Apixaban or Warfarin in Patients with an On-X Mechanical Aortic Valve

Efficacy and safety of mechanical pulmonary valve replacement: a comprehensive systematic review and meta-analysis

BACKGROUND

Pulmonary valve replacement (PVR) is the most common valve replacement procedure for pulmonary valve dysfunction in congenital heart diseases (CHD). Despite the long-term need for anticoagulation and potential bleeding complications in mechanical PVR (MPVR), prosthetic dysfunction and reoperation might occur less frequently. The major guidelines on the CHD management have no recommendation on the valve type for the PVR. So, we systematically reviewed the latest literature on the efficacy and safety of MPVR with different etiologies.

METHODS

This study followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. The protocol was registered with PROSPERO (CRD42023425339). A systematic search was conducted in PubMed, Scopus, Web of Science, and Embase. The primary outcomes evaluated include all-cause mortality, reintervention for mechanical prostheses, valvular thrombosis, thromboembolic events, prosthetic valve dysfunction, major bleeding events, right ventricular failure, and infective endocarditis. A random-effects model was employed for the meta-analysis. The quality of the studies was assessed using the Newcastle-Ottawa Scale.

RESULTS

The literature search was conducted up to June 12, 2023, and included 16 records in the qualitative synthesis, with 13 studies also included in the quantitative synthesis. Our systematic review indicates that the previously published patient-level analysis remains the most reliable evidence to date on MPVR, with 91%, 97%, and 95% 5-year freedom from valvular thrombosis, reintervention, and all-cause mortality, respectively. Our meta-analysis indicated low pooled incidence proportions of other outcomes as follows: Major bleeding (mean follow-up = 68.79 months, 16/336, 5% [95% CI 3-8]); Valvular dysfunction (mean follow-up = 68.89 months, 70/708, 10% [95% CI 8-12]); Thromboembolic events (mean follow-up = 78.28 months, 9/293, 3% [95% CI 2-6]); and Infectious endocarditis (mean follow-up = 42.03 months, 7/518, 1% [95% CI 1-3]).

CONCLUSIONS

Despite showing acceptable efficacy and safety in MPVR, there is still a significant knowledge gap in choosing the most appropriate prosthetic valve in patients undergoing PVR. High-quality research is warranted to resolve the existing gap in evidence.

Impact of Anticoagulation Therapy After Bioprosthetic and Homograft Pulmonary Valve Replacement

BACKGROUND

The effect of anticoagulation on early postoperative outcomes after pulmonary valve replacement (PVR) with bioprosthetic valves and homografts is not yet defined. We hypothesized that short-term anticoagulation would be associated with improved valve durability.

METHODS

Patients undergoing PVR or right ventricle-to-pulmonary artery conduits with a bioprosthetic or homograft valve >15 mm in diameter between January 2015 and April 2021 at Boston Children's Hospital were retrospectively compared by anticoagulation status. Survival, postoperative echocardiographic data, and the incidence of pulmonary valve reintervention and prosthetic valve dysfunction were compared using multivariable Cox and logistic regression analyses adjusted for a propensity score based on anticoagulation therapy.

RESULTS

Among 531 patients with a median follow-up of 1.16 years, 130 received anticoagulation therapy. Freedom from reintervention was 99%, 92%, and 86% at 1, 3, and 5 years, respectively. Adjusted for propensity score, there was no association between reintervention and anticoagulation (hazard ratio, 0.78; 95% CI, 0.18-3.47; P = .75). The propensity score-adjusted rates of valve dysfunction were 9% in anticoagulated patients and 15% in non-anticoagulated patients (odds ratio, 0.54; 95% CI, 0.18-1.56; P = .25). There was no difference in early major bleeding rates between groups (3.4% vs 2.4%, P = .59) or in other postoperative outcomes. Only 1 of 18 (6%) of all bleeding events in the anticoagulated group occurred after starting anticoagulation.

CONCLUSIONS

Anticoagulation therapy appeared safe with no association with major postoperative bleeding. However, additional follow-up is necessary to assess its impact on midterm to long-term valve durability after PVR.

