Ethnic differences in atrial fibrillation identified using implanted cardiac devices

Risk of stroke and intracranial hemorrhage in 9727 Chinese with atrial fibrillation in Hong Kong

BACKGROUND

Current risk schemes to predict ischemic stroke and intracranial hemorrhage (ICH) in atrial fibrillation (AF) are derived primarily using a Caucasian population.

OBJECTIVE

The purpose of this study was to describe the risk of ischemic stroke and ICH in a large contemporary "real world" cohort of Chinese AF patients in Hong Kong with detailed long-term follow-up.

METHODS

This observational study used a hospital-based cohort of Chinese patients with nonvalvular AF.

RESULTS

Among 9727 patients with nonvalvular AF (age 76.9 ± 12.5 years, 52.1% female), 3881 patients (39.9%) did not receive antithrombotic therapy, 3934 patients (40.4%) were taking aspirin, and 1912 (19.7%) were taking warfarin. After mean follow-up of 3.19 years, 847 patients (21.8%) without antithrombotic therapy developed ischemic strokes (annual risk 9.28%, 95% confidence interval [CI] 8.89%-9.70%). There was a progressively increase in annual risk of ischemic stroke with increasing CHADS2 and CHA2DS2VASc scores. The c-statistics revealed that CHA2DS2-VASc scores (0.525, 95% CI 0.509-0.541, P = .017) was better than CHADS2 scores (0.506, 95% CI 0.490-0.522, P = .584) in predicting ischemic stroke. Use of aspirin and of warfarin were associated with reduced annual risk of ischemic stroke by 18.7% and 52.7%, respectively (P <.05). The annual incidence of ICH in patients taking aspirin and warfarin was 0.77% per year and 0.80% per year, respectively. The adjusted net clinical benefit favored warfarin over aspirin or no therapy for almost all Chinese AF patients CHA2DS2-VASc score ≥1.

CONCLUSION

Chinese AF patients are at high risk for ischemic stroke. Analysis of the net clinical benefit favors the use of warfarin over aspirin or no therapy for stroke prevention in a broad range of Chinese AF patients.

Novel genetic markers associate with atrial fibrillation risk in Europeans and Japanese

OBJECTIVES

This study sought to identify nonredundant atrial fibrillation (AF) genetic susceptibility signals and examine their cumulative relations with AF risk.

BACKGROUND

AF-associated loci span broad genomic regions that may contain multiple susceptibility signals. Whether multiple signals exist at AF loci has not been systematically explored.

METHODS

We performed association testing conditioned on the most significant, independently associated genetic markers at 9 established AF loci using 2 complementary techniques in 64,683 individuals of European ancestry (3,869 incident and 3,302 prevalent AF cases). Genetic risk scores were created and tested for association with AF in Europeans and an independent sample of 11,309 individuals of Japanese ancestry (7,916 prevalent AF cases).

RESULTS

We observed at least 4 distinct AF susceptibility signals on chromosome 4q25 upstream of PITX2, but not at the remaining 8 AF loci. A multilocus score comprised 12 genetic markers demonstrated an estimated 5-fold gradient in AF risk. We observed a similar spectrum of risk associated with these markers in Japanese. Regions containing AF signals on chromosome 4q25 displayed a greater degree of evolutionary conservation than the remainder of the locus, suggesting that they may tag regulatory elements.

CONCLUSIONS

The chromosome 4q25 AF locus is architecturally complex and harbors at least 4 AF susceptibility signals in individuals of European ancestry. Similar polygenic AF susceptibility exists between Europeans and Japanese. Future work is necessary to identify causal variants, determine mechanisms by which associated loci predispose to AF, and explore whether AF susceptibility signals classify individuals at risk for AF and related morbidity.

Incident atrial fibrillation among Asians, Hispanics, blacks, and whites

BACKGROUND

Because the association between atrial fibrillation (AF) and race has only been rigorously compared in population-based studies that dichotomized participants as white or black, it is unclear whether white race confers elevated AF risk or black race affords AF protection.

METHODS AND RESULTS

The Healthcare Cost and Utilization Project was used to identify patients receiving hospital-based care in California between January 1, 2005 and December 31, 2009. The association between race and incident AF was examined using Cox proportional hazards models. Interaction analyses were performed to elucidate the mechanism underlying the race-AF association. Among 13 967 949 patients, 375 318 incident AF episodes were observed over a median 3.2 (interquartile range 1.8-4.3) years. In multivariable Cox models adjusting for patient demographics and established AF risk factors, blacks (hazard ratio, 0.84; 95% confidence interval, 0.82-0.85; P<0.001), Hispanics (hazard ratio, 0.78; 95% confidence interval, 0.77-0.79; P<0.001), and Asians (hazard ratio, 0.78; 95% confidence interval, 0.77-0.79; P<0.001) each exhibited a lower AF risk compared with whites. AF risk among whites was disproportionately higher in the absence of acquired cardiovascular risk factors and diminished or reversed in the presence of comorbid diseases. Although Hispanics and Asians also had a lower adjusted risk of incident atrial flutter compared with whites, the risk of flutter was significantly higher among blacks.

CONCLUSIONS

In a large hospital-based cohort, whites have an increased risk of AF whether compared with blacks, Asians, or Hispanics. The heightened AF risk among whites is most pronounced in the absence of cardiovascular comorbidities.

Atrial Fibrillation and Race - A Contemporary Review

Atrial fibrillation (AF) is the most commonly encountered clinical arrhythmia and is associated with adverse outcomes and increased healthcare costs. Racial variations in AF are recognized yet poorly understood. In this review we summarize racial differences in AF epidemiology, risk factors, genetics, and outcomes. We identify novel risk factors, inflammatory mediators and biomarkers associated with AF, which have had limited study in racial and ethnic minorities. We describe the mismatch between risk factor burden and AF. We highlight the limited participation of minorities in trials for AF management and stroke prevention that contrasts with observed racial variability in anticoagulation efficacy and practice. Throughout we provide specific strategies for future directions to address gaps in the epidemiology of racial differences and to meet identified racial disparities. We specifically identify areas for further research. We conclude that addressing disparities in prevention and healthcare resource allocation will likely improve AF-related outcomes in minorities.