Valve Malfunction Research Articles

High Resolution Simulation of Tri-Leaflet Aortic Heart Valve in an Idealized Aorta

Aortic valve replacement is a common procedure for many patients when their native aortic valve malfunction either because of aortic stenosis or aortic insufficiency. Due to the superior hemodynamic performance, Bio-prosthetic heart valve (bPHV) has been implanted in a large number of patients. bPHVs, however, have a number of drawbacks, including mechanically induced fatigue and leaflet tearing and calcification. Many of these complications are thought to be linked to hemodynamic factors and the mechanical forces imparted by the blood flow on blood cells. Previous works have shown that valve hemodynamics is greatly influenced by the fluid-structure interaction (FSI) of blood flow with tissues and/or valve leaflets, and the location where the valve is surgically implanted.

A New View of an Unusual Pacemaker Complication: Role of Three-Dimensional Transthoracic Echocardiography

Tricuspid regurgitation (TR) produced by endocavitary leads (EL) from permanent pacemakers and implantable cardiac defibrillators is a well-known complication of this procedure. The EL may damage or interfere with tricuspid valve function causing mechanical interference of the valve leaflets leading to incomplete valve closure. It is important to recognize this mechanical complication because it could be corrected by repositioning the lead. In this case report we demonstrate how three-dimensional transthoracic echocardiography permits to obtaining an en face view, which allows simultaneous visualization of the 3 moving leaflets during the cardiac cycle, their attachment to the tricuspid annulus and the pattern of leaflet coaptation. Thus, we propose three-dimensional transthoracic echocardiography as the tool of choice to evaluate TR related to EL, to evaluate the necessity of repositioning the lead if severe regurgitation or tricuspid valve malfunction are demonstrated.

Failure Analysis of a Gas Turbine Compressor in a Thermal Power Plant

This study presents the results of failure analysis of a 28 MW gas turbine at the Rei electrical power plant. The gas turbine failed during the shutdown period and near its second natural frequency at 4200 rpm. Initial inspections revealed that the compressor disk of stage 15 was fractured, and all of the stationary and rotary blades of stages 14–18 of the compressor had been detached or broken from the dovetail region of the disks. The fracture roots were investigated by performing finite element modeling and fractography analysis. It was shown that a crack was initiated from the disk edge on its interface with the rotor shaft and was propagated under cyclic loading. As a result of the malfunction of the compressor bleed valves, which led to compressor surge, the amplitude of vibration of the turbine rotor increased under aerodynamically induced forces. This increase in the natural frequency of the turbine, near the second natural frequency of the turbine, led to final ductile fracture of the compressor disk of stage 15. Finally, the turbine rotor stopped with the loud noise produced by the direct shearing of the fractured disk on the stator casing. Some recommendations are proposed to prevent similar failures in the future.

Unidirectional valve malfunction by the breakage or malposition of disc - two cases report -

Malfunction of the unidirectional valve in a breathing circuit system may cause hypercapnia from the rebreathing of expired gas, ventilation failure, and barotrauma. Capnography is a useful method for monitoring the integrity of the unidirectional valve. We experienced two cases of malfunction of a unidirectional valve which caused leakage and reverse flow, diagnosed early as a change of the capnographic waveform. One case was caused by expiratory unidirectional valve breakage. The other was caused by an incorrectly-assembled inspiratory unidirectional valve.

New antireflux self‐expandable metal stent for malignant lower biliary obstruction: In vitro and in vivo preliminary study

Antireflux plastic biliary stents prevent duodenal biliary reflux and improve the stent patency rate. However, the efficacy of the antireflux valve in a self-expandable metal stent (SEMS) for a malignant biliary obstruction has not been well established. We evaluated the efficacy of a SEMS with an antireflux valve using in vitro flow studies and determined the impact of reducing duodenobiliary reflux on the stent patency rate. In vitro testing was conducted using a bile perfusion system to evaluate the antegrade and retrograde flow resistance, and to determine the ideal shape for the valve. Then, a prospective case series in humans was conducted with an adequately designed SEMS with an antireflux valve. During the study period, five patients with an unresectable non-hilar malignant biliary obstruction underwent insertion of a SEMS with an antireflux valve. Placement of the SEMS with antireflux valve was successful on the first attempt in all patients, and no procedure-related complications occurred. Follow up was obtained in all cases. Serum bilirubin level did not decrease to the normal range within 1 month in four patients. Stent occlusions occurred in all four patients as a result of valve malfunctions due to sludge impaction or a clog. Therefore, the study was terminated early due to unexpected results. SEMS with an antireflux valve was ineffective in patients with non-hilar malignant biliary obstruction due to limitations on current stent technology.