Low-dose apixaban in HeartMate 3 LVAD patients, interim analysis of the ApixiVAD trial, a randomized controlled study

BACKGROUND

Left ventricular assist devices (LVADs) improve outcomes in advanced heart failure but require anticoagulation. Vitamin K antagonists (VKAs) have significant limitations, with labile international normalized ratios and suboptimal time in therapeutic range (TTR), associated with increased morbidity and mortality. Direct oral anticoagulant therapy has been contraindicated in LVAD patients.

METHODS

The ApixiVAD study, a 1:1 randomized, open-label pilot trial, compared the reduced-dose apixaban (2.5 mg twice daily) with standard VKAs in stable HeartMate 3 patients with TTR > 60%. Aspirin was not mandated. Primary outcomes included thromboembolic events, bleeding, and death.

RESULTS

Forty-four patients were randomized, 21 to apixaban and 23 to VKA. Median age was 55 years (50-64), and 6 were women (14%). The median time from LVAD implantation to randomization was 6 months (range 5-8). Patients were followed for a median of 6 months (2-8). Twenty-five (57%) were transplanted, 12 (27%) were still on treatment, and 5 (11%) had undergone a primary outcome. Event-free survival was similar between groups (hazard ratio [HR] 1.46, 95% confidence interval [CI] 0.64-3.35, p = 0.4, Cox model) as well as Blood product use at transplantation.

CONCLUSIONS

These interim results were obtained after the end of recruitment but before all patients reached the full follow-up duration. The rates of bleeding observed in the apixaban group were below those reported in large international studies without any increase in thrombosis, suggesting that apixaban 2.5 mg twice daily may offer an effective balance between bleeding risk and anticoagulation efficacy. These findings should be interpreted as preliminary and hypothesis-generating.

New targets for antithrombotic medications: seeking to decouple thrombosis from hemostasis

Arterial and venous thromboses are the leading causes of morbidity and mortality worldwide. Numerous antithrombotic agents are currently available with antiplatelet, thrombolytic/fibrinolytic, and anticoagulant activity. However, all the currently available antithrombotic agents carry a risk of bleeding that often prevents their use. This unfavorable risk-benefit profile is particularly challenging for patients with cancer-associated venous thromboembolism, patients with atrial fibrillation at a high risk of bleeding, and patients with end-stage renal disease. Patients with ischemic stroke and acute coronary syndromes have not yet found a favorable risk-benefit profile with anticoagulant therapy to help reduce the residual thromboembolic risk that remains after antiplatelet and lipid therapy. Two emerging classes of antithrombotic agents, factor (F)XI or activated factor Ⅺ (FⅪa) inhibitors and glycoprotein VI inhibitors, have shown promise in their ability to prevent pathologic thrombosis without increasing the risk of hemostatic-related bleeding in phase 2 studies. Among the FⅪ/FXIa inhibitors of coagulation, a parenterally administered monoclonal antibody (abelacimab) and 2 orally administered small molecule inhibitors (asundexian, milvexian) are collectively being studied in patients with atrial fibrillation, cancer-associated venous thromboembolism, acute coronary syndrome, and ischemic stroke. One parenterally administered glycoprotein VI antiplatelet agent (glenzocimab) is currently being studied in patients with ischemic stroke. If shown to be efficacious and safe in ongoing phase 3 studies, both classes of emerging antithrombotic agents have the potential to greatly improve outcomes for patients with challenging thrombotic conditions.

Choosing the optimal oral anticoagulant for stroke prevention in atrial fibrillation: direct oral anticoagulants vs vitamin K antagonists

Direct oral anticoagulants (DOACs) have replaced vitamin K antagonists (VKAs) for stroke prevention in many patients with atrial fibrillation, but VKAs may still be preferred in some situations. We use a case-based approach to present the evidence for the possible use of a VKA in preference to a DOAC in patients with atrial fibrillation and rheumatic mitral stenosis, high body mass index, frailty, and breakthrough stroke despite being prescribed a DOAC.

