Pathology Associates Of Lexington, P.A.
Pathology Associates Of Lexington, P.A.
Pathology Associates Of Lexington, P.A.
 Home | Pathology Group MembersOur Hospital  Search This Website:
        Lab Tests for Risk of Acute MI
      

Lipid profile (the primary risk test): 

 
  • Cholesterol levels, note: too high LDL and too low HDL fail to identify all with elevated risk. The liver produces 60-80% of the cholesterol a person needs. Total cholesterol (TC) travels in blood as lipoprotein droplets of varying sizes. Chylomicrons are huge and contain a tiny amount of cholesterol & are produced in the intestine, especially after a meal; very low density lipoproteins (VLDL) are large & have small amounts of cholesterol and are produced in the liver; low density lipoprotein (LDL) is rich in cholesterol and small (a mix of ordinarily small and very small), transporting cholesterol from the liver to cells in the body. Between VLDL and LDL is IDL (intermediate density lipoprotein. High density lipoprotein (HDL) is also cholesterol rich...but functions in the direction of removal of cholesterol.
 
  • acceptable levels:
    • a total cholesterol <200 is desirable and 240 or higher is "high". Yet, of the 1.1 million heart attacks in America each year, nearly 50% don't have high cholesterol!
    • An HDL level <35 is risky 

    • and an LDL cholesterol >130 is risky (>100 if you've already had an acute MI); borderline hi risk LDL is 130-159

    • CHD rarely develops when LDL <1005 and statin therapy reduces LDL & LDL reduction is the centerpiece of lipid therapy.

 

NOTE: well-done lipid profile testing interpreted in light of family history is the key lab-test mainstay. Such as homocysteine and Lp(a) (and probably the others) are used to help evaluate a high-risk patient who tests OK on the standard lipid profile1

 

Cholesterol particle size: LDL predominating as very small & dense particles (LDL pattern B) is likely risky5 (LDL pattern phenotype B...the "polydisperse pattern" [wide range of LDL particle sizes]). "LDL pattern B" is an independent risk marker...elevated risk even if all other factors normal, risk being 3x normal if predominating in the normal range & 6x if elevatd LDL with pattern B6. Proton nuclear magnetic resonance spectroscopy (NMR) lipoprofile: This measures amounts & sizes of particles in LDL and HDL3 and identifies 15 different profiles. The technical invention by biochemist, James D. Otvos, is exclusively licensed through Lipomed, Inc. of Raleigh, N. C. Size can also be reliably measured with ultracentrifugation, HPLC, PGGE (NDGGE), and PTGE...this latter method being explored for use by our lab.  

Lots of large VLDL particles are risky3 [or is it the small VLDL particles..."VLDL remnants"?5].  

"LDL pattern B" types often have low HDL6 (<35...maybe even <40 for males & <50 for women5), slightly elevated triglycerides (150-250, maybe even also 250-5005); and when so, if5 total LDL is elevated (<1305), may be referred to as the "atherogenic lipoprotein phenotype5" (if this pattern but total cholesterol & total triglyceride are in normal range= "atherogenic dyslipidemia"5)...and these have an increased tendency to coronary vasospasm6 (may have a prevalence as high as 33% of males and 14% of females). This group progresses most rapidly; and, once having heart disease, the progression is twice the rate of other settings6. But, this group responds best to treatment6.When atherogenic dyslipidemia is added to hypertension, insulin resistance (the most sensitive test for insulin resistance is elevated fasting plasma insulin level), and procoagulant (hypercoagulable) state= "the metabolic syndrome"5. When you have a combination of "LDL pattern B", elevated APO-B, and elevated resting plasma insulin levels, your cardiac risk is 20x normal! Treat pattern B with diet, exercise, and niacin (niacin increases particle size).

There are LDL droplets smaller than pattern B, such as IIIa, IIIb (these two associated with carotid artery disease), and the even smaller IVb (may be associated with plaque instability)6. You could have 50% "LDL pattern A" larger particles and 30% or more in the IIIa/IIIb range, you are at increased risk (anything greater than 20%)6.

Sizing by NMR is an expensive test...$300 to upwards of $600.[Liposcience file] [Berkeley HeartLab] [Atherotech]

 
© Copyright 1999 - 2006, all rights reserved, Pathology Associates Of Lexington, P.A.