Clare Neuwirth

Familial Hypercholesterolaemia Regression Study: a randomised trial of low-density-lipoprotein apheresis

Low-density-lipoprotein (LDL) apheresis has the theoretical advantage over anion-exchange resins and hydroxymethylglutaryl coenzyme A inhibitors of decreasing lipoprotein(a) as well as LDL. To confirm this advantage, patients with heterozygous familial hypercholesterolaemia and coronary artery disease were randomised to receive LDL apheresis fortnightly (with disposable dextran sulphate/cellulose columns) plus simvastatin 40 mg daily, or colestipol 20 g plus simvastatin 40 mg daily. Quantitative coronary angiography was repeated after a mean of 2.1 years in 20 patients undergoing apheresis and in 19 on combination drug therapy. Changes in serum lipoproteins were similar in both groups apart from greater lowering by apheresis of LDL cholesterol (3.2 vs 3.4 mmol/L in drug group, p = 0.03) and lipoprotein(a) (geometric means 14 vs 21 mg/dL, p = 0.03). There were no significant differences in primary angiographic endpoints per patient but lesion-based and segment-based secondary endpoints were biased in favour of the drug group (change in minimum lumen diameter of lesions 0.07 vs -0.004 mm, p = 0.046; change in mean lumen diameter of segments 0.02 vs -0.06 mm, p = 0.01). None of the angiographic changes correlated with lipoprotein(a) concentrations. Per patient changes in % diameter stenosis and minimum lumen diameter in the two groups were as or more favourable than those observed in five published trials that assessed lipid-lowering drug therapy by quantitative coronary angiography. Although LDL apheresis combined with simvastatin was more effective than colestipol plus simvastatin in reducing LDL cholesterol and lipoprotein(a), it was less beneficial in influencing coronary atherosclerosis and should be reserved for patients unresponsive to drugs. Decreasing lipoprotein(a) seems to be unnecessary if LDL cholesterol is reduced to 3.4 mmol/L or less.

Severe Hypercholesterolemia in Four British Families With the D374Y Mutation in the PCSK9 Gene Long-Term Follow-Up and Treatment Response

Objective—Analysis of long-term (30 years) clinical history and response to treatment of 13 patients with the D374Y mutation of PCSK9 (PCSK9 patients) from 4 unrelated white British families compared with 36 white British patients with heterozygous familial hypercholesterolemia attributable to 3 specific mutations in the low-density lipoprotein (LDL) receptor gene (LDLR) known to cause severe phenotype. Methods and Results—The PCSK9 patients, when compared with the LDLR patients, were younger at presentation (20.8±14.7 versus 30.2±15.7 years; P=0.003), had higher pretreatment serum cholesterol levels (13.6±2.9 versus 9.6±1.6 mmol/L; P=0.004) that remained higher during treatment with simvastatin (10.1±3.0 versus 6.5±0.9 mmol/L; P=0.006), atorvastatin (9.6±2.9 versus 6.4±1.0 mmol/L; P=0.006), or current lipid-lowering therapy, including LDL apheresis and partial ileal bypass in 2 PCSK9 patients (7.0±1.6 versus 5.4±1.0 mmol/L; P=0.001), and were affected >10 years earlier by premature coronary artery disease (35.2±4.8 versus 46.8±8.9 years; P=0.002). LDL from PCSK9 patients competed significantly less well for binding to fibroblast LDL receptors than LDL from either controls or LDLR patients. Conclusions—These British PCSK9 patients with the D374Y mutation have an unpredictably severe clinical phenotype, which may be a unique feature for this cohort, and requires early and aggressive lipid-lowering management to prevent cardiovascular complications.

Efficacy criteria and cholesterol targets for LDL apheresis.

Low density lipoprotein (LDL) apheresis is now accepted as the treatment of choice for patients with homozygous familial hypercholesterolaemia and for heterozygotes with cardiovascular disease refractory to lipid-lowering drug therapy. However, a paucity of evidence has meant that detailed guidance on the extent of cholesterol reduction required to prevent the onset or progression of cardiovascular disease in these high risk patients is lacking. This review defines criteria for expressing the efficacy of apheresis, proposes target levels of total and LDL cholesterol for homozygotes and heterozygotes based on recent follow-up studies and suggests a scheme for monitoring cardiovascular disease in these patients. Establishing a uniform approach to data collection would facilitate the setting up of national or multi-national registers and might eventually provide the information needed to formulate evidence-based guidelines for LDL apheresis.

Reperfusion Hemorrhage Following Acute Myocardial Infarction: Assessment with T2* Mapping and Effect on Measuring the Area at Risk

Research ethics committee approval and informed consent were obtained. The purpose of this study was to assess the feasibility of multiecho T2* mapping of the heart for detecting reperfusion hemorrhage following percutaneous primary coronary intervention (PPCI) for acute myocardial infarction, and to measure the effect of hemorrhage on quantifying the ischemic area at risk (IAR) on T2-weighted magnetic resonance images. Fifteen patients (mean age, 59 years; 13 men, two women) were imaged a mean of 3.2 days following PPCI. The mean area of hemorrhage, indicated by a T2* decay constant of less than 20 msec, was 5.0% +/- 4.9 (standard deviation) at the level of the infarct and this correlated with the infarct (r(2) = 0.76, P < .01) and microvascular obstruction (r(2) = 0.75, P < .01) volumes. When 5% or less hemorrhage was present, the IAR was underestimated by 50% at a standard deviation threshold level of five, compared with a boundary detection tool (21.8% vs 44.0%, P < .05). T2* mapping is feasible for quantifying post-reperfusion hemorrhage and boundary detection is required to accurately assess the IAR when hemorrhage is present.

