Heart attack is a serious medical event resulting from a blockage of blood flow to the heart muscle. A heart attack occurs with the sudden blockage of a major coronary artery. Coronary arteries are the blood vessels that carry oxygenated blood to the heart muscle. A blockage interrupts the blood flow in these vessels. Heart muscle served by the blocked vessels begins to die from lack of oxygen. The damage can affect the heart’s ability to pump blood to the body. Heart attack ranks as a major cause of death. If treatment begins within a few hours, however, much of the damage can be reversed.
The major arteries supplying oxygenated blood to the heart are the left coronary artery and the right coronary artery. They arise as the first branches from the aorta. The aorta is the main artery from the heart. It distributes oxygen-rich blood to all parts of the body. A third large heart vessel, called the circumflex artery, branches off from the left coronary artery.
How a heart attack occurs.
Sudden blockage does not usually occur in a healthy coronary artery. Rather, heart attack tends to originate in arteries damaged by the disease atherosclerosis. Atherosclerosis begins when fatty substances form deposits on the inner lining of the arteries. Over years, such deposits harden to form plaques. A plaque may partially block the flow of blood for years without causing symptoms. Arterial plaques cause inflammation in the artery walls. This inflammation can weaken the plaque, causing it to rupture. The ruptured plaque forms a blood clot. This clot may completely block the coronary artery, causing ischemia. In ischemia, the portion of heart muscle served by the blocked vessel ceases normal functioning due to lack of oxygen.
A person having a heart attack will experience symptoms of heart muscle ischemia. Common symptoms include mild to moderate pain beneath the sternum (breastbone). The pain may radiate into an arm or even the jaw. The pain may be so mild that the person mistakes it for stomach distress.
Heart attack can vary in severity, depending on the amount of muscle tissue affected. A severe heart attack may trigger an abnormal heart rhythm called ventricular fibrillation (VF). Without immediate treatment, VF can cause death within a few minutes. Less severe heart attacks may not cause unconsciousness or immediate death. Victims may experience nausea, excessive sweating, or weakness. The symptoms are caused by weakened or abnormal heartbeat resulting from ischemia. Some heart attacks present such mild symptoms that they go undetected for months or years.
Treatment.
A heart attack is a medical emergency. In cases of VF, a device called a defibrillator must be used immediately. This device delivers a brief electric shock to the heart. The shock may help in restoring the heart’s normal rhythm. A person with heart attack symptoms should call for emergency medical care immediately. If possible, the person should chew an aspirin tablet. Aspirin works to prevent blood clots, keeping the blockage from growing.
At a hospital, doctors treat heart attack with more powerful drugs called thrombolytic agents, that work to dissolve the blood clot. Other drugs called anticoagulants are given to prevent new blood clots from forming. Doctors usually follow with a procedure called cardiac catheterization. In this procedure, doctors insert a small tube into the heart by way of a large artery in the leg or arm. They use the tube to inject a special dye that can be seen an imaging device called an X-ray fluoroscope. The dye flows through the coronary arteries, revealing the location of the obstruction.
Doctors may insert a short, metal mesh tube called a stent into the vessel. The stent keeps the coronary artery open. In some circumstances, they may perform coronary bypass surgery instead. Bypass surgery makes use of a replacement vessel from the patient’s own body to carry blood around a blockage in one or more coronary arteries.
With prompt treatment, the heart muscle may suffer little permanent damage after a heart attack. Some patients may be limited in their activities. Survival and recovery depend on whether there is enough healthy heart muscle to maintain adequate blood flow in the body.
