Recovery of Smelter-Impacted Peat and Sphagnum Moss: a Microbial Perspective.

Peatlands store approximately one-half of terrestrial soil carbon and one-tenth of non-glacial freshwater. Some of these important ecosystems are located near heavy metal emitting smelters. To improve the understanding of smelter impacts and potential recovery after initial pollution controls in the 1970s (roughly 50 years of potential recovery), we sampled peatlands along a distance gradient of 134 km from a smelter in Sudbury, Ontario, Canada, an area with over a century of nickel (Ni) and copper (Cu) mining activity. This work is aimed at evaluating potential shifts in bacterial and archaeal community structures in Sphagnum moss and its underlying peat within smelter-impacted poor fens. In peat, total Ni and Cu concentrations were higher (0.062-0.067 and 0.110-0.208 mg/g, respectively) at sites close to the smelter and exponentially dropped with distance from the smelter. This exponential decrease in Ni concentrations was also observed in Sphagnum. 16S rDNA amplicon sequencing showed that peat and Sphagnum moss host distinct microbiomes with peat accommodating a more diverse community structure. The microbiomes of Sphagnum were dominated by Proteobacteria (62.5%), followed by Acidobacteria (11.9%), with no observable trends with distance from the smelter. Dominance of Acidobacteria (32.4%) and Proteobacteria (29.6%) in peat was reported across all sites. No drift in taxonomy was seen across the distance gradient or from the reference sites, suggesting a potential microbiome recovery toward that of the reference peatlands microbiomes after decades of pollution controls. These results advance the understanding of peat and Sphagnum moss microbiomes, as well as depict the sensitivities and the resilience of peatland ecosystems.

Peatland Microbial Community Composition Is Driven by a Natural Climate Gradient.

Peatlands are important players in climate change-biosphere feedbacks via long-term net carbon (C) accumulation in soil organic matter and as potential net C sources including the potent greenhouse gas methane (CH4). Interactions of climate, site-hydrology, plant community, and groundwater chemical factors influence peatland development and functioning, including C dioxide (CO2) and CH4 fluxes, but the role of microbial community composition is not well understood. To assess microbial functional and taxonomic dissimilarities, we used high throughput sequencing of the small subunit ribosomal DNA (SSU rDNA) to determine bacterial and archaeal community composition in soils from twenty North American peatlands. Targeted DNA metabarcoding showed that although Proteobacteria, Acidobacteria, and Actinobacteria were the dominant phyla on average, intermediate and rich fens hosted greater diversity and taxonomic richness, as well as an array of candidate phyla when compared with acidic and nutrient-poor poor fens and bogs. Moreover, pH was revealed to be the strongest predictor of microbial community structure across sites. Predictive metagenome content (PICRUSt) showed increases in specific genes, such as purine/pyrimidine and amino-acid metabolism in mid-latitude peatlands from 38 to 45° N, suggesting a shift toward utilization of microbial biomass over utilization of initial plant biomass in these microbial communities. Overall, there appears to be noticeable differences in community structure between peatland classes, as well as differences in microbial metabolic activity between latitudes. These findings are in line with a predicted increase in the decomposition and accelerated C turnover, and suggest that peatlands north of 37° latitude may be particularly vulnerable to climate change.

Right and left ventricular interaction in pulmonary hypertension: Insight from velocity vector imaging.