High End-Expiratory Airway Pressures Caused by Internal Obstruction of the Draeger Apollo® Scavenger System That Is Not Detected by the Workstation Self-test and Visual Inspection

High End-Expiratory Airway Pressures Caused by Internal Obstruction of the Draeger Apollo® Scavenger System That Is Not Detected by the Workstation Self-test and Visual Inspection

Ventriculoperitoneal shunt surgery and the incidence of shunt revision in adult patients with hemorrhage-related hydrocephalus

ObjectiveVentriculoperitoneal shunt surgery remains the most widely accepted neurosurgical procedure for the management of hydrocephalus. However, shunt failure and complications are common and may require multiple surgical procedures during a patient's lifetime. The purpose of this study is to evaluate the ventriculoperitoneal shunt surgery and the incidence of shunt revision in adult patients with hemorrhage-related hydrocephalus. MethodsAdult patients who underwent ventriculoperitoneal shunt placement for hemorrhage-related hydrocephalus from October 1990 to October 2009 were included in this study. Medical charts, operative reports, imaging studies, and clinical follow-up evaluations were reviewed and analyzed retrospectively. ResultsA total of 133 adult patients with the median age of 54.5 years were included. Among patients, 41% were males, and 62% Caucasians. The overall shunt revision rate was 51.9%. The shunt revision rate within the first 6 months after the initial placement of ventriculoperitoneal shunts was 45.1%. The median time to first shunt revision was 0.50 (95% CI, 0.24–9.2) months. No significant association was observed between perioperative variables (gender, ethnicity, hydrocephalus type, or hemorrhage type) and the shunt revision rate in these patients. Major causes of shunt revision include infection (3.6%), overdrainage (7.6%), obstruction (4.8%), proximal shunt complication (7.6%), distal shunt complication (3.6%), old shunt dysfunction (6.8%), valve malfunction (10.0%), externalization (3.6%), shunt complication (12.0%), shunt adjustment/replacement (24.0%) and other (16.4%). ConclusionAlthough ventriculoperitoneal shunting remains to be the treatment of choice for adult patients with post hemorrhage-related hydrocephalus, a thorough understanding of predisposing factors related to the shunt failure is necessary to improve treatment outcomes.

Tricuspid regurgitation after successful mitral valve surgery.

The tricuspid valve (TV) is inseparably connected with the mitral valve (MV) in terms of function. Any pathophysiological condition concerning the MV is potentially a threat for the normal function of the TV as well. One of the most challenging cases is functional tricuspid regurgitation (TR) after surgical MV correction. In the past, TR was considered to progressively revert with time after left-sided valve restoration. Nevertheless, more recent studies showed that TR could develop and evolve postoperatively over time, as well as being closely associated with a poorer prognosis in terms of morbidity and mortality. Pressure and volume overload are usually the underlying pathophysiological mechanisms; structural alterations, like tricuspid annulus dilatation, increased leaflet tethering and right ventricular remodelling are almost always present when regurgitation develops. The most important risk factors associated with a higher probability of late TR development involve the elderly, female gender, larger left atrial size, atrial fibrillation, right chamber dilatation, higher pulmonary artery systolic pressures, longer times from the onset of MV disease to surgery, history of rheumatic heart disease, ischaemic heart disease and prosthetic valve malfunction. The time of TR manifestation can be up to 10 years or more after an MV surgery. Echocardiography, including the novel 3D Echo techniques, is crucial in the early diagnosis and prognosis of future TV disease development. Appropriate surgical technique and timing still need to be clarified.

D226 弁装置の不具合発生傾向の分析 : 福島原発事故の前兆を探る(OS6 保全・設備診断技術)

D226 弁装置の不具合発生傾向の分析 : 福島原発事故の前兆を探る(OS6 保全・設備診断技術)

Surgical Outcome of Prosthetic Heart Valve Obstruction: Single Center Experience

Objective: Valve thrombosis defined as any thrombus not caused by infection attached to or near an operated valve that occludes part of the blood flow path and interferes with valve function. Treatment modalities are thrombolytic therapy, surgical thrombectomy and debridement, or re-replacement. The aim of this study is to review our experience in surgical thrombectomy and debridement for obstructed mechanical valve prosthesis, and the impact of the procedure on the outcome in comparison to re-replacement; Methods: The study was conducted retrospectively between 1995 to 2012 in Department of Cardiothoracic surgery, cardiology and internal medicine, Zagazig University Hospital. 92 patients with stuck valve were divided into two groups. Group (A): 54 patients with re replacement and Group (B): 38 patients treated by thrombectomy and debridement; Results: 92 patients with stuck valves the mean age was 38.4(±9.2), 68 male and 85 female in both groups. The large numbers of cases were mitral valve 35 (64.8%) patients in group A and 22 (57.9%) patients in group B, aortic malfunction in group A was 11 (20.4%)patients and 9 (23.7%) cases in group B, double valve malfunction was rare represent 8 (14.8%) and 7 (18.4%)cases in group A and group B respectively; Conclusion: We conclude that thrombectomy and debridement for malfunctioning mechanical valve is a safe, easy and rapid procedure to perform in some cases to avoid the risk of re replacement.

