Shortened telomere length is associated with paroxysmal atrial fibrillation among cardiovascular patients enrolled in the Intermountain Heart Collaborative Study.

BACKGROUND: Atrial fibrillation (AF) diminishes quality of life and accounts for approximately one-third of all strokes. Studies have associated mitochondrial dysfunction with both AF and telomere length (TL). OBJECTIVE: The purpose of this study was to test the hypothesis of a relationship between AF and TL. METHODS: Blood was collected from consenting participants in the Intermountain Heart Collaborative Study (n = 3576) and DNA extracted. TL was determined by multiplex quantitative polymerase chain reaction, normalized to a single copy gene, and reported as telomere/single gene ratio (t/s). Patient information was extracted from Intermountain Healthcare's electronic records database. Prevalent AF was determined by discharge ICD-9 code. AF subtype (paroxysmal [Px], persistent [Ps], long-standing persistent/permanent [Pm]) was determined by chart review. RESULTS: The t/s decreased with age (P <.00001). Subjects with a history of AF (n = 379 [10.6%] had shorter telomeres (mean t/s ± SD = 0.87 ± 0.29) compared to subjects without AF (mean t/s 0.95 ± 0.32, P <.0001). The association remained after adjustment for age (P = .017) and cardiovascular risk factors (P = .016). AF subtype was determined for 277 subjects; 110 (39.7%) had Px AF, 65 (23.5%) Ps, and 102 (36.8%) Pm AF. Mean t/s did not differ between Ps, Pm, and subjects without AF (0.94 ± 0.40, 0.94 ± 0.27, and 0.95 ± 0.32, respectively). However, the mean t/s for Px (0.81 ± 0.22) was significantly shorter than for Ps (P = .026), Pm (P = .004), or subjects without AF (P <.0001). CONCLUSION: The present study supports an association between Px AF and TL. Short TL may be a previously unrecognized risk factor for AF with potential applications in diagnosis and therapy.

A Possible Mechanistic Link Between the CYP2C19 Genotype, the Methadone Metabolite Ethylidene-1,5-Dimethyl-3,3-Diphenylpyrrolidene (EDDP), and Methadone-Induced Corrected QT Interval Prolongation in a Pilot Study.

BACKGROUND: Methadone use and methadone-associated sudden cardiac death have increased dramatically. Prolongation of the QT interval of the cardiac cycle predisposes to arrhythmia and is common among methadone users. OBJECTIVE: We studied the relationship between pharmacogenetic variables and methadone metabolites and QT prolongation. METHODS: Blood was obtained on days 1, 7, and 21 from consenting individuals initiating methadone treatment. Plasma methadone and ethylidene-1,5-dimethyl-3,3-diphenylpyrrolidene (EDDP) were measured using liquid chromatographic-electrospray ionization-tandem mass spectrometry. The corrected QT interval (QTc) from 12-lead electrocardiograms (ECGs) was obtained at baseline and at 21 days. RESULTS: Total plasma EDDP, (S)-EDDP, and (R)-EDDP concentrations were significantly higher for individuals carrying the CYP2C19*2 variant (n=8) than in 17 subjects carrying the CYP2C19 wild-type allele (p<0.004). Seventeen (68%) of 25 subjects experienced a QTc (Bazett) of 39.9±28.4 ms (mean±standard deviation). The methadone dose and the plasma EDDP concentration corrected for dose were both significantly associated with QTc at study termination and with change in QTc interval from baseline (∆QTc) (p<0.03 to p<0.0003). Based on a QTc increase, five subjects had a potentially increased arrhythmia risk. Compared with other participants, the mean dose for those individuals was higher (50.8 vs. 42.5 mg/day; p<0.04) as was the total plasma EDDP (36.8 vs. 21.0 ng/mL; p<0.002) and dose-corrected EDDP (0.27 vs. 0.16 ng/mL/mg; p<0.003). CONCLUSIONS: These results suggest that a notable change in the QTc interval was associated with both oral dose and increased methadone metabolism, as indicated by the higher plasma concentration of the principal methadone metabolite. The oral dose and plasma EDDP concentration may be useful in identifying individuals at risk for methadone-related arrhythmia.

