A meshfree method for simulating myocardial electrical activity

Image-based Cardiac Electrophysiology Simulation through the Meshfree Mixed Collocation Method

State-of-the-art solvers for in silico cardiac electro-physiology employ the Finite Element Method to solve complex anatomical models. While this is a robust and accurate tech-nique, it requires a high-quality mesh to prevent its accuracy from being severely deteriorated. The generation of a good quality mesh for realistic anatomical models can be very time-consuming, making the translation to the clinics challenging, especially if we try to use patient-specific geometries.Aiming to tackle this challenge, we propose an image-based model generation approach based on the meshfree Mixed Col-location Method. The flexibility provided by this method during model generation allows building meshfree models directly from the image data in an automatic procedure. Furthermore, this approach allows interpreting the simulation results directly in the voxel coordinates system of the image.We simulate electrical propagation in a porcine biventricular model with the proposed method and we compare the results with those obtained using the Finite Element Method. We conclude that the proposed method can generate results that are in good agreement with the Finite Element Method solution, alleviating the requirement of a mesh and user-input during modeling with only minimum efficiency overhead.

Risk factors of thromboembolism in nonvalvular atrial fibrillation patients with low CHA2DS2-VASc score

The risk of thromboembolism in patients with CHA2DS2-VASc score of 0 to 1 was low, and the anticoagulant therapy was not recommended. Although the CHA2DS2-VASc score was low, there were still many patients suffered from thrombotic events and stroke. We aim to investigate the risk factors of thrombotic events in nonvalvular atrial fibrillation (NVAF) patients with low CHA2DS2-VASc score.We retrospectively enrolled 595 consecutive NVAF patients with low CHA2DS2-VASc score (male: CHA2DS2-VASc = 0, female: CHA2DS2-VASc = 1). The general clinical data, blood biochemical data, and echocardiography results of the 595 patients were collected. Multivariate logistic regression models were used to evaluate risk factors of thrombosis. Receiver operating characteristic curve was used to identify the optimal cut-off value of the independent risk factors. A P value of <.05 (2-sided) was considered to be statistically significant.In multivariate analysis, lipoprotein (a) (Lp(a)) plasma level and left atrium diameter (LAD) were positively related to thromboembolism in NVAF patients with CHA2DS2-VASc score of 0 to 1 after adjustment for age, gender, and other variables (odds ratio [OR] = 1.02, 95% confidence interval [CI]: 1.01-1.03; OR = 1.13, 95% CI: 1.06-1.18). Lp(a) exerted a significant predictive value with area under the curve (AUC) of 0.62 (95% CI: 0.55-0.68, P < .01). The optimal cut-off value for Lp(a) predicting thrombotic events was 27.2 mg/dL (sensitivity 45.7%, specificity 73.4%). LAD showed a significant predictive value with AUC of 0.71 (95% CI: 0.64-0.78, P < .01). The optimal cut-off point for LAD predicting thrombotic events was 43.5 mm (sensitivity 47.1%, specificity 85.8%).High Lp(a) plasma level and left atrial dilatation might be independent risk factors of thrombotic events for NVAF patients with low CHA2DS2-VASc score.

Recurrent, late-onset pleural effusions in elderly patients receiving pacemaker therapy

Late-onset pacemaker-related pleural effusions (PEs) are rare and are often misdiagnosed with other entities. Our study aimed to detail the clinical features and management of PEs long after pacemaker insertion.We conducted a review of 6 consecutive elderly patients with PEs, who had undergone a new pacemaker insertion from September 2014 to January 2017. Also, the clinical characteristics and therapeutic courses of PEs were summarized.Two cases involved fluids after the first implantations, with pacing durations of 3 and 7 months. Two other cases developed PEs 3 or 4 months after the first replacement, with pacing durations of 6 and 11 years. Another 2 cases developed PEs 3 or 5 months following the second replacement, with total pacing durations of 16 and 18 years, respectively. The average interval was 4.17 months for the 6 cases from the time of the new pacemaker insertion to the occurrence of PEs. During the course, they had to be hospitalized repeatedly for thoracenteses because conventional treatments had only short-term effects. After the pacing settings were adjusted, PEs in all cases disappeared gradually. No patients were readmitted for PEs during the median follow-up period of 13 months.For elderly patients following implantation of a new pacemaker, PEs should be considered due to improper pacing settings, and corresponding adjustments to the device should be made.

