The conventional lipid panel in laboratory testing is limited in that it only assesses the “total” LDL and HDL. However, it’s the size of the lipid particles that matters. To evaluate the risk of heart attack or stroke, a Lipoprotein Particle Test would reveal more information.
There are five major subgroups of Low-Density Lipoproteins (LDL): IDL (intermediate density lipoprotein), I, II, III, and IV. IDL is the largest, least dense, and most buoyant, while LDL-IV is the smallest and most dense. Small LDL particles are also dense. These terms are often used interchangeably. The smaller the LDL particle, the more dangerous it is. In fact, small-dense LDL (LDLI-II and LDL-IV) are three times more atherogenic than buoyant LDL.
According to the National Cholesterol Education Program (NCEP), only about half of the variability in coronary heart disease risk can be attributed to conventional risk factors (i.e., LDL, HDL, and triglyceride levels). Other, more specific risk factors enhance the predictive power of cardiovascular disease in individuals. Small-dense LDL is one of these particular risk factors that may be independent of other lipid-related risk factors. Lipoproteins transport cholesterol throughout the body. But it is the actual lipoprotein particle, not the cholesterol within them, that penetrates the arterial wall and causes heart disease. That is why it is necessary to know the number of small LDL particles.
Why is Small-Dense LDL so Harmful?
Smaller particles of LDL can more easily penetrate the arterial wall than large LDL particles simply due to their size. Therefore, the smaller the LDL particle, the more likely it is to enter the arterial endothelium where it becomes oxidized and is taken up by a macrophage cell, which then becomes a foam cell. This cell eventually sticks together to build plaque within the arteries. Evidence also suggests that small-dense LDL is associated with vascular dementia.
It is also important to know how many LDL particles are present, in addition to their size. Just as small LDL particles can fit through the arterial lining more easily than large LDL particles, the more LDL particles there are, the more likely they will enter the arterial intima, regardless of size. It is, therefore, imperative to measure both the size (density) and the number of LDL particles.
NEW RISK FACTORS:
- Small-dense LDL: these atherogenic particles are easily oxidized and penetrate the arterial endothelium to form plaque.
- Lp(a): this small-dense LDL is involved in thrombosis.
- RLP (Remnant Lipoprotein) is very atherogenic, has a similar composition and density of plaque, is believed to be a building block of plaque, and does not need to be oxidized like other LDL particles.
- HDL2b is positively correlated with heart health because it is an indicator of how well excess lipids are removed.