Beyond routine blood tests that are done to assess a variety of condi- tions, some blood tests are speci?c to the diagnosis of cardiovascular disease. Blood tests can indicate the levels of lipids (cholesterol and triglycerides), cardiac enzymes (markers of cardiac damage), the oxygen content, and the amount of time it takes for your blood to clot (pro- thrombin time). Some newer blood tests detect injury to the heart muscle in a person who has had a symptom such as chest pain, shortness of breath, or light-headedness. These tests can be done quickly in an emergency setting for immediate detection of a heart attack.
For some types of blood tests, such as the lipid pro?le, you will be asked to fast overnight. For many heart-related blood tests, blood will be drawn from a vein or sometimes from an artery, rather than from a ?ngertip.

Lipid ProfileMeasuring the cholesterol circulating in your blood is a common, rou- tine test . Called a lipoprotein pro?le, or sometimes a lipid panel, the test measures the levels of your total cholesterol, low-density lipoproteins (LDL, the “bad” cholesterol), high-density lipoproteins (HDL, the “good” cholesterol), and triglycerides (the most common form of fat in the blood). This is to determine whether you need treat- ment or to check if a treatment is working.
If these measurements are not precise enough, a more sophisticated test, called a nuclear magnetic resonance lipid test, can be done to more precisely measure and classify subparticles of HDL and LDL. Other new tests, which may help to further assess risk, include measuring apoprotein levels such as apoprotein B, a component of LDL, and apoprotein A-1, a component of HDL. The usefulness of these tests is uncertain; currently, they are used mainly to decide if people with bor- derline high LDL and HDL levels need drug treatment.

Cardiac Enzymes

Testing your blood for certain cardiac enzymes (proteins), which are sometimes called cardiac markers because they indicate heart muscle injury, can be a way to detect damage to your heart from a heart attack very early in the course of the attack. If you are having chest pains, your doctor may order these tests to see if damage is being done to your heart. If you go to an emergency room because of warning signs of a heart attack , the doctor will probably do this analysis.
Small amounts of cardiac enzymes are found in the blood of healthy people. However, the heart muscle is rich in these enzymes, and they can leak into your blood in larger amounts if your heart is damaged by a heart attack. They may enter your bloodstream very early in an attack, before you realize you are having one, or before much heart tissue has been damaged.
One enzyme commonly measured to con?rm the existence of heart muscle damage is creatine kinase (CK). Different types of CK are found in heart muscles and in the skeleton. The enzyme type that most accu- rately con?rms heart damage is the form of CK known as CK-MB. The level of CK-MB found in the blood increases about 6 hours after the start of a heart attack and reaches its peak in about 18 hours. If you have had a symptom such as pain, testing for these markers can con?rm whether a heart attack has occurred.
Other cardiac markers called troponins (including troponin I and troponin T) have a role in heart muscle contraction and are very sensitive indicators of heart muscle damage. Their presence in your blood can indicate very mild damage to your heart that tests for creatine kinase don’t detect. Troponins increase in as little as 4 hours after the beginning of an attack and can remain elevated in your blood for 2 weeks.
Myoglobin is still another marker used to detect heart damage. It is a less speci?c marker of cardiac damage than one type of CK but has the advantage of being the very ?rst of the cardiac markers to rise after a heart attack, as early as a couple of hours after the heart damage occurs. This makes a blood test for myoglobin useful in determining whether someone who is having chest pain is having a heart attack.

Homocysteine

Homocysteine is an amino acid in your blood. Doctors have studied homocysteine closely because high levels of it appear to place you at higher risk of cardiovascular disease, regardless of your age or other risk factors. Some evidence suggests that homocysteine might damage the lining of your arteries and promote blood clots, but no direct cause- and-effect relationship has been established. Although homocysteine levels were at first strongly linked to heart disease, more recently researchers have found that link not as strong as they ?rst thought. The level of homocysteine in your blood may be partly hereditary, but it is also related to your diet. In some cases, an elevated level of homocys- teine results from a vitamin B12 de?ciency, so it is important that your doctor measure your level of vitamin B12 through a blood test.
Your doctor may test your homocysteine levels if you have a strong history of heart disease but you don’t have the obvious risk factors such as high cholesterol, high blood pressure, diabetes, and others. Eating a diet rich in folic acid and B vitamins helps reduce homocys- teine. Many doctors routinely recommend that those at risk for heart disease take folic acid and vitamin B complex. Other doctors rec- ommend the supplements only if homocysteine levels are elevated; however, recent research suggests folate supplements may block the action of naturally occurring folates and vitamin B that you eat in your diet.

Creactive Protein

Although high cholesterol is most often considered the major risk fac- tor for heart attack because of its role in the accumulation of plaque in the arteries, not all people who have heart attacks have arteries that are blocked in this way. Doctors have been studying the role of in?amma- tion within the arteries as a separate process that may contribute to the development of coronary artery disease. In?ammation may also explain why in some people, an artery recloses after a balloon angioplasty has been performed to open it.
In?ammation anywhere in your body causes swelling. If it occurs in your arteries, this swelling can reduce the blood ?ow to your heart. When in?ammation occurs, your body produces a substance called C-reactive protein. The level of C-reactive protein in your blood (detected by a blood test) is a strong predictor of heart disease, espe- cially in people who have had prior heart attacks.
No one is sure yet what causes the in?ammation in the arteries. It may be a bacterial agent such as Helicobacter pylori (which also causes stomach ulcers) or a viral agent such as the herpes simplex virus. Chlamydia pneumoniae, another type of bacteria, has been studied as a possible predictor of heart disease but with no clear evidence that the bacteria is involved. Some research suggests that in?ammation may damage the arterial wall in a speci?c way that increases the chance of blood clots that block the artery. Obesity and diabetes may also cause an increase in C-reactive protein levels. In fact, visceral or belly fat is the best predictor of an individual’s high level of C-reactive protein. If you are at a moderate or high risk for cardiovascular disease, measur- ing your C-reactive protein may help guide your treatment. You can lower your C-reactive protein with a heart-healthy diet and exercise to lose the belly fat, and also by quitting smoking.