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 14-38 days for explantation and assessment of the valve. Sheep were sacrificed between 71-155 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 endothelialisation (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.

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 the 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 2003-2015. 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 didn't change between the early (2003-2008) and late (2009-2015) study years. The peri-procedural complication rate (8.4% vs 10.4%, p=0.33) and in-hospital mortality (0.2% vs. 0.2%, p=0.9) 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=0.011).

CONCLUSION

This nationwide analysis shows that AF ablation in patients with mechanical valve prostheses bares similar risk of periprocedural complications and mortality as in patients without prosthetic valves. This article is protected by copyright. All rights reserved.

Pregnancy outcomes in women with mechanical prosthetic heart valves

Pregnancy outcomes in women with mechanical heart valves (MHV) remain poor. The thrombogenicity of MHV, the hypercoagulable state of pregnancy and limitations of current anticoagulation strategies combine to give a very high risk state. Recent additions to the literature in the form of registry data as well as meta-analyses and systematic reviews have highlighted the risks of thrombotic and haemorrhagic events in mothers and increased fetal complication rates. There remains a lack of consensus about the optimal anticoagulation approach to mitigate the risks to mother and fetus and registry data confirm poor quality of care. Current guidelines recommend the sequential use of heparin and vitamin K antagonists, but low molecular weight heparin is often used throughout the pregnancy, with inadequate monitoring in many instances. There is an urgent need to standardise the management of such women, which should be undertaken in specialist centres, supported by research on optimal anticoagulation regimens and the impact on pregnancy outcomes.

Use of mechanical valve prostheses in adults with tetralogy of Fallot

BACKGROUND

There are limited data about the outcomes mechanical prostheses in adults with tetralogy of Fallot (TOF). The purpose of the study was to describe the incidence of mechanical valve related adverse events (MVRAE), reoperation and all-cause mortality in TOF patients with mechanical valve prostheses.

METHODS

We reviewed the MACHD (Mayo Adult Congenital Heart Disease) database and identified all adult TOF patients with mechanical valve prostheses, 1990-2017. MVRAE was defined as valve thrombosis, endocarditis, embolic stroke or major bleeding complications.

RESULTS

A total of 44 prostheses were implanted in 29 patients (age 44 ± 13 years; men 18 [62%]), and 10 (36%) patients received multiple mechanical prostheses. The median number of prior sternotomies was 3 (range 2-7). Target intentional normalized ratio (INR) was 2.0-3.0 for patients with isolated mechanical aortic prostheses (n = 12, 41%), 2.5-4.0 for mechanical prostheses in non-aortic positions. There were no surgical deaths, and 10 MVRAE (endocarditis [n = 4], major bleeding complications [n = 5] and valve thrombosis [n = 1]) occurred in 7 (24%) patients during a median follow-up of 11 (5 18) years. The 10-year survival and freedom from reoperation were 87% and 95% respectively.

CONCLUSIONS

Surgical mortality and valve thrombosis for mechanical valve prostheses are low presumably due to appropriate patient selection and meticulous anticoagulation. Endocarditis and bleeding complications are major concerns. Further studies are required to determine the appropriate target INR that provides the optimal balance between preventing valve thrombosis and avoiding major bleeding complications mechanical valve prostheses in different positions.

Bilateral rectus sheath haematoma complicating dengue virus infection in a patient on warfarin for mechanical aortic valve replacement: a case report

Background

The management of Dengue virus infection can be challenging. Varied presentations and numerous complications intrinsic to dengue by itself increase the complexity of treatment and potential mortality. When burdened with the presence of additional comorbidities and the need to continue compulsory medications, clear stepwise definitive guidance is lacking and patients tend to have more complex complications and outcomes calling to question the clinical decisions that may have been taken. The use and continuation of warfarin in dengue virus infection is one such example.

Case presentation

We report a 65 year old South Asian female who presented with dengue fever. She had a history bronchial asthma, a prior abdominal surgery, and was on warfarin and maintained a therapeutically appropriate internationalized normalized ratio for a mechanical aortic valve replacement. Though preemptive decision to stop warfarin was taken with decreasing platelet counts, her clinical course was complicated with the development of bilateral rectus sheath haematoma’s requiring resuscitation with blood transfusions.

Conclusion

Though management of dengue viral fever has seen drastic evolution with recent updated guidance, clinical scenarios seen in the course of the illness still pose challenges to the managing physician. The need to continue obligatory anticoagulation which may seem counterintuitive during a complex disease such as dengue virus infection must be considered after understanding the potential risks versus that of its benefits. Though case by case decisions maybe warranted, a clear protocol would be very helpful in making clinical decisions, as the correct preemptive decision may potentially avert catastrophic and unpredictable bleeding events.

Mitral valve replacement for mitral stenosis: A 15-year single center experience

Objectives

Mitral valve replacement with either a bioprosthetic or a mechanical valve is the treatment of choice for severe mitral stenosis. However, choosing a valve implant type is still a subject of debate. This study aimed to evaluate and compare the early and late outcomes of mitral valve replacement [mechanical (MMV) vs. bioprosthetic (BMV)] for severe mitral stenosis.

Methods

A retrospective cohort study was performed on data involving mitral stenosis patients who have undergone mitral valve replacement with either BMV (n = 50) or MMV (n = 145) valves from 1999 to 2012. Data were collected from the patients’ records and follow-up through telephone calls. Data were analyzed for early and late mortality, New York Heart Association (NYHA) functional classes, stroke, pre- and postoperative echocardiographic findings, early and late valve-related complications, and survival. Chi-square test, logistic regression, Kaplan–Meier curve, and dependent proportions tests were some of the tests employed in the analysis.

Results

A total of 195 patients were included in the study with a 30-day follow-up echocardiogram available for 190 patients (97.5%), while 103 (53%) were available for follow-up over the telephone. One patient died early postoperatively; twelve patients died late in the postoperative period, six in the bioprosthesis group and six in the mechanical group. The late mortality had a significant association with postoperative stroke (p < 0.001) and postoperative NYHA Classes III and IV (p = 0.002). Postoperative NYHA class was significantly associated with age (p = 0.003), pulmonary disease (p = 0.02), mitral valve implant type (p = 0.01), and postoperative stroke (p = 0.02); 14 patients had strokes in the mechanical (9) and in the bioprosthetic (5) groups. NYHA classes were significantly better after the replacement surgeries (p < 0.001). BMV were significantly associated with worse survival (p = 0.03), worse NYHA postoperatively (p = 0.01), and more reoperations (p = 0.006). Survival was significantly better with MMV (p = 0.03). When the two groups were matched for age and mitral regurgitation, the analysis revealed that BMV were significantly associated with reoperations (p = 0.02) but not significantly associated with worse survival (p = 0.4) or worse NYHA (p = 0.4).

Conclusion

MMV replacement in mitral stenosis patients is associated with a lower reoperation rate, but there was no difference in survival compared with BMV replacement.

Aortic valve replacement in children: Options and outcomes

Several disease pathologies such as congenital heart disease and rheumatic fever can affect the aortic valve (AV) in children frequently necessitating intervention. While percutaneous or surgical AV repair is recommended as initial management strategy in children with AV disease, AV replacement (AVR) might become necessary in children with significant valve destruction and after repair or intervention failure. AVR in children is associated with distinct clinical and technical problems owing to several anatomic, social and prosthesis-related issues. In the current review, we list different AV substitutes, discuss their advantages and shortcomings, outline AVR results in children, and explore the divergence of outcomes in various age, anatomy and pathology subgroups; all in the aim to identify optimal AVR choice for each patient taking into consideration his unique anatomic and demographic characteristics.