OBJECTIVE: To evaluate whether global peak systolic strain (PSS) and peak systolic strain rate (PSSR) derived from velocity vector imaging (VVI) allow early recognition of regional and global right ventricular (RV) dysfunction and the impact of this on left ventricular (LV) function in patients with pulmonary hypertension (PHT). BACKGROUND: RV function is an important determinant of prognosis in patients with heart failure, pulmonary hypertension, heart transplant, and congenital heart diseases. However, evaluation of the right ventricle is often limited by its complex geometry and inadequate visualization of RV free wall. Furthermore, the impact of RV dysfunction on the LV function is not well elucidated. METHODS: Ninety-nine participants, 35 control patients with normal RV systolic pressure (RVSP) (<30 mm Hg) and 64 patients with PHT (25 with mild-to-moderate increase in RVSP [≥36 and <60 mm Hg] and 39 with severe increase in RVSP [≥60 mm Hg]), underwent comprehensive echo-Doppler assessment and velocity vector imaging (VVI) for strain rate analysis. RV regional peak systolic and diastolic tangential velocity, strain, and strain rate were obtained from the basal, mid and apical segments of the RV free wall and interventricular septum (IVS) from apical 4-chamber view at end-expiration. Similar data were obtained from eighteen LV segments from apical 4-chamber, 2-chamber, and long-axis views. RESULTS: Peak systolic strain, strain rate, and tangential velocity at all segments in the RV free wall and IVS were decreased compared to controls in patients with PHT (P < 0.001). Significant correlation (r > 0.60; P < 0.001) was noted between RVSP and systolic and diastolic strain and strain rate at basal segment in IVS and global RV function. Peak early diastolic strain rate at all segments was also decreased in PHT patients compared with control patients (P < 0.01). Furthermore, RV systolic and diastolic strain and strain rate were lower in group 2 with mild-to-moderate hypertension while the conventional echo parameters were normal. Except for IVS segments, other LV segments had no statistical differences in systolic and diastolic velocity, strain, and strain rate compared to controls. However, they were lower than the published normal range. CONCLUSIONS: Strain and strain rate derived from VVI demonstrates early recognition of systolic and diastolic RV dysfunction in patients with PHT compared to controls. PHT is associated with global and regional RV systolic and diastolic dysfunction. Systolic and diastolic strain and strain rate from LV was lower compared to controls but were not statistically significant. This may indicate subclinical LV dysfunction in these patients, suggesting that conventional LV function parameters may not be sensitive to recognize subclinical LV dysfunction.

Impact of Left Atrial Appendage Closure During Cardiac Surgery on the Occurrence of Early Postoperative Atrial Fibrillation, Stroke, and Mortality: A Propensity Score-Matched Analysis of 10 633 Patients.

BACKGROUND: Prophylactic exclusion of the left atrial appendage (LAA) is often performed during cardiac surgery ostensibly to reduce the risk of stroke. However, the clinical impact of LAA closure in humans remains inconclusive. METHODS: Of 10 633 adults who underwent coronary artery bypass grafting and valve surgery between January 2000 and December 2005, 9792 patients with complete baseline characteristics, surgery procedure, and follow-up data were included in this analysis. A propensity score-matching analysis based on 28 pretreatment covariates was performed and 461 matching pairs were derived and analyzed to estimate the association of LAA closure with early postoperative atrial fibrillation (POAF) (atrial fibrillation ≤30 days of surgery), ischemic stroke, and mortality. RESULTS: In the propensity-matched cohort, the overall incidence of POAF was 53.9%. In this group, the rate of early POAF among the patients who underwent LAA closure was 68.6% versus 31.9% for those who did not undergo the procedure (P<0.001). LAA closure was independently associated with an increased risk of early POAF (adjusted odds ratio, 3.88; 95% confidence interval, 2.89-5.20), but did not significantly influence the risk of stroke (adjusted hazard ratio, 1.07; 95% confidence interval, 0.72-1.58) or mortality (adjusted hazard ratio, 0.92; 95% confidence interval, 0.75-1.13). CONCLUSIONS: After adjustment for treatment allocation bias, LAA closure during routine cardiac surgery was significantly associated with an increased risk of early POAF, but it did not influence the risk of stroke or mortality. It remains uncertain whether prophylactic exclusion of the LAA is warranted for stroke prevention during non-atrial fibrillation-related cardiac surgery.

