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Unexplained fetal tachycardia:A case report

BACKGROUND This study aimed to explore the possible etiology and treatment of severe fetal tachycardia in the absence of organic disease and provide a reference for clinical management of severe fetal tachycardia.CASE SUMMARY A 29-year-old pregnant woman,with a gravidity 1 parity 0,presented with a fetal heart rate(FHR)of 243 beats per minute during a routine antenatal examination at 31+2 wk of gestation.Before termination of pregnancy at 38 wk of gestation,the FHR repeatedly showed serious abnormalities,lasting more than 30 min.However,the pregnant woman and the fetus had no clinical symptoms,and repeated examination revealed no organic lesions.The mother and the baby were regularly followed up.CONCLUSION This was a case of severe fetal tachycardia with no organic lesions and management based on clinical experience.

Peripartum Cardiomyopathy Complicated by Ventricular Tachycardia during Labor: A Case Report and Literature Review

Background: Peripartum cardiomyopathy (PPCM) is a rare disease that typically affects young, healthy women. Because PPCM is associated with significant mortality, timely diagnosis and management are essential. Ventricular tachycardia (VT) is a major complication and contributor to sudden death. Available data on VT in patients with PPCM are limited. Aim: This case report demonstrates the clinical presentation, antenatal care, and management of labor and delivery in a patient with PPCM complicated by VT. Case report: 36-year old patient G4P3 presents at 27 weeks gestation to the emergency department complaining of chest tightness, palpitations, and profuse sweating. Peripartum cardiomyopathy was diagnosed after her last pregnancy a few years prior. Ventricular tachycardia was diagnosed at this visit and treated successfully. The remainder of the pregnancy was uneventful until she had another episode of ventricular tachycardia during labor. Treatment using antiarrhythmics (diltiazem, amiodarone, adenosine) highlights the importance of prompt intervention and the need for a range of therapeutic options. Results: This case demonstrated successful VT management during pregnancy and labor, emphasizing multidisciplinary collaboration, influencing maternal and fetal outcomes positively, providing insights into optimal care strategies. Conclusion: Peripartum cardiomyopathy complicated by ventricular tachycardia is a life-threatening combination. This case highlights the importance of timely diagnosis and management with combined care between cardiologists, maternal fetal medicine specialists and anesthesiologists to prevent morbidities and sudden maternal death.

Optimal interval for delayed retrieval surgery with reciprocating morcellators after enucleation of giant prostatic hyperplasia in holmium laser enucleation of the prostate

Objective:The aim of this research was to evaluate the efficiency of reciprocating morcellation for removing giant benign prostatic hyperplasia during holmium laser enucleation of the prostate,investigate whether performing morcellation as a two-stage procedure improves tissue retrieval efficiency,and seek to determine the optimal interval between the two surgeries.Methods:This study included nine cases of holmium laser enucleation of the prostate with an enucleated prostate weight exceeding 200 g,indicative of substantial prostate enlargement.Morcellation was performed on Day 0(n=4),Day 4(n=1),Day 6(n=1),and Day 7(n=3).The intervals were compared regarding the morcellation efficiency,beach ball presence,and pathology.Results:The mean estimated prostate volume was 383(range 330e528)mL;the median enucleation weight was 252(interquartile range[IQR]222,342)g;and the median enucleation time was 83(IQR 62,100)min.The mean morcellation efficiency was 1.44(SD 0.55)g/min on Day 0 and 13.69(SD 2.46)g/min on day 7.The morcellation efficiency was 4.15 g/min and 10.50 g/min on Day 4 and Day 6,respectively,with significantly higher in the two-stage group compared to one-stage group(11.0 g/min vs.1.5 g/min;p=0.014).Efficiency was strongly correlated with intervals(p<0.001);the incidences of beach balls were 100%(4/4)and 60%(3/5)in the immediate and two-stage surgery groups,respectively.Conclusion:The efficiency of two-stage morcellation with reciprocating morcellators was highly related to the postoperative interval,with the maximum efficiency reached on Day 7.

