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Nadia S Nathan

Publications and source records attributed to Nadia S Nathan.

7 recordsLinked to original sources
PubMed2006

Utilizing FEM-Software to quantify pre- and post-interventional cardiac reconstruction data based on modelling data sets from surgical ventricular repair therapy (SVRT) and cardiac resynchronisation therapy (CRT).

BACKGROUND: Left ventricle (LV) 3D structural data can be easily obtained using standard transesophageal echocardiography (TEE) devices but quantitative pre- and intraoperative volumetry and geometry analysis of the LV is presently not feasible in the cardiac operation room (OR). Finite element method (FEM) modelling is necessary to carry out precise and individual volume analysis and in the future will form the basis for simulation of cardiac interventions. METHOD: A Philips/HP Sonos 5500 ultrasound device stores volume data as time-resolved 4D volume data sets. In this prospective study TomTec LV Analysis TEE Software was used for semi-automatic endocardial border detection, reconstruction, and volume-rendering of the clinical 3D echocardiographic data. With the software FemCoGen a quantification of partial volumes and surface directions of the LV was carried out for two patients data sets. One patient underwent surgical ventricular repair therapy (SVR) and the other a cardiac resynchronisation therapy (CRT). RESULTS: For both patients a detailed volume and surface direction analysis is provided. Partial volumes as well as normal directions to the LV surface are pre- and post-interventionally compared. CONCLUSION: The operation results for both patients are quantified. The quantification shows treatment details for both interventions (e.g. the elimination of the discontinuities for CRT intervention and the segments treated for SVR intervention). The LV quantification is feasible in the cardiac OR and it gives a detailed and immediate quantitative feedback of the quality of the intervention to the medical.

Arrhythmias, Cardiac↗
PubMed2006

Finite-element-method (FEM) model generation of time-resolved 3D echocardiographic geometry data for mitral-valve volumetry.

INTRODUCTION: Mitral Valve (MV) 3D structural data can be easily obtained using standard transesophageal echocardiography (TEE) devices but quantitative pre- and intraoperative volume analysis of the MV is presently not feasible in the cardiac operation room (OR). Finite element method (FEM) modelling is necessary to carry out precise and individual volume analysis and in the future will form the basis for simulation of cardiac interventions. METHOD: With the present retrospective pilot study we describe a method to transfer MV geometric data to 3D Slicer 2 software, an open-source medical visualization and analysis software package. A newly developed software program (ROIExtract) allowed selection of a region-of-interest (ROI) from the TEE data and data transformation for use in 3D Slicer. FEM models for quantitative volumetric studies were generated. RESULTS: ROI selection permitted the visualization and calculations required to create a sequence of volume rendered models of the MV allowing time-based visualization of regional deformation. Quantitation of tissue volume, especially important in myxomatous degeneration can be carried out. Rendered volumes are shown in 3D as well as in time-resolved 4D animations. CONCLUSION: The visualization of the segmented MV may significantly enhance clinical interpretation. This method provides an infrastructure for the study of image guided assessment of clinical findings and surgical planning. For complete pre- and intraoperative 3D MV FEM analysis, three input elements are necessary: 1. time-gated, reality-based structural information, 2. continuous MV pressure and 3. instantaneous tissue elastance. The present process makes the first of these elements available. Volume defect analysis is essential to fully understand functional and geometrical dysfunction of but not limited to the valve. 3D Slicer was used for semi-automatic valve border detection and volume-rendering of clinical 3D echocardiographic data. FEM based models were also calculated. METHOD: A Philips/HP Sonos 5500 ultrasound device stores volume data as time-resolved 4D volume data sets. Data sets for three subjects were used. Since 3D Slicer does not process time-resolved data sets, we employed a standard movie maker to animate the individual time-based models and visualizations. Calculation time and model size were minimized. Pressures were also easily available. We speculate that calculation of instantaneous elastance may be possible using instantaneous pressure values and tissue deformation data derived from the animated FEM.

Echocardiography, Three-Dimensional↗
PubMed2006

Mitral valve surgery simultaneous to coronary revascularization in patients with end-stage ischemic cardiomyopathy.

