Ablation of atrial fibrillation with the Epicor system: a prospective observational trial to evaluate safety and efficacy and predictors of success

<p>Abstract</p> <p>Background</p> <p>High intensity focused ultrasound (HIFU) energy has evolved as a new surgical tool to treat atrial fibrillation (AF). We evaluated safety and efficacy of AF ablation with HIFU and analyzed predictors of success in a prospective clinical study.</p> <p>Methods</p> <p>From January 2007 to June 2008, 110 patients with AF and concomitant open heart surgery were enrolled into the study. Main underlying heart diseases were aortic valve disease (50%), ischemic heart disease (48%), and mitral valve disease (18%). AF was paroxysmal in 29%, persistent in 31%, and long standing persistent in 40% of patients, lasting for 1 to 240 months (mean 24 months). Mean left atrial diameter was 50 ± 7 mm. Each patient underwent left atrial ablation with the Epicor system prior to open heart surgery. After surgery, the patients were treated with amiodarone and coumadin for 6 months. Follow-up studies including resting ECG, 24 h Holter ECG, and echocardiography were obtained at 6 and 12 months.</p> <p>Results</p> <p>All patients had successful application of the system on the beating heart prior to initiation of extracorporeal circulation. On average, 11 ± 1 ultrasound transducer elements were used to create the box lesion. The hand-held probe for additional linear lesions was employed in 83 cases. No device-related deaths occurred. Postoperative pacemaker insertion was necessary in 4 patients. At 6 months, 62% of patients presented with sinus rhythm. No significant changes were noted at 12 months. Type of AF and a left atrial diameter > 50 mm were predictors for failure of AF ablation.</p> <p>Conclusion</p> <p>AF ablation with the Epicor system as a concomitant procedure during open heart surgery is safe and acceptably effective. Our overall conversion rate was lower than in previously published reports, which may be related to the lower proportion of isolated mitral valve disease in our study population. Left atrial size may be useful to determine patients who are most likely to benefit from the procedure.</p

Abnormal P‐wave terminal force in lead V 1 is a marker for atrial electrical dysfunction but not structural remodelling

Aims There is a lack of diagnostic and therapeutic options for patients with atrial cardiomyopathy and paroxysmal atrial fibrillation. Interestingly, an abnormal P-wave terminal force in electrocardiogram lead V1 (PTFV1) has been associated with atrial cardiomyopathy, but this association is poorly understood. We investigated PTFV1 as a marker for functional, electrical, and structural atrial remodelling. Methods and results Fifty-six patients with acute myocardial infarction and 13 kidney donors as control cohort prospectively underwent cardiac magnetic resonance imaging to evaluate the association between PTFV1 and functional remodelling (atrial strain). To further investigate underlying pathomechanisms, right atrial appendage biopsies were collected from 32 patients undergoing elective coronary artery bypass grafting. PTFV1 was assessed as the product of negative P-wave amplitude and duration in lead V1 and defined as abnormal if ≥4000 ms*μV. Activity of cardiac Ca/calmodulin-dependent protein kinase II (CaMKII) was determined by a specific HDAC4 pull-down assay as a surrogate for electrical remodelling. Atrial fibrosis was quantified using Masson's trichrome staining as a measure for structural remodelling. Multivariate regression analyses were performed to account for potential confounders. A total of 16/56 (29%) of patients with acute myocardial infarction, 3/13 (23%) of kidney donors, and 15/32 (47%) of patients undergoing coronary artery bypass grafting showed an abnormal PTFV1. In patients with acute myocardial infarction, left atrial (LA) strain was significantly reduced in the subgroup with an abnormal PTFV1 (LA reservoir strain: 32.28 ± 12.86% vs. 22.75 ± 13.94%, P = 0.018; LA conduit strain: 18.87 ± 10.34% vs. 10.17 ± 8.26%, P = 0.004). Abnormal PTFV1 showed a negative correlation with LA conduit strain independent from clinical covariates (coefficient B: −7.336, 95% confidence interval −13.577 to −1.095, P = 0.022). CaMKII activity was significantly increased from (normalized to CaMKII expression) 0.87 ± 0.17 to 1.46 ± 0.15 in patients with an abnormal PTFV1 (P = 0.047). This increase in patients with an abnormal PTFV1 was independent from clinical covariates (coefficient B: 0.542, 95% confidence interval 0.057 to 1.027, P = 0.031). Atrial fibrosis was significantly lower with 12.32 ± 1.63% in patients with an abnormal PTFV1 (vs. 20.50 ± 2.09%, P = 0.006), suggesting PTFV1 to be a marker for electrical but not structural remodelling. Conclusions Abnormal PTFV1 is an independent predictor for impaired atrial function and for electrical but not for structural remodelling. PTFV1 may be a promising tool to evaluate patients for atrial cardiomyopathy and for risk of atrial fibrillation

