Clinical Practice Guidelines for the Perioperative Nutrition, Metabolic, and Nonsurgical Support of Patients Undergoing Bariatric Procedures - 2019 Update: Cosponsored by American Association of Clinical Endocrinologists/American College of Endocrinology, The Obesity Society, American Society for Metabolic and Bariatric Surgery, Obesity Medicine Association, and American Society of Anesthesiologists.

OBJECTIVE: The development of these updated clinical practice guidelines (CPGs) was commissioned by the American Association of Clinical Endocrinologists (AACE), The Obesity Society (TOS), American Society for Metabolic and Bariatric Surgery (ASMBS), Obesity Medicine Association (OMA), and American Society of Anesthesiologists (ASA) Boards of Directors in adherence with the AACE 2017 protocol for standardized production of CPGs, algorithms, and checklists. METHODS: Each recommendation was evaluated and updated based on new evidence from 2013 to the present and subjective factors provided by experts. RESULTS: New or updated topics in this CPG include: contextualization in an adiposity-based chronic disease complications-centric model, nuance-based and algorithm/checklist-assisted clinical decision-making about procedure selection, novel bariatric procedures, enhanced recovery after bariatric surgery protocols, and logistical concerns (including cost factors) in the current health care arena. There are 85 numbered recommendations that have updated supporting evidence, of which 61 are revised and 12 are new. Noting that there can be multiple recommendation statements within a single numbered recommendation, there are 31 (13%) Grade A, 42 (17%) Grade B, 72 (29%) Grade C, and 101 (41%) Grade D recommendations. There are 858 citations, of which 81 (9.4%) are evidence level (EL) 1 (highest), 562 (65.5%) are EL 2, 72 (8.4%) are EL 3, and 143 (16.7%) are EL 4 (lowest). CONCLUSIONS: Bariatric procedures remain a safe and effective intervention for higher-risk patients with obesity. Clinical decision-making should be evidence based within the context of a chronic disease. A team approach to perioperative care is mandatory, with special attention to nutritional and metabolic issues.

Clinical practice guidelines for the perioperative nutrition, metabolic, and nonsurgical support of patients undergoing bariatric procedures - 2019 update: cosponsored by American Association of Clinical Endocrinologists/American College of Endocrinology, The Obesity Society, American Society for Metabolic & Bariatric Surgery, Obesity Medicine Association, and American Society of Anesthesiologists.

OBJECTIVE: The development of these updated clinical practice guidelines (CPG) was commissioned by the American Association of Clinical Endocrinologists, The Obesity Society, the American Society of Metabolic and Bariatric Surgery, the Obesity Medicine Association, and the American Society of Anesthesiologists boards of directors in adherence to the American Association of Clinical Endocrinologists 2017 protocol for standardized production of CPG, algorithms, and checklists. METHODS: Each recommendation was evaluated and updated based on new evidence from 2013 to the present and subjective factors provided by experts. RESULTS: New or updated topics in this CPG include contextualization in an adiposity-based, chronic disease complications-centric model, nuance-based, and algorithm/checklist-assisted clinical decision-making about procedure selection, novel bariatric procedures, enhanced recovery after bariatric surgery protocols, and logistical concerns (including cost factors) in the current healthcare arena. There are 85 numbered recommendations that have updated supporting evidence, of which 61 are revised and 12 are new. Noting that there can be multiple recommendation statements within a single numbered recommendation, there are 31 (13%) Grade A, 42 (17%) Grade B, 72 (29%) Grade C, and 101 (41%) Grade D recommendations. There are 858 citations, of which 81 (9.4%) are evidence level (EL) 1 (highest), 562 (65.5%) are EL 2, 72 (8.4%) are EL 3, and 143 (16.7%) are EL 4 (lowest). CONCLUSIONS: Bariatric procedures remain a safe and effective intervention for higher-risk patients with obesity. Clinical decision-making should be evidence-based within the context of a chronic disease. A team approach to perioperative care is mandatory with special attention to nutritional and metabolic issues.

