Ventricular tachycardia induced by pacing algorithm designed to avoid atrial fibrillation.

A patient with a dual chamber pacemaker was admitted to the emergency room after out-of-hospital cardioversion for syncopal sustained monomorphic ventricular tachycardia. Device interrogation revealed an abnormally timed ventricular spike after a ventricular premature beat at the beginning of the event, caused by a pacemaker algorithm designed to avoid atrial fibrillation, non-competitive atrial pacing. Despite the absence of significant coronary lesions, in the setting of a vulnerable substrate - a hypokinetic and hyperechogenic region of ventricular myocardium - an upgrade to a dual-chamber implantable cardioverter-defibrillator was performed, and substrate ablation was planned.

Utility of Pacemaker With Sleep Apnea Monitor to Predict Left Ventricular Overload and Acute Decompensated Heart Failure.

Pacemakers with sleep apnea monitor (SAM) provide an easy tool to assess obstructive sleep apnea over long periods of time. The link between respiratory disturbances at night and the incidence of acute decompensated heart failure (ADHF) is not well established. We aimed at (1) determining the ability of SAM pacemakers to evaluate the extent of left ventricular overload and (2) assess the impact of respiratory disturbances at night on the occurrence of ADHF over 1-year of follow-up. We conducted a single-center prospective study. Consecutive patients with SAM pacemakers were comprehensively assessed. SAM automatically computes a respiratory disturbance index (RDI, apneas/hypopneas per hour - AH/h) in the previous night and the percentage of nights with RDI >20 AH/h in the previous 6 months. Thirty-seven patients were included (79.3 ± 11.2 years, 46% males). A high RDI in the previous night and a higher %nights with increased RDI were associated with increased NT-proBNP values (p = 0.008 and p = 0.013, respectively) and were the sole predictors of increased noninvasive pulmonary capillary wedge pressures (PCWP) in the morning of assessment (p = 0.031 and p = 0.044, respectively). Receiver operating characteristic curve analysis revealed an area under the curve of 0.804 (95% confidence interval 0.656 to 0.953, p = 0.002) for %nights with RDI >20 AH/h in the prediction of high PCWP. Patients with >12.5% of nights with RDI >20AH/h tended to have more ADHF during follow-up (log-rank p = 0.067). In conclusion, a high burden of apneas/hypopneas at night is associated with elevated NT-proBNP and PCWP values and an increased risk of ADHF over 1 year. These patients might benefit from early tailored clinical management.

Magnetically Hard Fe3Se4 Embedded in Bi2Se3 Topological Insulator Thin Films Grown by Molecular Beam Epitaxy.

We investigated the structural, magnetic, and electronic properties of Bi2Se3 epilayers containing Fe grown on GaAs(111) by molecular beam epitaxy. It is shown that, in the window of growth parameters leading to Bi2Se3 epilayers with optimized quality, Fe atom clustering leads to the formation of FexSey inclusions. These objects have platelet shape and are embedded within Bi2Se3. Monoclinic Fe3Se4 is identified as the main secondary phase through detailed structural measurements. Due to the presence of the hard ferrimagnetic Fe3Se4 inclusions, the system exhibits a very large coercive field at low temperature and room temperature magnetic ordering. Despite this composite structure and the proximity of a magnetic phase, the surface electronic structure of Bi2Se3 is preserved, as shown by the persistence of a gapless Dirac cone at Γ.