Risk profiles and one-year outcomes of patients with newly diagnosed atrial fibrillation in India: Insights from the GARFIELD-AF Registry.

BACKGROUND: The Global Anticoagulant Registry in the FIELD-Atrial Fibrillation (GARFIELD-AF) is an ongoing prospective noninterventional registry, which is providing important information on the baseline characteristics, treatment patterns, and 1-year outcomes in patients with newly diagnosed non-valvular atrial fibrillation (NVAF). This report describes data from Indian patients recruited in this registry. METHODS AND RESULTS: A total of 52,014 patients with newly diagnosed AF were enrolled globally; of these, 1388 patients were recruited from 26 sites within India (2012-2016). In India, the mean age was 65.8 years at diagnosis of NVAF. Hypertension was the most prevalent risk factor for AF, present in 68.5% of patients from India and in 76.3% of patients globally (P < 0.001). Diabetes and coronary artery disease (CAD) were prevalent in 36.2% and 28.1% of patients as compared with global prevalence of 22.2% and 21.6%, respectively (P < 0.001 for both). Antiplatelet therapy was the most common antithrombotic treatment in India. With increasing stroke risk, however, patients were more likely to receive oral anticoagulant therapy [mainly vitamin K antagonist (VKA)], but average international normalized ratio (INR) was lower among Indian patients [median INR value 1.6 (interquartile range {IQR}: 1.3-2.3) versus 2.3 (IQR 1.8-2.8) (P < 0.001)]. Compared with other countries, patients from India had markedly higher rates of all-cause mortality [7.68 per 100 person-years (95% confidence interval 6.32-9.35) vs 4.34 (4.16-4.53), P < 0.0001], while rates of stroke/systemic embolism and major bleeding were lower after 1 year of follow-up. CONCLUSION: Compared to previously published registries from India, the GARFIELD-AF registry describes clinical profiles and outcomes in Indian patients with AF of a different etiology. The registry data show that compared to the rest of the world, Indian AF patients are younger in age and have more diabetes and CAD. Patients with a higher stroke risk are more likely to receive anticoagulation therapy with VKA but are underdosed compared with the global average in the GARFIELD-AF. CLINICAL TRIAL REGISTRATION-URL: http://www.clinicaltrials.gov. Unique identifier: NCT01090362

On ISC PP and pP data and their use in delay time tomography of the Caribbean region

A major problem in P delay-time tomography is the inhomogeneous sampling of mantle structure by the P-wave ray paths resulting in low resolution in images of large regions of the upper mantle. Incorporation of PP and pP phases can improve the quality and reliability of tomographic images because they: (1) sample Earth structure not ordinarily sampled by direct P phases; (2) add rays that are oblique to rays of direct phases, which is especially important where the latter sample mantle structure in selected directions; and (3) pP data better constrain the earthquake focal depths. PP traveltimes have often been used in combination with P data in differential traveltime studies. We show that the assumptions and approximations necessary for this approach are problematic, and that they can be avoided when the P, PP and P data are used in tomographic inversion. We investigated the applicability of PP and pP delay times to the tomographic study of the aspherical mantle structure below the Caribbean region. The success of the application of data of the later arriving reflected waves depends critically on the quality of these data. We examined possible sources of error in the ISC PP and pP data and assessed the contribution to the delay times used in this study. For the Caribbean region, analyses of the ISC PP and pP delay times do not reveal biases due to effects of PP-waveform distortions, the asymmetry of the reflections, or due to misidentifications of phases that reflect at a surface other than that assumed. The noise level of PP and pP data is high with respect to data of the direct P-wave. This is accommodated by weighting with the inverse of the variance of the data of each of the three phases. The independent information that is revealed from the PP and pP data results in modifications of tomographic images based solely on P data. These modifications are important if the tomographic images are being used to understand the geodynamical history of convergent margins in the Caribbean region. We investigated the effect of adding data of later arriving phases to the ISC P data with sensitivity tests: we inverted synthetic delay times to which we added Gaussian noise with a standard error typical for the data of the three seismic phases. These tests demonstrate that the image resolution of shallow mantle structure is enhanced significantly by the incorporation of later arriving phases. Due to the absence of seismicity below 200 km the resolution improved less at deeper levels below the Caribbean region. In some poorly constrained parts of the solution the test results even indicate an apparent decrease of resolution. This is explained by changes in the rate of convergence of the inversion algorithm: in mantle regions where the effective sampling of structure improved by the addition of PP- and pP-wave ray paths, the convergence was speeded up at the expense of the convergence rate in regions where fewer or no PP- or pP-wave ray paths were added. A shortcoming of the resolution tests used in our study is that some specific problems of reported delay times are not reflected in synthetic data. We observe that ISC delay times of later arriving phases are not necessarily consistent with the reported hypocentral parameters, as most ISC-reported earthquake locations are computed from direct P-wave data. For the pP data, the inconsistency with event location not only results in a decrease of focal depths during relocation, but in a bias of the imaged velocity perturbations as well. This property of reported data is not modelled in resolution tests