CLINICAL PRACTICE GUIDELINES FOR THE PERIOPERATIVE NUTRITION, METABOLIC, AND NONSURGICAL SUPPORT OF PATIENTS UNDERGOING BARIATRIC PROCEDURES - 2019 UPDATE: COSPONSORED BY AMERICAN ASSOCIATION OF CLINICAL ENDOCRINOLOGISTS/AMERICAN COLLEGE OF ENDOCRINOLOGY, THE OBESITY SOCIETY, AMERICAN SOCIETY FOR METABOLIC & BARIATRIC SURGERY, OBESITY MEDICINE ASSOCIATION, AND AMERICAN SOCIETY OF ANESTHESIOLOGISTS - EXECUTIVE SUMMARY.

Objective: The development of these updated clinical practice guidelines (CPGs) was commissioned by the American Association of Clinical Endocrinologists (AACE), The Obesity Society, American Society of Metabolic and Bariatric Surgery, Obesity Medicine Association, and American Society of Anesthesiologists Boards of Directors in adherence with the AACE 2017 protocol for standardized production of CPGs, algorithms, and checklists. Methods: Each recommendation was evaluated and updated based on new evidence from 2013 to the present and subjective factors provided by experts. Results: New or updated topics in this CPG include: contextualization in an adiposity-based chronic disease complications-centric model, nuance-based and algorithm/checklist-assisted clinical decision-making about procedure selection, novel bariatric procedures, enhanced recovery after bariatric surgery protocols, and logistical concerns (including cost factors) in the current health-care arena. There are 85 numbered recommendations that have updated supporting evidence, of which 61 are revised and 12 are new. Noting that there can be multiple recommendation statements within a single numbered recommendation, there are 31 (13%) Grade A, 42 (17%) Grade B, 72 (29%) Grade C, and 101 (41%) Grade D recommendations. There are 858 citations, of which 81 (9.4%) are evidence level (EL) 1 (highest), 562 (65.5%) are EL 2, 72 (8.4%) are EL 3, and 143 (16.7%) are EL 4 (lowest). Conclusion: Bariatric procedures remain a safe and effective intervention for higher-risk patients with obesity. Clinical decision-making should be evidence based within the context of a chronic disease. A team approach to perioperative care is mandatory, with special attention to nutritional and metabolic issues. A1C = hemoglobin A1c; AACE = American Association of Clinical Endocrinologists; ABCD = adiposity-based chronic disease; ACE = American College of Endocrinology; ADA = American Diabetes Association; AHI = Apnea-Hypopnea Index; ASA = American Society of Anesthesiologists; ASMBS = American Society of Metabolic and Bariatric Surgery; BMI = body mass index; BPD = biliopancreatic diversion; BPD/DS = biliopancreatic diversion with duodenal switch; CI = confidence interval; CPAP = continuous positive airway pressure; CPG = clinical practice guideline; CRP = C-reactive protein; CT = computed tomography; CVD = cardiovascular disease; DBCD = dysglycemia-based chronic disease; DS = duodenal switch; DVT = deep venous thrombosis; DXA = dual-energy X-ray absorptiometry; EFA = essential fatty acid; EL = evidence level; EN = enteral nutrition; ERABS = enhanced recovery after bariatric surgery; FDA = U.S. Food and Drug Administration; G4G = Guidelines for Guidelines; GERD = gastroesophageal reflux disease; GI = gastrointestinal; HCP = health-care professional(s); HTN = hypertension; ICU = intensive care unit; IGB = intragastric balloon(s); IV = intravenous; LAGB = laparoscopic adjustable gastric band; LAGBP = laparoscopic adjustable gastric banded plication; LGP = laparoscopic greater curvature (gastric) plication; LRYGB = laparoscopic Roux-en-Y gastric bypass; LSG = laparoscopic sleeve gastrectomy; MetS = metabolic syndrome; NAFLD = nonalcoholic fatty liver disease; NASH = nonalcoholic steatohepatitis; NSAID = nonsteroidal anti-inflammatory drug; OA = osteoarthritis; OAGB = one-anastomosis gastric bypass; OMA = Obesity Medicine Association; OR = odds ratio; ORC = obesity-related complication(s); OSA = obstructive sleep apnea; PE = pulmonary embolism; PN = parenteral nutrition; PRM = pulmonary recruitment maneuver; RCT = randomized controlled trial; RD = registered dietician; RDA = recommended daily allowance; RYGB = Roux-en-Y gastric bypass; SG = sleeve gastrectomy; SIBO = small intestinal bacterial overgrowth; TOS = The Obesity Society; TSH = thyroid-stimulating hormone; T1D = type 1 diabetes; T2D = type 2 diabetes; VTE = venous thromboembolism; WE = Wernicke encephalopathy; WHO = World Health Organization.

