Shaped charge penetration into high-and ultrahigh-strength Steel-Fiber reactive powder concrete targets

Experiments on shaped charge penetration into high and ultrahigh strength steel-fiber reactive powder concrete(RPC) targets were performed in this paper.Results show that the variation of penetration depth and crater diameter with concrete strength is different from that of shaped charge penetration into normal strength concrete(NSC).The crater diameter of RPC is smaller than that of NSC penetrated by the shaped charge.The jet particles are strongly disturbed and hardly reach the crater bottom because they pass through the narrow channel formed by jet penetration into the RPC.The effects of radial drift velocity and gap effects of jet particles for a shaped charge penetration into RFC target are discussed.Moreover,a theoretical model is presented to describe the penetration of shaped charge into RPC target.As the concrete strength increases,the penetration resistance increases and the entrance crater diameter decreases.Given the drift velocity and narrow crater channel,the low-velocity jet particles can hardly reach the crater bottom to increase the penetration depth.Moreover,the narrow channel has a stronger interference to the jet particles with increasing concrete strength;hence,the gap effects must be considered.The drift velocity and gap effects,which are the same as penetration resistance,also have significant effects during the process of shaped charge penetration into ultrahigh-strength concrete,The crater profiles are calculated through a theoretical model,and the results are in good agreement with the experiments.

Ascending aortic dilatation rate after transcatheter aortic valve replacement in patients with bicuspid and tricuspid aortic stenosis: A multidetector computed tomography follow-up study

BACKGROUND: Current data is lacking about the progression of ascending aortic dilatation after transcatheter aortic valve replacement(TAVR) in aortic stenosis(AS) patients with bicuspid aortic valve(BAV) and tricuspid aortic valve(TAV). This study aims to assess the ascending aortic dilatation rate(mm/year) after TAVR in patients with BAV versus TAV using a multidetector computed tomography(MDCT) fol ow-up and to determine the predictors of ascending aortic dilatation rate.METHODS: Severe AS patients undergoing TAVR from March 2013 to March 2018 at our center with MDCT follow-ups were included. BAV and TAV were identified using baseline MDCT. Baseline and follow-up MDCT images were analyzed,and the diameters of ascending aorta were measured. Study end point is ascending aortic dilatation rate(mm/year). Furthermore,factors predicting ascending aortic dilatation rate were also investigated.RESULTS: Two hundred and eight patients were included,comprised of 86 BAV and 122 TAV patients. Five,4,3,2,and 1-year MDCT follow-ups were achieved in 7,9,30,46,and 116 patients. The ascending aortic diameter was significantly increased after TAVR in both BAV group(43.7±4.4 mm vs. 44.0±4.5 mm;P<0.001) and TAV group(39.1±4.8 mm vs. 39.7±5.1 mm;P<0.001). However,no difference of ascending aortic dilatation rate was found between BAV and TAV group(0.2±0.8 mm/year vs. 0.3±0.8 mm/year,P=0.592). Multivariate linear regression revealed paravalvular leakage(PVL) grade was independently associated with ascending aortic dilatation rate in the whole population and BAV group,but not TAV group. No aortic events occurred during follow-ups.CONCLUSION: Ascending aortic size continues to grow after TAVR in BAV patients,but the dilatation rate is mild and comparable to that of TAV patients. PVL grade is associated with ascending aortic dilatation rate in BAV patients post-TAVR.

A case of a successful post-transcatheter aortic valve replacement His bundle pacing

Dear editor,Transcatheter aortic valve replacement (TAVR) is a safe and effective treatment for severe aortic valve stenosis and aortic regurgitation. Multiple randomized trials have proved its therapeutic advantages in patients at any level of surgical risks.

Anemia and risk of periprocedural cerebral injury detected by diffusion-weighted magnetic resonance imaging in patients undergoing transcatheter aortic valve replacement

BACKGROUND: Anemia is prevalent in patients undergoing transcatheter aortic valve replacement(TAVR) and has been linked to impaired outcomes after the procedure. Few studies have evaluated the impact of anemia and new ischemic lesions post TAVR.METHODS: We prospectively enrolled 158 patients who received TAVR in our center. Anemia was defined according to the World Health Organization criteria as hemoglobin <12 g/dL in women and <13 g/dL in men. All patients underwent diffusion-weighted magnetic resonance imaging(DW-MRI) procedure before and within 4–7 days after TAVR. RESULTS: Anemia was present in 85(53.8%) patients who underwent TAVR, and 126(79.7%) patients had 718 new DW-MRI positive lesions with a mean of 4.54±5.26 lesions per patient. The incidence of new ischemic lesions was 81.2% in patients with anemia versus 78.1% in patients without anemia(P=0.629). Moreover, anemic patients had bigger total volume/lesions in the anterior cerebral artery/middle cerebral artery(ACA/MCA) and MCA regions compared to the non-anemic patients(31.89±55.78 mm^(3) vs. 17.08±37.39 mm^(3), P=0.049;and 54.54±74.72 mm^(3) vs. 33.75±46.03 mm^(3), P=0.034). Anemia was independently associated with the volume/lesion in the ACA/MCA(β=16.796, 95% confidence interval [95% CI] 2.001 to 31.591, P=0.026) and in the MCA zone(β=0.020, 95% CI 0.001 to 0.040, P=0.041). CONCLUSIONS: Patients with pre-procedural anemia may have bigger total volume/lesions in the ACA/MCA and MCA regions compared to the non-anemic patients. Whether the consequences of bigger total volume/lesions impact neurological and cognitive outcomes remains to be investigated.

Prediction of Short-Term Mortality after Valve Surgery： A Single Center＇s Perspective

To the Editor： Valve stenosis and regurgitation can lead to a series of symptoms, including chest distress and dyspnea. Valve replacement is an effective surgical procedure that improves patients＇ quality of life and life span and has played an increasingly important role in treating mitral valve diseases. Previous studies have reported different risk factors and independent predictors of increased mortality in patients with mitral valve replacement （MVR） and/or aortic valve replacement （AVR）. This study retrospectively reviewed data on patients undergoing valve surgery to determine the risk factors and predictors of short-term mortality in this patient population.