Massive inferior wall aneurysm presenting with ventricular tachycardia and refractory cardiomyopathy requiring multiple interventions:A case report

BACKGROUND Inferior wall left ventricular aneurysms are rare,they develop after transmural myocardial infarction(MI)and may be associated with poorer prognosis.We present a unique case of a large aneurysm of the inferior wall complicated by ventricular tachycardia(VT)and requiring surgical resection and mitral valve replacement.CASE SUMMARY A 59-year-old male was admitted for VT one month after he had a delayed presentation for an inferior ST-segment elevation MI and was discovered to have a large true inferior wall aneurysm on echocardiography and confirmed on coronary computed tomography(CT)angiography.Due to the sustained VT,concern for aneurysm expansion,and persistent heart failure symptoms,the patient was referred for surgical resection of the aneurysm with patch repair,mitral valve replacement,and automated implantable cardioverter defibrillator insertion with significant improvement in functional and clinical status.CONCLUSION Inferior wall aneurysms are rare and require close monitoring to identify electrical or contractile sequelae.Coronary CT angiography can outline anatomic details and guide surgical intervention to ameliorate life-threatening complications and improve performance status.

Wide QRS complex tachycardia in a patient with wide QRS complex sinus rhythm due to left bundle branch block pattern

A 58-year-old man with hypertension and half a year ago documented left bundle branch block(LBBB)in his past history presented with progressive dyspnea.A pre-admission echocardiography showed severely depressed systolic left ventricular function[ejection fraction(EF)=27%],diffuse hypokinesis and dilated heart chambers consistent with dilated cardiomyopathy(DCM).

Antitachycardia pacing programming in implantable cardioverter defibrillator:A systematic review

Implantable cardioverter defibrillator(ICD) programminginvolves several parameters. In recent years antitachycardia pacing(ATP) has gained an increasing importance in the treatment of ventricular arrhythmias, whether slow or fast. It reduces the number of unnecessary and inappropriate shocks and improves both patient's quality of life and device longevity. There is no clear indication regarding the type of ATP to be used, except for the treatment of fast ventricular tachycardias(188 bpm-250 bpm) where it has been shown a greater efficacy and safety of burst compared to ramp; 8 impulses in each sequence of ATP appears to be the best programming option in this setting. Beyond ATP use, excellent clinical results were obtained with programming standardization following these principles: extended detection time in ventricular fibrillation(VF) zone; supraventricular discrimination criteria up to 200 bpm; first shock in VF zone at the maximum energy in order to reduce the risk of multiple shocks. The MADIT-RIT trial and some observational registries have also recently demonstrated that programming with a widespread use of ATP, higher cut-off rates or delayed intervention reduces the number of inappropriate and unnecessary therapies and improves the survival of patients during mid-term follow-up.

Bidirectional rotating direct-current triboelectric nanogenerator with self-adaptive mechanical switching for harvesting reciprocating motion

Amid the growing interest in triboelectric nanogenerators(TENGs)as novel energy-harvesting devices,several studies have focused on direct current(DC)TENGs to generate a stable DC output for operating electronic devices.However,owing to the working mechanisms of conventional DC TENGs,generating a stable DC output from reciprocating motion remains a challenge.Accordingly,we propose a bidirectional rotating DC TENG(BiR-TENG),which can generate DC outputs,regardless of the direction of rotation,from reciprocating motions.The distinct design of the BiR-TENG enables the mechanical rectification of the alternating current output into a rotational-direction-dependent DC output.Furthermore,it allows the conversion of the rotational-direction-dependent DC output into a unidirectional DC output by adapting the configurations depending on the rotational direction.Owing to these tailored design strategies and subsequent optimizations,the BiR-TENG could generate an effective unidirectional DC output.Applications of the BiR-TENG for the reciprocating motions of swinging doors and waves were demonstrated by harnessing this output.This study demonstrates the potential of the BiR-TENG design strategy as an effective and versatile solution for energy harvesting from reciprocating motions,highlighting the suitability of DC outputs as an energy source for electronic devices.

