How does a doctor diagnose a heart attack?

Answer 1

This is quite a complicated question to answer briefly.

A heart attack is most commonly due to a sudden blockage in one of the blood vessels supplying the heart muscle. When one becomes blocked the blood supply to a part of the heart is cut off and because the heart muscle is constantly active, this area can rapidly start to die, hence the name "myocardial infarction" myocardium = "heart muscle", infarction = "death due to lack of blood supply". The underlying cause of this sudden blockage is most commonly a fatty deposit in these blood vessels called an atheroma.

There are several things that a doctor will look at.

The first and most obvious is how unwell the patient is. How bad are the symptoms? Does the pain go away when you give them drugs such as nitrates (which dilate blood vessels and let more blood through) or morphine? Are they very short of breath or is the person's blood pressure dropping? (this suggests the heart is damaged too much to be able to pump blood to the lungs and around the body).

You also need to look at the patient as a whole. A fairly young patient with no previous cardiac history will make a better recovery than a diabetic 90 year old man who is a smoker, is obese, who has had 3 previous heart attacks, also has heart failure and has had a triple cardiac bypass (although an obese, diabetic smoker with this history wouldn't live to be 90, but it's just for illustration :) )

One of the most important tests is the electrocardiogram (ECG). This is difficult to explain without a knowledge of how the ECG works. Wikipedia does a fairly neat job of it here:

http://en.wikipedia.org/wiki/Electrocardiogram

The ECG looks at electrical signals given off by the heart from several different angles. One view of the heart is called a "lead", so if there is an abnormality in an area, it will show up most in the direction of the lead that is looking at that side of the heart. If several of the leads have an abnormality it shows the area affected is large, so from the ECG you can sometimes determine whether a small or large proportion of the heart muscle is damaged.

You can also tell whether there is an acute blockage in the heart that may benefit from giving drugs to break down the clot. This is called ST elevation (or an ST elevation MI, or STEMI).

There are also some blood tests you can do. Some enzymes are released from the heart muscle when it is damaged which can be measured in the blood. These include one called creatine kinase and another called troponin. These tend to be higher when more muscle is damaged. However, going back to the first paragraph where I mentioned an atheroma, it is possible for somebody to have a very small amount of heart muscle damage because of a minor blockage, but a very unstable fatty deposit in the wall of the blood vessel, that might burst at any time and cause a large catastrophic blockage.

So in summary, assessing severity of a heart attack can be difficult and you need to look at:

1) The Patient as a whole, taking into account age, past medical history, cardiac risk factors (mainly hypertension, Diabetes, smoking, family history)

2) Severity of symptoms

3) ECG changes

4) Cardiac enzymes

I'm sure there are more things that a cardiology specialist would say but I'm just a junior doctor so please anyone amend this as you like!

Answer 2

A heart attack can be treated right away even before it is diagnosed. Treatment includes oxygen therapy, aspirin to thin your blood and prevent further blood clotting, Nitroglycerin to reduce your heart's workload and improve blood flow through the coronary arteries, and treatment for chest pain. Once a doctor give a diagnoses of a heart attack, they will promptly restore blood flow to the heart. The 2 main treatments are clot-busting medicines and angioplasty, which is a procedure used to open blocked coronary arteries.

Answer 3

A physician diagnoses a heart attack (also called an acute myocardial infarction, or AMI) based on the history, that is, the description of the symptoms the patient is experiencing, physical exam (albeit usually not terribly helpful for the diagnosis of AMI), and lab and EKG findings.

There are more than one type of heart attack. There is the ST elevation MI (STEMI) and the Non-ST segment elevation MI (NSTEMI). STEMI is diagnosed almost solely based on EKG findings and history. NSTEMI, by definition does not have any definite diagnostic criteria found on EKG, although the EKG may be abnormal. The diagnosis of NSTEMI is based on history and elevations of cardiac biomarkers.