In order to find the most suitable algorithm of T-wave end point detection for clinical detection, we tested three methods, which are not just dependent on the threshold value of T-wave end point detection, i.e. wavelet method, cumulative point area method and trapezium area method, in PhysioNet QT database (20 records with 3 569 beats each). We analyzed and compared their detection performance. First, we used the wavelet method to locate the QRS complex and T-wave. Then we divided the T-wave into four morphologies, and we used the three algorithms mentioned above to detect T-wave end point. Finally, we proposed an adaptive selection T-wave end point detection algorithm based on T-wave morphology and tested it with experiments. The results showed that this adaptive selection method had better detection performance than that of the single T-wave end point detection algorithm. The sensitivity, positive predictive value and the average time errors were 98.93%, 99.11% and (-2.33±19.70) ms, respectively. Consequently, it can be concluded that the adaptive selection algorithm based on T-wave morphology improves the efficiency of T-wave end point detection.
ObjectiveTo study the effects of visceral adipose tissue area (VTA) and subcutaneous adipose tissue area (STA) on pulmonary ventilation function (PVF), and then to evaluate the impact of abdominal fat distribution on PVF.Methods Patients who underwent both PVF examination and abdominal CT between January 1st and December 31st, 2017 were selected from the electronic medical record system of West China Hospital of Sichuan University. The demographic data and PVF indexes [vital capacity (VC), forced vital capacity (FVC), forced expiratory volume in one second (FEV1), and 1 s rate (FEV1/FVC)] were collected. VTA and STA were obtained by abdominal CT measurement. The correlations between PVF indexes and VTA or STA were compared. Results A total of 224 patients were included. According to the VTA/STA ratio, there were 92 cases (41.07%) in group VTA/STA<1 and 132 cases (58.93%) in group VTA/STA≥1. VTA was not correlated with FVC (rs=−0.078, P=0.244), but negatively correlated with VC (rs=−0.138, P=0.040), FEV1 (rs=−0.141, P=0.034) and FEV1/FVC (rs=−0.137, P=0.041); STA had no correlation with VC, FVC, FEV1 or FEV1/FVC (P>0.05). VTA/STA was negatively correlated with VC (rs=−0.220, P=0.001), FEV1 (rs=−0.273, P<0.001) and FEV1/FVC (rs=−0.380, P<0.001), but it had no correlation with FVC (rs=−0.083, P=0.214). In group VTA/STA<1, VTA/STA was negatively correlated with FEV1 (rs =−0.205, P=0.050) and FEV1/FVC (rs=−0.317, P=0.002), but it had no correlation with VC or FVC (P>0.05). In group VTA/STA≥1, VTA/STA was negatively correlated with VC, FVC, FEV1 and FEV1/FVC (P<0.05). Conclusions VTA and STA are negatively correlated with PVF. The ratio of VTA/STA can be used as an index to evaluate the effect of abdominal fat distribution on lung function.
Objective To observe the changes of force bearing area and pressures of the rabbit tibiofemoral contact area and the biomechanical reconstruction level of joint after meniscal allograft. Methods A total of 28 Japanese rabbits were involved, weighing 3.0-3.5 kg, male or female. Of 28 rabbits, 7 were selected as meniscus donors, the remaining 21 rabbits were randomized into group A (n=7), group B (n=7), and group C (n=7). Group A underwent single knee opening and suturing, group B underwent medial meniscus excision and suturing, and group C underwent medial meniscus allograft after medial meniscus excision and suturing. The rabbits were sacrified at 12 weeks after operation for biomechanical observation through biomechanical machine and color imaging system. The meniscus tissue specimens were harvested from groups A and C to perform histological and immunohistochemical staining. Results After operation, all rabbits in 3 groups survived to the end of experiment. There were significant differences in the force bearing area and pressures at 0-90° flexion between group B and groups A, C (P lt; 0.05) at 12 weeks, showing no significant difference between group A and group C (P gt; 0.05); and there were significant differences in the force bearing area and pressures at 120° flexion among 3 groups (P lt; 0.05). The histological observation showed that the number of cartilage cells and collagen fibers returned to normal in group C, and the immunohistochemical staining showed that transplanted meniscus of group C contained large amounts of collagen fibers consisting of collagen type I and collagen type II. After 12 weeks of operation, the collagen type I contents were 0.612 5 ± 0.059 8 in group A and 0.587 2 ± 0.063 9 in group C, showing no significant difference (t=0.765, P=0.465); the collagen type II contents were 0.772 4 ± 0.081 5 and 0.814 3 ± 0.051 7, respectively, showing no significant difference (t= —0.136, P=0.894). Conclusion The allograft of rabbit meniscus can significantly increase the force bearing area of the tibiofemoral contact area and reduce the average pressure. Therefore, biomechanically speaking, the meniscus allograft can protect the articular cartilage and reconstruct the biomechanical balance.