Step-wise relocation of ISC earthquake hypocenters for linearized tomographic imaging of slab structure

A vast volume of seismic phase data, computed from routinely determined hypocenter locations, is presently available for seismic imaging techniques such as tomographic inversion and residual sphere analysis. Routinely reported earthquake hypocenters, however, can be in error by several tens of kilometers. These biases in hypocenter location can result in the misidentification of seismic phases and the loss of structural signal in the seismic phase data. Thus, the value of these data in constraining seismic images is significantly reduced. Furthermore, hypocenter mislocations degrade the linearization of the tomographic problem and map into the images produced by tomographic inversion. To obtain adequate reference hypocenters for linearized inversion, we used iasp91 software and reported arrival times to reprocess ISC hypocenters and phase data for northwest Pacific earthquakes. Subsequently, we inverted P- and pP-wave residuals for Earth structure and source (mis)location. We describe this step-wise relocation of ISC hypocenters, which underlies the linearization of the tomographic inversion, and compare the relocation vectors before and after inversion. The hypocenter relocations determined prior to inversion are of the order of 10 km, which is significant with regard to both the estimated standard errors and the effect on travel-time residuals, and systematic with regard to earthquake position in the subducted slab. In contrast, the spatial components of the relocation vectors determined upon inversion of P and pP residuals are up to an order of magnitude smaller, do not reveal a correlation with location in the seismic zone, and do not generally exceed the noise level. The incorporation of pP data in the relocation was essential to remove the depth bias prior to inversion, to retrieve slab signal that might have been absorbed in mislocation, and to constrain the focal depth upon seismic inversion. Non-linear inversion schemes will not be efficient in removing the depth bias or in retrieving lost slab signal unless seismic phases that contain additional information about the depth bias, like the depth phase pP, are used

Global teleseismic earthquake relocation from improved travel times and procedures for depth determination

We relocate nearly 100,000 events that occurred during the period 1964 to 1995 and are well-constrained teleseismically by arrival-time data reported to the International Seismological Centre (ISC) and to the U.S. Geological Survey's National Earthquake Information Center (NEIC). Hypocenter determination is significantly improved by using, in addition to regional and teleseismic P and S phases, the arrival times of PKiKP, PKPdf, and the teleseismic depth phases pP, pwP, and sP in the relocation procedure. A global probability model developed for later-arriving phases is used to independently identify the depth phases. The relocations are compared to hypocenters reported in the ISC and NEIC catalogs and by other sources. Differences in our epicenters with respect to ISC and NEIC estimates are generally small and regionally systematic due to the combined effects of the observing station network and plate geometry regionally, differences in upper mantle travel times between the reference earth models used, and the use of later-arriving phases. Focal depths are improved substantially over most other independent estimates, demonstrating (for example) how regional structures such as downgoing slabs can severely bias depth estimation when only regional and teleseismic P arrivals are used to determine the hypocenter. The new data base, which is complete to about Mw 5.2 and includes all events for which moment-tensor solutions are available, has immediate application to high-resolution definition of Wadati-Benioff Zones (WBZs) worldwide, regional and global tomographic imaging, and other studies of earth structure