Real-time physiologic biomarker for prediction of atrial fibrillation recurrence, stroke, and mortality after electrical cardioversion: A prospective observational study.

BACKGROUND: Left atrial appendage emptying flow velocity (LAAEV) depends largely on left atrioventricular compliance and may play a role in mediating the perpetuation of atrial fibrillation (AF) and AF-related outcomes. METHODS: We identified 3,251 consecutive patients with sustained AF undergoing first-time successful transesophageal echocardiography (TEE)-guided electrical cardioversion who were enrolled in a prospective registry between May 2000 and March 2012. Left atrial appendage emptying flow velocity was stratified into quartiles: ≤20.2, 20.3-33.9, 34-49.9, and ≥50 cm/s. Multivariate Cox regression models were used to identify independent predictors of AF recurrence, ischemic stroke, and all-cause mortality. RESULTS: The mean (SD) age was 69 (12.6) years and 67% were men. Compared with the fourth quartile, patients in the first-third quartiles were significantly older, had higher CHA2DS2-VASc (congestive heart failure, hypertension, age ≥75 years, diabetes mellitus, stroke/transient ischemic attack [TIA], vascular disease, age 65-74 years, sex category) scores, greater frequency of atrial spontaneous echo contrast, and AF of longer duration. Kaplan-Meier analysis showed a decreased probability of event-free survival with decreasing quartiles of LAAEV. Five-year cumulative event rates across first-fourth quartiles were 83%, 80%, 73%, and 73% (P < .001) for first AF recurrence; 7.5%, 7.0%, 4.1%, and 4.0%, for stroke (P = .01); and 31.3%, 26.1%, 24.1%, and 19.4%, for mortality (P < .001), respectively. Multivariate Cox regression analysis revealed an independent association of the first and second quartiles with AF recurrence (P < .001 and P < .001, respectively) and stroke (P = .03, and P = .04, respectively), and of the first quartile with mortality (P = .003). CONCLUSIONS: Patients with decreased LAAEV have an increased risk of AF recurrence, stroke, and mortality after successful electrical cardioversion. Real-time measurement of LAAEV by TEE may be a useful physiologic biomarker for individualizing treatment decisions in patients with AF.

Implications of new-onset atrial fibrillation after cardiac surgery on long-term prognosis: a community-based study.

BACKGROUND: Postoperative atrial fibrillation (POAF) is a common complication after cardiac surgery. Data are lacking on the long-term prognostic implications of POAF. We hypothesized that POAF, which reflects underlying cardiovascular pathophysiologic substrate, is a predictive marker of late AF and long-term mortality. METHODS: We identified 603 Olmsted County, Minnesota, residents without prior documented history of AF who underwent coronary artery bypass graft and/or valve surgery from 2000 to 2005. Patients were monitored for first documentation of late AF or death at >30 days postoperatively. Multivariate Cox regression models were used to assess the independent association of POAF with late AF and long-term mortality. RESULTS: After a mean follow-up of 8.3 ± 4.2 years, freedom from late AF was less with POAF than no POAF (57.4% vs 88.9%, P < .001). The risk of late AF was highest within the first year at 18%. Univariate analysis demonstrated that POAF was associated with significantly increased risk of late AF [hazard ratio (HR), 5.09; 95% CI, 3.65-7.22] and long-term mortality (HR, 1.79; 95% CI, 1.38-2.22). After adjustment for age, sex, and clinical and surgical risk factors, POAF remained independently associated with development of late AF (HR, 3.52; 95% CI, 2.42-5.13) but not long-term mortality (HR, 1.16; 95% CI, 0.87-1.55). Conversely, late AF was independently predictive of long-term mortality (HR, 3.25; 95% CI, 2.42-4.35). Diastolic dysfunction independently influenced the risk of late AF and long-term mortality. CONCLUSIONS: Postoperative atrial fibrillation was an independent predictive marker of late AF, whereas late AF, but not POAF, was independently associated with long-term mortality. Patients who develop new-onset POAF should be considered for continuous anticoagulation at least during the first year following cardiac surgery.