Validation and quantification of genetic determinants of lipoprotein-a levels and predictive value for angiographic coronary artery disease.

Lipoprotein(a) (Lp[a]) has gained attention as a heritable coronary artery disease (CAD) risk factor and therapeutic target. Two genetic variants in the LPA gene have been reported to influence Lp(a) levels and increase CAD risk. The aim of this study was to prospectively test these variants for their associations with Lp(a) and CAD risk. Participants (n = 1,400) in the Intermountain Heart Collaborative Study Registry who had Lp(a) cholesterol levels determined at coronary angiography were genotyped for rs3798220 and rs1045587 in LPA. Variants were detected by Taqman polymerase chain reaction. Chi-square and linear and logistic regression tests were used as appropriate among genotypes for Lp(a) and angiographic CAD. Age averaged 63 years; 65% were men; and severe CAD was present in 57%, mild CAD in 12%, and no CAD in 31%. Minor allele frequencies were 0.023 for rs3798220 and 0.090 for rs10455872. In multivariate modeling, only rs10455872 (odds ratio [OR] 2.33, 95% confidence interval [CI] 1.67 to 3.33, p = 1.75 × 10⁻9) and rs3798220 (OR 1.99, 95% CI 0.99 to 4.00, p = 0.065) contributed to the prediction of elevated Lp(a) cholesterol. Lp(a) cholesterol was weakly associated with CAD (OR 1.17, 95% CI 1.00 to 1.37, p = 0.055). Rs10455872 strongly predicted prevalent CAD (per allele OR 1.43, 95% CI 1.07 to 1.91, p = 0.0172); the effect size for the rare rs3798220 variant was similar (dominant OR 1.47, 95% CI 0.81 to 2.67, p = 0.20), but power was limited to demonstrate significance. The combined genotype explained only a small percentage (≤4%) of variability in Lp(a) cholesterol and prevalence of angiographic CAD. In conclusion, heritable contributions of LPA rs10455872 and rs3798220 to Lp(a) cholesterol levels and to angiographic CAD were prospectively assessed in this study. The percentage of intersubject variability in Lp(a) cholesterol and the percentage of prevalent CAD explained were small.

Cardiovascular risk among patients on clopidogrel anti-platelet therapy after placement of drug-eluting stents is modified by genetic variants in both the CYP2C19 and ABCB1 genes.

Long-term (at least one year) dual anti-platelet therapy incorporating aspirin and clopidogrel is currently recommended following percutaneous coronary intervention with placement of a drug-eluting stent (DES). Genetic variants in both the ABCB1 and CYP2C19 genes have been associated with cardiovascular events among patients on clopidogrel. We examined the concurrent contribution of the CYP2C19 *2 and *17 alleles and the ABCB1 3435 alleles to one-year clinical risk among patients (n=1,034 on clopidogrel therapy following the placement of a DES. For CYP2C19*2, event rates were 8.4%, 10.9% and 44.4% for patients with 0, 1 and 2 *2 alleles, respectively (p=0.016). ABCB1 3435 was not associated with events in univariate analysis. However, 72% of patients with a *2 variant also possessed the ABCB1 3435 C allele; among these patients (*2/C genotype) the event rate for myocardial infarction (MI) was 14.2% vs. 6.9% for those lacking both *2 and C alleles (p=0.027) and for MI/death, 16.9% vs. 9.6% (p=0.046). Overall for all genotypes, the presence of the gain-of-function (protective) *17 allele significantly reduced the one-year rate of MI from 11.1% to 7.0% (p=0.045) and trended to reduce the combined rate of MI/death from 13.8% to 10.5% (p=0.182). In conclusion, the ABCB1 3435 locus and the *2 allele combine to impart a significant trend toward increased risk. This trend was largely reversed by the simultaneous carriage of one or two *17 alleles. These findings suggest that assessment of a combined genotype may improve risk assessment.

