The Experts below are selected from a list of 30033 Experts worldwide ranked by ideXlab platform
Simon G Duckett - One of the best experts on this subject based on the ideXlab platform.
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invasive acute Hemodynamic Response to guide left ventricular lead implantation predicts chronic remodeling in patients undergoing cardiac resynchronization therapy
2011Co-Authors: Simon G Duckett, Matthew Ginks, Anoop Shetty, Julian Bostock, Jaswinder Gill, Shoaib Hamid, Stam KapetanakisAbstract:Objectives We evaluated the relationship between acute Hemodynamic Response (AHR) and reverse remodeling (RR) in cardiac resynchronization therapy (CRT). Background CRT reduces mortality and morbidity in heart failure patients; however, up to 30% of patients do not derive symptomatic benefit. Higher proportions do not remodel. Multicenter trials have shown echocardiographic techniques are poor at improving Response rates. We hypothesized the degree of AHR at implant can predict which patients remodel. Methods Thirty-three patients undergoing CRT (21 dilated and 12 ischemic cardiomyopathy) were studied. Left ventricular (LV) volumes were assessed before and after CRT. The AHR (maximum rate of left ventricular pressure [LV-dP/dtmax]) was assessed at implant with a pressure wire in the LV cavity. Largest percentage rise in LV-dP/dtmax from baseline (atrial antibradycardia pacing or right ventricular pacing with atrial fibrillation) to dual-chamber pacing (DDD)-LV was used to determine optimal coronary sinus LV lead position. Reverse remodeling was defined as reduction in LV end systolic volume ≥15% at 6 months. Results The LV-dP/dtmax increased significantly from baseline (801 ± 194 mm Hg/s to 924 ± 203 mm Hg/s, p Conclusions Acute Hemodynamic Response to LV pacing is useful for predicting which patients are likely to remodel in Response to CRT both for dilated cardiomyopathy and ischemic cardiomyopathy. Using AHR has the potential to guide LV lead positioning and improve Response rates.
Stam Kapetanakis - One of the best experts on this subject based on the ideXlab platform.
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invasive acute Hemodynamic Response to guide left ventricular lead implantation predicts chronic remodeling in patients undergoing cardiac resynchronization therapy
2011Co-Authors: Simon G Duckett, Matthew Ginks, Anoop Shetty, Julian Bostock, Jaswinder Gill, Shoaib Hamid, Stam KapetanakisAbstract:Objectives We evaluated the relationship between acute Hemodynamic Response (AHR) and reverse remodeling (RR) in cardiac resynchronization therapy (CRT). Background CRT reduces mortality and morbidity in heart failure patients; however, up to 30% of patients do not derive symptomatic benefit. Higher proportions do not remodel. Multicenter trials have shown echocardiographic techniques are poor at improving Response rates. We hypothesized the degree of AHR at implant can predict which patients remodel. Methods Thirty-three patients undergoing CRT (21 dilated and 12 ischemic cardiomyopathy) were studied. Left ventricular (LV) volumes were assessed before and after CRT. The AHR (maximum rate of left ventricular pressure [LV-dP/dtmax]) was assessed at implant with a pressure wire in the LV cavity. Largest percentage rise in LV-dP/dtmax from baseline (atrial antibradycardia pacing or right ventricular pacing with atrial fibrillation) to dual-chamber pacing (DDD)-LV was used to determine optimal coronary sinus LV lead position. Reverse remodeling was defined as reduction in LV end systolic volume ≥15% at 6 months. Results The LV-dP/dtmax increased significantly from baseline (801 ± 194 mm Hg/s to 924 ± 203 mm Hg/s, p Conclusions Acute Hemodynamic Response to LV pacing is useful for predicting which patients are likely to remodel in Response to CRT both for dilated cardiomyopathy and ischemic cardiomyopathy. Using AHR has the potential to guide LV lead positioning and improve Response rates.
Matthew Ginks - One of the best experts on this subject based on the ideXlab platform.
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invasive acute Hemodynamic Response to guide left ventricular lead implantation predicts chronic remodeling in patients undergoing cardiac resynchronization therapy
2011Co-Authors: Simon G Duckett, Matthew Ginks, Anoop Shetty, Julian Bostock, Jaswinder Gill, Shoaib Hamid, Stam KapetanakisAbstract:Objectives We evaluated the relationship between acute Hemodynamic Response (AHR) and reverse remodeling (RR) in cardiac resynchronization therapy (CRT). Background CRT reduces mortality and morbidity in heart failure patients; however, up to 30% of patients do not derive symptomatic benefit. Higher proportions do not remodel. Multicenter trials have shown echocardiographic techniques are poor at improving Response rates. We hypothesized the degree of AHR at implant can predict which patients remodel. Methods Thirty-three patients undergoing CRT (21 dilated and 12 ischemic cardiomyopathy) were studied. Left ventricular (LV) volumes were assessed before and after CRT. The AHR (maximum rate of left ventricular pressure [LV-dP/dtmax]) was assessed at implant with a pressure wire in the LV cavity. Largest percentage rise in LV-dP/dtmax from baseline (atrial antibradycardia pacing or right ventricular pacing with atrial fibrillation) to dual-chamber pacing (DDD)-LV was used to determine optimal coronary sinus LV lead position. Reverse remodeling was defined as reduction in LV end systolic volume ≥15% at 6 months. Results The LV-dP/dtmax increased significantly from baseline (801 ± 194 mm Hg/s to 924 ± 203 mm Hg/s, p Conclusions Acute Hemodynamic Response to LV pacing is useful for predicting which patients are likely to remodel in Response to CRT both for dilated cardiomyopathy and ischemic cardiomyopathy. Using AHR has the potential to guide LV lead positioning and improve Response rates.