The effect of myocardial action potential duration on cardiac pumping efficacy: a computational study

BACKGROUND AND AIMS

Although studies on the relation between arrhythmias and the action potential duration (APD) have been carried out, most of them are based only on electrophysiological factors of the heart and lack experiments that consider cardiac mechanical and electromechanical characteristics. Therefore, we conducted this study to clarify the relevance of the shortening of APD of a cell in relation to the mechanical contraction activity of the heart and the associated risk of arrhythmia.

METHODS

The human ventricular model used in this study has two dynamic characteristics: electrophysiological conduction and mechanical contraction. The model simulating electrophysiological characteristics was consisted of lumped parameter circuit that can mimic the phenomenon of ion exchange through the cell membrane of myocyte and consisted of 214,319 tetrahedral finite elements. In contrast, the model simulating mechanical contraction characteristics was constructed to mimic cardiac contraction by means of the crossbridge of a myofilament and consisted of 14,720 hermite-based finite elements to represent a natural 3D curve of the cardiac surface. First, we performed a single cell simulation and the electrophysiological simulation according to the change of the APD by changing the electrical conductivity of the I Ks channel. Thus, we confirmed the correlation between APD and intracellular Ca2+ concentration. Then, we compared mechanical response through mechanical simulation using Ca2+ data from electrical simulation.

RESULTS

The APD and the sum of the intracellular Ca2+ concentrations showed a positive correlation. The shortened APD reduced the conduction wavelength of ventricular cells by shortening the plateau and early repolarization in myocardial cells. The decrease in APD reduced ventricular pumping efficiency by more than 60% as compared with the normal group (normal conditions). This change is caused by the decline of ventricular output owing to reduced ATP consumption during the crossbridge of myofilaments and decreased tension.

CONCLUSION

The shortening of APD owing to increased electrical conductivity of a protein channel on myocardial cells likely decreases the wavelength and the pumping efficiency of the ventricles. Additionally, it may increase tissue sensitivity to ventricular fibrillation, including reentry, and cause symptoms such as dyspnea and dizziness.

Mode of initiation and clinical significance of malignant rapid ventricular arrhythmias: An observational study

The purpose of this study was to explore the modes of initiation and clinical significance of malignant rapid ventricular arrhythmias (MRVAs).The surface 12-lead electrocardiogram (ECG) or sustained electrocardiomonitor graph was analyzed in 79 patients. All patients had at least 1 MRVA after being admitted to the hospital.According to the length of coupling interval of the initial premature ventricular contraction of MRVA, the modes of initiation of MRVA were divided into the following types: those initiated by premature ventricular contraction with short coupling intervals in patients with normal Q-T interval, and for which short-long-short sequences before MRVA precipitation were not observed; those initiated following short-long-short sequences, which were divided into 2 types according to the length of Q-T interval: a normal Q-T interval and a long Q-T interval. On the basis of the different modes of onset, treatments of MRVA were different.MRVAs have different modes of onset depending on the patients' underlying condition. Prompt recognition of the mode of onset is necessary to facilitate appropriate management. These findings could have important pathophysiologic and clinical implications.

Three-dimensional reduction and finite element analysis improves the treatment of pelvic malunion reconstructive surgery: A case report

RATIONALE

Pelvic malunion is a rare complication and is technically challenging to correct owing to the complex three-dimensional (3D) geometry of the pelvic girdle. Hence, precise preoperative planning is required to ensure appropriate correction. Reconstructive surgery is generally a 2- or 3-stage procedure, with transiliac osteotomy serving as an alternative to address limb length discrepancy.

PATIENT CONCERNS

A 38-year-old female patient with a Mears type IV pelvic malunion with previous failed reconstructive surgery was admitted to our department due to progressive immobilization, increasing pain especially at the posterior pelvic arch and a leg length discrepancy. The leg discrepancy was approximately 4 cm and rotation of the right hip joint was associated with pain.

DIAGNOSIS

Radiography and computer tomography (CT) revealed a hypertrophic malunion at the site of the previous posterior osteotomy (Mears type IV) involving the anterior and middle column, according to the 3-column concept, as well as malunion of the left anterior arch (Mears type IV).

