The Intersection of Genetics and Imaging in Cardiovascular Risk
In the era of precision medicine, clinicians are increasingly tasked with reconciling genetic risk factors with anatomical evidence of disease. Among the most challenging of these genetic factors is Lipoprotein(a) [Lp(a)], a highly heritable and independent risk factor for atherosclerotic cardiovascular disease (ASCVD). While traditional lipid panels focus on LDL cholesterol, Lp(a) presents a unique threat due to its pro-atherogenic, pro-inflammatory, and potentially pro-thrombotic properties. However, a significant clinical question has persisted: How should clinicians interpret Coronary Artery Calcium (CAC) scores in the presence of elevated Lp(a)?
A landmark multicohort study recently published in the Journal of the American College of Cardiology provides much-needed clarity. The study, titled Use of Coronary Artery Calcium Scoring in Individuals With Elevated Lipoprotein(a), rigorously evaluates whether CAC scoring retains its prognostic power in this high-risk genetic subgroup.
Highlights of the Multicohort Analysis
1. Independent Risk Predictors: Both elevated Lp(a) (>50 mg/dL) and a CAC score >0 were found to be independent and additive predictors of ASCVD events.
2. The Power of Zero: In individuals with a CAC score of 0, absolute event rates remained low (less than 5 per 1,000 person-years) even if their Lp(a) levels were significantly elevated.
3. Synergistic Danger: The combination of high Lp(a) (>50 mg/dL) and high CAC (≥300) resulted in a six-fold increase in ASCVD risk compared to those with low Lp(a) and no coronary calcium.
4. Clinical Utility: CAC scoring remains a robust tool for risk stratification in patients with high Lp(a), helping to guide the intensity of lipid-lowering therapies.
Background: The Challenge of Lipoprotein(a)
Lipoprotein(a) consists of an LDL-like particle covalently bound to apolipoprotein(a). Its levels are roughly 90% genetically determined and remain relatively stable throughout an individual’s life, unaffected by standard lifestyle modifications or traditional statin therapy. Approximately 20% of the global population has Lp(a) levels exceeding 50 mg/dL, the threshold generally considered to increase cardiovascular risk.
Historically, there has been concern that Lp(a) might preferentially drive the development of noncalcified plaque—lesions that are invisible to traditional CT-based CAC scoring. If this were the case, a CAC score of zero in a patient with high Lp(a) might provide a false sense of security. This study sought to determine if the presence of coronary calcium effectively captures the risk profile of these individuals.
Study Design: A Robust Multi-Ethnic Approach
The researchers utilized a pooled cohort consisting of 11,319 participants drawn from four major U.S.-based prospective studies: the Multi-Ethnic Study of Atherosclerosis (MESA), the Dallas Heart Study (DHS), the Atherosclerosis Risk in Communities (ARIC) study, and the Cardiovascular Health Study (CHS). All participants were free of known ASCVD at baseline.
The primary endpoint was incident ASCVD, defined as a composite of myocardial infarction, stroke, or coronary revascularization. The mean age of the participants was 56 years, with a balanced gender distribution (54% women). The cohort was followed for a mean of 14.8 years, providing a significant window to observe long-term cardiovascular outcomes.
Key Findings: Does CAC Scoring Withstand High Lp(a)?
The results of the study were definitive. The researchers observed 1,569 incident ASCVD events during the follow-up period. When analyzed independently, Lp(a) >50 mg/dL carried a Hazard Ratio (HR) of 1.24, while a CAC score >0 carried a significantly higher HR of 2.44.
The Prognostic Value of CAC = 0
One of the most clinically relevant findings pertains to the ‘Power of Zero.’ Among participants with a CAC score of 0, the incidence rate of ASCVD was 3.8 per 1,000 person-years for those with low Lp(a) and 4.9 per 1,000 person-years for those with elevated Lp(a). While the relative risk was slightly higher for the high Lp(a) group (HR 1.28), the absolute risk remained remarkably low. This suggests that in the absence of detectable coronary calcification, the short-to-medium-term risk of a major cardiovascular event is low, regardless of the patient’s genetic predisposition via Lp(a).
The Escalation of Risk with Calcification
As the CAC score increased, the presence of elevated Lp(a) acted as a potent risk multiplier. For individuals with CAC >0, the incidence rate jumped to 18.2 per 1,000 person-years for low Lp(a) and 21.2 per 1,000 person-years for high Lp(a). The most striking data was seen in the highest strata: individuals with both CAC ≥300 and Lp(a) >50 mg/dL faced a Hazard Ratio of 6.12. This indicates a profound synergistic effect between established atherosclerotic burden and the pro-inflammatory drive of Lp(a).
Expert Commentary: Integrating Findings into Clinical Practice
This study reinforces the utility of CAC as a ‘gatekeeper’ in primary prevention. For clinicians, the management of a patient with elevated Lp(a) often involves a difficult decision regarding the intensity of statin therapy or the introduction of non-statin therapies like ezetimibe or PCSK9 inhibitors.
Refining Primary Prevention
In patients with borderline or intermediate risk and elevated Lp(a), a CAC score of 0 can support a more conservative approach, focusing on lifestyle rather than aggressive pharmacotherapy, provided other risk factors are controlled. Conversely, any evidence of CAC in a patient with high Lp(a) should be met with aggressive intervention. The high HR of 6.12 in those with extensive calcification and high Lp(a) identifies a subgroup that may benefit most from the next generation of Lp(a)-lowering therapies currently in Phase 3 clinical trials, such as Pelacarsen and Olpasiran.
Mechanistic Insights
Why does CAC still work if Lp(a) promotes noncalcified plaque? The most likely explanation is that while Lp(a) may initiate early noncalcified lesions, the progression of atherosclerosis eventually leads to calcification in most individuals. Therefore, CAC remains a reliable surrogate for the total atherosclerotic burden, even if it does not visualize every individual lipid-rich plaque.
Study Limitations
While the study is robust, it is not without limitations. The use of a single baseline measurement for Lp(a) and CAC does not account for changes over time. Additionally, while the cohort was diverse, the findings may not be perfectly generalizable to all global populations, particularly those with different genetic backgrounds affecting Lp(a) isoform sizes. Finally, the study focused on ASCVD events; it did not specifically look at aortic valve stenosis, which is also strongly associated with elevated Lp(a).
Conclusion: A Roadmap for Personalized Prevention
The multicohort study by Bhatia et al. confirms that CAC scoring is not rendered obsolete by the measurement of Lipoprotein(a). Instead, the two markers are complementary. CAC provides a snapshot of the actual damage (the ‘burden’), while Lp(a) provides a measure of the genetic ‘velocity’ or risk potential. For the clinician, this means that CAC scoring remains a powerful tool to de-risk patients with high Lp(a) or to identify those who require the most intensive evidence-based interventions.
References
1. Bhatia HS, Fan Y, Dharmavaram G, et al. Use of Coronary Artery Calcium Scoring in Individuals With Elevated Lipoprotein(a): A Multicohort Study. J Am Coll Cardiol. 2026; (PMID: 41837904).
2. Tsimikas S. Lipoprotein(a): An elusive cardiovascular risk factor and a target for therapy. Nat Rev Cardiol. 2022;19(8):535-551.
3. Greenland P, Blaha MJ, Budoff MJ, Erbel R, Watson KE. Coronary Calcium Score and Cardiovascular Risk. J Am Coll Cardiol. 2018;71(4):434-447.