Objective To investigate the changing tendency of mitral valve coaptation area and coaptation index of moderate mitral regurgitation （MR） in a dog experiment，and provide evidence for predicting long-term surgical results. Methods Real-time three-dimensional transesophogeal echocardiography （RT-3D-TEE） images were obtained in 15 dogs via Philips IE33 echocardiography system，and animal experiment model was established. RT-3D-TEE images were taken by gradually narrowing the ascending aorta and increasing left ventricular pressure till moderate MR. Original data were analyzed using Philips Qlab 7.0 three-dimensional quantification software，and mitral valve coaptation area and coaptation index were calculated. Specimen coaptation index of the mitral leaflets was calculated after the animal experiment. Cutoff values of coaptation index and left ventricular pressure were calculated by receiver operating characteristic （ROC） curve. Results There was statistical difference in coaptation area （198±50）mm2 vs. （123±36）mm2，P＜0.05） and coaptationindex （0.25±0.06 vs. 0.13±0.03，P＜0.05） between non-MR state and MR status of the 15 dogs. The area under the ROC curve of coaptation index and moderate MR was 0.879±0.019 with 95% CI 0.843 to 0.916，and the cutoff value was 0.213（P＜0.05）. The area under the ROC curve of left ventricular pressure and moderate MR was 0.882±0.021 swith 95% CI 0.840 to 0.923，and the cutoff value was 225 （P＜0.05）. There was no statistical difference between specimen mitral valve area and early-diastolic mitral leaflet area，specimen coaptation area and coaptation area，specimen coaptation index and coaptation index （P＞0.05）. Early-diastolic mitral leaflet area was significantly correlated with specimen mitral valve area （r=0.937，P＜0.05）. Coaptation area was significantly correlated with specimen coaptation area （r=0.917，P＜0.05）. Coaptation index was significantly correlated with specimen coaptation index （r=0.946，P＜0.05）. The correlation of coaptation index and specimen coaptation index was higher than those of coaptation area and specimen coaptation area，and earlydiastolic mitral leaflet area and specimen mitral valve area. Conclusions Both coaptation area and coaptation index significantly decrease in MR status. Coaptation index can more precisely reflect MR degree，and provide reference for prognosis of mitral valve repair. RT-3D TEE can accurately measure mitral valve coaptation area and coaptation index.
Objective To investigate the risk factors of high peritoneal transport characteristics in patients with end-stage renal disease undergoing initial continuous ambulatory peritoneal dialysis. Method The clinical data of continuous ambulatory peritoneal dialysis patients who underwent initial peritoneal dialysis and catheterization in the Department of Nephrology, West China Hospital of Sichuan University from January 2011 to December 2017 and completed the peritoneal equilibration test were collected retrospectively. According to the ratio of dialysate to plasma ratio for creatinine at 4 hour [D/Pcr (4h)] in the standard peritoneal equilibration test, the patients were divided into 4 groups (low transport, low average transport, high average transport and high transport). Spearman correlation analysis was used to analyze the related factors of D/Pcr (4h). The risk factors of high peritoneal transport characteristics were analyzed by ordered multi classification logistic regression. Results A total of 647 patients were included. The average age of the patients was (45.85±14.03) years, and the average D/Pcr (4h) was 0.67±0.12. Among them, there were 89 cases (13.76%) in the high transport group, 280 cases (43.28%) in the high average transport group, 234 cases (36.17%) in the low average transport group and 44 cases (6.80%) in the low transport group. Diabetic patients with D/Pcr (4h) were higher than those without diabetes mellitus (0.72±0.12 vs. 0.66±0.12; t=−4.005, P<0.001). Correlation analysis showed that age and 24-h urine volume were positively correlated with D/Pcr (4h); serum albumin, triglyceride, potassium, calcium, magnesium, phosphorus, hemoglobin, serum uric acid and creatinine were negatively correlated with D/Pcr (4h); body surface area (BSA), high sensitivity C-reactive protein, ferritin, cholesterol, sodium, intact parathyroid hormone and estimated giomerular filtration rate had no correlation with D/Pcr (4h). Regression analysis showed that serum albumin [odds ratio (OR)=0.842, 95% confidence interval (CI) (0.809, 0.877), P<0.001], serum uric acid [OR=0.996, 95%CI (0.994, 0.998), P<0.001], magnesium [OR=0.389, 95%CI (0.156, 0.965), P=0.042], BSA [OR=3.916, 95%CI (1.121, 13.680), P=0.032] were correlated with the incidence of peritoneal high transport characteristics. Conclusion Low serum albumin, high BSA, low magnesium and low serum uric acid were independent risk factors for high transport characteristics in initial PD patients.
