Quinapril treatment curtails decline of global longitudinal strain and mechanical function in hypertensive rats.

Background: Left ventricular (LV) global longitudinal strain (GLS) has been proposed as an early imaging biomarker of cardiac mechanical dysfunction.

Objective: To assess the impact of angiotensin-converting enzyme (ACE) inhibitor treatment of hypertensive heart disease on LV GLS and mechanical function.

Methods: The spontaneously hypertensive rat (SHR) model of hypertensive heart disease ( n  = 38) was studied.

Multimodal imaging shows fibrosis architecture and action potential dispersion are predictors of arrhythmic risk in spontaneous hypertensive rats.

Hypertensive heart disease (HHD) increases risk of ventricular tachycardia (VT) and ventricular fibrillation (VF). The roles of structural vs. electrophysiological remodelling and age vs.

Non-Contact Intracardiac Potential Mapping Using Mesh-Based and Meshless Inverse Solvers.

Atrial fibrillation (AF) is the most common cardiac dysrhythmia and percutaneous catheter ablation is widely used to treat it. Panoramic mapping with multi-electrode catheters has been used to identify ablation targets in persistent AF but is limited by poor contact and inadequate coverage of the left atrial cavity. In this paper, we investigate the accuracy with which atrial endocardial surface potentials can be reconstructed from electrograms recorded with non-contact catheters.

Myocardial mesostructure and mesofunction.

The complex and highly organized structural arrangement of some five billion cardiomyocytes directs the coordinated electrical activity and mechanical contraction of the human heart. The characteristic transmural change in cardiomyocyte orientation underlies base-to-apex shortening, circumferential shortening, and left ventricular torsion during contraction. Individual cardiomyocytes shorten ∼15% and increase in diameter ∼8%.

Intracardiac Inverse Potential Mapping Using the Method of Fundamental Solutions.

Atrial fibrillation (AF) is the most prevalent cardiac dysrhythmia and percutaneous catheter ablation is widely used to treat it. Panoramic mapping with multi-electrode catheters can identify ablation targets in persistent AF, but is limited by poor contact and inadequate coverage. To investigate the accuracy of inverse mapping of endocardial surface potentials from electrograms sampled with noncontact basket catheters.

A novel system for mapping regional electrical properties and characterizing arrhythmia in isolated intact rat atria.

Detailed global maps of atrial electrical activity are needed to understand mechanisms of atrial rhythm disturbance in small animal models of heart disease. To date, optical mapping systems have not provided enough spatial resolution across sufficiently extensive regions of intact atrial preparations to achieve this goal. The aim of this study was to develop an integrated platform for quantifying regional electrical properties and analyzing reentrant arrhythmia in a biatrial preparation.

High-resolution 3D imaging and topological mapping of the lymph node conduit system.

The conduit network is a hallmark of lymph node microanatomy, but lack of suitable imaging technology has prevented comprehensive investigation of its topology. We employed an extended-volume imaging system to capture the conduit network of an entire murine lymph node (comprising over 280,000 segments). The extensive 3D images provide a comprehensive overview of the regions supplied by conduits, including perivascular sleeves and distinctive "follicular reservoirs" within B cell follicles, surrounding follicular dendritic cells.

Impaired Baroreflex Function in an Ovine Model of Chronic Heart Failure Induced by Multiple Coronary Microembolizations.

Testing new therapies in heart failure (HF) requires a chronic stable model of HF in large animals. Microembolization of the coronary arteries has been used to model HF previously; however, neural control has not been previously explored in this model. Thus the aim of this study was to further characterize neural control in this model of HF.

Microstructurally Motivated Constitutive Modeling of Heart Failure Mechanics.

Heart failure (HF) is one of the leading causes of death worldwide. HF is associated with substantial microstructural remodeling, which is linked to changes in left ventricular geometry and impaired cardiac function. The role of myocardial remodeling in altering the mechanics of failing hearts remains unclear.

Cardiac intramural electrical mapping reveals focal delays but no conduction velocity slowing in the peri-infarct region.

Altered electrical behavior alongside healed myocardial infarcts (MIs) is associated with increased risk of sudden cardiac death. However, the multidimensional mechanisms are poorly understood and described. This study characterizes, for the first time, the intramural spread of electrical activation in the peri-infarct region of chronic reperfusion MIs.

Shift of leading pacemaker site during reflex vagal stimulation and altered electrical source-to-sink balance.

Key Points: Vagal reflexes slow heart rate and can change where the heartbeat originates within the sinoatrial node (SAN). The mechanisms responsible for this process - termed leading pacemaker (LP) shift - have not been investigated fully. We used optical mapping to measure the effects of baroreflex, chemoreflex and carbachol on pacemaker entrainment and electrical conduction across the SAN.

Reconstruction of coronary circulation networks: A review of methods.

Building anatomically accurate models of the coronary vascular system enables potentially deeper understandings of coronary circulation. To achieve this, (a) images at different levels of vascular network-arteries, arterioles, capillaries, venules, and veins-need to be obtained through suitable imaging modalities; and (b) from images, morphological and topological information needs to be extracted using image processing techniques. While there are several modalities that enable the imaging of large vessels, microcirculation imaging-capturing vessels having diameter lesser than 100 μm-has to date been typically confined to small regions of the heart.

How Accurate Is Inverse Electrocardiographic Mapping? A Systematic In Vivo Evaluation.

Background: Inverse electrocardiographic mapping reconstructs cardiac electrical activity from recorded body surface potentials. This noninvasive technique has been used to identify potential ablation targets. Despite this, there has been little systematic evaluation of its reliability.

