High cholesterol levels and risk of CHD

Normally cholesterol is transported within the body by various protein carriers. These lipoproteins play a vital role not only in distribution of lipids but also in development of few pathological disorders such as atherosclerosis. So controlling cholesterol levels in the body is essential to prevent generation coronary heart diseases in future.

What are these lipids?

Lipids mainly contain two components such as cholesterol and triglycerides. Later are formed by esterification of free fatty acids with glycerol.

Cholesterol is mainly carried by LDL and HDL lipoproteins where as triglycerides are mainly transported by VLDL.

Comparatively triglycerides pose less risk than cholesterol for any pathological conditions like atherosclerosis or other cardiovascular disorders.

Of course, the raised triglyceride levels may increase the risk of atherosclerosis but it is not the root cause for it.

On the other hand, cholesterol acts as main causes for development of atherosclerosis when elevated at high levels.

What is good and bad cholesterol?

Just above, we have discussed that cholesterol transport in the body is mediated by LDL and HDL.

Are they both produce atherosclerosis?

Definitely they don’t. Here LDL cholesterol is pathological in producing atherosclerosis hence commonly denoted as bad cholesterol.

On the other hand, HDL levels in the blood protect the formation of atherosclerosis hence termed as good cholesterol.

It will be clear, if we think on what is atherosclerosis? It is a narrowing of blood vessel by formation of atheromatous plaque which is rich in lipids.

Which lipids?

Undoubtedly, it is LDL cholesterol. That’s why it is called as bad cholesterol.

LDL cholesterol is incorporated into the plaque formation where it forms fatty streaks which are further oxidised forming foam cells that occupy the core portion of the plaque in atheroma.

The quite opposite role is associated with HDL.

Being good cholesterol, it is really good for prevention of atherosclerosis as it is secreted from the tissues into the blood. So cholesterol can’t be incorporated into the plaque when it is present as HDL cholesterol.

LDL-Cholesterol levels

So now we know that LDL cholesterol is bad for coronary heart diseases (CHD) as it can produce atherosclerosis. Then what are the LDL levels to be maintained?

According to US national heart, lung and blood institute, the LDL levels are classifies as below.

Therefore it is optimal to maintain LDL cholesterol levels below 100 mg/dL in any patient.

But all these values may not be associated with similar risk in all patients. For example a patient with any risk factors like diabetes, hypertension and cigarette smoking should have more control of LDL cholesterol that a patient with a single risk factor.

Various risk factors that affect LDL levels and thereby risk of CHD are as follows.

So let’s see how the risk of coronary heart diseases (CHD) can be assessed in the patients based on the risk factors.

Patients with 0-1 risk factors

Most of patients initially fall in this category with no or single risk factor. In such patients, the LDL cholesterol should be maintained below 160 mg/dL.

So these patients need lifestyle modifications such as increase in physical activity, diet management, weigh control, avoiding of smoking etc.

Among these diet is very important and patients should take diet rich in fiber at the same time avoiding lipid diet high in saturated fatty acids.

Patients with 2 or more risk factors

Now patients with two or more risk factors should have further strict control of LDL cholesterol as they are associated with more risk for generation of coronary heart disease in next 10 years.

The goal of LDL-cholesterol in these patients is below 130 mg/dL.

As usual, these patients should start life style modifications if they found to have LDL cholesterol above 130 mg/dL.

Initiation of drug therapy depends on the total percentage of risk that is assessed by combination of all risk factors such as age, smoking, total cholesterol levels, HDL cholesterol and hypertension.

If the patient was found to have less than 10% of risk for CHD in next ten years, the drug therapy is started at LDL cholesterol above 160 mg/dL.

On the other hand, if total risk is from 10-20%, the drug therapy can be initiated whenever the LDL cholesterol levels are above 130 mg/dL.

Patients with CHD or its equivalents

This group of patients are at high risk greater than >20% for generation of CHD in next 10 years.

Few of the vascular disorders like peripheral artery disease, symptomatic carotid artery disease, enlargement of aorta and even diabetes all increase risk equivalent to CHD.

So it is not surprising that patients any of these conditions should have a goal of LDL cholesterol less than 100 mg/dL. In these patients life style modifications should be started whenever LDL cholesterol is ≥ 100 mg/dL and drug therapy at ≥ 130 mg/dL.

HDL cholesterol levels

HDL cholesterol acts as good cholesterol protecting from coronary heart diseases and patients should maintain a minimum level of HDL cholesterol.

So the patients should have HDL cholesterol above 40 mg/dL and for a better prevention of risk they should be nearer to 60 mg/dL.

Interestingly, if the HDL cholesterol levels are above 60 mg/dL they further decrease risk tendency and even they counteract one of the risk factor for CHD.

That’s why these levels are taken into consideration during risk assessment and HDL cholesterol above 60 mg/dL was given -1 factor as it decreases the risk count.

Total cholesterol

Total cholesterol in the body is not only coming from LDL cholesterol and HDL cholesterol but also from triglycerides. Even the later have less effect on atherosclerosis, approximately 20% of their levels can be added to the total cholesterol.

Therefore total cholesterol can be calculated as

TC =LDL + HDL + 20% of TG

For example, if a patient has 130 mg/dl of LDL cholesterol, 50 mg/dL of HDL cholesterol and 180 mg/dL of triglycerides, then total cholesterol will be

TC=130 + 50 + (20/100)*180

=216 mg/dl

What it indicates?

Just like LDL and HDL levels, total cholesterol levels are classified into three classes based on the the ideal and raised levels.

So in the above example, the patient is under borderline high therefore may start life style modifications, based on the presence of the other risk factors.

Are triglyceride levels important?

Definitely they are important. As we have seen above triglycerides also contribute for total cholesterol in the body and share risk for generation of atherosclerosis.

Under normal conditions, the triglyceride levels should be less than 150 mg/dL and when they cross 200 mg/dL they are considered as at high levels. Extreme high levels can be observed when they cross 500 mg/dL.

So, the goal of triglyceride levels is to maintain below 150 mg/dL when the patient has raised LDL cholesterol and with any risk factors.

On the other hand, triglyceride levels may be less than 200 mg/dL in those patients with LDL is under control and no significant risk factors.

Whatever may be the goal, it is better to control triglycerides below 150 mg/dL with life style modification such as physical exercise, proper diet and weight control.

Drugs like fibrates such as gemfibrozil, clofibrate and fenofibrate can be indicated for high levels of triglycerides which also reduce LDL cholesterol to a smaller extent.

But generally fibrates like gemfibrozil is not combined with statins such as atorvastatin due to risk of muscle pain and disintegration.

Conclusion

Atherosclerosis is one of the important pathological coronary heart diseases that can impact the life of the patient in the next few years. Cholesterol is one of the main source for generation of CHD, particularly in the form of LDL cholesterol.

So, LDL levels should be strictly controlled at a specified goal fixed by the total count of risk factors. They should be maintained at below 100 mg/dL, 130 mg/dL and 160 mg/dL in high risk, medium risk and low risk patients respectively.

Quite oppositely, HDL cholesterol levels should be raised and above 60 mg/dL they are protective. Triglycerides also influence the CHD by adding 20% contribution to the total cholesterol hence controlled below 200 mg/dL.