Clinical safety and effectiveness of a swallowable gas-filled intragastric balloon system for weight loss: consecutively treated patients in the initial year of U.S. commercialization.

BACKGROUND: Obesity is the most common chronic disease in the United States today. Additional therapies are needed to improve obesity treatment. OBJECTIVE: A swallowable, gas-filled intragastric balloon system was approved for the treatment of obesity by Food and Drug Administration in September 2016 and commercialization started January 2017. A registry was made available to physicians to capture evidence of safety and effectiveness with use. SETTING: United States private clinics, surgery centers, and hospitals. METHODS: This study is a retrospective analysis of a prospective registry of patients with body mass index (BMI) ≥25 kg/m2 that initiated therapy in the first year. Data on demographics, procedural timing, weight loss, adverse events, and device deficiencies were captured. RESULTS: The final analysis comprised 1343 patients across 108 treating physicians (mean age 45.7 ± 10.8 yr, 78.6% female, baseline BMI of 35.4 ± 5.4 kg/m2). Nonserious and serious adverse events were reported in 14.2% and .15% of patients, respectively. There were 7 balloon deflations, none caused obstruction. Weight loss in the indicated use (BMI 30-40 kg/m2) was 9.7 ± 6.1 kg and 10.0 ± 6.1% total body weight loss (TBWL). Weight loss in other BMI categories was 8.2 ± 5.6 kg or 10.3 ± 7.0% total body weight loss for BMI 25 to 29.9 kg/m2 and 11.6 ± 7.8 kg or percent total body weight loss 9.3 ± 6.0 for BMI >40 kg/m2. CONCLUSIONS: This swallowable gas-filled intragastric balloon system is safe and effective at inducing weight loss and offers physicians another tool for patients whose obesity has been resistant to noninvasive treatments.

Simulation and evaluation of freeze-thaw cryoablation scenarios for the treatment of cardiac arrhythmias.

BACKGROUND: Cardiac cryoablation is a minimally invasive procedure to treat cardiac arrhythmias by cooling cardiac tissues responsible for the cardiac arrhythmia to freezing temperatures. Although cardiac cryoablation offers a gentler treatment than radiofrequency ablation, longer interventions and higher recurrence rates reduce the clinical acceptance of this technique. Computer models of ablation scenarios allow for a closer examination of temperature distributions in the myocardium and evaluation of specific effects of applied freeze-thaw protocols in a controlled environment. METHODS: In this work multiple intervention scenarios with two freeze-thaw cycles were simulated with varying durations and starting times of the interim thawing phase using a finite element model verified by in-vivo measurements and data from literature. To evaluate the effects of different protocols, transmural temperature distributions and iceball dimensions were compared over time. Cryoadhesion durations of the applicator were estimated in the interim thawing phase with varying thawing phase starting times. In addition, the increase of cooling rates was compared between the freezing phases, and the thawing rates of interim thawing phases were analyzed over transmural depth. RESULTS: It could be shown that the increase of cooling rate, the regions undergoing additional phase changes and depths of selected temperatures depend on the chosen ablation protocol. Only small differences of the estimated cryoadhesion duration were found for ablation scenarios with interim thawing phase start after 90 s freezing. CONCLUSIONS: By the presented model a quantification of effects responsible for cell death is possible, allowing for the analysis and optimization of cryoablation scenarios which contribute to a higher clinical acceptance of cardiac cryoablation.

