Biventricular Pacing in Heart Failure: back to Basic in the pathophysiology of left bundle branch block to reduce the number of nonresponders

Cardiac resynchronization therapy is a novel nonpharmacologic approach to treating patients who have advanced heart failure with left bundle branch block (LBBB). Such a therapy is based on the original theory that synchronous biventricular pacing is able to reduce the interventricular delay caused by LBBB in patients with heart failure. Although there is convincing evidence that biventricular pacing increases the left ventricular ejection fraction, decreases mitral regurgitation, and improves symptoms caused by heart failure, the percentage of nonresponders to such therapy has been described as high as about one third of patients with heart failure having LBBB. Factors responsible for this relatively high prevalence are reviewed, the most important of them probably being left intraventricular dyssynchrony, which can persist after biventricular pacing, notwithstanding right and left interventricular resynchronization. Such a dyssynchrony, as evaluated by tissue Doppler imaging, may be because of the discordance between the site of the left ventricular pacing and the site of the left ventricular delay. Therefore, to characterize the pathophysiologic pattern of LBBB, the investigators suggest an assessment of the electromechanical dysfunction with a noninvasive reliable technique, such as tissue Doppler imaging, which can be repeated after biventricular pacing

Doppler myocardial imaging to evaluate the effectivenes of pacing sites in patients receving biventricular pacing

OBJECTIVES: The goal of this study was to compare the efficacy of biventricular pacing (BIV) at the most delayed wall of the left ventricle (LV) and at other LV walls. BACKGROUND: Biventricular pacing could provide additional benefit when it is applied at the most delayed site. METHODS: In 31 patients with advanced nonischemic heart failure, the activation delay was defined, in blind before BIV, by regional noninvasive Tissue Doppler Imaging as the time interval between the end of the A-wave (C point) and the beginning of the E-wave (O point) from the basal level of each wall. The left pacing site was considered concordant with the most delayed site when the lead was inserted at the wall with the greatest regional interval between C and O points (CO(R)). After BIV, patients were divided into group A (13/31) (i.e., paced at the most delayed site) and group B (18/31) (i.e., paced at any other site). RESULTS: After BIV, in all patients LV end-diastolic (LVEDV) and end-systolic (LVESV) volumes decreased (p = 0.025 and 0.001), LV ejection fraction (LVEF) increased (p = 0.002), QRS narrowed (p = 0.000), New York Heart Association class decreased (p = 0.006), 6-min walked distance (WD) increased (p = 0.046), the interval between closure and opening of mitral valve (CO) and isovolumic contraction time (ICT) decreased (p = 0.001 and 0.000), diastolic time (EA) and Q-P(2) interval increased (p = 0.003 and 0.000), while Q-A(2) interval and mean performance index (MPI) did not change. Group A showed greater improvement over group B in LVESV (p = 0.04), LVEF (p = 0.04), bicycle stress testing work (p = 0.03) and time (p = 0.08) capacity, CO (p = 0.04) and ICT (p = 0.02). CONCLUSIONS: After BIV, LV performance improved significantly in all patients; however, the greatest improvement was found in patients paced at the most delayed site

Full Micromagnetic Numerical Simulations of Thermal Fluctuations

Thermal fluctuations for fine ferromagnetic particles are studied with the full micromagnetic analysis based on numerical integration of the spatially discretized Langevin-Landau-Lifshitz equation. These results can be used as a basis for the formulation of a standard problem to test the implementation of thermal fluctuations in numerical micromagnetic codes. To this end an example of micromagnetic analysis of thermal fluctuations in an ellipsoidal magnetic nanoparticle is presented

The LuGRE project: a scientific opportunity to study GNSS signals at the Moon

The Lunar GNSS Receiver Experiment (LuGRE) is a joint NASA-Italian Space Agency (ASI) payload on the Firefly Blue Ghost Mission 1 with the goal to demonstrate GNSS-based positioning, navigation, and timing at the Moon. When launched, LuGRE will collect GPS and Galileo measurements in transit between Earth and the Moon, in lunar orbit, and on the lunar surface, and will conduct onboard and ground-based navigation experiments using the collected data. These investigations will be based on the observation of the data collected by a custom development performed by the company Qascom, based on the Qascom QN400-Space GNSS receiver. The receiver is able to provide, PVT solutions, the GNSS raw observables obtained by the real time operation, as well as snapshots of IF digital samples collected by the RF front-end at frequencies L1/E1 and L5/E5. These data will be the input for the different science investigations, that require then the development of proper analysis tools that will be the core of the ground segment during the mission. The current work done by the science team of NASA and ASI, which is supported by a research team at Politecnico di Torino, is planning the data acquisitions during the time windows dedicated to the LuGRE payload in the checkout, transit and surface mission phases