Anoop Shetty - One of the best experts on this subject based on the ideXlab platform.
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invasive acute Hemodynamic Response to guide left ventricular lead implantation predicts chronic remodeling in patients undergoing cardiac resynchronization therapy
2011Co-Authors: Simon G Duckett, Matthew Ginks, Anoop Shetty, Julian Bostock, Jaswinder Gill, Shoaib Hamid, Stam KapetanakisAbstract:Objectives We evaluated the relationship between acute Hemodynamic Response (AHR) and reverse remodeling (RR) in cardiac resynchronization therapy (CRT). Background CRT reduces mortality and morbidity in heart failure patients; however, up to 30% of patients do not derive symptomatic benefit. Higher proportions do not remodel. Multicenter trials have shown echocardiographic techniques are poor at improving Response rates. We hypothesized the degree of AHR at implant can predict which patients remodel. Methods Thirty-three patients undergoing CRT (21 dilated and 12 ischemic cardiomyopathy) were studied. Left ventricular (LV) volumes were assessed before and after CRT. The AHR (maximum rate of left ventricular pressure [LV-dP/dtmax]) was assessed at implant with a pressure wire in the LV cavity. Largest percentage rise in LV-dP/dtmax from baseline (atrial antibradycardia pacing or right ventricular pacing with atrial fibrillation) to dual-chamber pacing (DDD)-LV was used to determine optimal coronary sinus LV lead position. Reverse remodeling was defined as reduction in LV end systolic volume ≥15% at 6 months. Results The LV-dP/dtmax increased significantly from baseline (801 ± 194 mm Hg/s to 924 ± 203 mm Hg/s, p Conclusions Acute Hemodynamic Response to LV pacing is useful for predicting which patients are likely to remodel in Response to CRT both for dilated cardiomyopathy and ischemic cardiomyopathy. Using AHR has the potential to guide LV lead positioning and improve Response rates.
David A. Boas - One of the best experts on this subject based on the ideXlab platform.
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using prerecorded Hemodynamic Response functions in detecting prefrontal pain Response a functional near infrared spectroscopy study
2017Co-Authors: Ke Peng, David A. Boas, Meryem A Yucel, Christopher M Aasted, Sarah C Steele, David Borsook, Lino BecerraAbstract:Currently, there is no method for providing a nonverbal objective assessment of pain. Recent work using functional near-infrared spectroscopy (fNIRS) has revealed its potential for objective measures. We conducted two fNIRS scans separated by 30 min and measured the Hemodynamic Response to the electrical noxious and innocuous stimuli over the anterior prefrontal cortex (aPFC) in 14 subjects. Based on the estimated Hemodynamic Response functions (HRFs), we first evaluated the test–retest reliability of using fNIRS in measuring the pain Response over the aPFC. We then proposed a general linear model (GLM)-based detection model that employs the subject-specific HRFs from the first scan to detect the pain Response in the second scan. Our results indicate that fNIRS has a reasonable reliability in detecting the Hemodynamic changes associated with noxious events, especially in the medial portion of the aPFC. Compared with a standard HRF with a fixed shape, including the subject-specific HRFs in the GLM allows for a significant improvement in the detection sensitivity of aPFC pain Response. This study supports the potential application of individualized analysis in using fNIRS and provides a robust model to perform objective determination of pain perception.
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improved recovery of the Hemodynamic Response in diffuse optical imaging using short optode separations and state space modeling
2011Co-Authors: Louis Gagnon, David A. Boas, Katherine L Perdue, Douglas N Greve, Daniel M Goldenholz, Gayatri KaskhedikarAbstract:Diffuse Optical Imaging (DOI) allows the recovery of the Hemodynamic Response associated with evoked brain activity. The signal is contaminated with systemic physiological interference which occurs in the superficial layers of the head as well as in the brain tissue. The back-reflection geometry of the measurement makes the DOI signal strongly contaminated by systemic interference occurring in the superficial layers. A recent development has been the use of signals from small source-detector separation (1 cm) optodes as regressors. Since those additional measurements are mainly sensitive to superficial layers in adult humans, they help in removing the systemic interference present in longer separation measurements (3 cm). Encouraged by those findings, we developed a dynamic estimation procedure to remove global interference using small optode separations and to estimate simultaneously the Hemodynamic Response. The algorithm was tested by recovering a simulated synthetic Hemodynamic Response added over baseline DOI data acquired from 6 human subjects at rest. The performance of the algorithm was quantified by the Pearson R2 coefficient and the mean square error (MSE) between the recovered and the simulated Hemodynamic Responses. Our dynamic estimator was also compared with a static estimator and the traditional adaptive filtering method. We observed a significant improvement (two-tailed paired t-test, p < 0.05) in both HbO and HbR recovery using our Kalman filter dynamic estimator compared to the traditional adaptive filter, the static estimator and the standard GLM technique.
