Age-Specific Outcomes of Bioprosthetic vs. Mechanical Aortic Valve Replacement: Balancing Reoperation Risk with Anticoagulation Burden.

BACKGROUND: The choice of prosthesis for aortic valve replacement (AVR) remains challenging. The risk of anticoagulation complications vs. the risk of aortic valve reintervention should be weighed. This study compared the outcomes of bioprosthetic vs. mechanical AVR in patients older and younger than 50. METHODS: This retrospective study was conducted from 2009 to 2019 and involved 292 adult patients who underwent isolated AVR. The patients were divided according to their age (above 50 years or 50 years and younger) and the type of valves used in each age group. The outcomes of bioprosthetic valves (Groups 1a (>50 years) and 1b (≤50 years)) were compared with those of mechanical valves (Groups 2a (>50 years) and 2b (≤50 years)) in each age group. RESULTS: The groups had nearly equal rates of preexisting comorbidities except for Group 1b, in which the rate of hypertension was greater (32.6% vs. 14.7%; p = 0.025). This group also had higher rates of old stroke (8.7% vs. 0%, p = 0.011) and higher creatinine clearance (127.62 (108.82-150.23) vs. 110.02 (84.87-144.49) mL/min; p = 0.026) than Group 1b. Patients in Group 1a were significantly older than Group 2a (64 (58-71) vs. 58 (54-67) years; p = 0.002). There was no significant difference in the NYHA class between the groups. The preoperative ejection fraction and other echocardiographic parameters did not differ significantly between the groups. Re-exploration for bleeding was more common in patients older than 50 years who underwent mechanical valve replacement (p = 0.021). There was no difference in other postoperative complications between the groups. The groups had no differences in survival, stroke, or bleeding rates. Aortic valve reintervention was significantly greater in patients ≤ 50 years old with bioprosthetic valves. There were no differences between groups in the changes in left ventricular mass, ejection fraction, or peak aortic valve pressure during the 5-year follow-up. CONCLUSIONS: The outcomes of mechanical and bioprosthetic valve replacement were comparable in patients older than 50 years. Using bioprosthetic valves in patients younger than 50 years was associated with a greater rate of valve reintervention, with no beneficial effect on the risk of bleeding or stroke.

Choice of valve substitutes.

Infective endocarditis often necessitates surgical intervention, and the choice of valve substitute remains a topic of controversy and highly debatable due to the wide range of available options and recent technical advancements. This manuscript reviews the different valve substitutes in the context of infective endocarditis, including mechanical and bioprosthetic valves, homografts, xenografts, and tissue-engineered valves. The patient's age, sex, demographic location, intellectual quotient, comorbidities, available options, and the experience of the surgeon should all be taken into consideration while choosing the best valve substitute for that individual. While valve repair and reconstruction are preferred whenever feasible, valve replacement may be the only option in certain cases. The choice between mechanical and bioprosthetic valves should be guided by standard criteria such as age, sex, expected lifespan, associated comorbidities, and anticipated adherence to anticoagulation therapy and accessibility of medical facilities for follow-up. For patients with severe chronic illness or a history of intracranial bleeding or associated hematological disorders, the use of mechanical prostheses may be avoided. Homografts and bioprosthetic valves provide an alternative to mechanical valves, thereby decreasing the necessity for lifelong anticoagulation after surgery and diminishing the likelihood of bleeding complications. The manuscript also discusses specific valve substitutes for different heart valves (aortic, mitral, pulmonary, tricuspid positions) and highlights emerging techniques such as the aortic valve neocuspidization (Ozaki procedure) and tissue-engineered valves. Ultimately, the ideal valve substitute in IE should be evidence based on a comprehensive elucidation of clinical condition of the patient and available options.

Validation of large animal models in mechanical valve research: a histologic comparison.

