Two hundred thirty-nine patients with PAD undergoing LER had blood collected at baseline and were followed prospectively for MACE (myocardial infarction, stroke, cardiovascular death) for one year. Nineteen age, sex and LDL-C-matched control subjects without cardiovascular disease also had blood drawn. Subject LDL was exposed to sphingomyelinase and LDL aggregate size measured via dynamic light scattering.
Mean age was 72.3 ± 10.9 years, 32.6% were female, and LDL-cholesterol was 68 ± 25 mg/dL. LDL aggregation was inversely associated with triglycerides, but not associated with demographics, LDL-cholesterol or other risk factors. Maximal LDL aggregation occurred significantly earlier in subjects with PAD than in control subjects. 15.9% of subjects experienced MACE over one year. The 1st tertile (shortest time to maximal aggregation) exhibited significantly higher MACE (25% vs. 12.5% in tertile 2 and 10.1% in tertile 3, p = 0.012). After multivariable adjustment for demographics and CVD risk factors, the hazard ratio for MACE in the 1st tertile was 4.57 (95% CI 1.60-13.01; p = 0.004) compared to tertile 3. Inclusion of LDL aggregation in the Framingham Heart Study risk calculator for recurrent coronary heart disease events improved the c-index from 0.57 to 0.63 (p = 0.01).
We show that in the setting of very well controlled LDL-cholesterol, patients with PAD with the most rapid LDL aggregation had a significantly elevated MACE risk following LER even after multivariable adjustment. This measure further improved the classification specificity of an established risk prediction tool. Our findings support broader investigation of this assay for risk stratification in patients with atherosclerotic CVD.
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