Comprehensively characterizing heterogeneous and transversely isotropic properties of femur cortical bones.

Comprehensive characterization of the transversely isotropic mechanical properties of long bones along both the longitudinal and circumferential gradients is crucial for developing accurate mathematical models and studying bone biomechanics. In addition, mechanical testing to derive elastic, plastic, and failure properties of bones is essential for modeling plastic deformation and failure of bones. To achieve these, we machined a total of 336 cortical specimens, including 168 transverse and 168 longitudinal specimens, from four different quadrants of seven different sections of 3 bovine femurs. We conducted three-point bending tests of these specimens at a loading rate of 0.02 mm/s. Young's modulus, yield stress, tangential modulus, and effective plastic strain for each specimen were derived from correction equations based on classical beam theory. Our statistical analysis reveals that the longitudinal gradient has a significant effect on the Young's modulus, yield stress, and tangential modulus of both longitudinal and transverse specimens, whereas the circumferential gradient significantly influences the Young's modulus, yield stress, and tangential modulus of transverse specimens only. The differences in Young's modulus and yield stress between longitudinal specimens from different sections are greater than 40%, whereas those between transverse specimens are approximately 30%. The Young's modulus and yield stress of transverse specimens in the anterior quadrant were 18.81%/15.46% and 18.34%/14.88% higher than those in the posterior and lateral quadrants, respectively. There is no significant interaction between the longitudinal gradient and the circumferential gradient. Considering the transverse isotropy, it is crucial to consider loading direction when investigating the impact of circumferential gradients in the anterior, lateral, medial, and posterior directions. Our findings indicate that the conventional assumption of homogeneity in simulating the cortical bone of long bones may have limitations, and researchers should consider the anatomical position and loading direction of femur specimens for precise prediction of mechanical responses.

Atorvastatin Treatment for Atrial Fibrillation Reduces Serum High-Sensitivity C-Reactive Protein Levels.

We investigated whether serum hs-CRP levels predict the efficacy of atrial fibrillation (AF) treated with atorvastatin. Bibliographic databases were exhaustively searched for studies relevant to the research topic. Newcastle-Ottawa Scale (NOS) criteria, combined with the Quality Assessment of Diagnostic Accuracy Studies (QUADAS), were applied for study quality assessment. Our meta-analysis identified seven cohort studies (2006~2013), providing information on the change in serum hs-CRP levels in AF patients receiving atorvastatin therapy. After atorvastatin treatment, hs-CRP level in AF patients decreased significantly (SMD = 1.02, 95% CI: 0.58-1.47, P < 0.001). Subgroup analysis by country and hs-CRP detection methods suggested a negative relationship between atorvastatin treatment and hs-CRP levels among Chinese AF patients (SMD = 1.34, 95% CI: 1.00-1.69, P < 0.001) and by using ELISA method (SMD = 1.11, 95% CI: 0.51-1.71, P < 0.001), but not among Turkish population and using INA method (all P > 0.05). Egger's test showed no publication bias (P = 0.450). hs-CRP was clearly lowered in AF patients treated with atorvastatin, which may be helpful in the choice of statin agents for AF treatment. However, longer follow-ups are necessary to assess the clinical value of lowering hs-CRP in the clinical setting of AF treatment outcomes.

Tissue Factor Pathway Inhibitor-Coated Stents Inhibit Restenosis in a Rabbit Carotid Artery Model.

INTRODUCTION: Our aim was to study the efficacy and safety of tissue factor pathway inhibitor (TFPI)-coated stents in inhibiting restenosis in a rabbit carotid artery model. METHODS: Subculture was conducted in aorta smooth muscle cell, which was taken from male Wistar rat, and the 3-5-generation cells were taken for plasmid transfection and cytotoxicity experiment. TFPI microspheres were made of a TFPI plasmid which was enwrapped by poly-l-glutamic acid (PLGA). TFPI-coated stents (n = 7) and bare metal stents (n = 6) were implanted into prepared carotid artery stenosis model of New Zealand white rabbits. The transfection efficiency of TFPI gene and its influence on animal tissue, restenosis inhibition, and biochemical indicator were observed. RESULT: Tissue factor pathway inhibitor microspheres can transfect successfully into cells, and present no cytotoxicity. Autopsy results showed no pathological changes in liver and spleen of rabbits after implanting TFPI-coated stents. TFPI gene could transfect and express successfully in vessel wall cells, and thrombus was found in some lumens of bare metal stents group after 7 day, while no such thrombus was observed in coated stents group. Degree of hyperplasia of coronary endarterectomy in bare metal stents group was evidently higher than those in coated stents group. Obvious stent restenosis was discovered only in one case in bare metal stents group (diameter stenosis ≥50%). However, no case in coated stents group showed with stent restenosis. CONCLUSION: Tissue factor pathway inhibitor-coated stents could successfully transfect TFPI gene into vessel wall cells, thereby inhibiting restenosis without obvious side effect in the rabbit carotid artery model.

