Lp(a) could inform risk stratification of patients with a calcium score of 0
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Key takeaways:
- Elevated Lp(a) was tied to presence of any coronary plaque on coronary CT among asymptomatic individuals.
- More people with elevated Lp(a) had any plaque vs. those with lower Lp(a), despite a calcium score of 0.
Elevated lipoprotein(a), despite a coronary artery calcium score of 0, could portend coronary plaque burden and may be a potential marker for early atherosclerosis intervention, researchers reported.
The results of a community-level evaluation of the impact of Lp(a) on coronary plaque in asymptomatic individuals were published in Circulation: Cardiovascular Imaging.
“The idea was to see, in those patients who actually had disease, what we can discover might be evidence of contributors so we can better prevent cardiac events,” Jonathan Fialkow, MD, FACC, FAHA, deputy director of clinical cardiology at Miami Cardiac & Vascular Institute, part of Baptist Health South Florida, told Healio. “Quite frankly, a large percentage of people who have heart attacks don’t have those risk factors. So how can we be better and more precise in finding what would be easily and simply measured to stratify a person to say, ‘you may or may not be at a higher risk of a heart attack,’ so then you can do things to lower your risk.
“We know [Lp(a)] seems to associate with increased risk for heart attacks. What we established is that, in fact, in these patients who had an elevated Lp(a) compared with those that had a lower Lp(a), there was more evidence of atherosclerosis, and, in fact, the kind of atherosclerosis we’re more worried about on the coronary CT scans, than those that didn’t have Lp(a),” he said. “Lp(a) most likely is an additional thing we can start looking at when we want to predict who is at a higher risk for a heart attack or a cardiac event than otherwise.”
For the present cross-sectional analysis, Fialkow and colleagues evaluated participant data from the longitudinal, community-based, prospective MiHeart study that included 1,795 individuals not taking any lipid-lowering medications at baseline. The median age was 52 years, and nearly half of the overall cohort were Hispanic/Latino.
Participants were classified as having low Lp(a) (< 125 nmol/L; 83.8%) or elevated Lp(a) ( 125 nmol/L; 16.2%).
The main outcomes of interest included any plaque, CAC score more than 0, maximal stenosis of 50% or more, presence of any high-risk plaque feature and presence of two or more high-risk plaque features on coronary CT.
Lp(a), CAC score and coronary plaque
The researchers noted that the distribution of Lp(a) was similar across most subgroups; however, the proportion of women was higher among those with Lp(a) of 125 nmol/L or more (61% vs. 53%).
Additionally, the prevalence of most CV risk factors was also not significantly different between the two Lp(a) groups, except those with elevated Lp(a) had higher total cholesterol (median, 222 mg/dL vs. 208 mg/dL) and HDL levels (median, 61 mg/dL vs. 57 mg/dL).
After multivariable adjustment, elevated Lp(a) was independently associated with presence of any coronary plaque (OR = 1.4; 95% CI, 1.05-1.86) and presence of two or more high-risk plaque features (OR = 3.94; 95% CI, 1.82-8.52); however, only 35 participants had two or more high-risk plaque features.
Among the 1,200 participants with a CAC score of 0, individuals with elevated Lp(a) also had a higher percentage of any plaque compared with those with low Lp(a) (24.2% vs. 14.2%; P < .001), according to the study.
“In having high Lp(a) and CAC score of 0, we’re not ready to say you should be on therapy. That’s controversial,” Fialkow told Healio. “There are people who will say, ‘If your Lp(a) is high and your CAC score is 0, I’m going to treat you anyway by lowering your LDL with statins.’ This may say that if we’re looking to prevent an event, the calcium score of 0 may, in fact, trump high Lp(a).
“We’ve done a good job in identifying people at CV risk, but not good enough,” he said. “Many people have risk factors and we intervene and maybe they wouldn’t have had an event if we didn’t. More importantly, many people look good and the basic cardiac risk factors might be not high, but here’s an example of Lp(a) being validated to increase the risk of both atherosclerosis and high-risk features. This might be a valuable further stratification point, up or down to ultimately identify people at risk early and intervene to decrease the risks for those cardiac events.”
‘Intriguing and sometimes paradoxical’ results
In a related editorial, Patricia F. Rodriguez Lozano, MD, MS, assistant professor in the department of medicine, cardiovascular division, and Nisha Hosadurg, MD, fellow in advanced cardiovascular imaging at University of Virginia Health, discussed the “sometimes paradoxical” results of the present study.
“One may, as the authors, interpret this as aligning with the concept of the power of zero, which posits that a CAC score of zero carries a low risk of cardiovascular events,” the authors wrote. “It has however suggested that CAC and Lp(a) may be independent predictors of ASCVD risk. These results then raise a series of provocative questions: Can we truly be reassured by the absence of calcified plaque despite an elevated Lp(a)? Or, is elevated Lp(a), presumably with a lifetime exposure, regardless of a CAC score of zero equivalent to the same high risk as elevated CAC?
“The intriguing and sometimes paradoxical findings of this study underscore the complexity of cardiovascular risk assessment and the need for continued innovation in both diagnostic and therapeutic strategies,” they wrote. “As our understanding of Lp(a) evolves, so too must our approach to managing the risks it presents.”
For more information:
Jonathan Fialkow, MD, FACC, FAHA, can be reached at 7400 SW 87th Ave., Suite 100, Miami, FL 33173.
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