Jonathan Rosand

Variants conferring risk of atrial fibrillation on chromosome 4q25.

Atrial fibrillation (AF) is the most common sustained cardiac arrhythmia in humans and is characterized by chaotic electrical activity of the atria. It affects one in ten individuals over the age of 80 years, causes significant morbidity and is an independent predictor of mortality. Recent studies have provided evidence of a genetic contribution to AF. Mutations in potassium-channel genes have been associated with familial AF but account for only a small fraction of all cases of AF. We have performed a genome-wide association scan, followed by replication studies in three populations of European descent and a Chinese population from Hong Kong and find a strong association between two sequence variants on chromosome 4q25 and AF. Here we show that about 35% of individuals of European descent have at least one of the variants and that the risk of AF increases by 1.72 and 1.39 per copy. The association with the stronger variant is replicated in the Chinese population, where it is carried by 75% of individuals and the risk of AF is increased by 1.42 per copy. A stronger association was observed in individuals with typical atrial flutter. Both variants are adjacent to PITX2, which is known to have a critical function in left–right asymmetry of the heart.

Clinical diagnosis of cerebral amyloid angiopathy: validation of the Boston criteria.

The authors performed clinical–pathologic correlation to assess the validity of the Boston diagnostic criteria for cerebral amyloid angiopathy (CAA). Thirteen subjects were diagnosed clinically with probable CAA from among 39 patients with available pathologic tissue in a prospective cohort of subjects aged ≥55 years with primary lobar hemorrhage. All 13 individuals were confirmed neuropathologically as having CAA. This small pathologic series indicates that the diagnosis of probable CAA can be made during life with high accuracy.

Advanced age, anticoagulation intensity, and risk for intracranial hemorrhage among patients taking warfarin for atrial fibrillation

