Large-Scale Screening for Monogenic and Clinically Defined Familial Hypercholesterolemia in Iceland

Objective: Familial hypercholesterolemia (FH) is traditionally defined as a monogenic disease characterized by severely elevated LDL-C (low-density lipoprotein cholesterol) levels. In practice, FH is commonly a clinical diagnosis without confirmation of a causative mutation. In this study, we sought to characterize and compare monogenic and clinically defined FH in a large sample of Icelanders. Approach and Results: We whole-genome sequenced 49 962 Icelanders and imputed the identified variants into an overall sample of 166 281 chip-genotyped Icelanders. We identified 20 FH mutations in LDLR, APOB, and PCSK9 with combined prevalence of 1 in 836. Monogenic FH was associated with severely elevated LDL-C levels and increased risk of premature coronary disease, aortic valve stenosis, and high burden of coronary atherosclerosis. We used a modified version of the Dutch Lipid Clinic Network criteria to screen for the clinical FH phenotype among living adult participants (N=79 058). Clinical FH was found in 2.2% of participants, of whom only 5.2% had monogenic FH. Mutation-negative clinical FH has a strong polygenic basis. Both individuals with monogenic FH and individuals with mutation-negative clinical FH were markedly undertreated with cholesterol-lowering medications and only a minority attained an LDL-C target of <2.6 mmol/L (<100 mg/dL; 11.0% and 24.9%, respectively) or <1.8 mmol/L (<70 mg/dL; 0.0% and 5.2%, respectively), as recommended for primary prevention by European Society of Cardiology/European Atherosclerosis Society cholesterol guidelines. Conclusions: Clinically defined FH is a relatively common phenotype that is explained by monogenic FH in only a minority of cases. Both monogenic and clinical FH confer high cardiovascular risk but are markedly undertreated.

[Use of warfarin anticoagulation in patients with atrial fibrillation in Iceland.]

OBJECTIVE

Despite convincing evidence that warfarin anticoagulation reduces the risk of thromboembolism in patients with atrial fibrillation, recent data suggests that this therapy may be underutilized. Some patients are at higher risk than others and known risk factors for thromboembolism in nonvalvular atrial fibrillation include hypertension, diabetes, a prior history of a cerebrovascular accident or a transient ischemic attack and age over 65 years. Additionally, decreased left ventricular function and an enlarged left atrium increase the risk of emboli.

OBJECTIVE

To study the use of anticoagulation in patients with nonvalvular atrial fibrillation in Iceland we looked at the pattern of warfarin use in two different settings, the emergency room at a University Hospital in Reykjavik and those followed at the Solvangur Health Center, a primary health clinic, in Hafnarfjordur.

METHODS

Prospective data collection at the University Hospital and retrospective chart review at Solvangur Health Center.

RESULTS

A total of 68 patients (39 men, average age 73 years) with known preexisting atrial fibrillation were seen at the University Hospital during the 4 month study period. Thirty six (53%) were taking warfarin. Of the 32 not taking warfarin, 8 (25%) had a contraindication to anticoagulation. A large majority (96%) of the cohort had at least one risk factor for thromboembolism in atrial fibrillation. Fourteen (54%) of those not taking warfarin were on aspirin. At Solvangur Health Center, 40 of 71 patients (56%) (46 men, average age 72 years) with atrial fibrillation were taking warfarin while 4 of the 31 (13%) not on warfarin had a contraindication to the use of the medication. However, 14 (45%) of those not on warfarin were taking aspirin. In all 94% of the patients at Solvangur Health Center had at least one risk factor for thromboembolism.

CONCLUSIONS

The use of warfarin in patients with atrial fibrillation in Iceland was found to be less than optimal. We speculate that reluctance to use anticoagulants in the elderly and perhaps lack of awareness of the data showing benefit of anticoagulation may contribute to this. Given the relatively easy access of physicians to anticoagulation clinics, the added burden of following an anticoagulated patient is unlikely to be a factor.