Ia diastolic dysfunction: an echocardiographic grade.

OBJECTIVE: To demonstrate that a distinct group of patients with Grade Ia diastolic dysfunction who do not conform to present ASE/ESE diastolic grading exists. METHOD AND RESULTS: Echocardiographic and demographic data of the Grade Ia diastolic dysfunction were extracted and compared with that of Grades I and II in 515 patients. The mean of age of the cohort was 75 ± 9 years and body mass index did not differ significantly between the 3 groups (P = 0.45). Measurements of left atrial volume index (28.58 ± 7 mL/m(2) in I, 33 ± 10 mL/m(2) in Ia, and 39 ± 12 mL/m(2) in II P < 0.001), isovolumic relaxation time (IVRT) (100 ± 17 msec in I, 103 ± 21 msec in Ia, and 79 ± 15 msec in II P < 0.001), deceleration time (248 ± 52 msec in I, 263 ± 58 msec in Ia, and 217 ± 57 msec in II P < 0.001), medial E/e' (10 ± 3 in I, 18 ± 5.00 in Ia, and 22 ± 8 in II), and lateral E/e' (8 ± 3 in I, 15 ± 6 in Ia, and 18 ± 9 in II P < 0.001) were significantly different in grade Ia compared with I and II. These findings remained significant even after adjusting for age, gender, diabetes, and smoking. CONCLUSION: Patients with echocardiographic characteristics of relaxation abnormality (E/A ratio of <0.8) and elevated filling pressures (septal E/e' ≥15, lateral E/e' ≥12, average E/e' ≥13) should be graded as a separate Grade Ia group.

Left atrial anatomy and physiology: echo/Doppler assessment.

PURPOSE OF REVIEW: This article provides a state-of-the-art perspective of left atrial anatomy and physiology. RECENT FINDINGS: Left atrial structure and function can be used to reflect and quantify the physiologic state of complex disease processes. No single left atrial anatomic, functional, or clinical feature will adequately define a complex system. The state of combined left atrial structural and functional features (i.e., systems biology) defines disease clustering (i.e., commonality of underlying left atrial pathophysiology), cause and effect (i.e., left atrial dynamics impute disease events as consequences), disease classification (e.g., primary vs. secondary atrial fibrillation), and intensity of a pathophysiologic state (i.e., quantifiably infer the magnitude of a pathophysiologic perturbation), and helps explain complex pathophysiology (e.g., myocyte death vs. hibernation). SUMMARY: Individual left atrial structural and functional features do not define the state of complex systems. Systems biology and multifeature profiles of left atrial anatomy and physiology should be used to assist the prediction, management, and, ultimately, prevention of preclinical and overt complex disease processes.

Left atrial function: physiology, assessment, and clinical implications.

The interest in the left atrium (LA) has resurged over the recent years. In the early 1980s, multiple studies were conducted to determine the normal values of LA size. Over the past decade, LA size as an imaging biomarker has been consistently shown to be a powerful predictor of outcomes, including major public health problems such as atrial fibrillation, heart failure, stroke, and death. More recently, functional assessment of the LA has been shown to be, at least as, if not more robust, a marker of cardiovascular outcomes. Current available data suggest that the combined evaluation of LA size and LA function will augment prognostication. The aim of this review is to provide a critical appraisal of current echocardiographic techniques for the assessment of LA function and the implications of such assessment for prediction and disease prevention.

Suppressing peatland methane production by electron snorkeling through pyrogenic carbon in controlled laboratory incubations.

