Prevalence of heterozygous familial hypercholesterolemia and combined hyperlipidemia phenotype in very young survivors of myocardial infarction and their association with the severity of atheromatous burden.

Background: Heterozygous familial hypercholesterolemia (HeFH) and combined hyperlipidemia (CHL) phenotype are associated with premature myocardial infarction (MI).

Objective: To assess the prevalence of HeFH and CHL phenotype among young survivors of MI and compare patients' characteristics with these 2 lipid disorders.

Methods: We recruited 382 young survivors of MI (≤40 years). Fasting lipids, lipoprotein(a) [Lp(a)], apolipoprotein A-1, and apolipoprotein B (apoB) levels were determined. Using the Dutch Lipid Clinic Network (DLCN) algorithm, patients having definite or probable HeFH were identified. Patients with apoB levels >120 mg/dL and triglyceride levels >170 mg/dL (1.92 mmol/L) [>90th percentile of 326 age and sex-matched healthy controls] were classified as having CHL phenotype. Common carotid artery intima-media thickness (CCA-IMT) was measured by B-mode ultrasonography.

Results: Eighty-one patients (21.2%) had definite/probable HeFH and 62 (16.2%) had CHL phenotype. Twenty-three patients fulfilled the criteria for both HeFH and CHL phenotype and were removed from further comparisons. Patients with HeFH (n = 58) had higher levels of total cholesterol, low-density lipoprotein (LDL)-cholesterol, Lp(a), and apoB, whereas patients with CHL phenotype (n = 39) had higher levels of triglycerides and lower high-density lipoprotein (HDL)-cholesterol levels. The prevalence of metabolic syndrome was higher in patients with CHL phenotype compared to those with HeFH (67.0% vs 16.4%, P < .001). Patients with HeFH had more extensive coronary artery disease (3-vessel disease: 36.2% vs 12.8%, P = .011) and greater right CCA-IMT (0.67 ± 0.11 mm vs 0.56 ± 0.09 mm, P < .001) and left CCA-IMT (0.68 ± 0.10 mm vs 0.56 ± 0.08 mm, P < .001) compared to CHL phenotype patients.

Conclusions: Both HeFH and CHL phenotype are common among patients with premature MI. CHL phenotype compared to HeFH is associated with less atheromatous burden in coronary and carotid arteries at the time of first MI.