Imaging of subducted lithosphere beneath South America

Tomographic images are produced for the deep structure of the Andean subduction zone beneath western South America. The data used in the imaging are the delay times of P, pP and pwP phases from relocated teleseismic earthquakes in the region. Regionally, structural features larger than about 150 km are resolved by the data. Presentations of layer anomaly maps and cross sections reveal: (1) The Nazca slab is probably continuous laterally and at depth over most regions; (2) The offset between the north and south deep earthquake zones, containing the 1994 deep Bolivia main shock and its aftershocks, can be modelled by a northwest striking and steeply northeast dipping slab structure; and (3) The Nazca slab clearly penetrates the lower mantle beneath central South America, but is partly deflected in the southern deep zone

Tomographic inversion of P and pP data for aspherical mantle structure below the northwest Pacific region

To investigate the morphology of subducted slab in the mantle below northwest Pacific island arcs we inverted traveltime residuals for aspherical variations in P-wave propagation velocity relative to the radially symmetric iasp91 reference model. The tomographic method used is based on a step-wise linearization of the inversion problem. First, we relocated ISC (International Seismological Centre) hypocentres with re-identified P and pP phase data using the iasp91 traveltime tables. The variance of P residuals relative to iasp91 traveltimes was 17 per cent less than the variance of P data reported by the ISC relative to the Jeffreys-Bullen (J-B) traveltime tables. Second, we performed a linearized (LSQR) inversion for Earth structure and source relocation with the P and pP residuals obtained from the first step, using iasp91 as the reference model for seismic velocities. The incorporation of the depth phase pP in the tomographic inversions has two major advantages: (1) the pP data provide constraints on focal depth and thus reduce the trade-off between source relocation and structure; and (2) the pP ray paths improve the sampling of Earth structure in the shallow mantle and transition zone. We used more than 2 times 10⁶ and about 1 times 10⁵ P- and pP-wave traveltime residuals, respectively, from about 40 000 earthquakes with epicentres in the study region that were recorded at one or more of the 2300 globally distributed seismological stations considered in this study. We assessed the spatial resolution in the tomographic images with checker board-type sensitivity tests. These tests reveal high resolution of upper mantle and transition-zone structure, particularly below the central part of our study region. Structure with wavelengths of the order of 100 km is resolved below Japan, whereas structure with wavelengths of the order of 300 km is well resolved below the Kuril, Izu Bonin and Ryukyu arcs. Small-scale structure is poorly resolved in depth below the northern part of the Kuril-Kamchatka arc and below the Izu Bonin and Mariana arcs. This limits the interpretation of slab structure and mantle flow from tomographic images alone. With this limitation in mind, we conclude from the tomographic images that subducted slab deflects in the mantle transition zone below the geographical area encompassed by the Kuril basin, the Japan Sea, and the northern part of the Philippine Sea. This is in good agreement with the results of other recently published tomographic studies, the occurrence of earthquakes several hundred kilometres off the inclined Wadati-Benioff seismic zones, and inferences about ‘660 km’ discontinuity topography. In contrast, slab-like structures of high P-wave velocity are imaged in the lower mantle below the deepest earthquakes of the northern Kuril-Kamchatka and Mariana seismic zones. This is indicative of local slab penetration of the lower mantle. From tomographic images we cannot discern between compositionally or thermally induced variations in seismic velocity. However, with regard to the nature of the boundary between upper and lower mantle, our observations argue against either compositional mantle layering with large contrasts in intrinsic density or phase changes with steep Clapeyron slopes