X-ray polarization evidence for a 200-year-old flare of Sgr A.

The centre of the Milky Way Galaxy hosts a black hole with a solar mass of about 4 million (Sagittarius A* (Sgr A)) that is very quiescent at present with a luminosity many orders of magnitude below those of active galactic nuclei1. Reflection of X-rays from Sgr A* by dense gas in the Galactic Centre region offers a means to study its past flaring activity on timescales of hundreds and thousands of years2. The shape of the X-ray continuum and the strong fluorescent iron line observed from giant molecular clouds in the vicinity of Sgr A* are consistent with the reflection scenario3-5. If this interpretation is correct, the reflected continuum emission should be polarized6. Here we report observations of polarized X-ray emission in the direction of the molecular clouds in the Galactic Centre using the Imaging X-ray Polarimetry Explorer. We measure a polarization degree of 31% ± 11%, and a polarization angle of -48° ± 11°. The polarization angle is consistent with Sgr A* being the primary source of the emission, and the polarization degree implies that some 200 years ago, the X-ray luminosity of Sgr A* was briefly comparable to that of a Seyfert galaxy.

Vela pulsar wind nebula X-rays are polarized to near the synchrotron limit.

Pulsar wind nebulae are formed when outflows of relativistic electrons and positrons hit the surrounding supernova remnant or interstellar medium at a shock front. The Vela pulsar wind nebula is powered by a young pulsar (B0833-45, aged 11,000 years)1 and located inside an extended structure called Vela X, which is itself inside the supernova remnant2. Previous X-ray observations revealed two prominent arcs that are bisected by a jet and counter jet3,4. Radio maps have shown high linear polarization of 60% in the outer regions of the nebula5. Here we report an X-ray observation of the inner part of the nebula, where polarization can exceed 60% at the leading edge-approaching the theoretical limit of what can be produced by synchrotron emission. We infer that, in contrast with the case of the supernova remnant, the electrons in the pulsar wind nebula are accelerated with little or no turbulence in a highly uniform magnetic field.

Advancement of X-ray radiography using microfocus X-ray source in conjunction with amplitude grating and SOI pixel detector, SOPHIAS.

We show how to improve microfocus X-ray radiography by using the SOPHIAS silicon-on-insulator pixel detector in conjunction with an amplitude grating. Single-exposure multi-energy absorption and differential phase contrast imaging was performed using the single amplitude grating method. The sensitivity in differential phase contrast imaging in a two-pixel-pitch setup was enhanced by 39% in comparison with the previously reported method [Rev. Sci. Instrum. 81, 113702 (2010).] by analyzing charge-sharing effects. Small-angle-scattering imaging was also possible in the two-pixel-pitch setup by counting the number of X-ray photons passing the pixel boundaries.

Hitomi X-ray studies of Giant Radio Pulses from the Crab pulsar.

To search for giant X-ray pulses correlated with the giant radio pulses (GRPs) from the Crab pulsar, we performed a simultaneous observation of the Crab pulsar with the X-ray satellite Hitomi in the 2 - 300 keV band and the Kashima NICT radio observatory in the 1.4 - 1.7 GHz band with a net exposure of about 2 ks on 25 March 2016, just before the loss of the Hitomi mission. The timing performance of the Hitomi instruments was confirmed to meet the timing requirement and about 1,000 and 100 GRPs were simultaneously observed at the main and inter-pulse phases, respectively, and we found no apparent correlation between the giant radio pulses and the X-ray emission in either the main or inter-pulse phases. All variations are within the 2 sigma fluctuations of the X-ray fluxes at the pulse peaks, and the 3 sigma upper limits of variations of main- or inter-pulse GRPs are 22% or 80% of the peak flux in a 0.20 phase width, respectively, in the 2 - 300 keV band. The values become 25% or 110% for main or inter-pulse GRPs, respectively, when the phase width is restricted into the 0.03 phase. Among the upper limits from the Hitomi satellite, those in the 4.5-10 keV and the 70-300 keV are obtained for the first time, and those in other bands are consistent with previous reports. Numerically, the upper limits of main- and inter-pulse GRPs in the 0.20 phase width are about (2.4 and 9.3) ×10-11 erg cm-2, respectively. No significant variability in pulse profiles implies that the GRPs originated from a local place within the magnetosphere and the number of photon-emitting particles temporally increases. However, the results do not statistically rule out variations correlated with the GRPs, because the possible X-ray enhancement may appear due to a > 0.02% brightening of the pulse-peak flux under such conditions.