Association of Anaesthetists guidelines: the use of blood components and their alternatives

BACKGROUND

The administration of blood components and their alternatives can be lifesaving. Anaemia, bleeding and transfusion are all associated with poor peri-operative outcomes. Considerable changes in the approaches to optimal use of blood components and their alternatives, driven by the findings of large randomised controlled trials and improved haemovigilance, have become apparent over the past decade. The aim of these updated guidelines is to provide an evidence-based set of recommendations so that anaesthetists and peri-operative physicians might provide high-quality care.

METHODS

An expert multidisciplinary, multi-society working party conducted targeted literature reviews, followed by a three-round Delphi process to produce these guidelines.

RESULTS

We agreed on 12 key recommendations. Overall, these highlight the importance of organisational factors for safe transfusion and timely provision of blood components; the need for protocols that are targeted to different clinical contexts of major bleeding; and strategies to avoid the need for transfusion, minimise bleeding and manage anticoagulant therapy.

CONCLUSIONS

All anaesthetists involved in the care of patients at risk of major bleeding and peri-operative transfusion should be aware of the treatment options and approaches that are available to them. These contemporary guidelines aim to provide recommendations across a range of clinical situations.

Quality of warfarin management following transfer from an anticoagulation clinic to primary care

BACKGROUND

Advances in alternative oral anticoagulants has reduced use and clinician comfort with warfarin. Our specialty anticoagulation clinic (AC) operates at maximum capacity and must transfer patients to accept new referrals.

OBJECTIVES

To compare time within therapeutic range (TTR) during 6 months of AC care versus following transfer to primary care for a minimum of 6 months and to a maximum of 24 months. Secondarily, to compare frequency of INR assessments, proportion of INRs ≤1.5 and > 5, and rates of bleeding and thromboembolic events post-transfer to primary care.

METHODS

Mixed retrospective chart review and administrative audit with a before-after study design for patients managed by the University of Alberta's AC for at least 6 months that were transferred to primary care.

RESULTS

177 (27.7 %) patients were included, managed by the AC for 3.4 years (1.3, 7.9). TTR declined during the first 6 months post-transfer with AC care achieving 69.2 % and primary care 64.5 % (p = 0.02) and when compared to the 24-month interval (69.2 % vs 63.4 %; respectively; p = 0.003). A shorter interval between INRs in AC care was observed (28.9 (24.4) vs 34.5 (31.7) days, respectively; p = 0.0004). Similar numbers of critical INRs occurred between groups, whereas more INRs ≤1.5 occurred in primary care (7.3 % vs 4.7 %, respectively; p = 0.0003). Bleeding and thromboembolic event rates were balanced following transfer to primary care with both occurring at 9.4 % per patient year.

CONCLUSION

A decline in anticoagulation control after transfer to primary care was observed, which appeared to be driven by a greater proportion of subtherapeutic INRs.

Anticoagulants: From chance discovery to structure-based design

Taking a historical perspective, we review the discovery, pharmacology, and clinical evaluation of the old and new anticoagulants that have been approved for clinical use. The drugs are discussed chronologically, starting in the 1880s, and progressing through to 2024. The innovations in technology used to develop novel anticoagulants came in fits and starts and reflected the advances in science and technology over these decades, whereas the shift from anecdote to evidence-based use of anticoagulants was delayed until the principles of epidemiology and biostatistics were introduced into clinical trial design and to the approval process. Hirudin, heparin, and vitamin K antagonists were discovered by chance, and were used clinically before their mechanism of action was elucidated and before their net clinical benefits were evaluated in randomized clinical trials. Subsequent anticoagulants were designed based on a better understanding of the structure and function of coagulation proteins, including antithrombin, thrombin, and factor Xa, and underwent more rigorous preclinical and clinical evaluation before regulatory approval. By simplifying oral anticoagulation, the direct oral anticoagulants have revolutionized anticoagulation care and have enhanced the uptake of anticoagulation, but bleeding has not been eliminated and there is a need for more effective and convenient anticoagulants for thrombosis triggered by the contact pathway of coagulation. The newly developed factor XIa and XIIa inhibitors have the potential to address these unmet clinical needs and are undergoing clinical evaluation for several indications. SIGNIFICANCE STATEMENT: Anticoagulant therapy is the cornerstone of treatment and prevention of thrombosis, which remains a leading cause of morbidity and mortality worldwide. Elucidation of the structure and function of coagulation enzymes, their cofactors, and inhibitors, coupled with advances in structure-based design led to the discovery of more convenient, safer, and more effective anticoagulants that have revolutionized the management of thrombotic disorders.

