Prevalence and outcomes of familial hypercholesterolemia in young patients undergoing coronary bypass surgery
Authors: Deconinck O , Sharman J , Bishop W , Watts G F , Hardikar A , Dare L , Fenton C , Lees C , Pointon T , Black J A 
Published: November 2023

Abstract

Background
Familial hypercholesterolemia (FH) is an autosomal dominant genetic disorder of lipoprotein metabolism, with elevated low-density lipoprotein cholesterol (LDL) levels and increased risk of premature coronary disease. Appropriate management substantially reduces the risk of adverse events; however, FH is frequently under-recognised and under-treated. The prevalence of FH amongst younger patients undergoing coronary bypass surgery, as well as their clinical outcomes, has not been described.

Purpose
This study aimed to determine the prevalence of FH in patients undergoing coronary bypass surgery prior to age 60 years. The association of FH on attainment of LDL targets and subsequent adverse cardiovascular events was also determined.

Methods
A retrospective analysis of all patients undergoing coronary bypass surgery prior to the age of 60 years was conducted at an Australian tertiary hospital during the period April 2008 and July 2022. Exclusion criteria were severe renal or hepatic impairment, uncontrolled malignancy, severe inflammatory or infectious disease, or lipid data unavailable. Baseline demographics and risk factors at the time of surgery were identified by a search of the Statewide Cardiothoracic Database. Blood lipid levels (highest, pre-surgery and most recent) and clinical outcomes were obtained from digital medical records. Dutch Lipid Clinic Network Scores (DLCNS) were calculated for all patients and grouped as ‘unlikely FH’ (DLCNS &lt;3), ‘possible FH’ (DLCNS 3 – 5), or ‘probable / definite FH’ (DLCNS ³ 6). Attainment of LDL targets (&lt;1.8mmol/L and &lt;1.4mmol/L) and subsequent major adverse cardiovascular events (MACE) were compared between the ‘unlikely’ and ‘probable / definite’ FH groups.

Results
During the study period, 683 patients underwent coronary bypass procedures prior to the age of 60. 93 were excluded, leaving a study population of 590, with a median follow up of 7.9 years [IQR 4.7, 12.1]. Baseline characteristics are outlined in table 1. 80 patients (13.6%) were classified as ‘definite/probable FH’, 249 (42.2%) as ‘possible FH’ and 261 (44.2%) ‘unlikely FH’. As observed in table 2, patients with definite/probable FH had a significantly higher prevalence of uncontrolled lipids (81.2%) and MACE (21.3%) compared to patients with unlikely FH. For MACE, this result remained statistically significant after adjusting for age, sex, smoking status, hypertension, diabetes and surgery type (elective vs urgent) - OR 2.52 [95% CI 1.0 - 6.4].

Conclusion
FH is highly prevalent in young patients undergoing coronary bypass surgery. These patients are less likely to achieve LDL targets and are more likely to suffer adverse cardiovascular events in the years following surgery. Detection of these patients may improve LDL management and clinical outcomes as well as the yield of new cases through cascade testing of close relatives.Table 1:Baseline CharacteristicsTable 2:Outcomes