Towards Personalized Cardiology: Multi-Scale Modeling of the Failing Heart

BACKGROUND

Despite modern pharmacotherapy and advanced implantable cardiac devices, overall prognosis and quality of life of HF patients remain poor. This is in part due to insufficient patient stratification and lack of individualized therapy planning, resulting in less effective treatments and a significant number of non-responders.

METHODS AND RESULTS

State-of-the-art clinical phenotyping was acquired, including magnetic resonance imaging (MRI) and biomarker assessment. An individualized, multi-scale model of heart function covering cardiac anatomy, electrophysiology, biomechanics and hemodynamics was estimated using a robust framework. The model was computed on n=46 HF patients, showing for the first time that advanced multi-scale models can be fitted consistently on large cohorts. Novel multi-scale parameters derived from the model of all cases were analyzed and compared against clinical parameters, cardiac imaging, lab tests and survival scores to evaluate the explicative power of the model and its potential for better patient stratification. Model validation was pursued by comparing clinical parameters that were not used in the fitting process against model parameters.

CONCLUSION

This paper illustrates how advanced multi-scale models can complement cardiovascular imaging and how they could be applied in patient care. Based on obtained results, it becomes conceivable that, after thorough validation, such heart failure models could be applied for patient management and therapy planning in the future, as we illustrate in one patient of our cohort who received CRT-D implantation.

Probabilistic sparse matching for robust 3D/3D fusion in minimally invasive surgery

Classical surgery is being overtaken by minimally invasive and transcatheter procedures. As there is no direct view or access to the affected anatomy, advanced imaging techniques such as 3D C-arm computed tomography (CT) and C-arm fluoroscopy are routinely used in clinical practice for intraoperative guidance. However, due to constraints regarding acquisition time and device configuration, intraoperative modalities have limited soft tissue image quality and reliable assessment of the cardiac anatomy typically requires contrast agent, which is harmful to the patient and requires complex acquisition protocols. We propose a probabilistic sparse matching approach to fuse high-quality preoperative CT images and nongated, noncontrast intraoperative C-arm CT images by utilizing robust machine learning and numerical optimization techniques. Thus, high-quality patient-specific models can be extracted from the preoperative CT and mapped to the intraoperative imaging environment to guide minimally invasive procedures. Extensive quantitative experiments on 95 clinical datasets demonstrate that our model-based fusion approach has an average execution time of 1.56 s, while the accuracy of 5.48 mm between the anchor anatomy in both images lies within expert user confidence intervals. In direct comparison with image-to-image registration based on an open-source state-of-the-art medical imaging library and a recently proposed quasi-global, knowledge-driven multi-modal fusion approach for thoracic-abdominal images, our model-based method exhibits superior performance in terms of registration accuracy and robustness with respect to both target anatomy and anchor anatomy alignment errors.

Data-driven estimation of cardiac electrical diffusivity from 12-lead ECG signals

Diagnosis and treatment of dilated cardiomyopathy (DCM) is challenging due to a large variety of causes and disease stages. Computational models of cardiac electrophysiology (EP) can be used to improve the assessment and prognosis of DCM, plan therapies and predict their outcome, but require personalization. In this work, we present a data-driven approach to estimate the electrical diffusivity parameter of an EP model from standard 12-lead electrocardiograms (ECG). An efficient forward model based on a mono-domain, phenomenological Lattice-Boltzmann model of cardiac EP, and a boundary element-based mapping of potentials to the body surface is employed. The electrical diffusivity of myocardium, left ventricle and right ventricle endocardium is then estimated using polynomial regression which takes as input the QRS duration and electrical axis. After validating the forward model, we computed 9500 EP simulations on 19 different DCM patients in just under three seconds each to learn the regression model. Using this database, we quantify the intrinsic uncertainty of electrical diffusion for given ECG features and show in a leave-one-patient-out cross-validation that the regression method is able to predict myocardium diffusion within the uncertainty range. Finally, our approach is tested on the 19 cases using their clinical ECG. 84% of them could be personalized using our method, yielding mean prediction errors of 18.7ms for the QRS duration and 6.5° for the electrical axis, both values being within clinical acceptability. By providing an estimate of diffusion parameters from readily available clinical data, our data-driven approach could therefore constitute a first calibration step toward a more complete personalization of cardiac EP.