Analysis of The 2024 ESC/EACTS Guidelines For The Management Of Atrial Fibrillation

The 2024 European Society of Cardiology guidelines for atrial fibrillation (AF) emphasize a patient-centered approach to management, structured around the AF-CARE pathway: Comorbidity and risk factor management (C), Avoiding stroke and thromboembolism (A), Reducing symptoms through rate and rhythm control (R), and Evaluation and dynamic reassessment (E). This framework ensures that comorbidities such as hypertension, heart failure, diabetes, and obesity are effectively managed to prevent disease progression and improve outcomes. A key principle of the guidelines is shared decision making involving patients, families, caregivers, and healthcare teams to ensure individualized care that reflects patient preferences. The guidelines also stress healthcare equity, advocating for the elimination of disparities related to sex, ethnicity, disability, and socioeconomic status. For diagnosis, electrocardiographic confirmation of clinical AF is essential, followed by risk stratification using the CHA₂DS₂-VASc score to guide anticoagulation therapy. Direct oral anticoagulants are preferred for most patients because of their good safety profile. Stroke prevention is prioritized, with rhythm control as first-line treatment for suitable patients. For those with persistent symptoms despite medications, catheter ablation is recommended. Rate control strategies, including beta-blockers, digoxin, and calcium channel blockers, are used to manage heart rate and symptoms. Ongoing education for patients, families, and providers supports informed decision making and dynamic reassessment, optimizing patient outcomes and quality of life.

Ensuring Virtual Vigilance in Decentralized Clinical Trials

This Viewpoint discusses the increased use of decentralized clinical trials (DCTs) to improve efficiency in health research, highlights a number of risks to research rigor inherent in DCTs, and suggests ways in which DCT designers can better frame trial monitoring and oversight to ensure data integrity and avoid health inequities.

Contemporary Multi-modality Imaging of Prosthetic Aortic Valves

With the aging of the general population and the rise in surgical and transcatheter aortic valve replacement, there will be an increase in the prevalence of prosthetic aortic valves. Patients with prosthetic aortic valves can develop a wide range of unique pathologies compared to the general population. Accurate diagnosis is necessary in this population to generate a comprehensive treatment plan. Transthoracic echocardiography is often insufficient alone to diagnose many prosthetic valve pathologies. The integration of many imaging modalities, including transthoracic echocardiography, transesophageal echocardiography, cardiac computed tomography, cardiac magnetic resonance imaging, and nuclear imaging, is necessary to care for patients with prosthetic valves. The purpose of this review is to describe the strengths, limitations, and contemporary use of the different imaging modalities necessary to diagnose prosthetic valve dysfunction.

Low-dose warfarin with a novel mechanical aortic valve: Interim registry results at 5-year follow-up

OBJECTIVES

To evaluate whether warfarin targeted at an international normalized ratio of 1.8 (range, 1.5-2.0) after On-X mechanical aortic valve implant is safe for all patients.

METHODS

This prospective, observational clinical registry assessed adverse event rates in adult patients receiving low-dose warfarin (target international normalized ratio, 1.8; range, 1.5-2.0) plus daily aspirin (75-100 mg) during a 5-year period after On-X aortic valve implant. The primary end point is the combined rate of major bleeding, valve thrombosis, and thromboembolism overall and in 4 subgroups. The comparator is the Prospective Randomized On-X Anticoagulation Trial control group patients on standard-dose warfarin (international normalized ratio, 2.0-3.0) plus aspirin 81 milligrams daily.

RESULTS

A total of 510 patients were recruited at 23 centers in the United States, United Kingdom, and Canada between November 2015 and January 2022. This interim analysis includes 229 patients scheduled to complete 5-year follow-up by August 16, 2023. The linearized occurrence rate (in percent per patient-year) of the primary composite end point of major bleeding, valve thrombosis, and thromboembolism is 1.83% compared with 5.39% (95% confidence interval, 4.12%-6.93%) in the comparator group. Results are consistent in clinic-monitored and home-monitored patients and in those at high risk for thromboembolism. Major bleeding and total bleeding were reduced by 87% and 71%, respectively, versus the comparator group, without an increase in thromboembolic events.