Contamination resulting from aerosolized fluid during laparoscopic surgery.

BACKGROUND AND OBJECTIVES: Aerosolized droplets of blood can travel considerable distances on release of intra-abdominal pressure during laparoscopic surgery. This creates an environmental hazard for members of the surgical team. This study describes and provides a method of measurement of aerosolized blood contamination during evacuation of the pneumoperitoneum in laparoscopic surgery. METHODS: Samples were measured by removing a trocar from the abdomen while a pneumoperitoneum of 15 mm Hg was present. A white poster board was placed 24 inches above the incision to catch the released blood spatter. By use of machine vision, luminol fluorescence, and computerized spatial analysis, data from the boards were recorded, analyzed, and scored based on the distance, size, and quantity of particulate contamination. RESULTS: We analyzed 27 boards. Spatter was present on every board. The addition of luminol to the boards increased the amount of visible spatter. Most tests created <1000 blood spatters. Fluids are typically ejected as a fine mist. Every test included at least 1 blood spatter. The range of the average blood spatter size was 0.53×10(-3) to 7.11×10(-3) sq in. The amount of spatter detected did not show any apparent correlation with the patient's body mass index, the estimated blood loss, or the type of operation performed. CONCLUSIONS: Evacuation of the pneumoperitoneum during laparoscopic surgery results in consistent contamination. Most blood spatter is not visible to the naked eye. Our results suggest that all surgical participants should wear appropriate protective barriers and conscious measures should be undertaken to prevent environmental contamination during pneumoperitoneal evacuation.

Non-invasive imaging of cardiac electrophysiology in a cardiac resynchronization therapy defibrillator patient with a quadripolar left ventricular lead.

AIMS: The present study was aimed to assess epi- and endocardial ventricular electroanatomical activation during cardiac resynchronization therapy (CRT) by means of non-invasive imaging of cardiac electrophysiology (NICE) in a patient with a novel quadripolar LV lead. METHODS AND RESULTS: Non-invasive imaging of cardiac electrophysiology is a novel imaging tool which works by fusing data from high-resolution electrocardiogram (ECG) mapping with a model of the patient's individual cardiothoracic anatomy created from magnetic resonance imaging. This was performed in a cardiac resynchronization therapy defribrillator (CRT-D) patient with a quadripolar left ventricular (LV) lead. Beat-to-beat endocardial and epicardial ventricular activation sequences were computed using NICE during intrinsic conduction as well as during different pacing modes with different LV and biventricular (biV) pacing vectors. The spatial resolution of NICE enabled discrimination of the different pacing vectors during LV and biV pacing. Biventricular pacing resulted in a marked shortening of the total activation duration (TAD) of both ventricles when compared with intrinsic conduction and RV and LV pacing. CONCLUSION: Non-invasive imaging of cardiac electrophysiology facilitates non-invasive imaging of ventricular activation, which may be useful in CRT patients to locate the area of latest ventricular activation as the target area for LV lead placement. Moreover, especially in non-responders to CRT NICE may be further useful to determine the best electrical repositioning option.

Computer simulation of cardiac cryoablation: comparison with in vivo data.

Simulation of cardiac cryoablation by the finite element method can contribute to optimizing ablation results and understanding the effects of modifications prior to time-consuming and expensive experiments. In this work an intervention scenario using a 9 Fr 8 mm tip applicator applied to ventricular tissue was simulated using the effective heat capacity model based on Pennes' bioheat equation. Using experimentally obtained refrigerant flow rates and temperature profiles recorded by a thermocouple located at the tip of the applicator the cooling performance of the refrigerant was estimated and integrated by time and temperature dependent boundary conditions based on distinct phases of a freeze-thaw cycle. Our simulations exhibited a mean difference of approximately 6°C at the applicator tip compared to temperature profiles obtained during in vivo experiments. The presented model is a useful tool for simulation and validation of new developments in clinical cardiac cryoablation.