OBJECTIVES: Mechanical valves still require life-long anticoagulation. Preclinical animal testing is a crucial step in the assessment of valves; however, the chosen animal model should be carefully considered, and a well-controlled animal model of mechanical valve thrombosis has not been established yet. In this study, a histopathologic comparison was performed to evaluate the representativity of pigs and sheep as large animal models in bileaflet mechanical valve thrombosis research. METHODS: 10 pigs and 8 sheep were implanted with a bileaflet mechanical valve in pulmonary position. During follow-up, no anticoagulative therapy was administered. Pigs were sacrificed between 14 and 38 days for explantation and assessment of the valve. Sheep were sacrificed between 71 and 155 days. Thrombus samples were processed and (immuno)histochemical stainings were applied. A pathologist evaluated the samples morphologically and semiquantitatively and compared these samples to available slides from 3 human patients who underwent redo surgery for acute bileaflet mechanical valve thrombosis, caused by insufficient anticoagulation. RESULTS: All pigs showed macroscopically evident thrombi on the mechanical valve surface at sacrifice. In contrast, none of the sheep showed any sign of thrombus formation. Histology showed a high fibrin content in thrombi of both human and porcine cases (3/3 vs 8/10). Porcine thrombi showed more cellular organization (0/3 vs 6/10), more calcification (0/3 vs 9/10) and more endothelialization (0/3 vs 6/10). Inflammatory cells were present in all samples and were considered physiological. CONCLUSIONS: Contrary to sheep, pigs develop thrombi on their mechanical valves in the short-term if no anticoagulation is administered. Histologic comparison of human and porcine thrombi shows comparable findings. The pig model might serve interestingly for further research on valve thrombosis, if it shows not to be an overly aggressive model.

Aortic valve replacement in small aortic root- Bi-leaflet mechanical valve is superior to a Mono-leaflet mechanical valve.

Background: Patient prosthetic mismatch is a serious but avoidable complication of surgical aortic valve replacement (SAVR) complicated by a small aortic annulus. This study aims to compare early and midterm outcomes following aortic valve replacement (AVR) with a mono-leaflet (ML) valve and a bi-leaflet (BL) valve in a small aortic root. Methods and selection: From January 1st, 2017 to December 31st, 2019, 98 patients diagnosed with small aortic root underwent isolated aortic valve replacement with either TTK Chitra valve (Mono-leaflet/ ML group) or St. Jude medical valve (Bi-leaflet/ BL group) of size 17/ 19 mm. Echocardiography was analyzed from medical records and telephonic follow-up. Results: Baseline parameters were comparable. The ML group had 42 patients and the BL group had 56 patients. Aortic cross-clamp time, the incidence of severe patient prosthetic mismatch (p = 0.002) and mean, peak pressure gradients were high in the ML group. Duration of ventilation, intensive care unit (ICU) stay, the incidence of stroke, need for intra-aortic balloon pump, permanent pacemaker, dialysis, and left ventricular mass index in echocardiography were comparable between the two groups postoperatively. There was no early mortality in both group. Survival at the end of 5 years was 57 ± 14.4% in the ML group; 91.8 ± 4% in the BL group (p = 0.005). Univariate and multivariate analysis revealed elderly age as a risk factor for mortality. Conclusion: We conclude that aortic valve replacement without any root widening procedure, using a small-sized mechanical valve provides acceptable early outcomes. Bi-leaflet mechanical valves provide better hemodynamics and survival percentage.

Mechanical Tricuspid Valves Have Higher Rate of Reintervention: A Single Center Experience.

PURPOSE: We compared the composite outcome of tricuspid valve (TV) reintervention or heart failure (HF) admission in patients who underwent tricuspid valve replacement (TVR) with tissue vs. mechanical valves. PATIENTS AND METHODS: The study included 159 patients who underwent TVR from 2009 to 2019. We grouped the patients according to the valve's type into tissue valve group (n = 139) and mechanical valve group (n = 20). RESULTS: The mean age of patients was 52.4 ± 12.8 years, and 117 patients were females (73.6%). Hospital mortality occurred in 20 patients (12.6%); all of them were in the tissue valve group. The composite outcome of reintervention and HF readmission occurred in 8 patients with mechanical valves (40%) vs. 24 patients with tissue valves (17.3%), (P = 0.018). Predictors of reintervention and HF admission were female (subdistributional hazard ratio [SHR]: 1.38-34.3, P = 0.019), stroke (SHR: 1.25-8.76, P = 0.016), hypertension (SHR: 1.13-5.36, P = 0.024), and mechanical valves (SHR: 1.6-10.7, P = 0.003). In post hoc analysis, the difference in the composite outcome was derived from the difference in the reintervention rate that was higher in mechanical valves. Survival did not differ significantly between groups (P = 0.12). CONCLUSION: Mechanical TVs have a higher rate of composite outcome of reintervention or HF readmission than tissue TVs that are related mainly to higher rate of reintervention.

Using tissue mitral valves in younger patients: A word of caution.