Context The appropriate level of warfarin anticoagulation in elderly patients with atrial fibrillation has been debated because of an age-associated increase in intracerebral hemorrhage. Contribution Patients with atrial fibrillation and intracerebral hemorrhage who were receiving anticoagulation were matched with similar patients who did not develop intracerebral hemorrhage. Although intracerebral hemorrhage was associated with increasing age (especially > 85 years) and increasing international normalized ratios (INRs) (especially > 3.5), the incidence of intracerebral hemorrhage was not statistically different in patients with INRs less than 2.0 and those with INRs between 2.0 and 3.0. This was true even among those older than 75 years of age. Implications Risk for intracerebral hemorrhage is not diminished in elderly patients with atrial fibrillation when anticoagulation is maintained below an INR of 2.0. The Editors Intracranial hemorrhage is the most dangerous complication of warfarin anticoagulant therapy because of its high short-term risk for death and severe neurologic deficit (1-5). Warfarin is extremely effective in reducing the risk for ischemic stroke associated with atrial fibrillation (6, 7). However, fear of hemorrhage may prompt some physicians to avoid prescribing anticoagulation (8), especially in elderly patients, who appear to have a higher risk for hemorrhage (8-13). Prominent recent guidelines recommend using lower-intensity anticoagulation for the primary prevention of stroke in patients older than 75 years of age who have atrial fibrillation (14) and suggest a target international normalized ratio (INR) range of 1.6 to 2.5, despite evidence that the risk for ischemic stroke increases sharply at INRs less than 2.0 (15, 16). Previous studies have not thoroughly addressed the relationship of age and anticoagulation intensity to the risk for intracranial hemorrhage among patients with atrial fibrillation (1, 2). A study of 121 patients with warfarin-associated intracranial hemorrhage used the now-outdated prothrombin time ratio as a measure of anticoagulation intensity and did not specifically address risk in patients with atrial fibrillation (1). Earlier studies also included patients receiving anticoagulation for mechanical valves, whose risk-to-benefit ratio is different from that of patients with atrial fibrillation (1, 2, 17). As the number of individuals with atrial fibrillation increases (18-21) and as a greater proportion of older adults receive anticoagulant therapy (22), more precise data are needed about the association of age, INR, and risk for intracranial hemorrhage. Intracranial hemorrhage, although critically important, is an uncommon complication among patients with atrial fibrillation who are receiving anticoagulation. As a result, randomized trials and cohort studies have difficulty accumulating enough hemorrhage events to powerfully assess risk factors. To address these limitations, we performed a large casecontrol study to evaluate the relationship of increasing age and INR to the risk for intracranial hemorrhage among patients with nonvalvular atrial fibrillation. Methods Case-Patients We performed a casecontrol study comparing 2 groups: 1) case-patients with nonvalvular atrial fibrillation who developed intracranial hemorrhage while taking warfarin and 2) controls who were receiving anticoagulation for nonvalvular atrial fibrillation but did not develop intracranial hemorrhage. We found potential case-patients using the Partners HealthCare System Research Patient Data Registry, which can identify patients with specific International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) diagnoses by searching the Massachusetts General Hospital billing system. We searched for patients 18 years of age or older who had diagnoses of atrial fibrillation (ICD-9-CM code 427.31) and intracranial hemorrhage (ICD-9-CM codes 430, 431, 432.0, 432.1, 432.9) at any time from October 1993 to June 2002. By 1993, nearly all prothrombin time ratios at the hospital were reported as INRs. We reviewed medical records to confirm whether patients were eligible, that is, whether they had intracranial hemorrhage documented by computed tomography or magnetic resonance imaging and documentation of warfarin therapy for atrial fibrillation at the time of the event. We excluded patients who were not taking warfarin at the time of hemorrhage; those who were receiving anticoagulation for rheumatic heart disease, mitral stenosis, or mechanical valve placement; those whose event was an ischemic stroke with hemorrhagic conversion; or those in whom clinical factors may have led to hemorrhage independent of warfarin therapy. These factors included underlying anatomic brain abnormalities (such as tumors or aneurysms), antecedent major head trauma (skull fracture, trauma with loss of consciousness, motor vehicle injury, or neurosurgical procedures), or platelet count less than 50 109 cells/L. Starting in July 1994, consecutive patients with intracerebral hemorrhage have been enrolled through the Massachusetts General Hospital emergency department as part of a longitudinal cohort study (23). To validate our automated search strategy, we compared our case-patient list with the list of patients identified through the cohort study and found that our search strategy missed only 4 patients with intracerebral hemorrhage. We obtained data on patient date of birth, sex, and ethnicity from computerized records. The type of hemorrhage (intracerebral, subdural, subarachnoid, intraventricular, or epidural) was determined through review of radiology reports. Data on presenting symptoms, history of minor head trauma, concomitant aspirin use, and disposition status were obtained from review of the admission medical record and were recorded on a standardized data collection form. We recorded the INR measurement obtained closest to the onset of symptoms. If an INR was not available or fresh frozen plasma or vitamin K was administered before the measurement, we considered INR data missing. We reviewed medical charts for documentation of the following comorbid conditions: history of cerebrovascular disease (defined as previous ischemic stroke or carotid artery disease), hypertension, congestive heart failure, coronary artery disease, diabetes mellitus, and cancer (excluding nonmelanoma skin cancer). Controls Controls were sampled from patients managed by the Massachusetts General Hospital Anticoagulation Management Services clinic, which followed approximately 1000 patients receiving anticoagulation for atrial fibrillation at any given time during the study period. All patients who were followed in the anticoagulation clinic, received anticoagulation for atrial fibrillation, and had an INR measurement obtained in the same month and year as the given case date were assigned a random number. Six controls per case-patient were then randomly selected. We matched case-patients to controls by INR date to account for any technical changes in INR testing that may have occurred over time. Because of this sampling method, an individual patient could potentially serve as a control for more than 1 case-patient (24). Like case-patients, controls were 18 years of age or older; were receiving anticoagulation for atrial fibrillation; and had no documented rheumatic heart disease, mitral stenosis, or valve replacement. We sought data on potential confounders of the association of age, INR, and risk for intracranial hemorrhage, focusing on relevant comorbid conditions and combined use of aspirin with warfarin. We reviewed available computerized discharge summaries, outpatient clinic notes, and medication lists from up to 2 years before the admission date. If combination warfarin and aspirin use was not documented, patients were considered to not be taking aspirin. Statistical Analysis Case-patients were categorized by type of hemorrhage: intracerebral, subdural, and other (subarachnoid, intraventricular, or epidural). Clinical differences between types of hemorrhage were compared by using the KruskalWallis test for continuous variables (age and INR) and chi-square tests for categorical variables. We compared case-patients with controls by using multivariable conditional logistic regression, matching on INR date. Patient age was divided into 5-year intervals that were coded as indicator variables, and the odds of intracranial hemorrhage for each interval were compared with the odds of hemorrhage at a referent age of 70 to 74 years. The INR was divided into a set of ordered intervals that were coded as indicator variables. The relative odds for intracranial hemorrhage at each interval were calculated by using an INR of 2.0 to 3.0 as the referent category. In addition to age, INR, sex, and ethnicity, the following variables were included in the multivariable models to control for potential confounding effects of clinical factors and aspirin use: cerebrovascular disease, hypertension, congestive heart failure, coronary artery disease, diabetes mellitus, cancer, and concomitant aspirin use. If no records were available for review, comorbid conditions and aspirin use were coded as missing. We used multiple imputations for missing data on ethnicity, comorbid conditions, and aspirin use (25). We tested for interactions between age and INR and comorbid conditions using 2-way interactions. None of the interaction terms were included in the model if they were not statistically significant when tested collectively. We tested the models goodness of fit using the HosmerLemeshow method (26). Because the hospitals anticoagulation clinic did not follow some case-patients before the event, and since factors relating to differences in outpatient care and monitoring could have confounded our analyses, we repeated these analyses in the subgroup of case-patients managed by the anticoagulation clinic. These restricted analyses approximated