Assessment of severe reperfusion injury with T2* cardiac MRI in patients with acute myocardial infarction

Background In patients with acute myocardial infarction, restoration of coronary flow by primary coronary intervention (PCI) can lead to profound ischaemia-reperfusion injury with detrimental effects on myocardial salvage. Non-invasive assessment of interstitial myocardial haemorrhage by T2* cardiac MRI (T2*-CMR) provides a novel and specific biomarker of severe reperfusion injury which may be of prognostic value. Objective To characterise the determinants of acute ischaemia-reperfusion injury following ST elevation myocardial infarction (STEMI) using CMR. Methods and results Fifty patients with acute STEMI who had been successfully treated by PCI were studied. T2*-CMR was used to identify the presence of reperfusion haemorrhage and contrast enhancement was used to measure microvascular obstruction (MVO) and infarct size. Haemorrhagic ischaemia-reperfusion injury was present in 29 patients (58%) following PCI and occurred despite rapid revascularisation (mean 4.2±3.3 h). Haemorrhage was only present when the infarct involved at least 80% (mean±SD 91±5.3%) of the left ventricular wall thickness. There was a strong association between the extent of MVO and reperfusion haemorrhage (r2=0.87, p<0.001). Transmural infarcts (n=43) showed significantly impaired systolic wall thickening at the infarct mid point when reperfusion haemorrhage was present (21.5±16.7% vs 3.7±12.9%), p<0.0001) compared with non-haemorrhagic infarcts. Conclusions Severe reperfusion injury may occur when there is near-transmural myocardial necrosis despite early and successful revascularisation. Reperfusion haemorrhage is closely associated with the development of MVO. These findings indicate that, once advanced necrosis has developed, the potential for severe myocardial reperfusion injury is significantly enhanced.

Restoration of LDL receptor function in cells from patients with autosomal recessive hypercholesterolemia by retroviral expression of ARH1

Familial hypercholesterolemia is an autosomal dominant disorder with a gene-dosage effect that is usually caused by mutations in the LDL receptor gene that disrupt normal clearance of LDL. In the homozygous form, it results in a distinctive clinical phenotype, characterized by inherited hypercholesterolemia, cholesterol deposition in tendons, and severe premature coronary disease. We described previously two families with autosomal recessive hypercholesterolemia that is not due to mutations in the LDL receptor gene but is characterized by defective LDL receptor-dependent internalization and degradation of LDL by transformed lymphocytes from the patients. We mapped the defective gene to chromosome 1p36 and now show that the disorder in these and a third English family is due to novel mutations in ARH1, a newly identified gene encoding an adaptor-like protein. Cultured skin fibroblasts from affected individuals exhibit normal LDL receptor activity, but their monocyte-derived macrophages are similar to transformed lymphocytes, being unable to internalize and degrade LDL. Retroviral expression of normal human ARH1 restores LDL receptor internalization in transformed lymphocytes from an affected individual, as demonstrated by uptake and degradation of (125)I-labeled LDL and confocal microscopy of cells labeled with anti-LDL-receptor Ab.

Confirmed Locus on Chromosome 11p and Candidate Loci on 6q and 8p for the Triglyceride and Cholesterol Traits of Combined Hyperlipidemia

Background—Combined hyperlipidemia is a common disorder characterized by a highly atherogenic lipoprotein profile and increased risk of coronary heart disease. The etiology of the lipid abnormalities (increased serum cholesterol and triglyceride or either lipid alone) is unknown. Methods and Results—We assembled 2 large cohorts of families with familial combined hyperlipidemia (FCHL) and performed disease and quantitative trait linkage analyses to evaluate the inheritance of the lipid abnormalities. Chromosomal regions 6q16.1-q16.3, 8p23.3-p22, and 11p14.1-q12.1 produced evidence for linkage to FCHL. Chromosomes 6 and 8 are newly identified candidate loci that may respectively contribute to the triglyceride (logarithm of odds [LOD], 1.43; P =0.005) and cholesterol (LOD, 2.2; P =0.0007) components of this condition. The data for chromosome 11 readily fulfil the guidelines required for a confirmed linkage. The causative alleles may contribute to the inheritance of the cholesterol (LOD, 2.04 at 35.2 cM; P =0.0011) component of FCHL as well as the triglyceride trait (LOD, 2.7 at 48.7 cM; P =0.0002). Conclusions—Genetic analyses identify 2 potentially new loci for FCHL and provide important positional information for cloning the genes within the chromosome 11p14.1-q12.1 interval that contributes to the lipid abnormalities of this highly atherogenic disorder.