BACKGROUND: The debate about the optimal mitral valve prosthesis continues. We aimed to compare the early and late outcomes, including stroke, bleeding, survival, and reoperation after isolated mitral valve replacement (MVR) using tissue versus mechanical valves. METHODS: This retrospective cohort study included 291 patients who had isolated MVR from 2005 to 2015. Patients were grouped into the tissue valve group (n = 140) and the mechanical valve group (n = 151). RESULTS: There were no differences in duration of mechanical ventilation, hospital stay, and hospital mortality between groups. Fifteen patients required cardiac rehospitalization, nine in the tissue valve group, and six in the mechanical valve group (p = .44). Stroke occurred in nine patients, five with tissue valves, and four with mechanical valves (p = .66). Bleeding occurred in 22 patients, seven patients with tissue valves, and 15 patients with mechanical valves (p = .09). Freedom from reoperation was 95%, 93%, 84%, 67% at 3, 5, 7, and 10 years for tissue valve and 97%, 96%, 96%, and 93% for mechanical valves, respectively (p˂ .001). The median follow-up was 84 months (Q1: Q3: 38-139). Survival at 3, 5, 7, and 10 years was 94%, 91%, 89%, 86% in tissue valves and 96%, 93%, 91%, 91% in mechanical valves, respectively (p = .49). CONCLUSIONS: Tissue valve degeneration is still an issue even in the new generations of mitral tissue valves. The significant risk of reoperation in patients with mitral tissue valves should be considered when using those valves in younger patients. Mechanical valves remain a valid option for all age groups.

Kissing Balloon "Valvuloplasty" of Obstructed Mechanical Aortic Valve: When You Are Running Out of Options.

We report an unusual case where "stuck" bileaflet aortic prosthetic valve occluders were partly released by performing emergency balloon dilatation with 2 noncompliant balloons by a percutaneous femoral approach. (Level of Difficulty: Advanced.).

Mechanical versus bioprosthetic valve for aortic valve replacement: systematic review and meta-analysis of reconstructed individual participant data.

OBJECTIVES: The aim of this study was to compare biological versus mechanical aortic valve replacement. METHODS: We searched MEDLINE, Scopus and Cochrane Library databases for randomized clinical trials and propensity score-matched studies published by 14 October 2021 according to the Preferred Reporting Items for Systematic Reviews and Meta-analyses statement. Individual patient data on overall survival were extracted. One- and two-stage survival analyses and random-effects meta-analyses were conducted. RESULTS: A total of 25 studies were identified, incorporating 8721 bioprosthetic and 8962 mechanical valves. In the one-stage meta-analysis, mechanical valves cumulatively demonstrated decreased hazard for mortality [hazard ratio (HR): 0.79, 95% confidence interval (CI): 0.74-0.84, P < 0.0001]. Overall survival was similar between the compared arms for patients <50 years old (HR: 0.88, 95% CI: 0.71-1.1, P = 0.216), increased in the mechanical valve arm for patients 50-70 years old (HR: 0.76, 95% CI: 0.70-0.83, P < 0.0001) and increased in the bioprosthetic arm for patients >70 years old (HR: 1.35, 95% CI: 1.17-1.57, P < 0.0001). Meta-regression analysis revealed that the survival in the 50-70 year-old group was not influenced by the publication year of the individual studies. No statistically significant difference was observed regarding in-hospital mortality, postoperative strokes and postoperative reoperation. All-cause mortality was found decreased in the mechanical group, cardiac mortality was comparable between the 2 groups, major bleeding rates were increased in the mechanical valve group and reoperation rates were increased in the bioprosthetic valve group. CONCLUSIONS: Survival rates seem to not be influenced by the type of prosthesis in patients <50 years old. The survival advantage in favour of mechanical valves is observed in patients 50-70 years old, while in patients >70 years old bioprosthetic valves offer better survival outcomes.

Controlling the Flow Separation in Heart Valves Using Vortex Generators.

A comprehensive computational study is performed to investigate the effectiveness of vortex generators (VGs) applied to mechanical bi-leaflet heart valves. Co-rotating and counter-rotating VG configurations are compared to a control valve without VGs. Detailed flow fields are obtained and used to elucidate the underlying flow physics. It was found that VGs reduce flow separation over the leaflets and hence reduce the Reynolds shear stress (RSS) in the vicinity regions of heart valve. The co-rotating VG configuration demonstrates a better performance compared with the counter-rotating configuration in terms of the RSS, turbulent kinetic energy production and velocity distributions, especially in the peripheral jet flows. The fraction of blood damage in the co-rotating configuration shows a 4.7% reduction in comparison to the control case, while a 3.7% increase is observed in the counter-rotating configuration. The passive flow control technique of applying co-rotating VG illustrates a great potential to help mitigate the hemodynamic factors leading to potential blood damage risk.

Right atrium to left ventricle puncture for VT ablation in patients with mechanical aortic and mitral valves: A step-by-step approach.