Assessment of atrial fibrillation and vulnerability in patients with Wolff-Parkinson-White syndrome using two-dimensional speckle tracking echocardiography.

PURPOSE: The aim was to assess atrial fibrillation (AF) and vulnerability in Wolff-Parkinson-White (WPW) syndrome patients using two-dimensional speckle tracking echocardiography (2D-STE). METHODS: All patients were examined via transthoracic echocardiography and 2D-STE in order to assess atrial function 7 days before and 10 days after RF catheter ablation. A postoperative 3-month follow-up was performed via outpatient visit or telephone calls. RESULTS: Results showed significant differences in both body mass index (BMI) and supraventricular tachycardia (SVT) duration between WPW patients and DAVNP patients (both P<0.05). Echocardiography revealed that the maximum left atrial volume (LAVmax) and the left ventricular mass index (LVMI) in diastole increased noticeably in patients with WPW compared to patients with DAVNP both before and after ablation (all P<0.05). Before ablation, there were obvious differences in the levels of SRs, SRe, and SRa from the 4-chamber view (LA) in the WPW patients group compared with patients in the DAVNP group (all P<0.05). In the AF group, there were significant differences in the levels of systolic strain rate (SRs), early diastolic strain rate (SRe), and late diastolic strain rate (SRa) from the 4-chamber view (LA) both before and after ablation (all P<0.05). In the non-AF group, there were decreased SRe levels from the 4-chamber view (LA/RA) pre-ablation compared to post-ablation (all P<0.05). CONCLUSION: Our findings provide convincing evidence that WPW syndrome may result in increased atrial vulnerability and contribute to the development of AF. Further, RF catheter ablation of AAV pathway can potentially improve atrial function in WPW syndrome patients. Two-dimensional speckle tracking echocardiography imaging in WPW patients would be necessary in the evaluation and improvement of the overall function of RF catheter ablation in a long-term follow-up period.

[Coronary artery and myocardium lesion comparison post atrioventricular ring radiofrequency catheter ablation with different catheters].

OBJECTIVE: To analyze the extent of myocardium and coronary artery lesion post atrioventricular ring radiofrequency catheter ablation with different tip catheters. METHODS: Twenty-one healthy dogs were randomly divided into 64 degrees C/50 W/100 s, 64 degrees C/100 W/100 s, 45 degrees C/45 W/100 s groups and ablated by 4 mm tip catheter, 8 mm tip catheter and irrigated tip catheter respectively. Left atrioventricular ring and right atrioventricular ring ablation were performed in all dogs. After ablation, myocardium lesion volume was calculated as 1/6pi x length x width x depth. Histological examinations were performed at the myocardium tissue at ablation sites. RESULTS: The lesion depths post 8 mm tip catheter ablation (7.18 +/- 1.72) mm and irrigated tip catheter ablation (7.99 +/- 1.77) mm were similar and significantly deeper than that post 4 mm tip catheter ablation (4.54 +/- 1.38) mm, P < 0.01. Similar results were found in terms of lesion volume [(356.76 +/- 94.44) mm(3) post 8 mm tip catheter ablation, (391.69 +/- 109.54) mm(3) post irrigated tip catheter ablation and (191.34 +/- 74.52) mm(3) post 4 mm tip catheter ablation]. Five (5/42, 11.9%) transmural myocardium necrosis and 8 (8/42, 19%) coronary artery lesions were observed post ablations. CONCLUSION: The extents of post ablation myocardium and coronary artery lesion were significantly higher induced by 8 mm tip catheter and irrigate tip catheter compared those by 4 mm tip catheter.

Radiofrequency catheter ablation of idiopathic ventricular tachycardia and symptomatic premature ventricular contraction originating from valve annulus.

BACKGROUND: Radiofrequency catheter ablation (RFCA) has been established as an effective and curative therapy for ventricular tachycardia (VT) and severely symptomatic premature ventricular contraction (PVC) from the outflow tract in structurally normal hearts. This study aimed to investigate electrophysiologic characteristics and effects of RFCA for patients with idiopathic VT and symptomatic PVC originating from the valve annulus. METHODS: Characteristics of body surface electrocardiogram (ECG) and endocardiogram in a successful RFCA target were analyzed in 16 patients with idiopathic VT and symptomatic PVC originating from the valve annulus. Additionally, the ECG characteristics of VT or PVC were compared with those of manifest Wolff-Parkinson-White (WPW) syndrome originating from the same site of origin in 15 patients. RESULTS: Thirteen patients were successful, 2 recurrent and 1 failed. The recurrent cases underwent successful ablation the second time guided by the Ensite 3000 mapping system. In all patients with the WPW syndrome, the characteristics of QRS morphology were well matched with those of the VT and PVC that originated from corresponding sites of origin. CONCLUSIONS: RFCA is an effective curative therapy for VT and symptomatic PVC originating from the valve annulus. There are specific characteristics in ECG and the ablation site could be located by means of the WPW syndrome accessory pathway's algorithm.