Warfarin, hematoma expansion, and outcome of intracerebral hemorrhage

Background: Warfarin increases mortality of intracerebral hemorrhage (ICH). The authors investigated whether this effect reflects increased baseline ICH volume at presentation or increased ICH expansion. Methods: Subjects were drawn from an ongoing prospective cohort study of ICH outcome. The effect of warfarin on baseline ICH volume was studied in 183 consecutive cases of supratentorial ICH age ≥ 18 years admitted to the emergency department over a 5-year period. Baseline ICH volume was determined using computerized volumetric analysis. The effect of warfarin on ICH expansion (increase in volume ≥ 33% of baseline) was analyzed in 70 consecutive cases in whom ICH volumes were measured on all subsequent CT scans up to 7 days after admission. Multivariable analysis was used to determine warfarin’s influence on baseline ICH, ICH expansion, and whether warfarin’s effect on ICH mortality was dependent on baseline volume or subsequent expansion. Results: There was no effect of warfarin on initial volume. Predictors of larger baseline volume were hyperglycemia (p < 0.0001) and lobar hemorrhage (p < 0.0001). Warfarin patients were at increased risk of death, even when controlling for ICH volume at presentation. Warfarin was the sole predictor of expansion (OR 6.2, 95% CI 1.7 to 22.9) and expansion in warfarin patients was detected later in the hospital course compared with non-warfarin patients (p < 0.001). ICH expansion showed a trend toward increased mortality (OR 3.5, 95% CI 0.7 to 8.9, p = 0.14) and reduced the marginal effect of warfarin on ICH mortality. Conclusions: Warfarin did not increase ICH volume at presentation but did raise the risk of in-hospital hematoma expansion. This expansion appears to mediate part of warfarin’s effect on ICH mortality.