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coupling between somatosensory evoked potentials and Hemodynamic Response in the rat
2008Co-Authors: Maria Angela Franceschini, Ilkka Nissila, Solomon G Diamond, Giorgio Bonmassar, David A. BoasAbstract:Abstract We studied the relationship between somatosensory evoked potentials (SEP) recorded with scalp electroencephalography (EEG) and hemoglobin Responses recorded non-invasively with diffuse optical imaging (DOI) during parametrically varied electrical forepaw stimulation in rats. Using these macroscopic techniques we verified that the Hemodynamic Response is not linearly coupled to the somatosensory evoked potentials, and that a power or threshold law best describes the coupling between SEP and the hemoglobin Response, in agreement with the results of most invasive studies. We decompose the SEP Response in three components (P1, N1, and P2) to determine which best predicts the hemoglobin Response. We found that N1 and P2 predict the hemoglobin Response significantly better than P1 and the input stimuli (S). Previous electrophysiology studies reported in the literature show that P1 originates in layer IV directly from thalamocortical afferents, while N1 and P2 originate in layers I and II and reflect the majority of local cortico–cortical interactions. Our results suggest that the evoked hemoglobin Response is driven by the cortical synaptic activity and not by direct thalamic input. The N1 and P2 components, and not P1, need to be considered to correctly interpret neurovascular coupling.
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Coupling of the cortical Hemodynamic Response to cortical and thalamic neuronal activity
2005Co-Authors: Anna Devor, David A. Boas, István Ulbert, Andrew K. Dunn, Suresh N. Narayanan, Stephanie R. Jones, Mark L. Andermann, Anders M. DaleAbstract:Accurate interpretation of functional MRI (fMRI) signals requires knowledge of the relationship between the Hemodynamic Response and the neuronal activity that underlies it. Here we address the question of coupling between pre- and postsynaptic neuronal activity and the Hemodynamic Response in rodent somatosensory (Barrel) cortex in Response to single-whisker deflection. Using full-field multiwavelength optical imaging of hemoglobin oxygenation and electrophysiological recordings of spiking activity and local field potentials, we demonstrate that a point Hemodynamic measure is influenced by neuronal activity across multiple cortical columns. We demonstrate that the Hemodynamic Response is a spatiotemporal convolution of the neuronal activation. Therefore, positive Hemodynamic Response in one cortical column might be explained by neuronal activity not only in that column but also in the neighboring columns. Thus, attempts at characterizing the neurovascular relationship based on point measurements of electrophysiology and Hemodynamics may yield inconsistent results, depending on the spatial extent of neuronal activation. The finding that the Hemodynamic signal observed at a given location is a function of electrophysiological activity over a broad spatial region helps explain a previously observed increase of local vascular Response beyond the saturation of local neuronal activity. We also demonstrate that the oxy- and total-hemoglobin Hemodynamic Responses can be well approximated by space–time separable functions with an antagonistic center-surround spatial pattern extending over several millimeters. The surround “negative” Hemodynamic activity did not correspond to observable changes in neuronal activity. The complex spatial integration of the Hemodynamic Response should be considered when interpreting fMRI data.
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differences in the Hemodynamic Response to event related motor and visual paradigms as measured by near infrared spectroscopy
2003Co-Authors: G Jasdzewski, Gary E Strangman, Jennifer B Wagner, Kenneth K Kwong, Russell A Poldrack, David A. BoasAbstract:Several current brain imaging techniques rest on the assumption of a tight coupling between neural activity and Hemodynamic Response. The nature of this neurovascular coupling, however, is not completely understood. There is some evidence for a decoupling of these processes at the onset of neural activity, which manifests itself as a momentary increase in the relative concentration of deoxyhemoglobin (HbR). The existence of this early component of the Hemodynamic Response function, however, is controversial, as it is inconsistently found. Near infrared spectroscopy (NIRS) allows quantification of levels of oxyhemoglobin (HbO(2)) and HbR during task performance in humans. We acquired NIRS data during performance of simple motor and visual tasks, using rapid-presentation event-related paradigms. Our results demonstrate that rapid, event-related NIRS can provide robust estimates of the Hemodynamic Response without artifacts due to low-frequency signal components, unlike data from blocked designs. In both the motor and visual data the onset of the increase in HbO(2) occurs before HbR decreases, and there is a poststimulus undershoot. Our results also show that total blood volume (HbT) drops before HbO(2) and undershoots baseline, raising a new issue for neurovascular models. We did not find early deoxygenation in the motor data using physiologically plausible values for the differential pathlength factor, but did find one in the visual data. We suggest that this difference, which is consistent with functional magnetic resonance imaging (fMRI) data, may be attributable to different capillary transit times in these cortices.