[Effects of catheter ablation of ventricular tachycardia and premature ventricular contraction originating from left and right ventricular outflow tracts].

OBJECTIVE: To observe the ECG and electrophysiological characteristic of patients with idiopathic ventricular tachycardia (VT) and premature ventricular contraction (PVC) originating from left (LVOT) and right (RVOT) ventricular outflow tracts and assess the clinical effect of radio frequency catheter ablation (RFCA) on these patients. METHODS: RFCA was performed in 58 patients (10 with VT and 48 with PVC, 5 patients with VT from RVOT under the guidance of non-contact mapping system Ensite3000). VT or PVC originated from LVOT in 15 patients (12 out of 15 from left sinus of Valsalva) and RVOT in 43 patients. RESULTS: (1) R wave in II, III, aVF leads was the common characteristics of VT or PVC originated from LVOT and RVOT and difference in wave duration index and R/S-wave amplitude ratio in V(1) or V(2) could be used to define VT and PVC originated from LVOT or RVOT. (2) Ablation was successful in 55 out of 58 patients (9 patients with the 2nd ablation, evaluated as arrhythmia-free at 3 months post ablation without medication) and failed in 3 patients. One patient developed pericardial tamponade during ablation and recovered without complication after related treatments. CONCLUSIONS: RFCA is an effective, safe and curative therapy for VT or PVC originated from LVOT and RVOT. Non-contact mapping system (Ensite3000) is a safe and reliable tool to guide mapping and ablation in patients with complex VT and unstable hemodynamics.

Protective effects of pyrrolidine dithiocarbamate on myocardium apoptosis induced by adriamycin in rats.

BACKGROUND: Effects of pyrrolidine dithiocarbamate (PDTC) on programmed cell death are controversial. It is unclear if PDTC has the protective effects on myocardial apoptosis induced by adriamycin (ADR) in rats. The present study was undertaken to study the protective effects of pyrrolidine dithiocarbamate (PDTC) on myocardium apoptosis induced by adriamycin (ADR) in rats and its mechanisms. METHODS: Forty male Wistar rats were randomly divided into five groups: control, ADR, ADR+PDTC 50 mg/kg, ADR+PDTC 100 mg/kg and ADR+PDTC 200 mg/kg group. Myocardial apoptosis was detected by electron microscopic examination and TUNEL assay. Myocardium p53 gene expression was examined by RT-PCR analysis. Location and distribution of p53 was observed by immunohistochemical assay. Myocardial expression of p53 protein was assessed by Western blot analysis. Activity of NF-kappaB was evaluated by Electrophoretic Mobility Shift Assay. RESULTS: Myocardial apoptotic index, expression of p53 mRNA, expression of p53 protein and the binding activity of NF-kappaB decreased significantly in ADR+PDTC groups compared with ADR group. All these change were significantly correlated with dose of PDTC. CONCLUSION: PDTC has preventive effects on myocardial apoptosis induced by ADR, which is probably associated with inhibiting binding activity of NF-kappa B and further regulating apoptosis-related gene expression and translation, and inhibiting myocardial apoptosis.

[Clinical evaluation of catheter ablation for idiopathic ventricular arrhythmia originating from ventricular outflow tract].

OBJECTIVE: To study the ECG and electrophysiological characteristic of idiopathic ventricular tachycardia (VT) and premature ventricular contraction (PVC) originating from ventricular outflow tract and assess the clinical effect of radiofrequency catheter ablation (RFCA) for treatment. METHODS: 105 patients aged from 12 to 73 years old were treated with RFCA. Activation mapping, pace mapping and non-contact mapping system of Ensite 3000 were used during the procedure. RESULTS: (1) VT and PVC were successfully ablated in 97 out of the 105 patients (93.3%), 15 were recurrent but succeed in the second time. (2) 84 patients originated from right ventricle outflow tract (RVOT) and the remaining 21 patients from left ventricle outflow tract (LVOT). (3) 3 patients have the pericardial tamponade during ablation. CONCLUSION: RFCA is an effective and curative therapy for ventricular arrhythmia originating from ventricular outflow tract.