A randomized and clinical effectiveness trial comparing two pharmacogenetic algorithms and standard care for individualizing warfarin dosing (CoumaGen-II).

BACKGROUND: Warfarin is characterized by marked variations in individual dose requirements and a narrow therapeutic window. Pharmacogenetics (PG) could improve dosing efficiency and safety, but clinical trials evidence is meager. METHODS AND RESULTS: A Randomized and Clinical Effectiveness Trial Comparing Two Pharmacogenetic Algorithms and Standard Care for Individualizing Warfarin Dosing (CoumaGen-II) comprised 2 comparisons: (1) a blinded, randomized comparison of a modified 1-step (PG-1) with a 3-step algorithm (PG-2) (N=504), and (2) a clinical effectiveness comparison of PG guidance with use of either algorithm with standard dosing in a parallel control group (N=1866). A rapid method provided same-day CYP2C9 and VKORC1 genotyping. Primary outcomes were percentage of out-of-range international normalized ratios at 1 and 3 months and percentage of time in therapeutic range. Primary analysis was modified intention to treat. In the randomized comparison, PG-2 was noninferior but not superior to PG-1 for percentage of out-of-range international normalized ratios at 1 month and 3 months and for percentage of time in therapeutic range at 3 months. However, the combined PG cohort was superior to the parallel controls (percentage of out-of-range international normalized ratios 31% versus 42% at 1 month; 30% versus 42% at 3 months; percentage of time in therapeutic range 69% versus 58%, 71% versus 59%, respectively, all P<0.001). Differences persisted after adjustment for age, sex, and clinical indication. There were fewer percentage international normalized ratios ≥4 and ≤1.5 and serious adverse events at 3 months (4.5% versus 9.4% of patients, P<0.001) with PG guidance. CONCLUSIONS: These findings suggest that PG dosing should be considered for broader clinical application, a proposal that is being tested further in 3 major randomized trials. The simpler 1-step PG algorithm provided equivalent results and may be preferable for clinical application. CLINICAL TRIAL REGISTRATION: URL: http://www.clinicaltrials.gov. Unique identifier: NCT00927862.

Common Variants in 6 Lipid-Related Genes Discovered by High-Resolution DNA Melting Analysis and Their Association with Plasma Lipids.

BACKGROUND: Total cholesterol was among the earliest identified risk factors for coronary heart disease (CHD). We sought to identify genetic variants in six genes associated with lipid metabolism and estimate their respective contribution to risk for CHD. METHODS: For 6 lipid-associated genes (LCAT, CETP, LIPC, LPL, SCARB1, and ApoF) we scanned exons, 5' and 3' untranslated regions, and donor and acceptor splice sites for variants using Hi-Res Melting® curve analysis (HRMCA) with confirmation by cycle sequencing. Healthy subjects were used for SNP discovery (n=64), haplotype determination/tagging SNP discovery (n=339), and lipid association testing (n=786). RESULTS: In 17,840 bases of interrogated sequence, 90 variant SNPs were identified; 19 (21.1%) previously unreported. Thirty-four variants (37.8%) were exonic(16 non-synonymous), 28 (31.1%) in intron-exon boundaries, and 28 (31.1%) in the 5' and 3' untranslated regions. Compared to cycle sequencing, HRMCA had sensitivity of 99.4% and specificity of 97.7%. Tagging SNPs (n=38) explained >90% of the variation in the 6 genes and identified linkage disequilibrium (LD) groups. Significant beneficial lipid profiles were observed for CETP LD group 2, LIPC LD groups 1 and 7, and SCARB1 LD groups 1, 3 and 4. Risk profiles worsened for CETP LD group 3, LPL LD group 4. CONCLUSIONS: These findings demonstrate the feasibility, sensitivity, and specificity of HRMCA for SNP discovery. Variants identified in these genes may be used to predict lipid-associated risk and reclassification of clinical CHD risk.