Surface strains in the anterior leaflet of the functioning mitral valve

The mitral valve (MV) is a complex anatomical structure whose function involves a delicate force balance and synchronized function of each of its components. Elucidation of the role of each component and their interactions is critical to improving our understanding of MV function, and to form the basis for rational surgical repair. In the present study, we present the first known detailed study of the surface strains in the anterior leaflet in the functioning MV. The three-dimensional spatial positions of markers placed in the central region of the MV anterior leaflet in a left ventricle-simulating flow loop over the cardiac cycle were determined. The resulting two-dimensional in-surface strain tensor was computed from the marker positions using a C 0 Lagrangian quadratic finite element. Results demonstrated that during valve closure the anterior leaflet experienced large, anisotropic strains with peak stretch rates of 500%–1000%/s. This rapid stretching was followed by a plateau phase characterized by relatively constant strain state. We hypothesized that the presence of this plateau phase was a result of full straightening of the leaflet collagen fibers upon valve closure. This hypothesis suggests that the MV collagen fibers are designed to allow leaflet coaptation followed by a dramatic increase in stiffness to prevent further leaflet deformation, which would lead to valvular regurgitation. These studies represent a first step in improving our understanding of normal MV function and to help establish the principles for repair and replacement. © 2002 Biomedical Engineering Society

Surface strains in the anterior leaflet of the functioning mitral valve

The mitral valve (MV) is a complex anatomical structure whose function involves a delicate force balance and synchronized function of each of its components. Elucidation of the role of each component and their interactions is critical to improving our understanding of MV function, and to form the basis for rational surgical repair. In the present study, we present the first known detailed study of the surface strains in the anterior leaflet in the functioning MV. The three-dimensional spatial positions of markers placed in the central region of the MV anterior leaflet in a left ventricle-simulating flow loop over the cardiac cycle were determined. The resulting two-dimensional in-surface strain tensor was computed from the marker positions using a C 0 Lagrangian quadratic finite element. Results demonstrated that during valve closure the anterior leaflet experienced large, anisotropic strains with peak stretch rates of 500%–1000%/s. This rapid stretching was followed by a plateau phase characterized by relatively constant strain state. We hypothesized that the presence of this plateau phase was a result of full straightening of the leaflet collagen fibers upon valve closure. This hypothesis suggests that the MV collagen fibers are designed to allow leaflet coaptation followed by a dramatic increase in stiffness to prevent further leaflet deformation, which would lead to valvular regurgitation. These studies represent a first step in improving our understanding of normal MV function and to help establish the principles for repair and replacement. © 2002 Biomedical Engineering Society

EEG lateralization and seizure outcome following peri-insular hemispherotomy for pediatric hemispheric epilepsy.

To determine whether preoperative non-lateralizing scalp electroencephalography (EEG) influences seizure outcome following peri-insular hemispherotomy (PIH) in pediatric hemispheric epilepsy. Retrospective data was collected on all 45 pediatric patients who underwent PIH between 2005 and 2016. All underwent a basic pre-surgical evaluation consisting of detailed history and examination, neuropsychological assessment, MRI, and EEG. SPECT/PET, fRMI, or Wada testing were done in only eight patients. Seizure outcome was assessed using the Engel classification. Among those who underwent hemispherotomy, 20 (44%) were females. Mean age at surgery was 8 ± 4.3 years and mean duration of symptoms was 5.2 ± 3.7 years. The most common etiologies of hemispheric epilepsy were hemiconvulsion-hemiplegia epilepsy syndrome, Rasmussen encephalitis, and post-encephalitic sequelae, together comprising 27 (60%) patients. Among the 44 patients with follow-up data (mean duration 48 ± 33 months), seizure freedom (Engel class I) was attained by 41 (93.2%). Anti-epileptic medications were stopped or decreased in 36 (82%). Seventeen (38.6%) patients had non-lateralizing EEG. Seizure outcome was not related to lateralization of EEG activity. PIH provides excellent long-term seizure control in patients despite the presence of non-lateralizing epileptiform activity, although occurrence of acute postoperative seizures may be higher. Routine SPECT/PET may not be required in patients with a non-lateralizing EEG if there is good clinico-radiological concordance