In the first article in this series we talked about how your heart works in close partnership with your lungs. In Part II we learned about some common cardiac (heart) tests that involve procedures. Today, in third and final part of our series on the heart, we’ll discuss blood tests used to diagnose problems with the heart, and also a bit about how some cardiac medicines can affect your breathing.

Invasive and Non-invasive
To review - two main methods of medical testing are: Invasive and non-invasive. Invasive tests and procedures are when something is put into your body - a needle or a tube to gather or give blood, fluid, or tissue. In a non-invasive test, nothing is placed into your body. Blood tests are invasive because a needle goes into your body to obtain blood.

Here are a few (not all) commonly done blood tests to check on functions related to your heart. These tests require taking a small amount of blood, most likely one or two small tubes.

Cholesterol 
Although cholesterol is essential for us to live, high levels in circulating in the blood are strongly associated with the progression of atherosclerosis (sometimes referred to as “hardening of the arteries”), the thickening of blood vessels that carry oxygenated blood.

What is the doc looking for?

If you are more likely to have clogging in the arteries that supply your heart with oxygen.

What’s Good –What’s Not?
Here are some basic guidelines from the Mayo Clinic on “Total” Cholesterol
U.S. and some other countries  Canada and most of Europe
Below 200                                    Below 5.2                           Desirable
200-239                                       5.2-6.2                               Borderline high
240 and above                              Above 6.2                           High

Troponin 
Troponin is an enzyme that increases with recent heart damage. This test is usually done in the hospital when you’re actually having chest pain.

What is the doc looking for?
An increased level that may indicate that you’ve had a heart attack. This is a time-sensitive blood test, so it should be done within 24 hours of when your doctor suspects you may have had a heart attack.