Cardiovascular diseases: How to read your blood tests?
21 Oct 2020 • 1 comment
When you have a chronic cardiovascular disease, blood tests and a series of check-ups are regularly prescribed. But do you know what values you should be monitoring on these blood tests? Read our guide for patients with cardiovascular disease!
What are the different types of cardiovascular disease?
- Rheumatic heart disease, affecting the heart muscle and valves and resulting from rheumatic fever, caused by streptococcus bacteria or congenital heart defects (deformities of the heart structure already present at birth) which are responsible for example for heart failure. Heart failure is the inability of the myocardium (heart muscle) to ensure normal systemic blood flow, i.e. sufficient to carry out the body's functions. The first symptom is shortness of breath during exertion, which occurs even at rest in the more advanced stages, due to blood clogging in the lungs which "stagnates" and then fatigue and oedema may appear.
- Coronary heart disease (affecting the blood vessels that supply the heart muscle), such as heart attack.
- Cerebrovascular disease (affecting the blood vessels that supply the brain), such as stroke.
- Peripheral arterial disease (affecting the blood vessels that supply blood to the arms and legs).
- Deep vein thrombosis and pulmonary embolism (obstruction of the veins in the legs by a blood clot, which can break free and migrate to the heart or lungs).
How do you read your blood tests once you have been diagnoses with a cardiovascular disease?
A complete blood profile: FBC (Full blood count):
WBC (White blood cell count)
Female normal range: 4.0-11.0 x 109/L
Male normal range: 4.0-11.0 x 109/L
RBC (Red blood cell count)
Female normal range: 3.8-4.8 x1012/L
Male normal range: 4.4-5.5 x 1012/L
Female normal range: 120-150 g/L
Male normal range: 130-170 g/L
Female normal range: 0.40-0.50 g/L
Male normal range: 0.36-0.46 g/L
Platelet Count (PLT)
150-400 x 109/L
Why this test?
The full blood count is a test to check the types and numbers of cells in your blood and can give an indication of your general health, as well as provide important information about certain health problems you may have. It is used to monitor several types of diseases and is particularly useful in detecting anaemia (abnormally low red blood cell levels), which can be the cause of poor oxygenation of the organs.
Haemostasis screening tests:
BT (Bleeding Time, no longer widely performed in the UK)
2-7 minutes (Ivy method, incision)
APTT (Activated Partial Thromboplastin Time)
PT (Prothrombin Time)
Why this test?
It is essential to monitor haemostasis (the physiological process that stops bleeding) to prevent the pathological formation of blood clots. For example, the haemostasis test can be prescribed as a pre-therapeutic check-up before starting anticoagulant treatment.
Going further into haemostasis screening:
In certain conditions, particularly deep vein thrombosis or in the event of complications of a heart attack, the INR (International Normalised Ratio) may be monitored:
Target INR: 2.0-3.0 in general for patients on anticoagulant drugs
Note: target INRs are adapted according to individual situations and patient profiles, e.g. for patients at high risk of clot formation, the target INR is 3.0-4.0.
Why monitor INR?
It is the International Normalised Ratio, which is monitored when starting anticoagulant drugs like WARFARIN. It is an indicator of blood coagulation, and is in fact the clotting time ratio of a patient and a control value taken from the average PT from 20 or more healthy subjects. INR is used to determine the effective dose of medication that keeps the patient in the therapeutic zone and limits the risks inherent to the treatment. The lower the INR (below the target), the less fluid the blood is and vice versa. In all cases, it is imperative to be seen by a specialist (cardiologist, nephrologist, rheumatologist, endocrinologist, etc.).
Going further into haemostasis screening:
D-Dimer < 500 µg/L
Why monitor D-Dimer levels?
In certain diseases, in particular deep vein thrombosis or pulmonary embolism, the blood level of D-dimer is used to make a diagnosis. D-dimers are the end products of the degradation of fibrin (the final component of blood coagulation). Overall, D-dimers are the biological traces of the abnormal presence of a blood clot, responsible for the embolism.
Why monitor sodium levels?
High blood pressure is one of the most common conditions in the UK (affecting more than 1 in 4 adults in England) and is a serious cardiovascular risk factor which is strongly correlated with excessive salt (sodium) consumption.
Why monitor potassium levels?
Fluctuations in potassium are very dangerous, hypokalaemia (low level of potassium in the blood) and hyperkalaemia (high level of potassium in the blood) are responsible for heart arrhythmias or acid-base disorders that can be life-threatening.
Why monitor calcium levels?