In patients with mechanical valves in the aortic and mitral positions, percutaneous access to the left ventricle (LV) for catheter ablation (CA) of ventricular tachycardia (VT) is challenging. We have recently described a novel percutaneous trans-right atrial (RA) access to the LV via a femoral venous approach for CA of VT in patients with mechanical aortic and mitral valves. With this approach, an iatrogenic Gerbode-type of ventricular septal defect is created with direct puncture of the inferior and medial aspect of the RA anatomically adjacent to the inferior-septal LV. The technique involves the use of steerable sheaths, dedicated radiofrequency wires, and intracardiac echocardiography guidance. The procedure has been documented feasible and safe in a series of consecutive patients with aortic and mitral mechanical valves and VT related to LV substrate. In this study, the procedural details of this novel approach are described in a step-by-step fashion.

Safety of catheter ablation for atrial fibrillation in patients with mechanical prosthetic valves.

BACKGROUND: Catheter ablation (CA) for atrial fibrillation (AF) is increasingly utilized in recent years, with promising results. We aimed to investigate the nationwide trends in utilization and procedural complications of CA for AF in patients with mechanical prosthetic valves (MPVs). METHODS AND RESULTS: We drew data from the US National Inpatient Sample (NIS) database to identify cases of AF ablations in patients with MPVs, between 2003 and 2015. Sociodemographic and clinical data were collected, and incidence of procedural complications, mortality, and length of stay were analyzed. We compared the outcomes to a propensity-matched cohort of patients without MPVs. The study included a weighted total of 1898 CA for AF cases in patients with MPVs. The median age of the study population was 67 (61-75) years and 53% were males. Despite the increasing age and significant uptrend in the prevalence of individual comorbidities and Deyo-Charlson Comorbidity Index (CCI) over the years, the risk of peri-procedural complications and mortality in the study group did not change between the early (2003-2008) and late (2009-2015) study years. The peri-procedural complication rate (8.4% vs. 10.4%, p = .33) and in-hospital mortality (0.2% vs. 0.2%, p = .9) did not differ significantly between patients with MPVs and 1901 matched patients without MPVs. Length of stay was higher among patients with prior MPVs compared to the controls (4.0 ± 0.2 vs. 3.3 ± 0.2 days, p = .011). CONCLUSION: This nationwide analysis shows that AF ablation in patients with mechanical valve prothesis bares a similar risk of periprocedural complications and mortality as in patients without prosthetic valves.

Propensity-Matched Comparison of the Ross Procedure and Prosthetic Aortic Valve Replacement in Adults.

BACKGROUND: There has recently been renewed interest in the Ross procedure in adults. OBJECTIVES: The goal of this study was to compare long-term outcomes after the Ross procedure vs biological and mechanical aortic valve replacement (AVR) in adults (aged 18-50 years) undergoing aortic valve surgery. METHODS: Mandatory California and New York databases were queried between 1997 and 2014. Exclusion criteria included: ≥1 concomitant procedure, reoperations, infective endocarditis, intravenous drug use, hemodialysis, and out-of-state residency. Propensity matching (1:1:1) was used, resulting in 434 patients per group. The primary endpoint was all-cause mortality. Secondary endpoints were stroke, major bleeding, reoperation, and endocarditis. Median follow-up was 12.5 years (IQR: 9.3-15.7 years). RESULTS: At 15 years, actuarial survival after the Ross procedure was 93.1% (95% CI: 89.1%-95.7%), similar to that of the age-, sex-, and race-matched U.S. general population. It was significantly lower after biological AVR (HR: 0.42; 95% CI: 0.23-0.075; P = 0.003) and mechanical AVR (HR: 0.45; 95% CI: 0.26-0.79; P = 0.006). At 15 years, the Ross procedure was associated with a lower cumulative risk of reintervention (P = 0.008) and endocarditis (P = 0.01) than biological AVR. In contrast, at 15 years, the Ross procedure was associated with a higher cumulative incidence of reoperation (P < 0.001) but lower risks of stroke (P = 0.03) and major bleeding (P = 0.016) than mechanical AVR. Thirty-day mortality after valve-related complications was lowest after a reintervention. CONCLUSIONS: In young adults, the Ross procedure is associated with better long-term survival and freedom from valve-related complications compared with prosthetic AVR. This confirms the notion that a living valve substitute in the aortic position translates into improved clinically relevant outcomes.

Ventricular arrhythmia ablation in the presence of mechanical valve utilization and complications of catheter ablation for ventricular arrhythmia in patients with mechanical prosthetic valves.