Resolution of a left ventricular thrombus by the thrombolytic action of dabigatran.

A 77-year-old man was referred to our cardiovascular department for detailed examination after abnormal electrocardiography findings were obtained during a preoperative cataract surgery workup. Ultrasound echocardiography (UCG) and computed tomography (CT) revealed evidence of previous myocardial infarction with anteroseptal akinesis and a left ventricular (LV) thrombus (14 × 12 mm). Dabigatran (220 mg/day) was prescribed as an outpatient treatment, and the disappearance of the LV thrombus was confirmed by UCG and CT 27 days after dabigatran initiation. No thromboembolism occurred between treatment initiation and thrombus resolution. Our results indicate that dabigatran has thrombolytic action on an acute pre-existing intracardiac thrombus.

Characterization of bipolar electrograms during sinus rhythm for complex fractionated atrial electrograms recorded in patients with paroxysmal and persistent atrial fibrillation.

AIMS: Complex fractionated atrial electrogram (CFAE) has been reported to relate to maintain atrial fibrillation (AF). The aims of this study were to investigate the relationship between CFAE and background conditions during sinus rhythm (SR). METHODS AND RESULTS: Electroanatomical mapping using an EnSite Array was performed in 20 patients (paroxysmal AF:persistent AF = 16:4) who underwent pulmonary vein antrum isolation (PVAI). Contact bipolar electrograms were recorded before PVAI, during SR, and subsequently during induced AF. Peak-to-peak voltages and morphologies of the electrograms during SR were compared between sites with and without CFAE during AF. Among 1947 points obtained during SR, 974 (50%) were included in CFAE sites and 973 (50%) in non-CFAE sites. Electrogram amplitude during SR was higher at the CFAE sites than at the non-CFAE sites (2.4 +/- 1.7 vs. 1.9 +/- 1.9 mV; P < 0.0001), whereas fractionated or double electrograms were found in a similar range between the two areas (2 vs. 3%; P = 0.21). When analysed further in terms of AF termination by PVAI followed by confirmation of non-inducibility, the voltage of electrograms at the CFAE sites was lower (2.1 +/- 1.7 vs. 2.6 +/- 1.8 mV; P = 0.0001) and the morphology was more complex in patients without AF termination compared with those with AF termination. CONCLUSION: Our results suggest that in paroxysmal and persistent AF with minimally damaged LA, the CFAE sites in patients with AF termination by PVAI alone represent healthy atrial tissue with rapid electrical activity in response to an AF driver located in the pulmonary vein. However, in patients without AF termination, they represent more damaged tissue responsible for maintaining AF.

Radiofrequency catheter ablation of ventricular tachyarrhythmia under navigation using EnSite array.

BACKGROUND: EnSite array (EA) provides virtual activation of ventricular tachycardia (VT) and premature ventricular contraction (PVC) on a beat-to-beat basis. METHODS AND RESULTS: Fifty-five consecutive patients (age 52+/-16 years) with 79 VTs/PVCs undergoing EA-guided radiofrequency catheter ablation (RFA) were studied, of whom 7 patients had organic heart diseases. A virtual activation map showed that 66 VTs/PVCs originated from the right ventricle (RV), including the RV outflow tract in 57, lateral wall of RV in 4, His bundle region in 3 and tricuspid annulus in 2. Ten VTs/PVCs originated from the left ventricle (LV), including the LV endocardium in 7 and aortic sinus cusp in 3. The origins of 3 PVCs, one each in 3 patients, were not identified. Six of 38 VTs were sustained and the remaining 32 VTs were non-sustained. RFA eliminated all but 3 focal PVCs, and all macroreentrant VTs at a critical conducting pathway, which was identified by the combined use of contact voltage and virtual activation maps. There were 11+/-9 applications, and the radiofrequency energy and fluoroscopy time were 11,354+/-13,360 J and 30+/-21 min, respectively. All patients with acute success were free of any symptoms during a follow up of 21+/-11 months. CONCLUSIONS: EA-guided RFA is safe and effective for VT/PVC, irrespective of its origin, mechanism, sustainability, hemodynamic condition, and underlying heart disease.