Using dissolved H₂O in rhyolitic glasses to estimate palaeo-ice thickness during a subglacial eruption at Bláhnúkur(Torfajökull, Iceland)

The last decade has seen the refinement of a technique for reconstructing palaeo-ice thicknesses based on using the retained H2O and CO2 content in glassy eruptive deposits to infer quenching pressures and therefore ice thicknesses. The method is here applied to Bláhnúkur, a subglacially erupted rhyolitic edifice in Iceland. A decrease in water content from ~0.7 wt.% at the base to ~0.3 wt.% at the top of the edifice suggests that the ice was 400 m thick at the time of the eruption. As Bláhnúkur rises 350 m above the surrounding terrain, this implies that the eruption occurred entirely within ice, which corroborates evidence obtained from earlier lithofacies studies. This paper presents the largest data set (40 samples) so far obtained for the retained volatile contents of deposits from a subglacial eruption. An important consequence is that it enables subtle but significant variations in water content to become evident. In particular, there are anomalous samples which are either water-rich (up to 1 wt.%) or water-poor (~0.2 wt.%), with the former being interpreted as forming intrusively within hyaloclastite and the latter representing batches of magma that were volatile-poor prior to eruption. The large data set also provides further insights into the strengths and weaknesses of using volatiles to infer palaeo-ice thicknesses and highlights many of the uncertainties involved. By using examples from Bláhnúkur, the quantitative use of this technique is evaluated. However, the relative pressure conditions which have shed light on Bláhnúkur’s eruption mechanisms and syn-eruptive glacier response show that, despite uncertainties in absolute values, the volatile approach can provide useful insight into the mechanisms of subglacial rhyolitic eruptions, which have never been observed

Lithological influences on contemporary and long-term regolith weathering at the Luquillo Critical Zone Observatory

Lithologic differences give rise to the differential weatherability of the Earth’s surface and globally variable silicate weathering fluxes, which provide an important negative feedback on climate over geologic timescales. To isolate the influence of lithology on weathering rates and mechanisms, we compare two nearby catchments in the Luquillo Critical Zone Observatory in Puerto Rico, which have similar climate history, relief and vegetation, but differ in bedrock lithology. Regolith and pore water samples with depth were collected from two ridgetops and at three sites along a slope transect in the volcaniclastic Bisley catchment and compared to existing data from the granitic Río Icacos catchment. The depth variations of solid-state and pore water chemistry and quantitative mineralogy were used to calculate mass transfer (tau) and weathering solute profiles, which in turn were used to determine weathering mechanisms and to estimate weathering rates. Regolith formed on both lithologies is highly leached of most labile elements, although Mg and K are less depleted in the granitic than in the volcaniclastic profiles, reflecting residual biotite in the granitic regolith not present in the volcaniclastics. Profiles of both lithologies that terminate at bedrock corestones are less weathered at depth, near the rock-regolith interfaces. Mg fluxes in the volcaniclastics derive primarily from dissolution of chlorite near the rock-regolith interface and from dissolution of illite and secondary phases in the upper regolith, whereas in the granitic profile, Mg and K fluxes derive from biotite dissolution. Long-term mineral dissolution rates and weathering fluxes were determined by integrating mass losses over the thickness of solid-state weathering fronts, and are therefore averages over the timescale of regolith development. Resulting long-term dissolution rates for minerals in the volcaniclastic regolith include chlorite: 8.9 × 10‾¹⁴ mol m‾² s‾¹, illite: 2.1 × 10‾¹⁴ mol m‾² s‾¹ and kaolinite: 4.0 × 10‾¹⁴ mol m‾² s‾¹. Long-term weathering fluxes are several orders of magnitude lower in the granitic regolith than in the volcaniclastic, despite higher abundances of several elements in the granitic regolith. Contemporary weathering fluxes were determined from net (rain-corrected) solute profiles and thus represent rates over the residence time of water in the regolith. Contemporary weathering fluxes within the granitic regolith are similar to the long-term fluxes. In contrast, the long-term fluxes are faster than the contemporary fluxes in the volcaniclastic regolith. Contemporary fluxes in the granitic regolith are generally also slightly faster than in the volcaniclastic. The differences in weathering fluxes over space and time between these two watersheds indicate significant lithologic control of chemical weathering mechanisms and rates