Profiling the human response to physical exercise: a computational strategy for the identification and kinetic analysis of metabolic biomarkers.

BACKGROUND: In metabolomics, biomarker discovery is a highly data driven process and requires sophisticated computational methods for the search and prioritization of novel and unforeseen biomarkers in data, typically gathered in preclinical or clinical studies. In particular, the discovery of biomarker candidates from longitudinal cohort studies is crucial for kinetic analysis to better understand complex metabolic processes in the organism during physical activity. FINDINGS: In this work we introduce a novel computational strategy that allows to identify and study kinetic changes of putative biomarkers using targeted MS/MS profiling data from time series cohort studies or other cross-over designs. We propose a prioritization model with the objective of classifying biomarker candidates according to their discriminatory ability and couple this discovery step with a novel network-based approach to visualize, review and interpret key metabolites and their dynamic interactions within the network. The application of our method on longitudinal stress test data revealed a panel of metabolic signatures, i.e., lactate, alanine, glycine and the short-chain fatty acids C2 and C3 in trained and physically fit persons during bicycle exercise. CONCLUSIONS: We propose a new computational method for the discovery of new signatures in dynamic metabolic profiling data which revealed known and unexpected candidate biomarkers in physical activity. Many of them could be verified and confirmed by literature. Our computational approach is freely available as R package termed BiomarkeR under LGPL via CRAN http://cran.r-project.org/web/packages/BiomarkeR/.

Single-beat noninvasive imaging of ventricular endocardial and epicardial activation in patients undergoing CRT.

BACKGROUND: Little is known about the effect of cardiac resynchronization therapy (CRT) on endo- and epicardial ventricular activation. Noninvasive imaging of cardiac electrophysiology (NICE) is a novel imaging tool for visualization of both epi- and endocardial ventricular electrical activation. METHODOLOGY/PRINCIPAL FINDINGS: NICE was performed in ten patients with congestive heart failure (CHF) undergoing CRT and in ten patients without structural heart disease (control group). NICE is a fusion of data from high-resolution ECG mapping with a model of the patient's individual cardiothoracic anatomy created from magnetic resonance imaging. Beat-to-beat endocardial and epicardial ventricular activation sequences were computed during native rhythm as well as during ventricular pacing using a bidomain theory-based heart model to solve the related inverse problem. During right ventricular (RV) pacing control patients showed a deterioration of the ventricular activation sequence similar to the intrinsic activation pattern of CHF patients. Left ventricular propagation velocities were significantly decreased in CHF patients as compared to the control group (1.6±0.4 versus 2.1±0.5 m/sec; p<0.05). CHF patients showed right-to-left septal activation with the latest activation epicardially in the lateral wall of the left ventricle. Biventricular pacing resulted in a resynchronization of the ventricular activation sequence and in a marked decrease of total LV activation duration as compared to intrinsic conduction and RV pacing (129±16 versus 157±28 and 173±25 ms; both p<0.05). CONCLUSIONS/SIGNIFICANCE: Endocardial and epicardial ventricular activation can be visualized noninvasively by NICE. Identification of individual ventricular activation properties may help identify responders to CRT and to further improve response to CRT by facilitating a patient-specific lead placement and device programming.

Oncogenes and pathway identification using filter-based approaches between various carcinoma types in lung.

Lung cancer accounts for the most cancer-related deaths. The identification of cancer-associated genes and the related pathways are essential to prevent many types of cancer. In this paper, a more systematic approach is considered. First, we did pathway analysis using Hyper Geometric Distribution (HGD) and significantly overrepresented sets of reactions were identified. Second, feature-selection-based Particle Swarm Optimisation (PSO), Information Gain (IG) and the Biomarker Identifier (BMI) for the identification of different types of lung cancer were used. We also evaluated PSO and developed a new method to determine the BMI thresholds to prioritize genes. We were able to identify sets of key genes that can be found in several pathways. Experimental results show that our method simplifies features effectively and obtains higher classification accuracy than the other methods from the literature.

A cellular automaton framework for infectious disease spread simulation.