Low temperature quasi-superplasticity of ZK60 alloy prepared by reciprocating extrusion

Fine-grained ZK60 alloy was prepared by 2-pass reciprocating extrusion, and the low temperature superplasticity was conducted in a temperature range from 443 to 523 K and an initial strain rate ranging from 3.3×10^-4 to 3.3×10-2^s^-1. The results show that the alloy has an equiaxed grain structure with an average grain size of about 5.0μm, and the sizes of broken secondary particles and precipitates are no more than 175 and 50 nm, respectively. The alloy exhibits quasi-superplasticity with a maximum elongation of 270% at 523 K and an initial strain rate of 3.3×10^-4 s^-1. The strain rate sensitivity m is less than 0.2 at 443 and 473 K, and it is 0.42 at 523 K. The apparent activation energies at temperature below 473 K and at 523 K are less than 63.2 and 110.6 kJ/mol, respectively At temperature below 473 K, mainly intragranular sliding contributes to superplastic flow. At 523 K, grain boundary sliding is the dominant deformation mechanism, and dislocation creep controlled by grain boundary diffusion is considered to be the main accommodation mechanism.

Diagnosis and management of postural orthostatic tachycardia syndrome：A brief review

Postural orthostatic tachycardia syndrome （POTS） has been recognized since at least 1940.A review of the literature identifies differences in the definition for this condition and wide variations in treatment and outcomes.This syndrome appears to describe a group of conditions with differing pathophysiology,which requires treatment tailored to the true underlying disorder.Patients need to be fully evaluated to guide treatment.Further research is required to effectively classify the range of underlying pathophysioiogy that can produce this syndrome and to guide optimal management.

Repetitive narrow QRS tachycardia in a 61-year-old female patient with recent palpitations

A 61-year-old female patient suffering from recent onset palpitations and dyspnea on exertion with hypertension and mitral valve prolapse in her past history came to our outpatient department. Echocardiography revealed a mild mitral valve prolapse, slightly decreased left ventricular （LV） function （LV ejection fraction： 51%） and a mild mitral regurgitation.

Ventricular tachycardia ablation and substrate modification in ICD patients with electrical storm

The electrical storm （ES） is defined as a state of electrical instability with three or more sustained ventricular arrhythmias （VAs） occurring within twenty-four hours, which needs intravenous antiarrhythmic medications and frequent defibrillation. Recently, radiofrequency catheter ablation evolved as a sole therapy to terminate ES in patients with ICD, and the survival has been reported to be improved with successful ablation during follow-up. In this review, we briefly summarize substrate mapping and substrate ablation strategy in patients with ES, and discuss the reason of recurrence after ablation.

MICROSTRUCTURE OF Mg-6.4Zn-1.1Y ALLOY FABRICATED BY RAPID SOLIDIFICATION AND RECIPROCATING EXTRUSION

In order to explore the methods to prepare high-strength quasicrystal-reinforced magnesium alloys, the flakes of rapidly solidified Mg-6.4Zn-1.1 Y magnesium alloy with a thickness of 50-60μm were obtained by a melt spinning single-roller device, and the flakes were then processed into rods by reciprocating extrusion and direct extrusion. The microstructure of the alloy was analyzed by optical microscope and SEM, and the constituent phases were identified by XRD. Phase transformation and its onset temperature were determined by differential thermal analyzer （DTA）. The analysis result shows that rapid solidification for Mg-6.4Zn-I.IY alloy can inhibit the eutectic reactions, broaden the solid solubility of Zn in α-Mg solute solution, and impede the formation of Mg3 Y2Zn3 and MgZn2 compounds, and thus help the icosahedral Mg3 YZn6 quasicrystal formed directly from the melt. The microstructure of the flakes consists of the α-Mg solid solution and icosahedral Mg3 YZn6 quasicrystal. Dense rods can be made from the flakes by two-pass reciprocating extrusion and direct extrusion. The interfaces between flakes in the rods can be welded and jointed perfectly. During the reciprocating extrusion and direct extrusion process, more Mg3 YZn6 compounds are precipitated and distributed uniformly, whereas the rods possess fine microstructures inherited from rapidly solidified flakes. The rods contain only two phases： α- magnesium solid solution as matrix and fine icosahedral Mg3 YZn6 quasicrystal which disperses uniformly in the matrix.

