The Difference Between Heart Attack, Heart Failure, and Cardiac Arrest
I think fiction has done us a huge disservice when they conflate the above, but even my nursing students were kind of on the edge of not understanding this, so we're gonna talk about it here.
Heart Attack: A blockage in the coronary arteries
A heart attack, also called a myocardial infarction, is when one of the arteries that supplies the actual muscle of the heart gets blocked by a blood clot. When this happens, the muscle the artery was supplying starts to die. The more muscle impacted, or the longer the heart attack goes untreated, the worse the outcome for the patient.
Symptoms of this are different between men and women:
Treatment for a heart attack usually involves inserting a small tube into the wrist or groin, snaking it up to the blocked artery, and stenting open the blockage, thus returning blood flow to the heart muscle.
Heart Failure: A problem with the heart's ability to pump
Heart failure occurs when the heart is not beating hart enough or well enough to adequately get blood out to the body. This can occur for several reasons. It can be because of damage from a heart attack, because a valve in the heart isn't working right, from poorly functioning electrical system, or from long term exposure to untreated high blood pressure.
The symptoms of heart failure come both from blood collecting "in front" of the heart waiting to get pumped (swelling, shortness of breath, weight gain), and not enough blood getting pumped out to the body (dizziness, fatigue).
Heart failure is treated with medications that make the heart beat more normally and get rid of excess fluid to take workload off the heart. It can also be treated with surgery if the problem is with a valve, or with a pacemaker if the heart is beating too slowly.
Cardiac Arrest: A problem with the heart's electrical system
The heart beats in a synchronized way because it is made of muscle cells that are responsive to electricity. Special cells called pacemaker cells generate small electrical currents, which wash over the heart. When the cells are stimulated with that current, they contract, creating a beat.
Cardiac arrest occurs when that normally organized current becomes disorganized, and lots of cells, not just the pacemaker cells, start making their own currents. This can happen because of a lack of oxygen, too much or too little of particular electrolytes like potassium, an electrical shock, or damage to the muscle from a heart attack.
See below for a comparison between the normal electrical activity of the heart (top) and the disorganized rhythm of ventricular fibrillation:
When the electrical rhythm is disorganized, the heart isn't beating, just quivering, and no blood gets out to the body. This is treated with CPR to keep some blood flowing to vital organs, medications that can stabilize the heart's electrical system, and defibrillation. Defibrillation works by stopping the heart with an overwhelming amount of electricity and letting it restart (hopefully) in a normal rhythm.
If someone has no electrical activity in their heart (known as asystole), defibrillation won't work, but sometimes medication will.