Hemorrhage Burden Predicts Recurrent Intracerebral Hemorrhage After Lobar Hemorrhage

Background and Purpose— Small asymptomatic cerebral hemorrhages detectable by gradient-echo MRI are common in patients with intracerebral hemorrhage (ICH), particularly lobar ICH related to cerebral amyloid angiopathy (CAA). We sought to determine whether hemorrhages detected at the time of lobar ICH predict the major clinical complications of CAA: recurrent ICH or decline in cognition and function. Methods— Ninety-four consecutive survivors of primary lobar ICH (age ≥55) with gradient-echo MRI at presentation were followed in a prospective cohort study for 32.9±24.0 months. A subset of 34 subjects underwent a second MRI after a stroke-free interval of 15.8±6.5 months. Study endpoints were recurrent symptomatic ICH or clinical decline, defined as onset of cognitive impairment, loss of independent functioning, or death. Results— The total number of hemorrhages at baseline predicted risk of future symptomatic ICH (3-year cumulative risks 14%, 17%, 38%, and 51% for subjects with 1, 2, 3 to 5, or ≥6 baseline hemorrhages, P = 0.003). Higher numbers of hemorrhages at baseline also predicted increased risk for subsequent cognitive impairment, loss of independence, or death (P = 0.002) among subjects not previously demented or dependent. For subjects followed after a second MRI, new microhemorrhages appeared in 17 of 34 and predicted increased risk of subsequent symptomatic ICH (3-year cumulative risks 19%, 42%, and 67% for subjects with 0, 1 to 3, or ≥4 new microhemorrhages, P = 0.02), but not subsequent clinical decline. Conclusions— Hemorrhages identified by MRI predict clinically important events in survivors of lobar ICH. Detection of microhemorrhages may be useful for assessing risk in ICH patients and as a surrogate marker for clinical studies.

Apolipoprotein E Genotype and the Risk of Recurrent Lobar Intracerebral Hemorrhage

BACKGROUND Recurrent lobar intracerebral hemorrhage is the hallmark of cerebral amyloid angiopathy. The factors that predispose patients to early recurrence of lobar hemorrhage are unknown. One candidate is the apolipoprotein E gene, since both the epsilon2 and the epsilon4 alleles of apolipoprotein E appear to be associated with the severity of amyloid angiopathy. METHODS We performed a prospective, longitudinal study of consecutive elderly patients who survived a lobar intracerebral hemorrhage. The patients were followed for recurrent hemorrhagic stroke by interviews at six-month intervals and reviews of medical records and computed tomographic scans. RESULTS Nineteen of 71 enrolled patients had recurrent hemorrhages during a mean follow-up period of 23.9+/-14.8 months, yielding a 2-year cumulative rate of recurrence of 21 percent. The apolipoprotein E genotype was significantly associated with the risk of recurrence. Carriers of the epsilon2 or epsilon4 allele had a two-year rate of recurrence of 28 percent, as compared with only 10 percent for patients with the common apolipoprotein E epsilon3/epsilon3 genotype (risk ratio, 3.8; 95 percent confidence interval, 1.2 to 11.6; P=0.01). Early recurrence occurred in eight patients, four of whom had the uncommon epsilon2/epsilon4 genotype. Also at increased risk for recurrence were patients with a history of hemorrhagic stroke before entry into the study (two-year recurrence, 61 percent; risk ratio, 6.4; 95 percent confidence interval, 2.2 to 18.5; P<0.001). CONCLUSIONS The apolipoprotein E genotype can identify patients with lobar intracerebral hemorrhage who are at highest risk for early recurrence. This finding makes possible both the provision of prognostic information to patients with lobar hemorrhage and a method of targeting and assessing potential strategies for prevention.

Imaging of amyloid burden and distribution in cerebral amyloid angiopathy.

Cerebrovascular deposition of β‐amyloid (cerebral amyloid angiopathy [CAA]) is a major cause of hemorrhagic stroke and a likely contributor to vascular cognitive impairment. We evaluated positron emission tomographic imaging with the β‐amyloid–binding compound Pittsburgh Compound B (PiB) as a potential noninvasive method for detection of CAA. We hypothesized that amyloid deposition would be observed with PiB in CAA, and based on the occipital predilection of CAA pathology and associated hemorrhages, that specific PiB retention would be disproportionately greater in occipital lobes.