Valve Dynamic and Thermal Cycle Model in Stepless Capacity Regulation for Reciprocating Compressor

The existing researches of stepless capacity regulation system by depressing the suction valve for reciprocation compressor always adopt hypothesis that the compressor valves are open or close instantaneously, the valve dynamic has not been taken account into thermal cycle computation, the influence of capacity regulation system on suction valves dynamic performance and cylinder thermal cycle operation has not been considered. This paper focuses on theoretical and experimental analysis of the valve dynamic and thermal cycle for reciprocating compressor in the situation of stepless capacity regulation. The valve dynamics equation, gas forces for normal and back flow, and the cylinder pressure varying with suction valve unloader moment during compression thermal cycle are discussed. A new valve dynamic model based on L-K real gas state equation for reciprocating compressor is first deduced to reduce the calculation errors induced by the ideal gas state equation. The variations of valve dynamic and cylinder pressure during part of compression stroke are calculated numerically. The calculation results reveal the non-normal thermal cycle and operation condition of compressor in stepless capacity regulation situation. The numerical simulation results of the valve dynamic and thermal cycle parameters are also verified by the stepless capacity regulation experiments in the type of 3L-10/8 reciprocating compressor. The experimental results agree with the numerical simulation results, which show that the theoretical models proposed are effective and high-precision. The proposed theoretical models build the theoretical foundation to design the real stepless capacity regulation system.

RECIPROCATING EXTRUSION OF IN SITU Mg_2Si REINFORCED Mg-Al BASED COMPOSITE

M92Si reinforced Mg-Al based composite with high amount o/silicon was prepared by permanent mould casting, and then extruded by reciprocating extrusion （RE） after the composite was processed by homogenization heat treatment. The effect of RE processing on the morphology and size of M92Si and the mechanical properties of the com- posite were investigated, to develop new ways to refine the M928i phase and improve its shape. The result showed that RE was very useful in refining the M92Si phase. The more the RE processing passes, the better the refining effect would be. Moreover, the uniform distribution of M928i phases would be more in the composite. After the composite was processed by RE for 12 passes, most M92Si phases were equiaxed, with granular diameter below 20 μm, and distributed uniformly in the matrix of the composite. The mechanical properties of the composite could be increased prominently by RE processing, and were much higher than that in the as-cast state. As the temperature rises, the tensile strength is reduced. For the composite RE processed for 12 passes, the tensile strength, yield strength, and elongation are 325.9 MPa, 211.4 MPa, and 3.3% at room temperature, whereas, 288.2 MPa, ,207.7 MPa, and 7.8%, respectively, at 150℃. In comparison with the properties at room temperature, the tensile strength and yield strength are high and only decrease by 11.6% and 1.8% at 150℃. The M928i reinforced Mg-Al based composite possesses good heat resistance at 150℃. The excellent resistance to effect of heat is attributed to the high melting tempera- ture and good thermal stability of fine Mg2Si phases, which are distributed uniformly in the composite, and effectively hinder the grain boundary gliding and dislocation movement.

Fluid-solid Interaction Model for Hydraulic Reciprocating O-ring Seals

Elastohydrodynamic lubrication characteristics of hydraulic reciprocating seals have significant effects on sealing and tribology performances of hydraulic actuators, especially in high parameter hydraulic systems. Only elastic deformations of hydraulic reciprocating seals were discussed, and hydrodynamic effects were neglected in many studies. The physical process of the fluid-solid interaction effect did not be clearly presented in the existing fluid-solid interaction models for hydraulic reciprocating O-ring seals, and few of these models had been simultaneously validated through experiments. By exploring the physical process of the fluid-solid interaction effect of the hydraulic reciprocating O-ring seal, a numerical fluid-solid interaction model consisting of fluid lubrication, contact mechanics, asperity contact and elastic deformation analyses is constructed with an iterative procedure. With the SRV friction and wear tester, the experiments are performed to investigate the elastohydrodynamic lubrication characteristics of the O-ring seal. The regularity of the friction coefficient varying with the speed of reciprocating motion is obtained in the mixed lubrication condition. The experimental result is used to validate the fluid-solid interaction model. Based on the model, The elastohydrodynamic lubrication characteristics of the hydraulic reciprocating O-ring seal are presented respectively in the dry friction, mixed lubrication and full film lubrication conditions, including of the contact pressure, film thickness, friction coefficient, liquid film pressure and viscous shear stress in the sealing zone. The proposed numerical fluid-solid interaction model can be effectively used to analyze the operation characteristics of the hydraulic reciprocating O-ring seal, and can also be widely used to study other hydraulic reciprocating seals.

