A combination of programmed parameters utilizing higher detection rate, longer detection intervals, empiric ATP, and optimized SVT discriminators reduced ICD therapies without increasing arrhythmic syncope and was associated with reduction in all-cause mortality among ICD patients.

Claims data suggest that TVP complications are more common than previously reported, affecting nearly 1 in 6 patients by 3 years and contributing to considerable incremental U.S. health care cost.

Previous studies of reentrant arrhythmias in the heart have been performed in computer models and tissue experiments. We hypothesized that confluent monolayers of cardiac cells can provide a simple, controlled, and reproducible experimental model of reentry. Neonatal rat ventricular cells were cultured on 22-mm-diameter coverslips and stained with the voltage-sensitive dye RH-237. Recordings of transmembrane potentials were obtained from 61 sites with the use of a contact fluorescence imaging system. An electrical field stimulus, followed by a point stimulus, induced 39 episodes of sustained reentry and 21 episodes of nonsustained reentry. Sustained reentry consisted of single-loop (n ϭ 18 monolayers) or figure-of-eight (n ϭ 4) patterns. The cycle length, action potential duration at 80% repolarization, and conduction velocity were (in means Ϯ SE) 358 Ϯ 33 ms, 118 Ϯ 12 ms, and 12.9 Ϯ 1.0 cm/s for single loop and 311 Ϯ 78 ms, 137 Ϯ 18 ms, and 7.8 Ϯ 1.3 cm/s for figure-of-eight, respectively. Electrical termination by 6-to 13-V/cm field pulses or 15-to 20-V point stimuli was successful in 60% of the attempts. In summary, highly stable reentry can be induced, sustained for extensive periods of time, and electrically terminated in monolayers of cultured neonatal rat cardiac myocytes. arrhythmia; cardiac electrophysiology; voltage-sensitive dye; optical mapping UNIDIRECTIONAL CONDUCTION block and formation of wave breaks during propagation in heart muscle can result in self-sustained propagation of electrical and mechanical activity, in which an activation wave front can reenter the same area after propagating around a fixed anatomic or functional obstacle (9). Functional reentry is generally accepted to be the major mechanism underlying many monomorphic and polymorphic tachycardias, which can evolve into irregular electrical activity such as atrial or ventricular flutter and fibrillation. Although the initiation and cardioversion of functional reentry have been subjects of numerous theoretical and experimental studies (2-4, 12, 23, 24, 27, 31, 33), there still exists a need for the development of new model systems that can aid in the understanding and treatment of these life-threatening arrhythmias.The use of cultured monolayers of cardiac cells as a simplified model for the study of functional cardiac electrophysiology offers many advantages, including: 1) control of the cell microenvironment, 2) elimination of excitation-contraction decouplers that are used for optical mapping but may alter the electrophysiological properties of the cells (17, 18), 3) removal of large scale tissue heterogeneities such as blood vessels, connective tissue, or rotational anisotropy, and 4) the certainty that the electrophysiological signals are produced from a known layer of cells, thus enabling a one-to-one correspondence with two-dimensional computer simulations and nonlinear dynamic theory. Currently, there is a gap between the computer simulations, which assume an ideal homogeneous excitable media, and tissue experiments, where ...

