Myocardial Infarction or Heart Attack

Myocardial infarction is the medical term for a heart attack. When the blood supply in the coronary artery is stopped for any reason, the heart muscle begins to die. Blocked blood flow in the coronary artery can occur under certain circumstances. Typically at least 20 minutes of a completely or almost completely blocked artery occurs before a significant amount of heart muscle begins to infarct (die). Cholesterol build up in the coronary arteries is the most common cause of myocardial infarction. There are different types of heart attacks. The EKG helps determine what type of heart attack the patient is experiencing.

STEMI: ST Elevation Myocardial Infarction

STEMI is the type of heart attack that is seen on TV and movies where someone usually gets severe chest pain and clutches their chest. These patients usually require emergency opening of a blocked artery. In this case the coronary artery supplying the heart is typically 100% blocked. Usually a medicine, a balloon, or cardiac stent is used to reopen the channel of blood so it can reach the muscle of the heart. “Clot busting” drugs such as tPA is typical in this scenario, but its second best to primary percutaneous coronary intervention (pPCI). Primary percutaneous coronary intervention is when a coronary artery is opened with a balloon and a stent. A coronary angiogram is done first, prior to see the blocked artery.

NSTEMI: Non-ST Elevation Myocardial Infarction

Ruptured Plaque NSTEMI

A NSTEMI is a heart attack that is similar to a STEMI, but the artery is usually not 100% blocked. The coronary artery usually has a greater than 70% blockage. Sometimes the artery is less than 70% blocked, but there is a hazy appearance on the coronary angiogram. This type of heart attack requires a heart catheterization (coronary angiogram) to view the arteries and determine which artery has the blockage. No clot busting drugs are used on this type of myocardial infarction.

Demand Ischemia or Type II Myocardial infarction

This type of myocardial infarction usually involves multiple blocked arteries (not always). The body undergoes some sort of systemic stress such as pneumonia, COPD flare, or infection; there is an imbalance of demand form the heart and the blood flow supplied to it by coronary arteries. The patient may or may not have chest pain. Abnormal laboratory values return during routine lab testing suggesting heart damage. This is a different kind of heart attack that usually only requires a keen cardiologist and medicines. Sometimes a stress test is done to evaluate for underlying blocked arteries and how significant they are.

Troponin Assay

The troponin enzyme is detected by routine laboratory tests. This detects if there has been any insult to the heart. It is a very sensitive test and may detect levels in the ng/dl concentration. The result from troponin assay is used together with the medical history of the patient and EKG to determine if and what type of heart attack the patient is suffering from. If the troponin assay is normal, there is no heart attack. However, the patient may still be suffering from blocked arteries and/or angina.

myocardial infarction schematic

STEMI video

NSTEMI video

What can I do if I think I am having a heart attack?

If you think you are suffering from a myocardial infarction, call 911 immediately.  Many patients wait too long to be evaluated for chest pain.  Some medical officials recommend taking a full dose aspirin or 325mg and chewing it.  This is usually good practice, after you have called 911.

If you have a history of coronary artery disease and heart attacks, you are familiar with your heart attack symptoms.  If you have nitro, take 1 and sit down.  Wait 5 minutes and take another nitro if the pain has not resolved.  If in 5 minutes, your pain persists, take you last nitro and call 911 immediately.  Your symptoms are likely not to improve without expert medical care under a cardiologist.