Northern peatlands are experiencing more frequent and severe fire events as a result of changing climate conditions. Recent studies show that such a fire-regime change imposes a direct climate-warming impact by emitting large amounts of carbon into the atmosphere. However, the fires also convert parts of the burnt biomass into pyrogenic carbon. Here, we show a potential climate-cooling impact induced by fire-derived pyrogenic carbon in laboratory incubations. We found that the accumulation of pyrogenic carbon reduced post-fire methane production from warm (32 °C) incubated peatland soils by 13-24%. The redox-cycling, capacitive, and conductive electron transfer mechanisms in pyrogenic carbon functioned as an electron snorkel, which facilitated extracellular electron transfer and stimulated soil alternative microbial respiration to suppress methane production. Our results highlight an important, but overlooked, function of pyrogenic carbon in neutralizing forest fire emissions and call for its consideration in the global carbon budget estimation.

Beyond the usual suspects: methanogenic communities in eastern North American peatlands are also influenced by nickel and copper concentrations.

Peatlands both accumulate carbon and release methane, but their broad range in environmental conditions means that the diversity of microorganisms responsible for carbon cycling is still uncertain. Here, we describe a community analysis of methanogenic archaea responsible for methane production in 17 peatlands from 36 to 53 N latitude across the eastern half of North America, including three metal-contaminated sites. Methanogenic community structure was analysed through Illumina amplicon sequencing of the mcrA gene. Whether metal-contaminated sites were included or not, metal concentrations in peat were a primary driver of methanogenic community composition, particularly nickel, a trace element required in the F430 cofactor in methyl-coenzyme M reductase that is also toxic at high concentrations. Copper was also a strong predictor, likely due to inhibition at toxic levels and/or to cooccurrence with nickel, since copper enzymes are not known to be present in anaerobic archaea. The methanogenic groups Methanocellales and Methanosarcinales were prevalent in peatlands with low nickel concentrations, while Methanomicrobiales and Methanomassiliicoccales were abundant in peatlands with higher nickel concentrations. Results suggest that peat-associated trace metals are predictors of methanogenic communities in peatlands.

C-reactive protein, left atrial volume, and atrial fibrillation: a prospective study in high-risk elderly.

BACKGROUND: The data regarding the interrelationships of high-sensitive C-reactive protein (CRP), left atrial (LA) volume, and atrial fibrillation (AF) are sparse. Additionally, while LA volume has been shown to be useful for prediction of AF in low-to-moderate risk populations, its predictive value in clinically high-risk populations is unknown. METHODS: SAFHIRE (Study of Atrial Fibrillation in High Risk Elderly) is an ongoing prospective study of the pathophysiology of first AF in persons aged > or = 65 years with > or = 2 other AF risk factors [systemic hypertension, proven coronary artery disease, heart failure (HF), diabetes]. Participants are followed annually, and undergo an interview, physical examination, blood work, electrocardiogram, and echocardiogram assessment. RESULTS: Of 800 participants, mean age of 74 +/- 6 years, 34 developed first AF over 1.7+/- 0.9 years. A history of systemic hypertension and proven coronary artery disease was present in 97% and 78%, respectively. CRP was unrelated to LA volume on univariable or multivariable analyses (P > 0.10), and not predictive of first AF on univariable or multivariable models (all P > 0.10). Indexed LA volume was an independent predictor of first AF (unadjusted P< 0.0001; age and sex adjusted P = 0.0006; adjusted for multiple factors, HR 1.3/5 ml per m(2), 95% CI, 1.09 to 1.48, P = 0.001). CONCLUSION: In this elderly population at high clinical risk for the development of first AF, CRP was unrelated to LA volume and nonpredictive of first AF, while indexed LA volume was incremental to clinical risk factors for the prediction of first AF.

Acute weight gain and diastolic dysfunction as a potent risk complex for post stem cell transplant atrial fibrillation.

