High Lipoprotein(A) Is Often the Culprit in “Young” Heart Attacks
While doctors routinely test for other lipoproteins like HDL and LDL cholesterol, few test for lipoprotein(a) [lp(a)], a fatty particle in the blood, which can triple the risk of having a heart attack or stroke at an early age.
For most people, lp(a) is nothing to worry about. Levels are strongly determined by genetics and the majority of people produce very little of it.
But up to one in five Americans have perilously high levels of it in their blood. Studies show that diet and exercise have almost no impact on lp(a), and cholesterol-lowering drugs only modestly lower it.
“People don’t know about it, physicians don’t know about it, and we have to get an education program out there, but that’s expensive,” said Dr. Henry N. Ginsberg, the Irving Professor of Medicine at Columbia University and a leading expert on lp(a). “I would say that somewhere between 15 to 20 percent of the population would clearly benefit from knowing that this is their problem.”
Lp(a) was discovered in 1963 by a Norwegian scientist, Kare Berg, who noticed that it was especially common among people with coronary heart disease. No one knows precisely what purpose lp(a) serves in the body, though some scientists speculate that it may have a beneficial role such as helping to repair injured cells or preventing infections by binding to pathogens in the blood.
But the downside of excessive lp(a) is clear: It accelerates the formation of plaque in the arteries, and it promotes blood clots.
Studies suggest that the threshold for high lp(a) begins around 30 milligrams per deciliter of blood. Heart disease risk jumps for those in the 80th percentile, with lp(a) levels above 60, and climbs sharply for the 5 percent of the population with lp(a) levels between 150 and 300, according to Dr. Ginsberg at Columbia. “Those people can be disasters in terms of cardiovascular risk,” he said.
Yet many people at high risk do not fit the typical profile of a person with heart disease. Sandra Revill Tremulis was a health-conscious medical device executive who moonlighted as an aerobics instructor, followed a strict diet, and maintained 16 percent body fat, equivalent to that of an elite athlete. Her LDL and total cholesterol levels were low, and at age 39, her Framingham risk score, which gauges heart disease risk, put her odds of having a heart attack in her 40s at just 1 percent.
“Only a small percentage of physicians know about this,” she said. “The biggest challenge for patients is finding knowledgeable physicians who know about this and can help them.”
Dr. Lloyd-Jones at Northwestern said that testing for lp(a) should be considered for people with early-onset cardiovascular disease — which means younger than age 50 for men and age 60 for women — or a strong family history of it. Since high lp(a) is hereditary, those who have it often have a parent, sibling or grandparent who suffered a premature heart attack or stroke. When one person has it, it’s important to test other family members too.
Two medications, niacin and a class of drugs known as PCSK9 inhibitors, have been shown to modestly reduce lp(a) levels. But niacin, a B vitamin, has many side effects, and PCSK9 inhibitors, which are not approved for lp(a) lowering, are not usually covered by insurance for that purpose and can cost as much as $14,000 a year.
At least one drug company, Ionis Pharmaceuticals, is developing a drug specifically to combat lp(a), but the drug is still in mid-stage testing and it could be years before it reaches the market.