Mitral Valve Malfunction of a St. Jude Medical Prosthetic due to Pannus Formation and Thrombosis

Mitral Valve Malfunction of a St. Jude Medical Prosthetic due to Pannus Formation and Thrombosis

More malfunctioning Medos Hakim programmable valves: cause for concern?

In recent years, the authors have noticed a growing number of programmable valve defects at their institution. Therefore, they conducted this study to evaluate the increased incidence of malfunctioning valves. They investigated all revisions that had been performed at their institution between 1994 and 2010 for dislodgement of the stator of a standard Medos Hakim programmable valve with a prechamber. Fifteen valves were removed because of dislodged stators. The valves had been implanted between May 16, 1993, and December 27, 2002, and were explanted between February 19, 2006, and January 22, 2010. Thus, the valves had been in place for a mean period of 11 years (median 11 years, range 7-14 years). The percentage of dislodged stators was almost 3% (15 of 546 valves). Particularly noteworthy is that all malfunctioning valves were found in children who had been younger than 1 year of age at the time of implantation. Medos Hakim programmable valve malfunctions are rare events but should receive careful attention. When the pressure setting cannot be adjusted, a malfunction should always be suspected and radiographic imaging should be performed to assess the valve. Stator dislodgement is the most serious form of valve adjustment failure.

Adjustable Intragastric Balloons: A 12-Month Pilot Trial in Endoscopic Weight Loss Management

Intragastric balloons are associated with (1) early period intolerance, (2) diminished effect within 3–4 months, and (3) bowel obstruction risk mandating removal at 6 months. The introduction of an adjustable balloon could improve comfort and offer greater efficacy. A migration prevention function, safely enabling prolonged implantation, could improve efficacy and weight maintenance post-extraction. The first implantations of an adjustable balloon with an attached migration prevention anchor are reported. The primary endpoint was the absence of bowel perforation, obstruction, or hemorrhage. Eighteen patients with mean BMI of 37.3 were implanted with the Spatz Adjustable Balloon system (ABS) for 12 months. Balloon volumes were adjusted for intolerance or weight loss plateau. Mean weight loss at 24 weeks was 15.6 kg with 26.4% EWL (percent of excess weight loss) and 24.4 kg with 48.8% EWL at 52 weeks. Sixteen adjustments were successfully performed. Six downward adjustments alleviated intolerance, yielding additional mean weight loss of 4.6 kg. Ten upward adjustments for weight loss plateau yielded a mean additional weight loss of 7 kg. Seven balloons were removed prematurely. Complications necessitating early removal included valve malfunction (1), gastritis (1), Mallory–Weiss tear (1), NSAID (2× dose/2 weeks) perforating ulcer (1), and balloon deflation (1). Two incidents of catheter shear from the chain: one passed uneventfully and one caused an esophageal laceration without perforation during extraction. The Spatz ABS has been successfully implanted in 18 patients. (1) Upward adjustments yielded additional weight loss. (2) Downward adjustments alleviated intolerance, with continued weight loss. (3) Preliminary 1-year implantation results are encouraging.

Detection of Valve Malfunction after Mechanical MVR using Digital Phonocardiography

We present the case of a 63-year-old female patient who developed severe chronic dyspnea two years after mechanical mitral valve replacement (MVR). Conventional cardiac diagnostics including echocardiography, fluoroscopy, right and left heart catheterization could not detect any malfunction. Only digital phonocardiography was able to show alterations of the typical acoustic signal. Based on the symptoms, the clinical history and these abnormal findings the decision was taken to reoperate. Intraoperatively, a ruptured tendinous chord was found, impeding the inferior leaflet. Redo MVR was performed.