The material properties and volume proportion of the fibers as well as the cross-sectional area proportion of nucleus pulposus vary greatly in different studies. The effect of these factors on the mechanical behavior of intervertebral discs (IVDs) are uncertain. The IVDs finite element models with different parameters were created to investigate the pressure, height, rotation, stress, and strain of the IVDs under loads: pure compression, rotation after compression or axial moment after compression. The results showed that the material properties of fibers had great impact on the mechanical behavior of IVDs, especially on the rotation angle. When the fiber volume ratio was small, its changes had a significant impact on the rotation angle of the IVDs. The area proportions of nucleus pulposus had relatively little effect on the mechanical behavior of IVDs. The IVDs rotation should be observed when validating the model. By adjusting the elastic modulus or volume ratio of fibers within a reasonable range, a model that could simulate the mechanical behavior of normal IVDs could be obtained. It was reasonable to make the area proportion of nucleus pulposus within 25%–50% for the IVDs finite element model. This study provides guidance and reference for finite element modeling of the IVDs and the investigation of the IVDs degeneration mechanism.
Ginger moxibustion has the effect of regulating zang-fu organs and activating qi and blood circulation. When used, ginger paste is required to be close to human skin. Currently, the ginger box used clinically in the hospital can't meet the requirement of large area fitting human skin, and the efficacy of ginger moxibustion is significantly reduced. In this study, a flexible ginger paste box was proposed, which was composed of flexible components polydimethylsiloxane (PDMS), spring and wire netting. The large flexibility of the structure made it fit well with human skin. Finite element method was used to study the fitting degree between ginger paste box and waist soft tissue. Finite element models of flexible ginger paste box and waist soft tissue were established based on Hypermesh and Abaqus software. The equivalent contact area between the flexible ginger paste box and waist was obtained by numerical simulation under different PDMS unilateral thickness, spring wire diameter, wire netting diameter and ginger paste layer thickness. The four parameters were taken as the influencing factors, and the equivalent contact area was taken as the optimization objective. The typical value analysis and variance analysis of S/N were performed by Taguchi method, and the results showed that among the four influencing factors, the wire netting diameter had the largest influence on equivalent contact area and its contribution rate reached 41.98%. The contribution rates of PDMS unilateral thickness, spring wire diameter and ginger paste layer thickness reached 36.48%, 13.97% and 6.50%, respectively. The optimized PDMS unilateral thickness, spring wire diameter, wire netting diameter and ginger paste layer thickness were 1.5, 0.4, 0.15, 35 mm, respectively, and the equivalent contact area was 95.60 cm2. The optimized flexible ginger paste box with great fitting performance can improve the effect of ginger moxibustion.