INTERVENTIONS

The surgery was planned virtually via 3D reconstruction, using the patient's CT, and subsequently performed via transiliac osteotomy and symphysiotomy. Finite element method (FEM) was used to plan the osteotomy and osteosynthesis as to include an estimation of the risk of implant failure.

OUTCOMES

There was not incidence of neurological injury or infection, and the remaining leg length discrepancy was ≤ 2 cm. The patient recovered independent, pain free, mobility. Virtual 3D planning provided a more precise measurement of correction parameters than radiographic-based measurements. FEM analysis identified the highest risk for implant failure at the symphyseal plate osteosynthesis and the parasymphyseal screws. No implant failure was observed.

LESSONS

Transiliac osteotomy, with additional osteotomy or symphysiotomy, was a suitable surgical procedure for the correction of pelvic malunion and provided adequate correction of leg length discrepancy. Virtual 3D planning enabled precise determination of correction parameters, with FEM analysis providing an appropriate method to predict areas of implant failure.

Echocardiography and Electrocardiography Variables Correlate With the New York Heart Association classification: An Observational Study of Ischemic Cardiomyopathy Patients

The aim of our study was to determine whether combinations of ultrasound echocardiography (UCG) and electrocardiography (EKG) parameters correlated with the functional status of ischemic cardiomyopathy (ICM) patients according to the New York Heart Association (NYHA) classification system.We assessed 536 elderly Chinese ICM patients according to the NYHA criteria, which included 196 patients with type 2 diabetes mellitus (T2DM). All of the patients underwent UCG. Transmural dispersion of ventricular repolarization was examined using EKG. Cumulative odds logistic regression was performed to evaluate associations between NYHA class and the demographic, clinical, UCG, and EKG variables based on the odds ratio (OR) and 95% confidence interval (CI). A Pearson analysis was also performed to examine correlations between the NYHA classification and the UCG and EKG variables.Based on the NYHA assessment, 140, 147, 138, and 111 patients were identified as class I, II, III and IV, respectively. A comparison of UCG and EKG variables based on T2DM status showed that CO and Tp-e differed significantly between all NYHA classes (P < .05 for all), with values of each increasing with increasing NYHA class regardless of T2DM status. Multivariate logistic regression analysis showed that the disease course (OR: 1.30; 95% CI: 1.20-1.40), heart rate (OR: 1.16; 95% CI: 1.12-1.21), T wave peak to endpoint (Tp-e; OR: 1.22; 95% CI: 1.18-1.27), dispersion of the QT interval (OR: 0.98; 95% CI: 0.95-1.22), left ventricular fractional shortening (OR: 0.82; 95% CI: 0.78-0.87), cardiac output (CO; OR: 5.58; 95% CI: 3.08-10.13) were significantly associated with the NYHA class (P < .0001 for all). A Pearson correlation analysis showed that Tp-e (r = 0.75982, P < .0001), CO (r = 0.56072, P < .0001), and stroke volume (r = -0.14839, P = .0006) significantly correlated with the NYHA class.An index consisting of Tp-e and CO will be useful for corroborating the results of the NYHA assessment of ICM patients.

Oncostatin M was associated with thrombosis in patients with atrial fibrillation

The mechanism underlying thrombosis in atrial fibrillation (AF) is not yet clearly understood. Oncostatin M (OSM), as a member of IL-6 family, is involved in atherosclerosis-mediated thrombosis. The present study hypothesizes that OSM and its downstream factors play a role in thrombogenesis in AF.The specimens of left atrial appendages collected from patients with rheumatic mitral stenosis who underwent valve replacement were divided into 3 groups: sinus rhythm, AF(+)/thrombus(-), and AF(+)/thrombus(+) group. The macrophage infiltration in atrial tissue was assessed by immunohistochemistry, and the amount of OSM, tissue factor (TF), and tissue factor pathway inhibitors (TFPIs) was detected by Western blot.The infiltration of the M1 macrophages was significantly increased in the AF with thrombus group compared with the sinus rhythm group (P = .03). Moreover, the expression of OSM and TF was much higher in the AF with thrombus group compared with the sinus rhythm group (P = .02, .009, respectively) while the TFPI was decreased in the AF with thrombus group (P = .04).OSM might be correlated with thrombosis in patients with AF mediated by TF and TFPI.