Determinants of Variable Response to Statin Treatment in Patients With Refractory Familial Hypercholesterolemia

Abstract—Interindividual variability in low density lipoprotein (LDL) cholesterol (LDL-C) response during treatment with statins is well documented but poorly understood. To investigate potential metabolic and genetic determinants of statin responsiveness, 19 patients with refractory heterozygous familial hypercholesterolemia were sequentially treated with placebo, atorvastatin (10 mg/d), bile acid sequestrant, and the 2 combined, each for 4 weeks. Levels of LDL-C, mevalonic acid (MVA), 7-&agr;-OH-4-cholesten-3-one, and leukocyte LDL receptor and hydroxymethylglutaryl coenzyme A reductase mRNA were determined after each treatment period. Atorvastatin (10 mg/d) reduced LDL-C by an overall mean of 32.5%. Above-average responders (&Dgr;LDL-C −39.5%) had higher basal MVA levels (34.4±6.1 &mgr;mol/L) than did below-average responders (&Dgr;LDL-C −23.6%, P <0.02; basal MVA 26.3±6.1 &mgr;mol/L, P <0.01). Fewer good responders compared with the poor responders had an apolipoprotein E4 allele (3 of 11 versus 6 of 8, respectively;P <0.05). There were no baseline differences between them in 7-&agr;-OH-4-cholesten-3-one, hydroxymethylglutaryl coenzyme A reductase mRNA, or LDL receptor mRNA, but the latter increased in the good responders on combination therapy (P <0.05). Severe mutations were not more common in poor than in good responders. We conclude that poor responders to statins have a low basal rate of cholesterol synthesis that may be secondary to a genetically determined increase in cholesterol absorption, possibly mediated by apolipoprotein E4. If so, statin responsiveness could be enhanced by reducing dietary cholesterol intake or inhibiting absorption.

The use of next-generation sequencing in clinical diagnosis of familial hypercholesterolemia

Purpose:Familial hypercholesterolemia is a common Mendelian disorder associated with early-onset coronary heart disease that can be treated by cholesterol-lowering drugs. The majority of cases in the United Kingdom are currently without a molecular diagnosis, which is partly due to the cost and time associated with standard screening techniques. The main purpose of this study was to test the sensitivity and specificity of two next-generation sequencing protocols for genetic diagnosis of familial hypercholesterolemia.Methods:Libraries were prepared for next-generation sequencing by two target enrichment protocols; one using the SureSelect Target Enrichment System and the other using the PCR-based Access Array platform.Results:In the validation cohort, both protocols showed 100% specificity, whereas the sensitivity for short variant detection was 100% for the SureSelect Target Enrichment and 98% for the Access Array protocol. Large deletions/duplications were only detected using the SureSelect Target Enrichment protocol. In the prospective cohort, the mutation detection rate using the Access Array was highest in patients with clinically definite familial hypercholesterolemia (67%), followed by patients with possible familial hypercholesterolemia (26%).Conclusion:We have shown the potential of target enrichment methods combined with next-generation sequencing for molecular diagnosis of familial hypercholesterolemia. Adopting these assays for patients with suspected familial hypercholesterolemia could improve cost-effectiveness and increase the overall number of patients with a molecular diagnosis.Genet Med 15 12, 948–957.Genetics in Medicine (2013); 15 12, 948–957. doi:10.1038/gim.2013.55

The Extracranial Carotid Artery in Familial Hypercholesterolemia: Relationship of Intimal-Medial Thickness and Plaque Morphology with Plasma Lipids and Coronary Heart Disease

Background Increased frequency of coronary heart disease in familial hypercholesterolaemia is well documented but the association with carotid atherosclerosis is less well established. The ultrasound appearances of the carotid arteries in familial hypercholesterolaemia patients without symptomatic cerebrovascular disease were therefore investigated. Methods 59 patients (34 men, 25 women; mean age 46.6 (± 12.1 years) were prospectively studied using ultrasound examination of the extracranial carotid vessels. Intimal-medial thickness was measured 1 cm proximal to the carotid bulb and morphology of plaque was classified as heterogeneous or homogeneous according to echogenicity. Results 44 (75.0%) of the patients had carotid artery disease. On stepwise logistic regression, significant predictors of the presence of carotid artery disease were age (P = 0.014), serum triglycerides at time of examination (P = 0.013), coexistent coronary heart disease (P = 0.03) and the cholesterol-years score (CYS) (P = 0.015). Heterogeneous carotid plaque was associated with a higher plasma level of Lp(a) (P = 0.035), TG (P = 0.024), CYS (P = 0.0003) and the presence of CHD (P = 0.001). Matched pairs (n = 22) of patients, where the only variable was Lp(a), showed a marked increase in heterogeneous plaque frequency in those with high Lp(a) levels (P <0.03). Conclusion Asymptomatic carotid artery disease occurs in a high proportion of familial hypercholesterolaemia patients. The presence of heterogeneous carotid plaque is significantly associated with the presence of coronary heart disease, the calculated cholesterol-years score, hypertriglyceridaemia and raised levels of Lp(a).