The management of atrial fibrillation (AF) following stem cell transplant (SCTX) is often challenging because of the universal presence of profound bone marrow suppression. The incidence of and risk factors for AF/flutter following SCTX are not well known. A total of 395 multiple myeloma (MM) patients consecutively underwent SCTX between 2002 and 2005 at the Mayo Clinic, and 383 of whom, mean age 57 +/- 9 years, had no history of evidence of AF/flutter constituted the study population. During 1,002 person-years of follow up, 39 (10%) patients developed first AF/flutter (incidence of 39 per 1,000 person years), and 28 of these (72%) occurred within 21 days of SCTX. In multivariable-adjusted analyses, weight gain of > or = 7% in the 1st week post-SCTX (HR 3.68; P = 0.0120) and presence of diastolic dysfunction at MM diagnosis (HR 2.294; P = 0.0082) were independent predictors of AF/flutter. The risk of AF/flutter post-SCTX increased by about ninefold when both factors were present. Compared to age and sex-matched MM patients without SCTX, the risk of AF/flutter differed significantly only over the 1st year after MM diagnosis, during which SCTX was performed for the majority. Beyond the 1st year, there was no significant difference in risk of AF/flutter between the two groups. The data suggested that SCTX was associated with significantly increased risk of first AF/flutter, which typically occurred within the first 21 days of the transplant. Weight gain of > or = 7% was strongly predictive of first AF/flutter, and the risk was augmented by the presence of diastolic dysfunction at baseline.

Minimum vs. maximum left atrial volume for prediction of first atrial fibrillation or flutter in an elderly cohort: a prospective study.

AIMS: We sought to compare the predictive power and reproducibility between minimum and maximum left atrial (LA) volume for the development of first atrial fibrillation (AF)/flutter. METHODS AND RESULTS: This prospective study included 574 adults, mean age 74+/-6 years, in sinus rhythm, and had no history or evidence of prior atrial arrhythmias. During a mean follow-up of 1.9+/-1.2 years, 30 (5.2%) developed first AF/flutter. The 3-year risk estimates of freedom from AF/flutter by tertiles of minimum and maximum LA volumes were, respectively, 97, 87, and 74% (P<0.0006) and 94, 85, and 78% (P=0.03). Minimum LA volume was incremental to clinical and other echocardiographic parameters of AF/flutter prediction [per tertile, hazard ratio (HR) 2.4], as was maximum LA volume (per tertile, HR 1.8) in a separate model. When both volumes were entered into the same model and adjusting for covariates, minimum but not maximum LA volume retained significance. However, in terms of interobserver reproducibility, maximum LA volume compared more favourably (mean difference 3.1+/-7.1 vs. 7.4+/-7.3 mL/m(2)). CONCLUSION: Minimal LA volume was an independent predictor of first AF/flutter. Although it was marginally superior to maximal LA volume in terms of predictive ability, the interobserver variability was greater.

Obesity as a risk factor for the progression of paroxysmal to permanent atrial fibrillation: a longitudinal cohort study of 21 years.

AIMS: Obesity has been shown to be a risk factor for first atrial fibrillation (AF), but whether it is associated with progression from paroxysmal to permanent AF is unknown. METHODS AND RESULTS: In this longitudinal cohort study, Olmsted County, MN residents confirmed to have developed paroxysmal AF during 1980-2000 were identified and followed passively to 2006. The interrelationships of body mass index (BMI), left atrial (LA) size, and progression to permanent AF were analysed. Of a total of 3248 patients (mean age 71 +/- 15 years; 54% men) diagnosed with paroxysmal AF, 557 (17%) progressed to permanent AF (unadjusted incidence, 36/1000 person-years) over a median follow-up period of 5.1 years (interquartile range 1.2-9.4). Adjusting for age and sex, BMI independently predicted the progression to permanent AF (hazard ratio, HR 1.04, CI 1.03-1.06; P < 0.0001). Compared with normal BMI (18.5-24.9 kg/m(2)), obesity (30-34.9 kg/m(2)) and severe obesity (>or=35 kg/m(2)) were associated with increased risk for progression [HR 1.54 (CI 1.2-2.0; P = 0.0004) and 1.87 (CI 1.4-2.5; P < 0.0001, respectively)]. BMI remained highly significant even after multiple adjustments. In the subgroup with echocardiographic assessment (n = 744), LA volume was incremental to BMI for independent prediction of progression after multiple adjustments, and did not weaken the association between BMI and progression to permanent AF (HR 1.04; CI 1.02-1.05; P < 0.0001). CONCLUSION: There was a graded risk relationship between BMI and progression from paroxysmal to permanent AF. This relationship was not weakened by LA volume, which was independent of and incremental to BMI for the prediction of progression to permanent AF.

