Lipoprotein(a) Linked to Heart Attacks
Genetic Study Shows Heart Attack Increase From Lipoprotein(a), a Type of Cholesterol
June 9, 2009 -- Genetic testing confirms that high levels of a type of cholesterol known as lipoprotein(a) are associated with an increased risk for heart attacks, but the clinical implications of the finding are unclear.
Lipoprotein(a) has long been suspected of contributing to cardiovascular risk. But this new research offers the strongest evidence yet identifying it as an independent risk factor for heart attack.
The study appears in the June 10 issue of the Journal of the American Medical Association.
LDL, HDL, and Lp(a)
Like low-density lipoprotein (LDL), lipoprotein(a) levels can be determined with a simple blood test.
But unlike LDL or high-density lipoprotein (HDL), lipoprotein(a) is not routinely measured because it has not been clear if doing so provides additional information about who should be taking cholesterol-lowering drugs.
Lipoprotein(a), also known as Lp(a), consists of LDL cholesterol bound to the protein apolipoprotein(a).
Some people are genetically predisposed to have a lot of lipoprotein(a) and others very little. Because of this, Lp(a) levels can vary greatly from person to person.
This wide genetic variability made lipoprotein(a) an ideal candidate for a new type of research that may offer an alternative to long and expensive randomized trials for identifying risk factors for disease.
Instead of lowering lipoprotein(a) levels with drugs, the researchers assessed genetic variations in the gene that controls Lp(a) levels in the blood of close to 45,000 participants in three large long-term, follow-up studies conducted in Denmark.
They found that heart attack risk increased as lipoprotein(a) levels rose, based upon the underlying genetic code. The association was seen in all three studies.
“These findings are consistent with a causal association of elevated lipoprotein(a) levels with increased (heart attack) risk,” study co-author Borge Nordestgaard, MD, and colleagues write.
Clinical Implications ‘Limited’
Nordestgaard tells WebMD that the findings justify a large, randomized intervention trial designed to target lipoprotein(a).
However, a cardiologist with the NIH’s National Heart Lung and Blood Institute tells WebMD that the new study does little to define how to use Lp(a) measurements.