In this paper, a cellular automaton framework for processing the spatiotemporal spread of infectious diseases is presented. The developed environment simulates and visualizes how infectious diseases might spread, and hence provides a powerful instrument for health care organizations to generate disease prevention and contingency plans. In this study, the outbreak of an avian flu like virus was modeled in the state of Tyrol, and various scenarios such as quarantine, effect of different medications on viral spread and changes of social behavior were simulated.The proposed framework is implemented using the programming language Java. The set up of the simulation environment requires specification of the disease parameters and the geographical information using a population density colored map, enriched with demographic data.The results of the numerical simulations and the analysis of the computed parameters will be used to get a deeper understanding of how the disease spreading mechanisms work, and how to protect the population from contracting the disease. Strategies for optimization of medical treatment and vaccination regimens will also be investigated using our cellular automaton framework.In this study, six different scenarios were simulated. It showed that geographical barriers may help to slow down the spread of an infectious disease, however, when an aggressive and deadly communicable disease spreads, only quarantine and controlled medical treatment are able to stop the outbreak, if at all.

Sensitivity- and effort-gain analysis: multilead ECG electrode array selection for activation time imaging.

Methods for noninvasive imaging of electric function of the heart might become clinical standard procedure the next years. Thus, the overall procedure has to meet clinical requirements as an easy and fast application. In this paper, we propose a new electrode array which improves the resolution of methods for activation time imaging considering clinical constraints such as easy to apply and compatibility with routine leads. For identifying the body-surface regions where the body surface potential (BSP) is most sensitive to changes in transmembrane potential (TMP), a virtual array method was used to compute local linear dependency (LLD) maps. The virtual array method computes a measure for the LLD in every point on the body surface. The most suitable number and position of the electrodes within the sensitive body surface regions was selected by constructing effort gain (EG) plots. Such a plot depicts the relative attainable rank of the leadfield matrix in relation to the increase in number of electrodes required to build the electrode array. The attainable rank itself was computed by a detector criterion. Such a criterion estimates the maximum number of source space eigenvectors not covered by noise when being mapped to the electrode space by the leadfield matrix and recorded by a detector. From the sensitivity maps, we found that the BSP is most sensitive to changes in TMP on the upper left frontal and dorsal body surface. These sensitive regions are covered best by an electrode array consisting of two L-shaped parts of approximately 30 cm x 30 cm and approximately 20 cm x 20 cm. The EG analysis revealed that the array meeting clinical requirements best and improving the resolution of activation time imaging consists of 125 electrodes with a regular horizontal and vertical spacing of 2-3 cm.

Cardiac anisotropy: is it negligible regarding noninvasive activation time imaging?

The aim of this study was to quantify the effect of cardiac anisotropy in the activation-based inverse problem of electrocardiography. Differences of the patterns of simulated body surface potential maps for isotropic and anisotropic conditions were investigated with regard to activation time (AT) imaging of ventricular depolarization. AT maps were estimated by solving the nonlinear inverse ill-posed problem employing spatio-temporal regularization. Four different reference AT maps (sinus rhythm, right-ventricular and septal pacing, accessory pathway) were calculated with a bidomain theory based anisotropic finite-element heart model in combination with a cellular automaton. In this heart model a realistic fiber architecture and conduction system was implemented. Although the anisotropy has some effects on forward solutions, effects on inverse solutions are small indicating that cardiac anisotropy might be negligible for some clinical applications (e.g., imaging of focal events) of our AT imaging approach. The main characteristic events of the AT maps were estimated despite neglected electrical anisotropy in the inverse formulation. The worst correlation coefficient of the estimated AT maps was 0.810 in case of sinus rhythm. However, all characteristic events of the activation pattern were found. The results of this study confirm our clinical validation studies of noninvasive AT imaging in which cardiac anisotropy was neglected.

A model based approach for multi-lead ECG array layout selection.

