Heart attack

A heart attack is a colloquial term referring to a serious, sudden heart condition that presents as varying degrees of chest pain, weakness, sweating, nausea and vomiting, sometimes causing loss of consciousness. A heart attack is a medical emergency.

The medical term for a heart attack is acute myocardial infarction, often abbreviated as AMI or MI. "Acute" means sudden, "myo" refers to muscle, and "cardium" refers to the heart, i.e. to the heart muscle (myocardium). "Infarction" is a medical term describing tissue death (necrosis) caused by an obstruction of blood flow.

Causes

The underlying mechanism of a heart attack is the destruction of heart muscle cells due to a lack of oxygen. If these cells are not supplied with sufficient oxygen by the coronary arteries to meet their metabolic demands, they die.

A common cause of heart attack is atherosclerosis: a gradual buildup of fat-containing substances (plaque) in the walls of the arteries can erupt and cause a blood clot (thrombus) to form; this thrombus can then cause a sudden clogging of the coronary arteries. This is one reason why older people are more susceptible to heart attacks.

Heart attacks can also occur if the work load of the heart suddenly rises and the necessary oxygen cannot be supplied quickly enough. This is why extreme stress or physical exertion can result in heart attacks.

Diagnosis

Some associated symptoms include dizziness, nausea, shortness of breath and diaphoresis (excessive sweating). In the absence of these symptoms, sharp chest pain which goes away promptly when the patient stops moving chest and arm muscles often is not associated with a heart attack; but a sharp chest pain that persists despite lack of movement is a strong indicator of a heart attack.

Heart attacks sometimes occur with atypical pain or in the absence of classical symptoms, particularly in women, who may experience simply chest discomfort, a sensation of uncomfortable chest pressure, cold sweats, nausea, or pain in the arm, back, jaw, or stomach (so called anginal equivalents). Women are just as likely to die of a heart attack as men.

First Aid

If you are having a heart attack, call for help immediately. Many people have died needlessly because they were afraid or unwilling to admit that they were having a heart attack until too late. If possible, take an aspirin because it makes blood clots less likely to form. Find other people who can get help and administer CPR should your heart stop beating.

A heart attack is a life-threatening medical emergency which demands immediate activation of the emergency medical services. Immediate transport by ambulance to a hospital where advanced cardiac life support is available needs to be arranged. Calm the patient as much as possible.

If the patient is conscious and able to swallow, it may be advisable to give one baby aspirin. Look to see if the patient has nitroglycerin tablets or patches available, particularly if they have been the victim of prior heart attacks. As a first-aider, you may assist a conscious patient in taking these self-rescue medications.

In wilderness first aid, a possible heart attack justifies medical evacuation by the fastest available means, including MEDEVAC, even in the earliest or precursor stages. The patient will rapidly be incapable of further exertion and have to be carried out. Note the correlation between age, exertion and the onset of chest pain.

Field Care (for EMTs)

Transport immediately if breathing and pulse are present. ("Load and go.") Place on oxygen therapy by mask and calm the patient. Monitor closely (with electrocardiogram if available).

Be prepared to apply advanced cardiac life support including defibrillation and (at the paramedic level) injection of medications into the heart per protocol. If equipment is not available, perform CPR if the heart stops beating.

About 20% of patients die before they reach the hospital; the cause of death is often fibrillation.

Clinical Treatment

A heart attack is treated with thrombolytic drugs (such as urokinase, streptokinase, or alteplase (recombinant tissue plasminogen activator)), heparin, and medication to prevent arrhythmia. Immediate or delayed treatment with angioplasty or coronary artery bypass surgery is another option. Following a heart attack, a patient's heart rhythm is closely monitored: antiarrhythmic medication may be needed. Some people at risk for coronary disease are prescribed medication to prevent heart attacks (such as aspirin or Plavix (clodipogrel)).

Doctors traveling by commercial aircraft: oxygen is available on board and the first aid kit on jetliners contains basic cardiac drugs used in advanced cardiac life support. If treating a potential heart attack while in the air, ask the stewardess to get this kit for you. The pilot will divert the flight to the nearest airport.

See also Ischaemic heart disease.

Reference

• U.S. Department of Health and Human Services (public domain text)