Background-Although right ventricular pacing can contribute to cardiomyopathy, the impact of complete atrioventricular block (cAVB) on heart failure (HF) development in pacemaker patients has not been well characterized. We evaluated the incidence and time course for developing HF after pacemaker implantation for cAVB. Methods and Results-A MarketScan database identified patients undergoing dual-chamber pacemaker implantation from 2008 to 2014. Patients with cAVB were identified by an atrioventricular node ablation or diagnosis of third-degree AVB.Patients with ≥1 year of continuous MarketScan enrollment before and after implant and without a previous diagnosis of HF were dichotomized into those with cAVB and without AVB. The primary end point was new HF assessed over acute (0-6 months) and chronic (6 months to 4 years) phases post-pacemaker implantation. The cohort included 6994 cAVB patients and 14 208 patients without AVB, followed for 2.35 years (interquartile range, 1.62-3.39 years). After adjustment for baseline covariates, patients with cAVB experienced an increased risk of new-onset HF in the acute phase (hazard ratio, 1.62; 95% confidence interval, 1.48-1.79; P<0.001). Although the risk of HF remained elevated among those with cAVB in the chronic phase, the effect was attenuated (hazard ratio, 1.16; 95% confidence interval, 1.08-1.25; P<0.001). After pacemaker implantation, younger patients (≤55 years of age) and those with an antecedent history of atrial fibrillation experienced the highest risk of HF associated with cAVB. Conclusions-Patients with a diagnosis of cAVB, and thus presumed to have a higher burden of right ventricular pacing, experienced an increased risk of new-onset HF after pacemaker implantation compared with those without AVB. Better tools are needed to identify patients at high risk of developing HF in the setting of right ventricular pacing and to determine whether these patients benefit from upfront biventricular pacing. Study PopulationPatients were selected for study inclusion if they were implanted with a de novo dual-chamber pacemaker (Current Procedural Terminology code 33208 and Healthcare Common Procedure Coding System codes C1785 and C2619) from any manufacturer between April 1, 2008, and March 31, 2014. Patients with a left ventricular lead placed (Current Procedural Terminology codes 33224 or 33225) at the time of pacemaker implantation were excluded. De novo implants were identified as pacemaker patients without a previous device implantation and without a remote or in-office pacemaker follow-up visit in the 1 year before implantation. An enrollment indicator confirmed active inclusion in the MarketScan databases for each patient per month. Patients were required to have at least 1 year of continuous enrollment in the MarketScan database before and after pacemaker implantation and to be ≥18 and ≤100 years of age at the time of pacemaker implantation.To evaluate the impact of atrioventricular block (AVB) on the development of HF after pacemaker implantation, patients wi...

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BACKGROUND | Glycemic control is suboptimal in many individuals with type 2 diabetes. Although use of flash continuous glucose monitoring (CGM) has demonstrated A1C reductions in patients with type 2 diabetes treated with a multiple daily injection or insulin pump therapy regimen, the glycemic benefit of this technology in patients with type 2 diabetes using nonintensive treatment regimens has not been well studied.METHODS | This retrospective, observational study used the IBM Explorys database to assess changes in A1C after flash CGM prescription in a large population with suboptimally controlled type 2 diabetes treated with nonintensive therapy. Inclusion criteria were diagnosis of type 2 diabetes, age ,65 years, treatment with basal insulin or noninsulin therapy, naive to any CGM, baseline A1C $8%, and a prescription for the FreeStyle Libre flash CGM system during the period between October 2017 and February 2020. Patients served as their own control subject.RESULTS | A total of 1,034 adults with type 2 diabetes (mean age 51.6 6 9.2 years, 50.9% male, baseline A1C 10.1 6 1.7%) were assessed. More patients received noninsulin treatments (n 5 728) than basal insulin therapy (n 5 306). We observed a significant reduction in A1C within the full cohort: from 10.1 6 1.7 to 8.6 6 1.8%; D 21.5 6 2.2% (P ,0.001). The largest reductions were seen in patients with a baseline A1C $12.0% (n 5 181, A1C reduction 23.7%, P ,0.001). Significant reductions were seen in both treatment groups (basal insulin 21.1%, noninsulin 21.6%, both P ,0.001).CONCLUSION | Prescription of the flash CGM system was associated with significant reductions in A1C in patients with type 2 diabetes treated with basal insulin or noninsulin therapy. These findings provide evidence for expanding access to flash CGM within the broader population of people with type 2 diabetes.

In this observational study of CRT-D devices, use of a quadripolar, compared to a bipolar LV lead, was associated with a reduction in LV lead deactivation, replacement, and mortality.

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