Developing atherosclerosis, plaque rupture, and subsequent clotting of a coronary artery is the most common cause of heart attacks. Signs and symptoms commonly appear immediately and are due to a lack of oxygen in the affected tissue. Cardiac arrest is unpredictable and if it occurs is ultimately due to a change in the electrical impulses and conduction pattern in the specialized cardiac nerves that stimulate normal cardiac contractions. An injury to these nerves blocks the conduction pathway. The block prevents or delays the electrical impulses from reaching their destination and causes cardiac arrest. The potential for arrest from a heart attack is directly related to the type, location, and size of the compromised tissue. If the blocked artery services the specialized conduction cells that coordinate the pumping action of the heart, arrest occurs within seconds or minutes. If the blocked artery services the heart’s contractile fibers rather than its specialized conduction cells, the pumping action of the heart may be compromised. A reduction in the heart’s ability to pump blood efficiently may cause a back pressure in the pulmonary vessels and force fluid into the alveoli causing respiratory distress, fatigue, swelling in the hands and feet, indigestion and loss of appetite. Complete pump failure and arrest may develop if a significant amount of heart muscle has been injured and the heart cannot continue to meet the body’s demands for nutrients. Emergency aspirin therapy increases the chance of survival, minimizes permanent damage, and improves recovery. The longer arrest is delayed the more likely the patient will survive without immediate hospital treatment.
The classic signs and symptoms of a heart attack are non-traumatic chest pain or pressure often accompanied by respiratory distress, sweating, and pale skin. The pain may mimic indigestion and is typically described as pressure or squeezing. The pain may radiate to the patient’s neck or arms (classically the left arm but can be either arm or both); in women the pain often radiates to between or under the shoulder blades. The patient is weak and tired, often denying the possibility of a heart attack.
Aspirin is one of the best drugs available for the emergency treatment of a heart attack: Aspirin is an anti-platelet agent; it interferes with the clotting process and may be safely given with other blood thinning agents (clopidogrel, warfarin) in an emergency during a suspected heart attack. Chewable baby aspirin reaches therapudic levels in a patient's blood within five minutes and takes fourteen minutes to produce maximal platelet inhibition. (In contrast, a swallowed tablet of the same dose takes 26 minutes to produce maximal platelet inhibition.) The emergency dose is 162-325 mg (2-4 baby aspirin) per incident.
Given the high incidence of atherosclrosis in today's world it makes sense to carry a small bottle of chewable baby aspirin in your first aid kit when traveling with adults, especially those with a cardiac history. If you suspect a client, student, or friend is having a heart attack, limit their exercise (carry them if possible), administer 2-4 chewable baby aspirin, and begin an urgent evacuation to the nearest hospital. If respiratory distress is present allow the patient to sit or support them in a sitting position during the evacuation. High flow oxygen is helpful during transport.
That said, while aspirin is a relatively "safe" drug there are a few instances when you absolutely don't want to use it:
Want more information on this and other wilderness medicine topics? Take one of our wilderness medicine courses. Guides and expedition leaders should consider taking our Wilderness First Responder course.
Looking for a reliable field reference? Consider consider purchasing one of our print or digital handbooks; our digital handbook apps are available in English, Spanish, and Japanese. Updates are free for life. A digital SOAP note app is also available.