Mitral valve regurgitation (MVR), occurring as a result of myocardial ischemia and global left ventricular (LV) dysfunction, predicts a poor outcome in terms of survival and morbidity. Between 1995 and 2003, 180 consecutive patients with impaired LV function and chronic ischemic MVR underwent cardiac surgery. Fifty-four patients (group I), MVR (grade III-IV) underwent simultaneous MV surgery and coronary artery bypass grafting (CABG); 40 patients (group II), MVR (grade II-III), and 86 patients (group III), MVR (grade I-II), underwent CABG alone. In group I, MV repair was performed in 36 patients (group IA) and MV replacement in 18 (group IB). The incidence of hospital death was similar between groups. The actuarial event-free survival was significantly lower in group than in groups II and III (P = 0.0045) and I (P = 0.038). The overall actuarial survival was significantly higher in group IA than in group IB (P = 0.027). Postoperatively, the LV ejection fraction (P < 0.001), LV end-diastolic diameter (P < 0.001), LV end-systolic diameter (P < 0.01), and cardiac index (P < 0.001) improved significantly in group I. The regurgitation fraction decreased significantly in Groups I and III after surgery (P < 0.001 and P = 0.003, respectively). Both MV repair and replacement that preserves subvalvular apparatus in patients with end-stage ischemic myocardiopathy offer an acceptable outcome. Mitral valve repair simultaneous to CABG improves significantly the LV function and its geometry. In patients with mild to moderate mitral regurgitation, CABG alone may be performed with good overall survival, but with lower event-free survival than those undergoing concomitant mitral valve repair.

Aged↗
PubMed2004

Feasibility of rapid and automated importation of 3D echocardiographic left ventricular (LV) geometry into a finite element (FEM) analysis model.

BACKGROUND: Finite element method (FEM) analysis for intraoperative modeling of the left ventricle (LV) is presently not possible. Since 3D structural data of the LV is now obtainable using standard transesophageal echocardiography (TEE) devices intraoperatively, the present study describes a method to transfer this data into a commercially available FEM analysis system: ABAQUS. METHODS: In this prospective study TomTec LV Analysis TEE Software was used for semi-automatic endocardial border detection, reconstruction, and volume-rendering of the clinical 3D echocardiographic data. A newly developed software program MVCP FemCoGen, written in Delphi, reformats the TomTec file structures in five patients for use in ABAQUS and allows visualization of regional deformation of the LV. RESULTS: This study demonstrates that a fully automated importation of 3D TEE data into FEM modeling is feasible and can be efficiently accomplished in the operating room. CONCLUSION: For complete intraoperative 3D LV finite element analysis, three input elements are necessary: 1. time-gaited, reality-based structural information, 2. continuous LV pressure and 3. instantaneous tissue elastance. The first of these elements is now available using the methods presented herein.

Echocardiography, Three-Dimensional↗
PubMed2004

Severe argatroban-induced coagulopathy in a patient with a history of heparin-induced thrombocytopenia.

Heparin-induced thrombocytopenia is a serious complication of heparin therapy, and it remains a therapeutic challenge in the subset of patients requiring cardiopulmonary bypass. Alternative anticoagulation strategies include lepirudin, danaparoid, bivalirudin, and argatroban, or a combination of unfractionated heparin with a platelet antagonist. Argatroban is eliminated by a hepatic route, making it a practical option for patients with renal insufficiency. However, the lack of an effective antidote poses a significant problem. We present a patient with a history of heparin-induced thrombocytopenia with thrombosis who underwent a redo aortic valve replacement. Although the level of anticoagulation achieved with argatroban was initially adequate, its persistence after the completion of cardiopulmonary bypass proved to be life threatening.

Aged↗
PubMedDate not supplied

Anomalous origin of the right pulmonary artery from the ascending aorta.

OBJECTIVES: The aim was to review our experience with the surgical repair of the anomalous origin of the right pulmonary artery (AORPA) from the aorta. MATERIALS AND METHOD: Between January 1991 and March 2001, five patients with AORPA underwent surgical correction. One patient presented isolated AOPA from the aorta. Implantation of the anomalous PA to the main PA trunk was performed by (1). direct anatomosis employing an autologous pericardial patch in two patients; (2). using an aortic flap in two patients with AORPA; and (3). using an aortic and pulmonary flaps in another patient. The mean follow-up time was 27 months. RESULTS: One patient died due to progressive heart failure unresponsive to inotropic support. Early postoperative pulmonary hypertension crisis was identified in patient 4, that was managed by intravenous prostacyclin. The same patient necessitated mechanical ventilation for 11 days. The mean residual gradient for all survivors was 9.5 +/- 4 mmHg. The postoperative Tc-99 m scintigraphy demonstrated 72 +/- 4.5(%) lung perfusion. At follow-up the survival was 100%. None of the followed patients required reoperation. CONCLUSION: The AORPA from the aorta is a rare but important entity, necessitating a scrupulous preoperative and intraoperative evaluation. The techniques employing autologous tissues for enlarging and lengthening the AORPA seem to be associated with better results in terms of postoperative restenosis.

Anastomosis, Surgical↗