Ice-confined construction of a large basaltic volcano—Austurfjöll massif, Askja, Iceland

Austurfjöll is the largest basaltic glaciovolcanic massif at Askja volcano (Central Iceland), and through detailed studies of its volcanological and geochemical characteristics, we provide a detailed account of the sequence and structure of the ice-confined construction of a large Icelandic basaltic volcano. In particular, Austurfjöll represents a geometry of vents, and resulting glaciovolcanic morphology, not previously documented in ice-confined basaltic volcanoes. Austurfjöll was constructed during two major phases of basaltic volcanism, via seven eruptive episodes through disperse fissure-dominated eruptions. The earliest episode involved a rare and poorly exposed example of subaerial activity, and this was succeeded by six episodes involving the eruption of ice-confined pillow lavas and numerous overlapping fissure eruptions of phreatomagmatic tephra. Evidence of local subaerial lavas and tephras indicates the local growth of eruptive centers above englacial lake levels, and subsequent flooding, but no prolonged subaerial activity. Localized ice-contact facies, paleowater levels, and diamictons indicate the position and thickness of the ice was variable during the construction of Austurfjöll, and eruptive activity likely occurred in multiple and variable level meltwater lakes during the last glacial period. Lithofacies evidence including gradational transitions from effusive to explosive deposits, superposition of fragmental facies above coherent facies, and drainage channels suggest that changes in eruptive style were driven largely by external factors such as drainage and the increasing elevation of the massif. This study emphasizes the unique character of Austurfjöll, being composed of large pillow lava sheets, numerous (> 40) overlapping glaciovolcanic tindars, and only localized emergent deposits, as a product of its prolonged ice-confined eruptive history, contrasts with previous descriptions of tuyas and tindars

Extracorporeal Life Support in cardiopulmonary resuscitation of non-postcardiotomy patients. Single center experience in 103 patients

Purpose: Extracorporeal membrane oxygenation has been successfully used to support patients with cardiac arrest failing to respond to conventional cardiopulmonary resuscitation Pre-implant factors being indicative for success are unknown up to now. The study describes single centre experience with special focus on differences between survivors and non-survivors. Method: Between 2002 and 2009, 103 patients were supported within the scope of CPR by means of ECMO. Besides primary diagnosis, duration and outcome, pH, lactate, MAP, ASAT, bilirubine, catecholamine dosage and oxygenation ratio before ECMO, after 2h, 1 day, 2 days, at explantation and 1 day post explantation were analyzed. Results: 103 patients (51.2±16 years), 35 women, 68 men were analyzed. Primary cardiac failure lead to CPR in 52%. Duration of support was 4.8±0.6 days. 29 (28.1%) of patients survived to hospital discharge. On ECMO support pH, lactate and mean arterial pressure improved significantly. Catecholamine dosage was significantly reduced after ECMO implantation. Demographic data and primary diagnosis revealed no significant influence on outcome. Although pH, lactate, mean arterial pressure and bilirubine were indicative with regard to outcome in the course of ECMO support, there was no predictive value before ECMO implantation. Conclusion: ECMO support during cardiopulmonary resuscitation reliably improves the circulatory and respiratory situation. Considering observed survival critical patient selection is mandatory. This turns out to be difficult since clinically relevant factors show only limited predictive value. Future research should focus on better defining a population that may be best of all suited for the use of ECMO support in CPR