From the Journals

Lp(a) tied to more early CV events than familial hypercholesterolemia


 

Many more people are at risk for early cardiovascular events because of raised lipoprotein(a) levels than from having familial hypercholesterolemia (FH), a new study suggests.

The Danish study set out to try and establish a level of Lp(a) that would be associated with a cardiovascular risk similar to that seen with FH. As there are many different definitions of FH, results showed a large range of Lp(a) values that corresponded to risk levels of the different FH definitions.

However, if considering one of the broadest FH definitions (from MEDPED – Make Early Diagnoses, Prevent Early Deaths), which is the one most commonly used in the United States, results showed that the level of cardiovascular risk in patients with this definition of FH is similar to that associated with Lp(a) levels of around 70 mg/dL (0.7 g/L).

“While FH is fairly unusual, occurring in less than 1% of the population, levels of Lp(a) of 70 mg/dL or above are much more common, occurring in around 10% of the White population,” Børge Nordestgaard, MD, Copenhagen University Hospital, said in an interview. Around 20% of the Black population have such high levels, while levels in Hispanics are in between.

“Our results suggest that there will be many more individuals at risk of premature MI or cardiovascular death because of raised Lp(a) levels than because of FH,” added Dr. Nordestgaard, the senior author of the current study.

Dr. Nordestgaard explained that FH is well established to be a serious condition. “We consider FH to be the genetic disease that causes the most cases of early heart disease and early death worldwide.”

“But we know now that raised levels of Lp(a), which is also genetically determined, can also lead to an increased risk of cardiovascular events relatively early in life, and when you look into the numbers, it seems like high levels of Lp(a) could be more common than FH. We wanted to try and find the levels of Lp(a) that corresponded to similar cardiovascular risk as FH.”

The Danish study was published in the Journal of the American College of Cardiology.

The authors note that the 2019 joint European Society of Cardiology and European Atherosclerosis Society guidelines suggested that an Lp(a) level greater than 180 mg/dL (0.8 g/L) may confer a lifetime risk for heart disease equivalent to the risk associated with heterozygous FH, but they point out that this value was speculative and not based on a direct comparison of risk associated with the two conditions in the same population.

For their study, Dr. Nordestgaard and colleagues analyzed information from a large database of the Danish population, the Copenhagen General Population Study, including 69,644 individuals for whom data on FH and Lp(a) levels were available. As these conditions are genetically determined, and the study held records on individuals going back several decades, the researchers were able to analyze event rates over a median follow up time of 42 years. During this time, there were 4,166 cases of myocardial infarction and 11,464 cases of atherosclerotic cardiovascular disease (ASCVD).

Results showed that Lp(a) levels associated with MI risk equivalent to that of clinical FH ranged from 67 to 402 mg/dL depending on the definition used for FH. The Lp(a) level corresponding to the MI risk of genetically determined FH was 180 mg/dL.

In terms of risk of ASCVD events, the levels of Lp(a) corresponding to the risk associated with clinical FH ranged from 130 to 391 mg/dL, and the Lp(a) level corresponding to the ASCVD risk of genetically determined FH was 175 mg/dL.

“All these different definitions of FH may cause some confusion, but basically we are saying that if an individual is found to have an Lp(a) above 70 mg/dL, then they have a similar level of cardiovascular risk as that associated with the broadest definition of FH, and they should be taken as seriously as a patient diagnosed with FH,” Dr. Nordestgaard said.

He estimated that these individuals have approximately a doubling of cardiovascular risk, compared with the general population, and risk increases further with rising Lp(a) levels.

The researchers also found that if an individual has both FH and raised Lp(a) they are at very high risk, as these two conditions are independent of each other.

Although a specific treatment for lowering Lp(a) levels is not yet available, Dr. Nordestgaard stresses that it is still worth identifying individuals with raised Lp(a) as efforts can be made to address other cardiovascular risk factors.

“We know raised Lp(a) increases cardiovascular risk, but there are also many other factors that likewise increase this risk, and they are all additive. So, it is very important that individuals with raised Lp(a) levels address these other risk factors,” he said. “These include stopping smoking, being at healthy weight, exercising regularly, eating a heart-healthy diet, and aggressive treatment of raised LDL, hypertension, and diabetes. All these things will lower their overall risk of cardiovascular disease.”

And there is the promise of new drugs to lower Lp(a) on the horizon, with several such products now in clinical development.

Dr. Nordestgaard also points out that as Lp(a) is genetically determined, cascade screening of close relatives of the individual with raised Lp(a) should also take place to detect others who may be at risk.

Although a level of Lp(a) of around 70 mg/dL confers similar cardiovascular risk than some definitions of FH, Dr. Nordestgaard says lower levels than this should also be a signal for concern.

“We usually say Lp(a) levels of 50 mg/dL are when we need to start to take this seriously. And it’s estimated that about 20% of the White population will have levels of 50 mg/dL or over and even more in the Black population,” he added.

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