BACKGROUND: Catheter ablation (CA) for ventricular arrhythmias (VAs) is increasingly utilized in recent years. We aimed to investigate the nationwide trends in utilization and procedural complications of CA for VAs in patients with mechanical valve (MV) prosthesis. METHODS: We drew data from the US National Inpatient Sample database to identify cases of VA ablations, including premature ventricular contraction and ventricular tachycardia, in patients with MVs, between 2003 and 2015. Sociodemographic and clinical data were collected and the incidence of catheter ablation complications, mortality, and length of stay were analyzed. We compared the outcomes to a propensity-matched cohort of patients without prior valve surgery. RESULTS: The study population included a weighted total of 647 CA cases in patients with prior MVs. The annual number of ablations almost doubled, from 34 ablations on average during the "early years" (2003-2008) to 64 on average during the "late years" (2009-2015) of the study (p = .001). Length of stay at the hospital did not differ significantly between patients with MVs and 649 matched patients without prior MVs (5.4 ± 0.4, 4.7 ± 0.3 days, respectively, p = .12). The data revealed a trend toward a higher incidence of complications (12.6% vs. 7.5% respectively, p = .14) and mortality (3.7% vs. 0.7%, respectively, p = .087) among patients with MVs compared to the matched control group, not reaching statistical significance. CONCLUSION: The data show increased utilization of VA ablations in patients with MVs and a trend toward a higher incidence of in-hospital mortality and complications compared to the propensity-matched control group without MVs.

Mechanical Valves for On-Board Flow Control of Inflatable Robots.

Inflatable robots are becoming increasingly popular, especially in applications where safe interactions are a priority. However, designing multifunctional robots that can operate with a single pressure input is challenging. A potential solution is to couple inflatables with passive valves that can harness the flow characteristics to create functionality. In this study, simple, easy to fabricate, lightweight, and inexpensive mechanical valves are presented that harness viscous flow and snapping arch principles. The mechanical valves can be fully integrated on-board, enabling the control of the incoming airflow to realize multifunctional robots that operate with a single pressure input, with no need for electronic components, cables, or wires. By means of three robotic demos and guided by a numerical model, the capabilities of the valves are demonstrated and optimal input profiles are identified to achieve prescribed functionalities. The study enriches the array of available mechanical valves for inflatable robots and enables new strategies to realize multifunctional robots with on-board flow control.

Mechanical Versus Bioprosthetic Valve Replacement in the Tricuspid Valve Position: A Systematic Review and Meta-Analysis.

BACKGROUND: The ideal prosthesis for tricuspid valve replacement (TVR) continues to be debated. There are few published data comparing mechanical and bioprosthetic valves, and all are retrospective studies with relatively small sample sizes. AIM: This study was conducted to compare mechanical and bioprosthetic valves for TVR. METHOD: A literature search of six databases (PubMed, EMBASE, Ovid, ScienceDirect, JSTOR, and Wiley Blackwell's online library) was performed with the keywords "tricuspid valve disease, tricuspid valve replacement and (bioprosthetic or mechanical)". Primary outcomes were hospital mortality, long-term survival, tricuspid valve reoperation, valve failure, thrombosis, and thrombo-embolism. Risk ratio (RR) was used to compare dichotomous parameters and time-to-event outcomes. "Survival and re-interventions" were pooled using a meta-analysis of hazard ratios (HR). Publication bias was accessed using a funnel plot. RESULTS: A total of 23 retrospective studies involving 945 mechanical and 1,332 biological tricuspid prostheses were included. The studies were published between January 2002 and September 2019. Hospital mortality (30-day mortality) did not differ between groups (RR, 0.83; 95% confidence interval [CI], 0.66-1.05; p=0.12). Long-term survival was evaluated in 15 studies, and it was not significantly different between patients with mechanical compared with those with bioprosthetic valves (pooled HR, 0.97; 95% CI, 0.61-1.54; p=0.88). Freedom from tricuspid valve reoperation was assessed in eight studies, and no difference was found between the groups (pooled HR, 1.03; 95% CI, 0.63-1.69; p=0.89). Valve failure in the 5-year postoperative period was evaluated by seven studies, and there was no statistically significant difference between the two groups (pooled RR, 1.33; 95% CI, 0.42-4.27; p=0.63). CONCLUSIONS: The results of this meta-analysis suggest an equal risk of 30-day and late mortality, reoperation, and 5-year valve failure in patients with mechanical versus biological TVR. The choice of the prosthesis in the tricuspid position should depend mainly on the patient's risk factors and no superiority of one prosthesis over the other in this position.