Bipolar electrogram amplitudes in the left atrium are related to local conduction velocity in patients with atrial fibrillation.

AIMS: It is unclear how the amplitude of bipolar electrogram relates to the local conduction velocity (CV) in patients with atrial fibrillation (AF). For 50 AF patients (paroxysmal/persistent AF: 40/10 patients), contact bipolar voltage maps of the left atrium (LA) were constructed during sinus rhythm using EnSite version 6.0J in a point-by-point recording fashion. Patients were divided into Groups A (n = 16), B (n = 19), and C (n = 15) according to the level of the lowest electrogram amplitudes: <0.5, 0.5-0.75, and 0.75-1.0 mV, respectively. Low-voltage zone (LVZ) was defined separately for these groups as a bipolar electrogram amplitude of <0.5, 0.5-0.75, and 0.75-1.0 mV, respectively. The local CV through the LVZ and non-LVZ was calculated along the direction of local activation within each zone for all groups. METHODS AND RESULTS: Low-voltage zone was consistently found at the septal, anterior, and posterior LA in all groups. In Group A, CV through the LVZ was significantly slower compared with the non-LVZ (0.8 +/- 0.5 vs. 1.4 +/- 0.6 m/s, P = 0.004), but those through the LVZ and non-LVZ were similar in Group B (1.2 +/- 0.5 vs. 1.3 +/- 0.5 m/s, P = 0.07) and Group C (1.5 +/- 0.5 vs. 1.4 +/- 0.6 m/s, P = 0.79). The percentage of points showing fractionated or double potentials in the LVZ was significantly more in Group A (76/293 points, 26%) than in Group B (11/185 points, 6%), and Group C (7/135 points, 5%) (P < 0.0001 and P < 0.0001, respectively). CONCLUSION: There was a significant slowing of local conduction in the LVZ defined as <0.5 mV and was frequently associated with fractionated or double potentials in patients with AF.

Atrial fibrillation ablation with esophageal cooling with a cooled water-irrigated intraesophageal balloon: a pilot study.

INTRODUCTION: A left atrioesophageal fistula is an uncommon but devastating complication that may occur during atrial fibrillation (AF) ablation, and may be due to thermal injury occurring during the radiofrequency (RF) ablation. We examined the feasibility of an esophageal cooling (ECO) method using a cooled water-irrigated intraesophageal balloon (IB). METHODS AND RESULTS: Eight patients with drug-refractory AF underwent RF catheter ablation to encircle the ipsilateral pulmonary veins. During the RF ablation at the posterior left atrium, the esophageal lumen was cooled using a 9-Fr. IB catheter with a balloon length of 40 mm and diameter of 10 mm, in which cooled water, with a water temperature of 4.5 +/- 3.1 degrees C, was irrigated while the luminal esophageal temperature (LET) was measured with an intraesophageal probe placed at a site close to the tip of the ablation catheter. In the control, the LET increased from 36.4 +/- 0.8 degrees C to 40.5 +/- 1.7 degrees C within 26.1 +/- 8.2 seconds during 3.9 +/- 1.2 RF energy applications, whereas with the ECO the LET decreased to 30.2 +/- 2.9 degrees C at baseline (P<0.01 vs control), and increased only to 33.5 +/- 2.9 degrees C (P<0.01 vs control) at most, within 30 seconds during 3.9 +/- 1.2 RF energy applications. All pulmonary veins were successfully isolated in all patients without any complications. During a follow-up period of 3.1 +/- 1.2 months, no esophageal injuries were observed and all but one patient have been free from any symptoms. CONCLUSIONS: Use of an IB successfully lowers LET. This might have the potential of preventing esophageal injury, although further study is required.