In this study an approach for testing electrode array schemes with respect to their ability to improve the resolution of methods for activation time imaging is proposed. First local linear dependency maps are computed using a virtual array method. These maps depict the torso surface areas where the body surface potential is most sensitive to changes in the transmembrane potential. The optimal number and position of the electrodes within the sensitive body surface regions was selected by constructing effort gain (EG) plots. Such a plot depicts the relative attainable rank of the leadfield matrix in relation to the increase in number of electrodes required to build the electrode array. From the sensitivity maps it was found that the BSP is most sensitive to changes in TMP on the upper left frontal and dorsal body surface. The EG analysis revealed that the optimal array meeting clinical requirements and improving the resolution of activation time imaging consists of 125 electrodes.

Semiautomatic volume conductor modeling pipeline for imaging the cardiac electrophysiology noninvasively.

In this paper we present an approach for extracting patient individual volume conductor models (VCM) using volume data acquired from Magnetic Resonance Imaging (MRI) for computational biology of electrical excitation in the patient's heart. The VCM consists of the compartments chest surface, lung surfaces, the atrial and ventricular myocardium, and the blood masses. For each compartment a segmentation approach with no or little necessity of user interaction was implemented and integrated into a VCM segmentation pipeline to enable the inverse problem of electrocardiography to become clinical applicable. The segmentation pipeline was tested using volume data from ten patients with structurally normal hearts.

Rank Based Selection of Electrode Positions for a Multi-Lead ECG Electrode Array.

Methods for noninvasive imaging of electrical function of the heart seem to become a clinical standard procedure the next years. Thus, the overall procedure has to meet clinical requirements as easy and fast application. In this study we propose a new electrode array meeting clinical requirements such as easy to apply and compatibility with routine leads. Within body surface regions of high sensitivity, identified in a prior, information content based study, the number of required electrodes was optimized using effort-gain plots. These plots were generated by applying a so called type one detector criterion. The optimal array was selected from a set of 12 electrode arrays. Each of them consists of two L-shaped regular spaced parts. The optimal array was found by comparing several layouts and electrode densities to the electrode array we use for clinical studies. It consists of 125 electrodes with a regular spacing between 2cm and 3cm.

A comparison of noninvasive reconstruction of epicardial versus transmembrane potentials in consideration of the null space.

We compare two source formulations for the electrocardiographic forward problem in consideration of their implications for regularizing the ill-posed inverse problem. The established epicardial potential source model is compared with a bidomain-theory-based transmembrane potential source formulation. The epicardial source approach is extended to the whole heart surface including the endocardial surfaces. We introduce the concept of the numerical null and signal space to draw attention to the problems associated with the nonuniqueness of the inverse solution and show that reconstruction of null-space components is an important issue for physiologically meaningful inverse solutions. Both formulations were tested with simulated data generated with an anisotropic heart model and with clinically measured data of two patients. A linear and a recently proposed quasi-linear inverse algorithm were applied for reconstructions of the epicardial and transmembrane potential, respectively. A direct comparison of both formulations was performed in terms of computed activation times. We found the transmembrane potential-based formulation is a more promising source formulation as stronger regularization by incorporation of biophysical a priori information is permitted.

Simulation of atrial electrophysiology and body surface potentials for normal and abnormal rhythm.

The effect of different atrial electrical activation sequences (sinus rhythm and atrial flutter circling in the right atrium) on the body surface potentials is investigated in this study. A realistic volume conductor model consisting of atria, lungs, chest and blood masses is generated from image stacks recorded by magnetic resonance imaging. The electrical sources-the transmembrane potentials-within the atrial volumetric model are simulated for different atrial rhythms employing a cellular automaton capable of considering different parameters depending on the specific properties of the tissues. The potentials on the torso surface are computed applying the finite element method for solving the differential equations derived from the bidomain theory. Both the simulated atrial activation patterns and the computed torso potentials for atrial sinus rhythm and atrial flutter are in qualitatively and quantitatively good agreement with data measured in humans. The simulation of body surface potentials generated by different electrical activation sequences in the atria or ventricles allows testing and assessing noninvasive imaging of cardiac electrophysiology, as both the potentials on the body surface and the reference activation in the heart are available.