Calcium is an important mineral responsible for cardiac muscle contraction (abnormal levels can cause arrhythmia, for example), but it can also have a negative impact on the coronary arteries. In particular, it is responsible for coronary calcification (which can worsen atherosclerosis, explained below).
A renal panel is used to help monitor and diagnose conditions affecting kidney function, notably kidney failure, which could aggravate cardiovascular disease.
Why monitor urea levels?
Levels of urea increase in cases of kidney failure (called uraemia). High levels of urea are not unique to kidney failure and can also occur in the case of high protein diets, dehydration or infection.
Female normal range: 45-84 µmol/L
Male normal range: 59-104 µmol/L
Why monitor creatinine levels?
Creatinine levels reflect kidney function. Creatinine is a product of skeletal muscle breakdown. It is mainly eliminated by the kidneys (by glomerular filtration but also by tubular secretion). Kidney function can be estimated from the renal clearance of creatinine or from its concentration in the blood using formulas for estimating the glomerular filtration rate (GFR).
Investigating an inflammatory condition:
CRP (C-reactive protein)
ESR (Erythrocyte sedimentation rate): the time it takes red blood cells to fall to the bottom of a test tube
Normal rate for females 17-69 years: <20 mm/hr
Normal rate for females >70 years: <35 mm/hr
Normal rate for males 17-69 years: <14 mm/hr
Normal rate for males >70 years: <30 mm/hr
Why this test?
This test is used to rule out myocarditis (infection of the myocardium, the heart muscle). CRP and SV are elevated when there is an inflammatory reaction, which may be caused by an infection.
Triglycerides: <1.7 mmol/L
Why monitor triglyceride levels?
Triglycerides are lipids circulating in the blood that are produced by liver synthesis and diet. A high level of triglycerides (>1.7 mmol/L) contributes to the development of cardiovascular disease.
Total cholesterol: <5.0 mmol/L
HDL cholesterol: >1 mmol/L in men, >1.2mmol/L in women
LDL cholesterol: <3 mmol/L
What is good or bad cholesterol?
It depends on the cholesterol-transporting protein: HDL cholesterol is transported by high density lipoproteins (HDL) while LDL cholesterol is transported by low density lipoproteins (LDL).
HDL proteins allow the body to eliminate excess cholesterol by transporting it back to the liver: this is called "good cholesterol". In contrast, LDL proteins are responsible for distributing cholesterol to the various organs and are responsible for the build-up of fat on the artery walls and thus the phenomenon of atherosclerosis.
Why is it important to have a lipid panel done if you have a cardiovascular disease?
Screening for dyslipidaemia (changes in the concentrations of lipids in the blood) is very important in cases of coronary or cerebrovascular problems.
Indeed, most frequently, the starting point of cardiovascular diseases is based on the mechanism of atherosclerosis. It involves the progressive build-up of fat on the inner walls of the blood vessels. This results in the formation of a plaque called an "atheroma". Over time, the impact on blood circulation is dangerous. Silently and slowly, atheroma plaques causes stenosis (narrowing) of the artery, which reduces the blood flow to the organs, especially the vital organs (heart and brain), and has consequences for exercise. Plaques can also be a "trap" for blood clots: when the blood passes through the narrowed area, it tends to deposit clot particles. Sometimes this threatening atheroma plaque can suddenly rupture, causing the blood vessel to become completely obstructed.
To avoid the silent progression of this type of disease, it is essential to carry out a regular lipid panel for patients at risk and every 5 years for patients over 50 years of age.
Normal fasting blood sugar level: 3.9-5.4 mmol/L
Why this test?
This test is to be carried out to monitor the onset of diabetes, which is a cardiovascular risk factor, i.e. a factor aggravating a cardiovascular condition.
Note: Being slightly outside the "reference values" does not always mean that there is an underlying condition. You should always seek the advice of a healthcare professional.
What to watch for in all heart conditions: Cardiovascular risk factors
Smoking, diabetes, high blood pressure, kidney damage, high cholesterol, obesity or being overweight, excessive alcohol consumption, a sedentary lifestyle and stress are the cardiovascular risk factors that can be controlled most of the time.
Therefore, having a healthy and balanced lifestyle plays an important role in the prevention of cardiovascular disease. In particular, a balanced diet with regular consumption of fruit and vegetables and regular physical activity is recommended.
Conversely, heredity, gender and age are cardiovascular risk factors that cannot be influenced.
*Note: Reference rates/values listed for each test may vary from one medical laboratory or practice to another and according to certain factors such as gender, age, etc. Always consult with your prescribing doctor for any questions about your results.
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