Blackout during meals: A case report of swallow syncope due to sinus arrest.

A 79-year-old male, with a history of percutaneous coronary intervention (PCI), was referred to our cardiovascular department for a detailed examination of blackout caused by sinus arrest only during meals. Ultrasound echocardiography showed normal cardiac contraction with no asynergy, irrespective of the remaining stenotic coronary lesion. An electrophysiological study revealed deteriorated atrioventricular nodal conduction at a Wenckebach point of 70 beats per minute. However, sinus node function was normal as demonstrated by a sinus node recovery time of 1369 ms. Coronary angiography showed triple-vessel disease including the remaining stenotic coronary lesion, and a PCI was performed on the right coronary artery. Nevertheless, sinus arrest during meals was unchanged. Swallow syncope was partially improved by dietary modification; however, pacemaker implantation (PMI) was performed eventually, and the patient became asymptomatic after PMI. .

Ventricular pacing inhibition by oversensing due to diaphragmatic myopotential during deep inspiration.

An 80-year-old man, who had dilated cardiomyopathy with right ventricular (RV) dilatation, underwent implantable cardioverter defibrillator (ICD) implantation for advanced atrioventricular block and primary prevention of sudden cardiac death. Tined and screw-in leads were placed on the right atrial appendage and RV apex, respectively. Ventricular pacing inhibition was detected after surgery due to oversensing by diaphragmatic myopotential occurring only during deep inspiration. We performed re-surgery and switched the screw-in lead for a tined lead. The diaphragmatic myopotential decreased, thereby improving oversensing by diaphragmatic myopotential and ventricular pacing inhibition. It might be beneficial to use a tined lead when placing the ventricular lead at the RV apex for implantation of a pacemaker or ICD if oversensing of diaphragmatic myopotential is observed using a screw-in lead. .

Real-time 3-dimensional imaging of the esophagus and left atrium with a noncontact mapping system.

BACKGROUND: Recognizing the relative location of the esophagus to the left atrial posterior wall (LAPW) is required to avoid esophageal injury during atrial fibrillation ablation. METHODS AND RESULTS: The 24 patients undergoing circumferential pulmonary vein isolation (CPVI) each had the geometry of their left atrium (LA) and esophagus constructed by a noncontact mapping system with EnSite version 6.0J. The esophageal course relative to the LAPW was found to be to the left in 12, middle in 8, right in 2, and obliquely left-to-right in 2 patients, and in 13 patients (54%) it was located on or near either the left or right CPVI line. The mean distance between the esophagus and LAPW was shorter at the bottom line of the LAPW connecting both inferior pulmonary veins (3 +/- 3 mm) than at the LA roof line connecting both superior pulmonary veins (6 +/- 6 mm, P<0.01). CONCLUSIONS: The location of the esophagus relative to the LAPW varies with the patient, but a close location to either CPVI line was found in approximately 50% and a close location between the esophagus and LAPW was found in the inferior and middle locations in most patients.

Catheter ablation of premature ventricular contractions originating from the His bundle region.

We describe a 35-year-old man with idiopathic frequent premature ventricular contractions (PVCs) originating from the His-bundle region, where a low frequency ventricular potential was recorded in the bipolar recording and QR pattern in the unipolar recording. Electro-anatomical mapping revealed a confined low voltage zone (<1.2 mV) in the His-bundle region, and the activation spread out radially to the entire right ventricle. The PVCs were successfully abolished without any atrioventricular block by a step-wise incremental radiofrequency energy application to the His-bundle region. The patient has remained free from PVCs or any symptoms without medication during a 23 month follow-up period.