Amyloid beta peptides in human plasma and tissues and their significance for Alzheimer's disease.

BACKGROUND: We evaluated the amounts of amyloid beta (Abeta)) peptides in the central nervous system (CNS) and in reservoirs outside the CNS and their potential impact on Abeta plasma levels and Alzheimer's disease (AD) pathology. METHODS: Amyloid beta levels were measured in (1) the plasma of AD and nondemented (ND) controls in a longitudinal study, (2) the plasma of a cohort of AD patients receiving a cholinesterase inhibitor, and (3) the skeletal muscle, liver, aorta, platelets, leptomeningeal arteries, and in gray and white matter of AD and ND control subjects. RESULTS: Plasma Abeta levels fluctuated over time and among individuals, suggesting continuous contributions from brain and peripheral tissues and associations with reactive circulating proteins. Arteries with atherosclerosis had larger amounts of Abeta40 than disease-free vessels. Inactivated platelets contained more Abeta peptides than activated ones. Substantially more Abeta was present in liver samples from ND patients. Overall, AD brain and skeletal muscle contained increased levels of Abeta. CONCLUSIONS: Efforts to use plasma levels of Abeta peptides as AD biomarkers or disease-staging scales have failed. Peripheral tissues might contribute to both the circulating amyloid pool and AD pathology within the brain and its vasculature. The wide spread of plasma Abeta values is also due in part to the ability of Abeta to bind to a variety of plasma and membrane proteins. Sources outside the CNS must be accounted for because pharmacologic interventions to reduce cerebral amyloid are assessed by monitoring Abeta plasma levels. Furthermore, the long-range impact of Abeta immunotherapy on peripheral Abeta sources should also be considered.

Nanotechnology and Health.

: Potential adverse health effects associated with exposure to engineered or synthesized nanomaterials have not been reported in humans; however, there is accumulating evidence from animal studies that exposure to some nanomaterials is harmful. While there is uncertainty as to the likelihood, frequency, and intensity of exposures experienced by those working around engineered nanoparticles, the American College of Occupational and Environmental Medicine has developed this guidance document for occupational medicine physicians and their colleagues to offer prudent preventive recommendations on the topics of exposure monitoring, exposure controls, and medical surveillance.

Changing trends of hospital utilization in patients after their first episode of atrial fibrillation.

A marked increase in hospitalization for patients with atrial fibrillation (AF) has previously been noted. Whether this increase is related to a change in the prevalence of AF or a change in the pattern of practice with respect to the management of AF remains unclear. To determine the trends in hospital utilization after first AF in a community-based setting (Olmsted County, Minnesota), residents diagnosed with first AF from 1980 to 2000 were identified and followed until 2004. The primary outcome of interest was hospital admission for cardiovascular reasons. Of a total of 4,498 subjects (73 +/- 14 years old, 51% men), 2,503 (56%) were admitted to the hospital for cardiovascular causes >or=1 time during a mean follow-up of 5.5 +/- 5.0 years. Risk of first hospitalization was greatest during the first year of AF (cumulative incidence 31%, 95% confidence interval [CI] 30 to 32). First hospitalization was strongly related to age (p <0.0001) but not to sex (p = 0.38). From 1980 to 2000, the age-and sex-adjusted rate of first hospitalization increased, on average, by 2.5% a year (95% CI 1.8 to 3.2, p <0.0001), even after multivariable adjustment for co-morbidities. When we excluded all hospital admissions for the purposes of AF management, the increase in hospitalization was only 0.8% per year (95% CI 0.05 to 1.6, p = 0.04), which was no longer significant after multivariable adjustment for co-morbidities (p = 0.25). In conclusion, the marked increase in hospitalization after first AF diagnosis from 1980 to 2000 appeared to be largely driven by the changing practice pattern in AF management.