Response of microbial communities to long-term fertilization depends on their microhabitat

The objective of this study was to characterize the microbial communities attached to clay (< 2 μm), fine silt (2-20 μm), coarse silt (20-63 μm) and sand-sized fractions [> 63 μm; including particulate organic matter (POM)] of an arable soil and analyse their response to more than 100 years of two different fertilization regimes. Mild ultrasonic dispersal, wet-sieving and centrifugation allowed the separation of soil particles with the majority of bacterial cells and DNA still attached. Fertilizations increased soil organic carbon (SOC), total DNA and the abundance of bacterial, archaeal and fungal rRNA genes more strongly in the larger-sized fractions than in fine silt, and no effect was seen with clay, the latter representing above 70% of the total microbial populations. A highly positive correlation was found between microbial rRNA genes and the surface area provided by the particles, while the correlation with SOC was lower, indicating a particle-size-specific heterogeneous effect of SOC. The prokaryotic diversity responded more strongly to fertilization in the larger particles but not with clay. Overall, these results demonstrate that microbial responsiveness to long-term fertilization declined with smaller particle sizes and that especially clay fractions exhibit a high buffering capacity protecting microbial cells against changes even after 100 years under different agricultural management.

Semen collection and artificial inseminationin cockatiels (Nymphicus hollandicus)--a potential model for psittacines

STUDY

Since many psittacine species are endangered and also rare in captivity, the number of offspring produced from breeding is crucial. Many potential breeding birds in species conservation programs are force-paired, and the eggs of many clutches are frequently infertile. Furthermore, male infertility is a common problem. The use of artificial insemination may increase the number of fertile eggs.

MATERIAL AND METHODS

In this study, 32 cockatiels (Nymphicus hollandicus) were divided into two groups. In one group, the males were endoscopically sterilised. The males of the other group were used as semen donors. After collection using a novel massage technique, semen samples were examined microscopically to assess contamination and quality. Samples with medium to high sperm concentrations, medium to high motility and no contaminants were used for intracloacal artificial insemination of hens in the group with sterile males.

RESULTS

In total, 74.2% of all attempts to collect semen were successful. Insemination resulted in fertilisation of 17 of 23 eggs (73.9%), which was slightly lower than the natural fertilisation rate (88.4%). No negative effects were observed on the oviposition interval of the inseminated hens throughout the entire study.

CLINICAL RELEVANCE

Easily applicable in veterinary practice, this study demonstrates that the use of artificial insemination may be a valuable tool to address reproductive failure of psittacines in breeding projects.

Finite dose skin mass balance including the lateral part: comparison between experiment, pharmacokinetic modeling and diffusion models

This work investigates in vitro finite dose skin absorption of the model compounds flufenamic acid and caffeine experimentally and mathematically. The mass balance in different skin compartments (donor, stratum corneum (SC), deeper skin layers (DSL), lateral skin parts and acceptor) is analyzed as a function of time. For both substances high amounts were found in the lateral skin compartment after 6h of incubation, which emphasizes not to elide these parts in the modeling. Here, three different mathematical models were investigated and tested with the experimental data: a pharmacokinetic model (PK), a detailed microscopic two-dimensional diffusion model (MICRO) and a macroscopic homogenized diffusion model (MACRO). While the PK model was fitted to the experimental data, the MICRO and the MACRO models employed input parameters derived from infinite dose studies to predict the underlying diffusion process. All models could satisfyingly predict or describe the experimental data. The PK model and MACRO model also feature the lateral parts.

Erythropoietin-driven signalling and cell migration mediated by polyADP-ribosylation

Background:

Recombinant human erythropoietin (EPO) is the leading biotechnology engineered hormone for treatment of anaemia associated with chronic conditions including kidney failure and cancer. The finding of EPO receptors on cancer cells has raised the concern that in addition to its action in erythropoiesis, EPO may promote tumour cell growth. We questioned whether EPO-induced signalling and consequent malignant cell manifestation is mediated by polyADP-ribosylation.

Methods:

Erythropoietin-mediated PARP (polyADP-ribose polymerase-1) activation, gene expression and core histone H4 acetylation were examined in UT7 cells, using western blot analysis, RT–PCR and immunofluorescence. Erythropoietin-driven migration of the human breast epithelial cell line MDA-MB-435 was determined by the scratch assay and in migration chambers.