[Regional denervation after myocardial infarction and its effect on ventricular repolarization].

OBJECTIVE: To investigate whether myocardial infarction (MI) causes heterogeneity of sympathetic innervation and to evaluate the effects of sympathetic stimulation on myocardial repolarization in the regions of denervation after MI. METHODS: Fourteen dogs were randomly divided into 2 equal groups: MI Group, undergoing ligation of the left anterior descending coronary artery, and Control Group, undergoing sham operation. Four weeks later thoracotomy was performed for the second time, the effective refractory period (ERP) of the non-infarcted myocardium at the base of heart proximal to the infarcted myocardium and the ERP of the non-infarcted myocardium at the cardiac apex distal to the infarcted myocardium by S(1)S(2) programmed stimulation. Then the left satellite ganglion was exposed, ligated, cut, and stimulated at the proximal end, and ERP was determined at the above mentioned regions again. After the ERP measurement the heart was taken out to undergo immunohistochemistry to observe the distribution of tyrosine hydroxylase (TH) positive nerve fibers. RESULTS: The ERP of the non-infarcted myocardium at the base of heart proximal to the infarcted myocardium was not significantly different from that of the non-infarcted myocardium at the cardiac apex distal to the infarcted myocardium before sympathetic stimulation in both groups. In MI Group, however, the ERP of the non-infarcted myocardium at the base of heart proximal to the infarcted myocardium was significantly shortened after stimulation at the satellite ganglion (141 ms +/- 10 ms) in comparison with that before the stimulation (162 ms +/- 9 ms, P < 0.01); and the ERP of the non-infarcted myocardium at the cardiac apex distal to the infarcted myocardium after sympathetic stimulation (157 ms +/- 8 ms) was not significantly different from that before sympathetic stimulation (161 ms +/- 6 ms), however, was significantly longer than that of the non-infarcted myocardium at the base of heart proximal to the infarcted myocardium (P < 0.05). In Control Group the ERP values of both the basal and apical regions were significantly shorter than those before stimulation at the same region (both P < 0.01), however, there were no significant differences in the ERP values at the same region before and after the stimulation for the 2 regions. Immunohistochemistry showed that TH positive nerve fibers were distributed in the whole heart of Control Group and in the heart base of MI Group, and no TH positive nerve fiber was seen in the cardiac apex of MI Group. CONCLUSION: Regional denervation occurs after MI; Spatial variation of regional sympathetic innervation leads to heterogeneity in cardiac repolarization after sympathetic stimulation.

Effects of Losartan on acute atrial electrical remodeling.

BACKGROUND: Atrial electrical remodeling (AER) contributes to the maintainance of atrial fibrillation (AF). This study was to compare the effects of Losartan with those of Diltiazem on tachycardia-induced acute AER in rabbits. METHODS: Twenty-one rabbits paced with maximal atrial capture rate for 3 hours in the right atrium (RA) were randomly divided into saline group, Diltiazem group and Losartan group. After autonomic blockage, we measured atrial effective refractory period (AERP), AERP rate adapting feature, AERP dispersion and RA conduction time at basic cycle lengths (BCLs) of 200 ms and 150 ms at baseline, 0.5 hour, 1 hour, 2 and 3 hours after rapid atrial pacing. RESULTS: In the saline group, there was a prompt decrease in AERP as a result of rapid atrial pacing, and AERP200 and AERP150 were shortened sharply within 0.5 hour of pacing (30.2 +/- 10.5 ms and 24.1 +/- 9.1 ms, respectively). The AERP did not change dramatically in the Diltiazem and Losartan groups. In the saline group, the value of (AERP200-AERP150)/50 ms in high RA was 0.17 +/- 0.08 at baseline and became significantly smaller at 0.5 hour (0.08 +/- 0.06), 1 hour (0.09 +/- 0.06), 2 hours (0.08 +/- 0.04) and 3 hours (0.09 +/- 0.05) (all P < 0.05), suggesting a reduction of rate adaptation of AERP. The value of (AERP200-AERP150)/50 ms in high RA did not change during the 3 hours of pacing in both Diltiazem and Losartan groups. In the saline group, AERP dispersion increased significantly at 2 and 3 hours (P < 0.05). However, Diltiazem could not prevent the increase of AERP dispersion at 3 hours (P < 0.05). During Losartan infusion, the AERP dispersion was no longer increased after rapid atrial pacing. There was no significant difference in RA conduction time among the three groups. CONCLUSION: Like calcium antagonist Diltiazem, Losartan could prevent AERP shortening and preserve rate adaptation of AERP after rapid atrial pacing. Losartan is more effective than Diltiazem in inhibiting the increase of AERP dispersion.