Deweyan tools for inquiry and the epistemological context of critical pedagogy

This article develops the notion of resistance as articulated in the literature of critical pedagogy as being both culturally sponsored and cognitively manifested. To do so, the authors draw upon John Dewey\u27s conception of tools for inquiry. Dewey provides a way to conceptualize student resistance not as a form of willful disputation, but instead as a function of socialization into cultural models of thought that actively truncate inquiry. In other words, resistance can be construed as the cognitive and emotive dimensions of the ongoing failure of institutions to provide ideas that help individuals both recognize social problems and imagine possible solutions. Focusing on Dewey\u27s epistemological framework, specifically tools for inquiry, provides a way to grasp this problem. It also affords some innovative solutions; for instance, it helps conceive of possible links between the regular curriculum and the study of specific social justice issues, a relationship that is often under-examined. The aims of critical pedagogy depend upon students developing dexterity with the conceptual tools they use to make meaning of the evidence they confront; these are background skills that the regular curriculum can be made to serve even outside social justice-focused curricula. Furthermore, the article concludes that because such inquiry involves the exploration and potential revision of students\u27 world-ordering beliefs, developing flexibility in how one thinks may be better achieved within academic subjects and topics that are not so intimately connected to students\u27 current social lives, especially where students may be directly implicated

Magnetic resonance imaging of abnormal ventricular septal motion in heart diseases: a pictorial review

The purpose of this article is to illustrate the usefulness of MR imaging in the clinical evaluation of congenital and acquired cardiac diseases characterised by ventricular septal wall motion abnormality. Recognition of the features of abnormal ventricular septal motion in MR images is important to evaluate the haemodynamic status in patients with congenital and acquired heart diseases in routine clinical practice

A modified echocardiographic protocol with intrinsic plausibility control to determine intraventricular asynchrony based on TDI and TSI

<p>Abstract</p> <p>Background</p> <p>Established methods to determine asynchrony suffer from high intra- and interobserver variability and failed to improve patient selection for cardiac resynchronization therapy (CRT). Thus, there is a need for easy and robust approaches to reliably assess cardiac asynchrony.</p> <p>Methods and Results</p> <p>We performed echocardiography in 100 healthy subjects and 33 patients with left bundle branch block (LBBB). To detect intraventricular asynchrony, we combined two established methods, i.e., tissue synchronization imaging (TSI) and tissue Doppler imaging (TDI). The time intervals from the onset of aortic valve opening (AVO) to the peak systolic velocity (S') were measured separately in six basal segments in the apical four-, two-, and three-chamber view. Color-coded TSI served as an intrinsic plausibility control and helped to identify the correct S' measuring point in the TDI curves. Next, we identified the segment with the shortest AVO-S' interval. Since this segment most likely represents vital and intact myocardium it served as a reference for other segments. Segments were considered asynchronous when the delay between the segment in question and the reference segment was above the upper limit of normal delays derived from the control population. Intra- and interobserver variability were 7.0% and 7.7%, respectively.</p> <p>Conclusion</p> <p>Our results suggest that combination of TDI and TSI with intrinsic plausibility control improves intra- and interobserver variability and allows easy and reliable assessment of cardiac asynchrony.</p

The variable functional effects of the pacing site in normal and scarred ventricles

The pacing site has been shown to influence functional improvement with cardiac resynchronization therapy. We evaluated the effects of the pacing site on left ventricular (LV) function in an animal model. Equilibrium radionuclide angiography was acquired in sinus rhythm (NSR) and with ventricular pacing, from three pacing sites in seven normal and eight infarcted dogs. QRS duration, electrical activation pattern, wall motion, LV ejection fraction (EF), synchrony of ventricular contraction, and mean arterial pressure (MAP), were related to the pacing site and infarct size, during each of 120 episodes. Little changed during pacing in normals. In infarcted dogs, LV wall motion, and synchrony worsened, LVEF and MAP often fell. These changes related to altered activation patterns which were influenced by the pacing site but were not related to infarct size. Hemodynamic and functional LV changes after infarction were found to vary with the pacing site and associated conduction and synchrony

Optimal left ventricular lead position assessed with phase analysis on gated myocardial perfusion SPECT

The aim of the current study was to evaluate the relationship between the site of latest mechanical activation as assessed with gated myocardial perfusion SPECT (GMPS), left ventricular (LV) lead position and response to cardiac resynchronization therapy (CRT). The patient population consisted of consecutive patients with advanced heart failure in whom CRT was currently indicated. Before implantation, 2-D echocardiography and GMPS were performed. The echocardiography was performed to assess LV end-systolic volume (LVESV), LV end-diastolic volume (LVEDV) and LV ejection fraction (LVEF). The site of latest mechanical activation was assessed by phase analysis of GMPS studies and related to LV lead position on fluoroscopy. Echocardiography was repeated after 6 months of CRT. CRT response was defined as a decrease of a parts per thousand yen15% in LVESV. Enrolled in the study were 90 patients (72% men, 67 +/- 10 years) with advanced heart failure. In 52 patients (58%), the LV lead was positioned at the site of latest mechanical activation (concordant), and in 38 patients (42%) the LV lead was positioned outside the site of latest mechanical activation (discordant). CRT response was significantly more often documented in patients with a concordant LV lead position than in patients with a discordant LV lead position (79% vs. 26%, p < 0.01). After 6 months, patients with a concordant LV lead position showed significant improvement in LVEF, LVESV and LVEDV (p < 0.05), whereas patients with a discordant LV lead position showed no significant improvement in these variables. Patients with a concordant LV lead position showed significant improvement in LV volumes and LV systolic function, whereas patients with a discordant LV lead position showed no significant improvements.Cardiovascular Aspects of Radiolog