Discrimination of ventricular tachycardia and localization of its exit site using surface electrocardiography

Differential diagnosis of supraventricular tachycardia (SVT) and ventricular tachycardia (VT) is of paramount importance for appropriate patient management. Several diagnostic algorithms for discrimination of VT and SVT based on surface electrocardiogram (ECG) analysis have been proposed. Following established diagnosis of VT,a specific origination tachycardia site can be supposed according to QRS complex characteristics. This review aims to cover comprehensive and comparative description of the main VT diagnostic algorithms and to present ECG characteristics which permit to suggest the most common VT origination sites.

Rare presentation of intralobar pulmonary sequestration associated with repeated episodes of ventricular tachycardia

Arterial supply of an intralobar pulmonary sequestration(IPS) from the coronary circulation is extremely rare. A significant coronary steal does not occur because of dual or triple sources of blood supply to sequestrated lung tissue. We present a 60-year-old woman who presented to us with repeated episodes of monomorphic ventricular tachycardia(VT) in last 3 mo. Radio frequency ablation was ineffective. On evaluation, she had right lower lobe IPS with dual arterial blood supply, i.e., right pulmonary artery and the systemic arterial supply from the right coronary artery(RCA). Stress myocardial perfusion scan revealed significant inducible ischemia in the RCA territory. Coronary angiogram revealed critical stenosis of proximal RCA just after the origin of the systemic artery supplying IPS. The critical stenosis in the RCA was stented. At 12 mo follow-up, she had no further episodes of VT or angina.

Low doses of intravenous epinephrine for refractory sustained monomorphic ventricular tachycardia

We report three cases of sustained monomorphic ventricular tachycardia(VT) in the setting of coronary artery disease,resistant to beta-blockers in two patients and to amiodarone in all,successfully terminated by low doses of intravenous(IV) epinephrine.VT was the first manifestation of coronary artery disease in one patient,whereas the other two patients had a previous history of myocardial infarction and were recipients of an implantable cardioverter-defibrillator(ICD).One of these two patients experienced an arrhythmic storm.All had hemodynamic instability at the time of epinephrine administration.A single slow administration of IV epinephrine(0.5 to 1 mg administered over 30 to 60 s) restored sinus rhythm after 30-90 s with only minor side effects.In the ICD patient with recurrent VT and several cardioversions due to transformation of VT to ventricular fibrillation,epinephrine injection led to the avoidance of further shocks.Although potentially harmful,low doses of IV epinephrine used alone or in combination with beta-blocker treatment and electrical cardioversion may be an alternative effective therapy for sustained monomorphic VT refractory to amiodarone.The role of epinephrine in the termination of VT should be studied further,especially in patients pre-treated with amiodarone in combination with beta-blockers.

MICROSTRUCTURES AND PROPERTIES OF RECIPROCATINGLY EXTRUDED Mg-6.4Zn-1.1Y ALLOYS

An icosahedral Mg3 YZn6 quasicrystalline phase can be produced in Mg-Zn- Y system alloys when a proper amount of Zn and Y is contained, and it is feasible to prepare the quasicrystal phase-reinforced low-density magnesium alloy. In this article, phase constituents and the effect of reciprocating extrusion on microstructures and properties of the as-cast Mg-6.4Zn-1.1 Y alloy are analyzed. The microstructure of the as-cast Mg-6.4Zn-1.1 Y alloy consists of the α-Mg solid solution, icosahedral Mg3YZn6 quasicrystal, and Mg3 Y2Zn3 and MgZn2 compounds. After the alloy was reciprocatingly extruded for four passes, grains were refined, Mg3 Y2 Zn3 and MgZn2 phases dissolved into the matrix, whereas, Mg3 YZn6 precipitated and distributed uniformly. The alloy possesses the best performance at this state; the tensile strength, yield strength, and elongation are 323.4 MPa, 258.2 MPa, and 19.7%, respectively. In comparison with that of the as-cast alloy, the tensile strength, yield strength, and elongation of the reciprocatingly extruded alloy increase by 258.3%, 397.5%, and 18 times, respectively. It is concluded that reciprocating extrusion can substantially improve the properties of the as-cast Mg-6.4Zn-1.1 Y alloy, particularly for elongation. The high performance of the Mg-6.4Zn-1.1 Y alloy after reciprocating extrusion can be attributed to dispersion strengthening and grain-refined microstructures.