Blood tests

Blood tests can provide a great deal of information on your general health and, as a result, form part of our standard diagnostic tests for all of our cardiac patients. There are also additional blood tests that specifically test for indicators of heart function. These include:

Cardiac troponin

Cardiac troponin is a protein complex that is released into the blood when cardiac muscle cells are damaged, for instance during a heart attack. Even if a patient's ECG results are unremarkable, raised troponin levels in the blood can indicate damage to the heart muscle, which may have been sustained either as a result of a heart attack or other causes.

There are three different types of cardiac troponins (cTn): cTnT (which binds to tropomyosin), cTnI (which is inhibitory), and cTnC (which binds to calcium ions). The troponins cTnT and cTnI are particularly important as diagnostic markers as they are released from myocardial (heart muscle) cells. Troponin levels in the blood can remain elevated for a number of days following the start of a heart attack.

Lactate dehydrogenase (LDH)

Lactate dehydrogenase (LDH) is an enzyme that is present in almost all body tissues. Blood tests can test for LDH levels in blood plasma (serum). When cells die, their components - including LDH - are released into the blood. As a result, increased LDH in the blood is indicative of higher-than-normal tissue death.

It can indicate a higher than normal number of cardiac muscle cells dying, such as during a heart attack. As damage to other cells in the body, including those in the lungs, liver, gall bladder, muscles and blood, can also lead to increased LDH levels, diagnosis of a heart attack requires other parameters to be tested as well.

Creatine kinase

Creatine kinase (CK) is an enzyme that can be found within all types of muscle cells. CK-MB is a form of CK that is found in myocardium (heart muscle). An increase in CK levels in the blood combined with a simultaneous increase in the ratio of CK-MB to CK is indicative of damage to the heart muscle, and suggests that a heart attack is occurring. Further investigations will also be required in order to confirm the diagnosis.

H-FABP

H-FABP (heart type fatty acid binding protein) is a protein involved in active fatty acid metabolism and is mainly found in heart muscle tissue. When heart muscle cells begin to die off as a result of a heart attack, H-FABP is released into the blood, where it can be detected after only a very short time. It can therefore provide prompt confirmation of a suspected heart attack.

C-reactive protein (CRP)

Inflammation in the body leads to a sharp increase in the levels of C-reactive protein (CRP) in the blood. An increase in CRP levels can be indicative of inflammation as a result of, e.g. a bacterial infection affecting either the heart valves, pericardium (inner lining of the heart), myocardium (cardiac muscle) or pericardium (fluid-filled sac around the heart).

Due to the fact that raised CRP levels are associated with a wide variety of inflammatory conditions such as appendicitis, pneumonia and urinary tract infections, further investigations will be required in order to be able to make an accurate diagnosis.

Procalcitonin (PCT)

Procalcitonin (PCT) is the precursor of the hormone calcitonin. Procalcitonin is released into the blood in response to inflammation. Although an increase in PCT levels can be indicative of severe bacterial infections such as sepsis or endocarditis, this test cannot be used in isolation.

An accurate diagnosis will require further tests and investigations.

Brain natriuretic peptide (BNP)

Brain natriuretic peptide is a cardiac hormone that is produced in the human heart muscle and released into the blood stream in response to an excessive stretching of the ventricles. Excessive stretching of the ventricles can occur as a result of reduced heart function, i.e. heart failure.