Impact of individual and cumulative coronary risk factors on coronary flow reserve assessed by dobutamine stress echocardiography.

Traditional cardiovascular risk factors have been shown to cause microvascular dysfunction. Most studies that have evaluated microcirculation rely on invasive measurement tools. We used dobutamine stress echocardiography, a validated method to measure coronary flow velocity (CFV) and coronary flow reserve (CFR), in a previously unstudied population without known significant coronary artery disease to determine the impact of traditional risk factors on CFR. Consecutive patients who had no evidence of regional wall motion abnormalities at rest or during dobutamine stress echocardiography were studied. Left anterior descending artery CFV was measured at baseline and at peak dobutamine stress and CFR was calculated as the ratio of peak stress CFV to baseline CFV. Fifty-nine consecutive patients (28 men) with mean age of 66.8+/-14.5 years were studied. CFR was lower in patients with diabetes mellitus (DM) compared with those without (1.7+/-0.74 vs 2.48+/-0.98, p<0.007), in patients with hypertension compared with those without (2+/-0.8 vs 2.6+/-0.9, p<0.02), and in obese patients compared with nonobese patients (1.6+/-0.5 vs 2+/-0.6, p<0.02). CFR was further impaired in the presence of DM with hypertension, DM with obesity, DM with a wide pulse pressure (>50 mm Hg), and obesity with a wide pulse pressure. In a multivariate model, DM, obesity, and wide pulse pressure were significantly associated with variation in CFR (p<0.0008). In conclusion, CFR was abnormal in patients with DM, hypertension, and obesity. CFR impairment is exaggerated as the number of risk factors increases. Despite a negative dobutamine stress echocardiographic result, aggressive risk factor assessment and control should be implemented in patients with coronary risk factors due to an underlying abnormal CFR.

Left atrial reservoir function as a potent marker for first atrial fibrillation or flutter in persons > or = 65 years of age.

The aim of this prospective study was to evaluate the incremental value of left atrial (LA) function for the prediction of risk for first atrial fibrillation (AF) or atrial flutter. Maximum and minimum LA volumes were quantitated by echocardiography in 574 adults (mean age 74 +/- 6 years, 52% men) without a history or evidence of atrial arrhythmia. During a mean follow-up period of 1.9 +/- 1.2 years, 30 subjects (5.2%) developed electrocardiographically confirmed AF or atrial flutter. Subjects with new AF or atrial flutter had lower LA reservoir function, as measured by total LA emptying fraction (38% vs 49%, p <0.0001) and higher maximum LA volumes (47 vs 40 ml/m(2), p = 0.005). An increase in age-adjusted risk for AF or atrial flutter was evident when the cohort was stratified according to medians of LA emptying fraction (< or =49%: hazard ratio 6.5, p = 0.001) and LA volume (> or =38 ml/m(2): hazard ratio 2.0, p = 0.07), with the risk being highest for subjects with concomitant LA emptying fractions < or =49% and LA volume > or =38 ml/m(2) (hazard ratio 9.3, p = 0.003). LA emptying fraction (p = 0.002) was associated with risk for first AF or atrial flutter after adjusting for baseline clinical risk factors for AF or atrial flutter, left ventricular ejection fraction, diastolic function grade, and LA volume. In conclusion, reduced LA reservoir function markedly increases the propensity for first AF or atrial flutter, independent of LA volume, left ventricular function, and clinical risk factors.