Results:

We have found that EPO treatment induced PARP activation. Moreover, EPO-driven c-fos and Egr-1 gene expression as well as histone H4 acetylation were mediated via polyADP-ribosylation. Erythropoietin-induced cell migration was blocked by the PARP inhibitor, ABT-888, indicating an essential role for polyADP-ribosylation in this process.

Conclusions:

We have identified a novel pathway by which EPO-induced gene expression and breast cancer cell migration are regulated by polyADP-ribosylation. This study introduces new possibilities regarding EPO treatment for cancer-associated anaemia where combining systemic EPO treatment with targeted administration of PARP inhibitors to the tumour may allow safe treatment with EPO, minimising its possible undesirable proliferative effects on the tumour.

Automatic region-of-interest segmentation and pathology detection in magnetically guided capsule endoscopy

Magnetically-guided capsule endoscopy (MGCE) was introduced in 2010 as a procedure where a capsule in the stomach is navigated via an external magnetic field. The quality of the examination depends on the operator's ability to detect aspects of interest in real time. We present a novel two step computer-assisted diagnostic-procedure (CADP) algorithm for indicating gastritis and gastrointestinal bleedings in the stomach during the examination. First, we identify and exclude subregions of bubbles which can interfere with further processing. Then we address the challenge of lesion localization in an environment with changing contrast and lighting conditions. After a contrast-normalized filtering, feature extraction is performed. The proposed algorithm was tested on 300 images of different patients with uniformly distributed occurrences of the target pathologies. We correctly segmented 84.72% of bubble areas. A mean detection rate of 86% for the target pathologies was achieved during a 5-fold leave-one-out cross-validation.

[Urinary bladder perforation caused by a loosened acetabular reinforcement ring]

Reinforcement cages are widely used for the treatment of large acetabular bone defects. We report the case of a loosened Burch-Schneider reinforcement ring causing a recurrent macrohaematuria due to a perforation of the urinary bladder. After performing several diagnostic procedures, the patient underwent interdisciplinary revision surgery. Due to the severe destruction of the acetabular bone stock and an infection of the total hip prosthesis as confirmed by fresh frozen section, the hip prosthesis was explanted. At the last follow-up the patient was free of infect-related symptoms and was able to walk with one crutch.

[Incidence of anterior intertrochanteric ossifications after total hip arthroplasty--a retrospective long-term follow-up study]

AIM

This retrospective study investigates the incidence of anterior intertrochanteric ossifications (AIO), especially in comparison with heterotopic ossifications classified according to Brooker. A classification system of AIO regarding short-term results (< 1 year after surgery) was introduced in 2003: AIO occurred solely in 13 % of all cases (ossifications according to Brooker grade 0) and would have been "overlooked" without a lateral X-ray. The incidence of AIO combined with ossifications according to Brooker > 0 was 48.8 % of all cases. Our study reports long-term results, furthermore correlations between ossifications and clinical outcome, rated by the Harris hip score (HHS) and range of motion (ROM), are evaluated.

MATERIAL AND METHODS

149 cementless total hip arthroplasties (Hofer-Imhof threaded cup, straight stem), implanted into 140 patients from November 1991 to December 1994 underwent complete clinical and radiological follow-up from December 2005 to October 2006. The average age of the 81 female and 59 male patients at the time of implantation was 64 years. Without exception, a conventional, transgluteal approach (Bauer) was performed. All patients received indomethacin prophylaxis for 8 consecutive days after surgery. Current X-rays (a.-p. and lateral view) were evaluated in comparison with the former X-rays.

RESULTS

AIO were found in 77 cases (51.7 %), heterotopic ossifications corresponding to Brooker in 93 cases (62.4 %), a combination of AIO and Brooker in 58 cases (38.9 %) and solitary AIO in 19 cases (12.8 %). HHS and ROM were not significantly altered by ossifications.

CONCLUSION

Our long-term findings compare with the short-term results (indicating lack of new bone formation [heterotopic ossification] after more than one year after surgery, as previously described in the literature concerning ossifications according to Brooker) and verify the incidence rate of solitary AIO. Despite a minor correlation with clinical outcome, AIO could be considered as a possible indicator for predilection of heterotopic bone formation, especially if revision arthroplasty or THA of the contralateral side is needed.