ObjectiveTo investigate the effects of meniscectomy and transplantation repair of the knee on the stress area and average pressure of the tibiofemoral articular surface so as to provide a reference for the relevant basic and clinical researches. MethodsSeven qualified right knee joints from adult men cadavers were selected. Required structure was retained after careful dissection. The pressure-sensitive paper was clipped to the proper size in accordance with the measured size of the tibial platform to reserve. The experiment was divided into 4 groups: normal knee group (group A), knee meniscus injury group (group B), knee meniscectomy group (group C), and knee meniscus transplantation group (group D). A horizontal incision above the meniscus was made in the position of knee joint capsule, and the pressure-sensitive paper was placed into the medial and lateral space of the knee joint, then the proximal tibia and distal femur were fixed stably and finally a universal mechanical machine was used for testing in appropriate environmental conditions (the knee joints were given longitudinal 700 N pressure at 0° extension and 30, 60, 90, and 120° flexion for continuous 120 seconds) until the full color reaction. The knee models were prepared, and then the universal mechanical machine was used to perform a test according to the method stated above respectively. The pressure-sensitive paper was removed, and the color negative films were separated and marked. Colorful image analysis system was used to calculate and analyze the stress area and average pressure after the scanner being used to collect image information. ResultsThe stress area was gradually reduced and the average pressure was gradually increased with increasing flexion angle of the knee. There was significant difference in the stress area and the average pressure between various flexion angles in 4 groups (P<0.05). Group C had significantly lower stress area and significantly higher average pressure than the other 3 groups (P<0.05), but no significant difference was found among groups A, B, and D (P>0.05). ConclusionThe stress of the tibiofemoral articular surface significantly increases after knee meniscus injury or resection, and the average pressure significantly increases. The stress of the tibiofemoral articular surface can be restored to almost normal after meniscus transplantation. Therefore, the injured meniscus should also be retained or repaired in the static state.
Valve transplantation is often used in the treatment of aortic valve insufficiency. However, after surgery, the reconstructed aortic roots have an expansion phenomenon, in which the lack of valve height causes the aortic valve to close again. In this paper, the effects of different aortic valve height design on valve opening and closing performance were studied. The optimal surgical plan was obtained by in vitro numerical simulation, providing technical support and theoretical basis. In this paper, six groups of three-dimensional geometric models with a valve height increment of ± 0.5 mm were established with a root diameter of 26.0 mm and a valve height of 14.0 mm. Through the structural mechanics calculation and analysis of the parameters such as maximum stress, valve area and contact force of the model, reasonable geometrical dimensions are obtained. The study found that the maximum stress values of the six groups of models ranged from 640 to 690 kPa, which was consistent with the results of the literature; the three-group models with valve heights of 13.5 mm, 14.0 mm, and 14.5 mm were within a reasonable range. The contact force value of the 6 groups of leaflets increased with the increase of valve height. Studies have shown that the height of the aortic valve has an effect on the aortic valve closure performance. A valve height that is too small or too large will reduce the aortic systolic valve area and affect the aortic function.
ObjectiveTo investigate the association between the imaging markers of ischemic cerebral small vessel disease and the occurrence of large hemispheric infarction (LHI).MethodsWe consecutively enrolled the patients with cerebral infarction in the middle cerebral artery blood supply area who admitted to the Department of Neurology, West China Hospital, Sichuan University between January 1st, 2015 and March 30th, 2016, and underwent head CT/MRI scans within one month of onset. LHI was defined as: the hypodensity was larger than 1/2 of the blood supply area of middle cerebral artery or more than 1/3 of the cerebral hemisphere within 6 hours on head CT at admission, or the infarction area was larger than 2/3 of the ipsilateral hemisphere on head MRI at admission. The basic clinical data and imaging data were collected, and the independent predictors of LHI and its independent correlation with ischemic cerebrovascular disease were explored by univariate and multivariate analyses.ResultsA total of 503 patients were included, 111 (22.1%) with LHI and 392 (77.9%) with non-LHI. Compared with the non-LHI patients, the LHI patients had a lower prevalence of white matter lesions, a lower Fazekas score, a lower prevalence of Fazekas score > 1, a lower prevalence of lacunae, a lower proportion of diabetes mellitus, a higher atrial fibrillation proportion of history, a shorter time from onset to treatment, a higher National Institute of Health Stroke Scale (NIHSS) score at admission, and a lower Glasgow Coma scale score; the distributions of TOAST types and locations of vascular stenosis were different (P<0.05). Multivariate analyses showed that white matter lesions [odds ratio (OR)=0.182, 95% confidence interval (CI) (0.050, 0.660), P=0.010], higher Fazekas score [OR=0.770, 95% CI (0.611, 0.970), P=0.027], and Fakazes score > 1 [OR=0.490, 95%CI (0.259, 0.928), P=0.029] were independent protective factors of LHI, while lacunae was not an independent factor of LHI [OR=0.583, 95% CI (0.265, 1.279), P=0.178]. Higher NIHSS score and history of atrial fibrillation were independent risk factors for LHI (P<0.001).ConclusionsThe occurrence and severity of white matter lesions (higher Fazekas score and Fazekas score > 1) are more in non-LHI group, and are independently related to the occurrence of LHI. The results suggest that ischemic preconditioning may have a protective effect on brain.