Development of 3-D Intramural and Surface Potentials in the LV: Microstructural Basis of Preferential Transmural Conduction.

Introduction: Extracellular potentials measured on the heart surfaces are used to infer events that originate deep within the heart wall. We have reconstructed intramural potentials in three dimensions for the first time, and compare these with epicardial and endocardial surface potentials and cardiac microstructure.

Methods And Results: Extracellular potentials from intramural point stimulation were measured from a high density 3-D electrode array in the in vivo pig LV.

Increased cardiac work provides a link between systemic hypertension and heart failure.

The spontaneously hypertensive rat (SHR) is an established model of human hypertensive heart disease transitioning into heart failure. The study of the progression to heart failure in these animals has been limited by the lack of longitudinal data. We used MRI to quantify left ventricular mass, volume, and cardiac work in SHRs at age 3 to 21 month and compared these indices to data from Wistar-Kyoto (WKY) controls.

Organ-wide 3D-imaging and topological analysis of the continuous microvascular network in a murine lymph node.

Understanding of the microvasculature has previously been limited by the lack of methods capable of capturing and modelling complete vascular networks. We used novel imaging and computational techniques to establish the topology of the entire blood vessel network of a murine lymph node, combining 63,706 confocal images at 2 μm pixel resolution to cover a volume of 3.88 mm(3).

Comparison of diffusion tensor imaging by cardiovascular magnetic resonance and gadolinium enhanced 3D image intensity approaches to investigation of structural anisotropy in explanted rat hearts.

Background: Cardiovascular magnetic resonance (CMR) can through the two methods 3D FLASH and diffusion tensor imaging (DTI) give complementary information on the local orientations of cardiomyocytes and their laminar arrays.

Methods: Eight explanted rat hearts were perfused with Gd-DTPA contrast agent and fixative and imaged in a 9.4T magnet by two types of acquisition: 3D fast low angle shot (FLASH) imaging, voxels 50 × 50 × 50 μm, and 3D spin echo DTI with monopolar diffusion gradients of 3.

Forward problem of electrocardiography: is it solved?

Background: The relationship between epicardial and body surface potentials defines the forward problem of electrocardiography. A robust formulation of the forward problem is instrumental to solving the inverse problem, in which epicardial potentials are computed from known body surface potentials. Here, the accuracy of different forward models has been evaluated experimentally.

Image-based motion correction for optical mapping of cardiac electrical activity.

Optical mapping, with membrane-bound, voltage-sensitive dyes, is widely used for in vitro recording of cardiac electrical activity. The spatial registration of such maps is lost when the heart moves with respect to a fixed photodetector array and contraction can generate substantial artifact if background fluorescence is not uniformly distributed. While motion artifact is commonly suppressed with electromechanical uncoupling agents, there are circumstances where these are undesirable.

Transmural variation and anisotropy of microvascular flow conductivity in the rat myocardium.

Transmural variations in the relationship between structural and fluid transport properties of myocardial capillary networks are determined via continuum modeling approaches using recent three-dimensional (3D) data on the microvascular structure. Specifically, the permeability tensor, which quantifies the inverse of the blood flow resistivity of the capillary network, is computed by volume-averaging flow solutions in synthetic networks with geometrical and topological properties derived from an anatomically-detailed microvascular data set extracted from the rat myocardium. Results show that the permeability is approximately ten times higher in the principal direction of capillary alignment (the "longitudinal" direction) than perpendicular to this direction, reflecting the strong anisotropy of the microvascular network.

Dietary supplementation with either saturated or unsaturated fatty acids does not affect the mechanoenergetics of the isolated rat heart.

Abstract It is generally recognized that increased consumption of polyunsaturated fatty acids, fish oil (FO) in particular, is beneficial to cardiac and cardiovascular health, whereas equivalent consumption of saturated fats is deleterious. In this study, we explore this divergence, adopting a limited purview: The effect of dietary fatty acids on the mechanoenergetics of the isolated heart per se. Mechanical indices of interest include left-ventricular (LV) developed pressure, stroke work, cardiac output, coronary perfusion, and LV power.

Dietary pre-exposure of rats to fish oil does not enhance myocardial efficiency of isolated working hearts or their left ventricular trabeculae.

Numerous epidemiological studies, supported by clinical and experimental findings, have suggested beneficial effects of dietary fish or fish oil supplementation on cardiovascular health. One such experimental study showed a profound (100%) increase in myocardial efficiency (i.e.

A working heart-brainstem preparation of the rat for the study of reflex mediated autonomic influences on atrial arrhythmia development.

Vagal nerve activity has been shown to play a role in the formation and maintenance of atrial fibrillation (AF). Nerves on the atria are now increasingly being targeted using ablation-based therapies for the treatment of paroxysmal AF. In vivo, changes in vagal activity are part of an integrated autonomic profile that invariably involves accompanying modulations in sympathetic activity.

Novel methods for characterization of paroxysmal atrial fibrillation in human left atria.

Introduction: More effective methods for characterizing 3D electrical activity in human left atrium (LA) are needed to identify substrates/triggers and microreentrant circuit for paroxysmal atrial fibrillation (PAF). We describe a novel wavelet-based approach and wave-front centroid tracking that have been used to reconstruct regional activation frequency and electrical activation pathways from non-contact multi-electrode array.

Methods: Data from 13 patients acquired prior to ablation for PAF with a 64 electrode noncontact catheter positioned in the LA were analysed.