Meta-analysis identifies six new susceptibility loci for atrial fibrillation

Atrial fibrillation is a highly prevalent arrhythmia and a major risk factor for stroke, heart failure and death. We conducted a genome-wide association study (GWAS) in individuals of European ancestry, including 6,707 with and 52,426 without atrial fibrillation. Six new atrial fibrillation susceptibility loci were identified and replicated in an additional sample of individuals of European ancestry, including 5,381 subjects with and 10,030 subjects without atrial fibrillation (P < 5 × 10−8). Four of the loci identified in Europeans were further replicated in silico in a GWAS of Japanese individuals, including 843 individuals with and 3,350 individuals without atrial fibrillation. The identified loci implicate candidate genes that encode transcription factors related to cardiopulmonary development, cardiac-expressed ion channels and cell signaling molecules.

Genetic risk factors for ischaemic stroke and its subtypes (the METASTROKE collaboration): a meta-analysis of genome-wide association studies.

Summary Background Various genome-wide association studies (GWAS) have been done in ischaemic stroke, identifying a few loci associated with the disease, but sample sizes have been 3500 cases or less. We established the METASTROKE collaboration with the aim of validating associations from previous GWAS and identifying novel genetic associations through meta-analysis of GWAS datasets for ischaemic stroke and its subtypes. Methods We meta-analysed data from 15 ischaemic stroke cohorts with a total of 12 389 individuals with ischaemic stroke and 62 004 controls, all of European ancestry. For the associations reaching genome-wide significance in METASTROKE, we did a further analysis, conditioning on the lead single nucleotide polymorphism in every associated region. Replication of novel suggestive signals was done in 13 347 cases and 29 083 controls. Findings We verified previous associations for cardioembolic stroke near PITX2 (p=2·8×10−16) and ZFHX3 (p=2·28×10−8), and for large-vessel stroke at a 9p21 locus (p=3·32×10−5) and HDAC9 (p=2·03×10−12). Additionally, we verified that all associations were subtype specific. Conditional analysis in the three regions for which the associations reached genome-wide significance (PITX2, ZFHX3, and HDAC9) indicated that all the signal in each region could be attributed to one risk haplotype. We also identified 12 potentially novel loci at p<5×10−6. However, we were unable to replicate any of these novel associations in the replication cohort. Interpretation Our results show that, although genetic variants can be detected in patients with ischaemic stroke when compared with controls, all associations we were able to confirm are specific to a stroke subtype. This finding has two implications. First, to maximise success of genetic studies in ischaemic stroke, detailed stroke subtyping is required. Second, different genetic pathophysiological mechanisms seem to be associated with different stroke subtypes. Funding Wellcome Trust, UK Medical Research Council (MRC), Australian National and Medical Health Research Council, National Institutes of Health (NIH) including National Heart, Lung and Blood Institute (NHLBI), the National Institute on Aging (NIA), the National Human Genome Research Institute (NHGRI), and the National Institute of Neurological Disorders and Stroke (NINDS).

Genome-wide association study identifies a variant in HDAC9 associated with large vessel ischemic stroke.

Genetic factors have been implicated in stroke risk, but few replicated associations have been reported. We conducted a genome-wide association study (GWAS) for ischemic stroke and its subtypes in 3,548 affected individuals and 5,972 controls, all of European ancestry. Replication of potential signals was performed in 5,859 affected individuals and 6,281 controls. We replicated previous associations for cardioembolic stroke near PITX2 and ZFHX3 and for large vessel stroke at a 9p21 locus. We identified a new association for large vessel stroke within HDAC9 (encoding histone deacetylase 9) on chromosome 7p21.1 (including further replication in an additional 735 affected individuals and 28,583 controls) (rs11984041; combined P = 1.87 × 10−11; odds ratio (OR) = 1.42, 95% confidence interval (CI) = 1.28–1.57). All four loci exhibited evidence for heterogeneity of effect across the stroke subtypes, with some and possibly all affecting risk for only one subtype. This suggests distinct genetic architectures for different stroke subtypes.