Ex vivo hemodynamic assessment of mechanical aortic valve gradients using a high‐fidelity pressure wire

Accurate assessment of prosthetic mechanical valve malfunction is challenging for non-invasive and invasive techniques. We evaluated a 0.014-inch pressure-sensing coronary guidewire to assess mechanical valve dysfunction. Several case reports have shown that transaortic pressure gradients can be recorded using a 0.014-inch guidewire during cardiac catheterization. We performed an ex vivo study measuring the effects of sequentially crossing the center of each valve with a 6 French coronary angiographic catheter, a 0.035-inch guidewire, and a 0.014-inch pressure-sensing guidewire on valve dysfunction using the following 23 mm bileaflet and tilting-disc aortic valves: St. Jude Regent™, CarboMedics, Medtronic Hall™, and Björk-Shiley Monostut. A left heart model pulse duplicator recorded 10 consecutive cycles. For all valves, the greatest increase in valve regurgitation occurred with the 6 French catheter, causing a reduction in aortic valve back pressure and cardiac output, with an increase in leakage rate, regurgitant fraction, and energy loss. In comparison to the 0.035-inch guidewire, the 0.014-inch guidewire had greater regurgitation for St. Jude, lower for Medtronic Hall, and equivalent for CarboMedics and Björk-Shiley valves. For the CarboMedics valve, the 0.035-inch guidewire caused a significant increase in regurgitant fraction and energy loss, while the pressure wire had no change compared to baseline. The degree of regurgitation caused by the 0.014-inch guidewire varies with the type of mechanical aortic valve. While prior case reports have shown that valve hemodynamics may be measured using a pressure-sensing guidewire, valve regurgitation occurs when crossing a St. Jude, Medtronic Hall, or Björk-Shiley aortic valve.

Identifying and Managing Technical Faults in the Anesthesia Machine

The potential for catastrophe resulting from anesthetic equipment failure and the failure of training programs to adequately prepare residents to detect and manage equipment failure prompted the Israel Board of Anesthesiologists to include simulation-based testing in the Objective Structured Clinical Evaluation component of the Israeli Board Examination in Anesthesiology. We used simulation-based scenarios to measure the performance of residents while (a) checking the anesthesia machine before the first morning case, (b) checking the anesthesia machine between cases, (c) managing an oxygen pipeline failure, and (d) managing an expiratory valve failure. During board examination, 3 of 28 examinees failed to correctly check at least 70% of the items on the anesthesia machine checkout list before the first morning case and 3 of 30 failed to correctly check 70% of the items between cases. Although all examinees recognized inadequate oxygen cylinder pressure and a malfunctioning valve, 1 of 31 examinees failed to open the O(2) cylinder, 6 of 31 did not disconnect the anesthesia machine from the central oxygen supply, 14 of 31 could not explain how to minimize the use of oxygen, 2 of 30 failed to find the faulty valve, and 15 of 30 could not give the correct differential diagnosis. During simulation-based board examination most senior anesthesia residents became aware of equipment failures but many failed to correctly diagnosis and manage the failure.

Azoospermia and maturation arrest: malfunction of valves in erect poster of humans leads to hypoxia in sperm production site

Maturation arrest (MA) of spermatogenesis is diagnosed on histology as interruption of spermatogenesis before the final stage without impairment of Sertoli or Leydig cells. It is considered a condition of irreversible or absolute infertility. Varicocele, which represents impairment in the testicular venous drainage system, has been shown to be a bilateral disease. Malfunction of the valves increase the hydrostatic pressure in the testicular venous system that exceeds the pressure in the arterial system leading to hypoxia in the testicular microcirculation and in the seminiferous tubules, the sperm production site. Sperm production deteriorates, and ultimately progresses to azoospermia. Our prediction was that MA, if genetic factors are excluded, is the final stage of long standing hypoxia. This would indicate that MA is not always an independent disease entity, but may represent progressive process of deterioration of the testicular parenchyma beyond azoospermia. By histology and electron microscopy, our prediction confirmed, at least partially, that MA is associated with degenerative ischaemic changes in the seminiferous tubules. Adequate treatment of bilateral varicocele by microsurgery or super-selective sclerotherapy of the internal spermatic veins including associated network of venous bypasses, vertically oriented, may resume the flow of oxygenated blood. If irreversible damages did not occur and ischaemia is not too long standing, limited sperm production may be restored, at least partially.

Transaortic chordae and pannus removal without redo mitral valve replacement in prosthetic mitral valve malfunction

Both anterior and posterior chordae of the mitral valve are occasionally spared during mitral valve surgery to preserve left ventricular function. In this report, a 43-year-old woman who had undergone mitral valve replacement surgery with anterior and posterior chordal preservation 9 years ago subsequently had mitral valve pannus and anterior chordae covering the prosthetic valve, which led to valve malfunction. Prosthetic mitral valve function was successfully recovered by performing transaortic pannus and chordae removal, avoiding redo mitral valve replacement.

All Valve Malfunctions Are Not the Same

All Valve Malfunctions Are Not the Same

Prosthetic Valve Malfunction Caused by Chordal Entrapment Detected by Transesophageal Echocardiography

Prosthetic Valve Malfunction Caused by Chordal Entrapment Detected by Transesophageal Echocardiography