Browsing by Subject "Echocardiography"

Now showing 1 - 3 of 3
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    Echocardiographic Evaluation of Left Ventricular Recovery After Refractory Out-of-Hospital Cardiac Arrest
    (2020-12) Kalra, Rajat
    Background: The mechanisms and degree of myocardial recovery during treatment with venoarterial extracorporeal membrane oxygenation (VA-ECMO) are unclear. We performed a descriptive study to evaluate myocardial recovery and changes in parameters of myocardial loading using echocardiography. Methods: We used a retrospective cohort design to evaluate patients with refractory ventricular tachycardia/ventricular fibrillation out-of-hospital cardiac arrest who were treated with the Minnesota Resuscitation Consortium protocol. Left ventricular ejection fraction (LVEF), end-diastolic diameter (LVEDD), end-systolic diameter (LVESD), and fractional shortening were assessed using serial echocardiography. One-way analysis of variance (ANOVA) was used to compare parameters over six hospitalization stages. Two-way ANOVA was used to compare these parameters between patients that died during the index hospitalization and patients that survived. Results: 77 patients had >1 echocardiographic turndown evaluations. Thirty-eight patients survived to discharge and 39 patients died. Of 39 in-hospital deaths, 17 patients died before VA-ECMO decannulation and 22 patients died after VA-ECMO decannulation. Among all patients, LVEF improved from 9.7±10.1% from the first echocardiogram after rewarming to 43.1±13.1% after decannulation (p<0.001) and fractional shortening ratio improved from 0.14±0.12 to 0.31±0.14 (p<0.001). The LVEDD and LVESD remained stable (p=0.36 and p=0.12, respectively). Patients that died had a lower LVEF by an average of 6.93% (95% confidence interval: -10.0 to -3.83, p<0.001), but other parameters were similar. Conclusion: Refractory cardiac arrest patients treated with VA-ECMO experience significant recovery of ventricular function during treatment. We postulate that this primarily occurs via reduction of LV preload.
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    Left ventricular mechanics during right ventricular pacing.
    (2010-07) Burns, Kevin Victor
    Despite the routine use of right ventricle (RV) pacemakers to treat sinus node dysfunction, atrioventricular (AV) block, and other electrical abnormalities in the heart, recent studies have demonstrated that chronically RV-paced patients have an increased the risk of hospitalization, heart failure (HF), and death. Dyssynchronous electrical and mechanical activation of the left ventricle (LV) has been demonstrated in animal models of acute RV pacing. In humans, acute and chronic RV pacing have been demonstrated to impair LV systolic function and induce longitudinal or radial mechanical dyssynchrony. However, the 3-dimensional LV mechanics that result from acute and chronic RV pacing have not been fully explained. Recent advances in echocardiographic image analysis, including tissue Doppler imaging (TDI) and speckle tracking echocardiography (STE), can quantify LV motion in multiple planes throughout the LV. This dissertation will examine the effects of RV pacing on LV mechanics and synchrony in longitudinal, radial, and rotational planes of motion. We hypothesize that acute RV pacing will result in reduced and dyssynchronous longitudinal, radial and rotational LV function. We further hypothesize that these alterations to normal LV function may lead to HF during chronic RV pacing, and that this type of HF is structurally and functionally different than HF due to other causes. These results may provide insight into the mechanisms responsible for pacing-induced LV dysfunction, and enable physicians to better track cardiac function in paced patients, and modify treatments or design new therapies for patients requiring ventricular pacing.
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    The Sheep as a Translational Model for Next Generation Valve Replacement Devices: A Multimodal Cardiac Imaging Study
    (2024) Carney, John
    The development of catheter-based cardiac valve replacement devices, or transcatheter valves, has ushered in a new era in the treatment of patients with valvular disease. Prior to clinical study, regulators require comprehensive in vivo safety studies of novel cardiac devices in large animal models. The domestic sheep model has been widely used to evaluate predicate surgically implanted valves, therefore its use to assess valve durability, thromboembolic complications and biocompatibility is well documented and understood. However, the model’s cardiac valvular anatomy and hemodynamics both pre- and postoperatively remains largely unstudied to date, presenting a gap in the knowledge and understanding of the model and the translation of preclinical device findings to clinical use. The purpose of this thesis was to characterize, propose and standardize methods for the use of cardiac computed tomography (CT), echocardiography (echo) and four-dimensional flow magnetic resonance imaging (4D MRI) in assessing naïve and implanted prosthetic valves in the sheep model. Resulting anatomic and hemodynamic data was analyzed statistically and reported to create the first cardiac valve reference intervals for sheep, to be used as comparator data in future studies of next-generation cardiac valve devices in the model. Looking to the future of preclinical in vivo studies, we demonstrate the use of machine learning algorithms and their potential predictive role in determining cardiac anatomy of the sheep model, as well as in-life outcomes to help investigators better assess, interpret, and translate preclinical study outcomes to clinical use. Finally, we present a number of articles documenting our use of the sheep model in next generation cardiac valve replacement studies and background pathology of the model to be used to more effectively interpret study findings. We envision this thesis improving future preclinical research studies of novel cardiac device technology in the sheep through understanding of the model, refinements in animal use, and ultimately interpretation of future study results.