Clinical and radiological testing for subclinical atherosclerosis in first-degree relatives of patients with premature coronary artery disease: feasibility and diagnostic yield

Background

Premature atherosclerotic cardiovascular disease (ASCVD) is highly heritable. The screening of first-degree relatives (FDR) of patients with premature ASCVD is recommended but not routinely performed, and the diagnostic yield of different approaches to such screening is unknown.

Purpose

To determine the feasibility and diagnostic yield of clinical and radiological screening of FDRs of patients with premature coronary artery disease (CAD) in clinical setting.

Method

We recruited FDRs of patients with angiographically-proven CAD with stenosis of ≥50% who presented at the age of ≤50 years for males and ≤55 years for females. After clinical and laboratory assessment, patients with no personal history of cardiovascular disease underwent either coronary computed tomography angiography (CCTA), coronary calcium scoring assessment (CAC), or carotid ultrasound (CUS). Subclinical atherosclerosis was defined as 1) CAC score >100 Agatston units or >75% percentile for age and sex; 2) Stenosis >50% in at least one coronary artery or segment involvement scores >50th percentile in males and >75th in females; or, 3) Carotid plaque on ultrasonography.

Results

We enrolled 220 FDRs between 2017 and 2020, 129 completed clinical assessment (Figure 1). Of them, 28 (21.7%) had a personal history of ASCVD and 101 were tested for subclinical atherosclerosis. The characteristics of these patients are shown in Table 1. The most prevalent cardiovascular risk factors were dyslipidemia (40.6%), hypertension (22.8%), and obesity (21.8%). When assessed with the Framingham risk score calculator without adjustment for family history, only 5.1% and 28.6%, of patients had high or moderate cardiovascular risk, respectively. After adjusting for family history and the presence of statin-indicated conditions, 39.6% and 14.9% of patients were placed in high and moderate risk groups, respectively. Subclinical atherosclerosis was found in 43.6% of all patients (Figure 1) and 57.7% of patients over 40 years of age. The diagnostic yield of procedures was 29.6% for CUS, 37.8% for CCTA and 61.1% for CAC scoring. After the radiological assessment, 13.9% of patients were reclassified to a higher risk group (Table 1).

Conclusion

Non-invasive cardiovascular imaging detected subclinical atherosclerosis in 43.6% of healthy patients with a family history of premature ASCVD, moving 1 in 7 patients to a higher risk group and suggesting that this screening approach may improve risk prediction in this population.

Funding Acknowledgement

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Canadian Institutes of Health Research.St. Paul's Hospital Foundation and the Vancouver General Hospital Foundation. Figure 1Table 1

Development and validation of algorithms for the detection of statin myopathy signals from electronic medical records

The purpose of this study was to develop and validate sensitive algorithms to detect hospitalized statin-induced myopathy (SIM) cases from electronic medical records (EMRs). We developed four algorithms on a training set of 31,211 patient records from a large tertiary hospital. We determined the performance of these algorithms against manually curated records. The best algorithm used a combination of elevated creatine kinase (>4× the upper limit of normal (ULN)), discharge summary, diagnosis, and absence of statin in discharge medications. This algorithm achieved a positive predictive value of 52-71% and a sensitivity of 72-78% on two validation sets of >30,000 records each. Using this algorithm, the incidence of SIM was estimated at 0.18%. This algorithm captured three times more rhabdomyolysis cases than spontaneous reports (95% vs. 30% of manually curated gold standard cases). Our results show the potential power of utilizing data and text mining of EMRs to enhance pharmacovigilance activities.

Novel mutations in scavenger receptor BI associated with high HDL cholesterol in humans

The scavenger receptor class B, member 1 (SR-BI), is a key cellular receptor for high-density lipoprotein (HDL) in mice, but its relevance to human physiology has not been well established. Recently a family was reported with a mutation in the gene encoding SR-BI and high HDL cholesterol (HDL-C). Here we report two additional individuals with extremely high HDL-C (greater than the 90th percentile for age and gender) with rare mutations in the gene encoding SR-BI. These mutations segregate with high HDL-C in family members of each proband and are associated with a 37% increase in plasma HDL-C in heterozygous individuals carrying them. Both mutations occur at highly conserved positions in the large extracellular loop region of SR-BI and are predicted to impair the function of the SR-BI protein. Our findings, combined with the prior report of a single mutation in the gene encoding SR-BI, further validate that mutations in SR-BI are a rare but recurring cause of elevated HDL-C in humans.

Cholesterol efflux via ATP-binding cassette transporter A1 (ABCA1) and cholesterol uptake via the LDL receptor influences cholesterol-induced impairment of beta cell function in mice

AIMS/HYPOTHESIS

Cellular cholesterol accumulation is an emerging mechanism for beta cell dysfunction in type 2 diabetes. Absence of the cholesterol transporter ATP-binding cassette transporter A1 (ABCA1) results in increased islet cholesterol and impaired insulin secretion, indicating that impaired cholesterol efflux leads to beta cell dysfunction. In this study, we aimed to determine the role of the LDL receptor (LDLr) in islet cholesterol uptake and to assess the contributions of cholesterol uptake compared with efflux to islet cholesterol levels.

METHODS

Islet cholesterol and beta cell function were assessed in mice lacking LDLr (Ldlr(-/-)), or apolipoprotein E (Apoe(-/-)), as well as in mice with beta-cell-specific deficiency of Abca1 crossed to Ldlr(-/-) mice.

RESULTS

Hypercholesterolaemia resulted in increased islet cholesterol levels and decreased beta cell function in Apoe(-/-) mice but not in Ldlr(-/-) mice, suggesting that the LDL receptor is required for cholesterol uptake leading to cholesterol-induced beta cell dysfunction. Interestingly, when wild-type islets with functional LDL receptors were transplanted into diabetic, hypercholesterolaemic mice, islet graft function was normal compared with Ldlr(-/-) islets, suggesting that compensatory mechanisms can maintain islet cholesterol homeostasis in a hypercholesterolaemic environment. Indeed, transplanted wild-type islets had increased Abca1 expression. However, lack of the Ldlr did not protect Abca1(-/-) mice from islet cholesterol accumulation, suggesting that cholesterol efflux is the critical regulator of cholesterol levels in islets.

CONCLUSIONS/INTERPRETATION

Our data indicate that islet cholesterol levels and beta cell function are strongly influenced by LDLr-mediated uptake of cholesterol into beta cells. Cholesterol efflux mediated by ABCA1, however, can compensate in hypercholesterolaemia to regulate islet cholesterol levels in vivo.