Browsing by Author "Thompson, Richard"

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    Clinical recommendations for cardiovascular magnetic resonance mapping of T1, T2, T2* and extracellular volume: A consensus statement by the Society for Cardiovascular Magnetic Resonance (SCMR) endorsed by the European Association for Cardiovascular Imaging (EACVI)
    (2017-10-09) Messroghli, Daniel R; Moon, James C; Ferreira, Vanessa M; Grosse-Wortmann, Lars; He, Taigang; Kellman, Peter; Mascherbauer, Julia; Nezafat, Reza; Salerno, Michael; Schelbert, Erik B; Taylor, Andrew J; Thompson, Richard; Ugander, Martin; van Heeswijk, Ruud B; Friedrich, Matthias G
    Abstract Parametric mapping techniques provide a non-invasive tool for quantifying tissue alterations in myocardial disease in those eligible for cardiovascular magnetic resonance (CMR). Parametric mapping with CMR now permits the routine spatial visualization and quantification of changes in myocardial composition based on changes in T1, T2, and T2*(star) relaxation times and extracellular volume (ECV). These changes include specific disease pathways related to mainly intracellular disturbances of the cardiomyocyte (e.g., iron overload, or glycosphingolipid accumulation in Anderson-Fabry disease); extracellular disturbances in the myocardial interstitium (e.g., myocardial fibrosis or cardiac amyloidosis from accumulation of collagen or amyloid proteins, respectively); or both (myocardial edema with increased intracellular and/or extracellular water). Parametric mapping promises improvements in patient care through advances in quantitative diagnostics, inter- and intra-patient comparability, and relatedly improvements in treatment. There is a multitude of technical approaches and potential applications. This document provides a summary of the existing evidence for the clinical value of parametric mapping in the heart as of mid 2017, and gives recommendations for practical use in different clinical scenarios for scientists, clinicians, and CMR manufacturers.
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    Mechanisms of Early Filling in the Left Ventricle
    (2017) Burrowes, Lindsay; Shrive, Nigel; Tyberg, John; Sudak, Les; Thompson, Richard; Mehta, Sudarshan (Raj)
    Filling of the left ventricle (LV) occurs in two phases; early filling and late filling. Late filling, the mitral flow “A-wave”, is a result of the left atrial contraction. Early filling, manifest as the “E-wave”, is thought to be substantially due to diastolic suction (DS), a phenomenon whereby the LV aspirates blood and fills itself independent of atrial activity. The presence and importance of DS has been the source of much debate within the scientific literature, dating back to the early 20th century. It has been said that DS is important in order for the LV to fill efficiently as the heart adjusts to varying demands, for example, an increased heart rate due to exercise. The presence of a favourable pressure gradient (PG) that drives blood flow from the LA towards the LV has been well established. Additional studies have shown that, under abnormally small end-systolic volumes (ESV), or, with impeding LV inflow, a negative transmural pressure is recorded, which was considered evidence of suction. The purpose of this study was to vary the working conditions of the heart in a porcine model, and measure DS in two different ways and compare these measures of DS to ESV as well as ejection fraction (EF). By varying the working conditions of the heart using drug interventions (isoproterenol, phenylephrine & metoprolol), as well as volume loading, the amount of DS at different states was determined. The volume of filling due to suction, VDS, as well as the amount of energy resulting from suction (via a backwards decompression wave, BDW), are both indicative that ESV decreases as the amount of DS increases. As EF increased, both measures of DS also increased. Additionally, results for VDS display that DS is still present at ESV larger than baseline ESV. Finally, comparing the two measures of DS to each other showed good agreement. DS is often suggested to be a result of elastic recoil of the LV after contracting below an unstressed state. However, our findings that VDS exists at large ESV would contradict that DS is only a result of elastic recoil, suggesting that further studies must be conducted focusing on DS at large ESV.
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    P1.14 Analysis of Left Ventricular Filling Dynamics
    (2015-11-23) Burrowes, Lindsay; Satriano, Alessandro; Thompson, Richard; Shrive, Nigel; Tyberg, John
    Abstract Diastolic filling of the left ventricle (LV) occurs in two phases, early and late filling. Early filling, manifest as the “E-wave”, is thought to be substantially due to diastolic suction (DS), a phenomenon where the LV aspirates blood and fills itself, independent of atrial activity. Late filling, resulting in the mitral flow “A-wave” is a result of left atrial contraction. Adequate filling of the LV is necessary to maintain normal heart function at rest and under stress. DS is thought to be an important mechanism in the efficiency of filling. To study DS, we have invasively measured pressure and used cardiac MRI to evaluate cavitary volume and flow in an animal model to quantify different measures of DS under varied experimental conditions. The amount of filling due to DS (VDS), determined by the change in volume between mitralvalve opening and LV pressure minimum of the pressure-volume loop (Katz 1930), is related to the measured end systolic volume (ESV). As ESV decreases the VDS increases. The smaller the ESV, the larger the recoil energy of the LV as it relaxes towards resting volume. This contributes increased energy for the suction of blood into the ventricle in early filling. Wave intensity analysis (the separation of forward and backwards waves and wave type) and intraventricular pressure gradients will also be considered in order to determine which best describes DS and whether they can be used together to better understand changes in filling dynamics under varied loading conditions.