in the heart lung machine. The oxygenated blood is then returned to the body. The main aorta is clamped off (cross clamped) during CABG surgery to maintain a bloodless field and to allow bypasses to be connected to the aorta. The most commonly used bypass vessel is the saphenous vein from the leg. Bypass grafting involves sewing the graft vessels to the coronary arteries beyond the narrowing or blockage. The other end of this vein is attached to the aorta.
Tests (cont.) Tilt -table Test – • PURPOSE- The tilt-table test is designed to detect one of the most common causes of fainting, postural hypotension (orthostatic hypotension). Postural hypotension is a common cause of an episode of temporary loss of consciousness. Postural hypotension results from changing body position from a prone, supine or sitting position to a more vertical position. Poor tone of the nerves to blood vessels in the legs can cause a disproportionate distribution of blood to the legs, instead of to the brain, so a person feels lightheaded and may even faint. • PROCEDURE-It involves placing a patient on a table with a foot-support. The table is then tilted upward. The tilt-table may start off in a horizontal position and be tilted by degrees to a vertical position. The patient's blood pressure and pulse and symptoms are recorded with the patient in each position.
Treatment Options • The immediate goal of treatment is to quickly open the blocked artery and restore blood flow to the heart muscle; a process called "reperfusion." Once the artery is open, the heart attack is generally halted and the patient becomes pain free. Early reperfusion minimizes the extent of heart muscle damage and preserves the pumping function of the heart. Delay in establishing reperfusion can result in irreversible death to the heart muscle cells and reduced pumping force of the remaining heart muscle. The amount and health of the remaining heart muscle is the major determinant of the future quality of life and longevity for a patient after a heart attack. Optimal benefit is obtained if reperfusion can be established in the first 4- 6 hours of a heart attack. • Certain clot dissolving medicines (thrombolytic agents) such as tissue plasminogen activator (TPA) or TNK given intravenously can successfully open up to 80% of acutely occluded coronary arteries. The earlier these agents are administered, the better the success at opening the artery, and the more effective the preservation of heart muscle. If thrombolytic administration is given too late (more than 6 hours after the onset of the heart attack), most of the muscle damage may have already occurred. When there will be a potential delay in the ability to perform PTCA, either if the hospital does not have a catheterization laboratory with the ability to perform PTCA, or if there are logistic reasons why PTCA will be delayed, thrombolytic therapy is then be promptly administered to allow prompt reperfusion. PTCA may then be performed in patients who fail to respond to thrombolytic therapy. Thrombolytic therapy carries a significant bleeding risk, such that some patients are not candidates for this therapy (patients with recent surgery or major trauma, recent stroke, bleeding ulcer, or other related conditions.
Symptoms A Heart Attack may cause some or all of these symptoms : • Pain, pressure, fullness, discomfort or squeezing in the center of the chest • Stabbing chest pain • Radiating pain to shoulder(s), neck, back, arm(s) or jaw • Shortness of breath or difficulty breathing • Pounding heartbeats (palpitations) or feeling extra heartbeats • Upper abdominal pain • Nausea, vomiting or severe indigestion • Sweating for no apparent reason • Dizziness with weakness • Sudden extreme fatigue • Panic with feeling of impending doom • Most people report flu-like symptoms.
Statistics • Approximately one million Americans suffer a heart attack annually. Four hundred thousand of these victims die as a result. • Approximately 90% to 95% of heart attack victims who reach the hospital survive. • The 5% to 10% who later die are those who have suffered major heart muscle damage, or who suffer an "extension" or enlargement of their heart attack. • Heart attacks frequently occur from 4:00 A.M. to 10:00 A.M. due to higher adrenaline amounts released from the adrenal glands during the morning hours. • 1.5 million heart attacks occur in the United States each year with 500,000 deaths. • A heart attack occurs about every 20 seconds with a heart attack death about every minute. • The National Registry of Myocardial Infarctions (New England Journal Med., 22Jul99) reports that women have a worse outcome than men after having a heart attack. Data showed that women under the age of 50 had twice the mortality of men after having a heart attack. Variances likely reflect increased severity of the disease in younger women.
Statistics (cont.) • Almost 14 million Americans have a history of heart attack or angina. • About 50% of deaths occur within one hour of the heart attack ––outside a hospital. • There is a 6% to 9% early mortality from heart attack for those who survive long enough to reach the hospital. • From 1983 to 1993, heart attack deaths fell about 30% overall but have not fallen nearly as much for women. • Studies show the most common time for a heart attack to occur is Monday morning. Saturday morning ranks second. Another common time is during the early morning hours, when blood platelets are stickier. • 60% of women erroneously listed cancer as the leading cause of death among women. Deaths from all cancers in the USA are half as common as deaths from cardiovascular disease. • Chewing an uncoated aspirin right away, at the first sign of chest discomfort or distress, can reduce the amount of damage to the heart muscle during a heart attack. • Costs related to heart attack exceed 60 billion dollars per year.
Works Cited • www.womensheartfoundation.org • www.medicinenet.com