CONCLUSIONS

Interim results support the continued safety of the On-X aortic mechanical valve with a target international normalized ratio of 1.8 plus low-dose aspirin through 5 years after implant, with or without home monitoring.

Changes in Time in Therapeutic Range Within a Warfarin Anticoagulation Clinic Following Introduction of Direct Oral Anticoagulants

Background: As direct oral anticoagulants (DOACs) have become widely recommended as first-line anticoagulation therapy, patients who remain on warfarin are likely those unable to afford, adhere to, or utilize DOAC therapy due to the presence of a contraindication. It is currently unknown how availability of DOACs have affected populations being managed at warfarin (VKA) anticoagulation clinics. Methods: This was a retrospective chart review assessing warfarin-treated patients at an outpatient anticoagulation clinic. The primary endpoint was the 6-month time in therapeutic range (TTR) before and after DOACs were recommended as first-line therapy by clinical guidelines. Study periods were January to June 2015, before DOACs were recommended over VKA, and January to June 2022, when DOACs were often recommended over VKA. TTR, demographic changes, and the presence of contraindications to DOAC therapy in the clinic population between the two time periods were assessed. Results: No difference in 6-month TTR was observed between study periods (59% in 2015 vs 63% in 2022; P = .45). Patient demographics did not significantly vary, which may be due to the clinic retaining 45% of patients between both time periods. Contraindications to DOAC therapy were identified in 39% of the 2015 group and 49% of the 2022 group (P = .18). The most common contraindication was indication for anticoagulation. Conclusion: Availability of DOACs did not seem to significantly affect the population or management of warfarin-treated patients at an outpatient anticoagulation clinic, however, contraindications and potential challenges to use of DOAC therapy are present in many patients.

From the INVICTUS Trial to Current Considerations: It's Not Time to Retire Vitamin K Inhibitors Yet!

Atrial fibrillation (AF) is a common arrhythmia in clinical practice, and oral anticoagulation is the cornerstone of stroke prevention in AF. Direct oral anticoagulants (DOAC) significantly reduce the incidence of intracerebral hemorrhage with preserved efficacy for preventing stroke compared to vitamin K antagonists (VKA). However, the pivotal randomized controlled trials (RCTs) of DOAC excluded patients with valvular heart disease, especially mitral stenosis, which remains an exclusion criterion for DOAC use. The INVICTUS study was a large multicenter global RCT aimed at evaluating the role of DOAC compared to VKA in stroke prevention among patients with rheumatic valvular AF. In this study, rivaroxaban failed to prove superiority over VKA in preventing the composite primary efficacy endpoints of stroke, systemic embolism, myocardial infarction, and death. Unfortunately, the bleeding rates were not lower with rivaroxaban either. The death and drug discontinuation rates were higher in the DOAC arm. Close to the heels of the dismal results of INVICTUS, an apixaban trial in prosthetic heart valves, PROACT-Xa, was also prematurely terminated due to futility. Hence, for AF complicating moderate-to-severe mitral stenosis or prosthetic valve VKA remains the standard of care. However, DOAC can be used in patients with surgical bioprosthetic valve implantation, TAVR, and other native valve diseases with AF, except for moderate-to-severe mitral stenosis. Factor XI inhibitors represent a breakthrough in anticoagulation as they aim to dissociate thrombosis from hemostasis, thereby indicating a potential to cut down bleeding further. Multiple agents (monoclonal antibodies-e.g., osocimab, anti-sense oligonucleotides-e.g., fesomersen, and small molecule inhibitors-e.g., milvexian) have garnered positive data from phase II studies, and many have entered the phase III studies in AF/Venous thromboembolism. Future studies on conventional DOAC and new-generation DOAC will shed further light on whether DOAC can dethrone VKA in valvular heart disease.

Novel horizons in anticoagulation: the emerging role of factor XI inhibitors across different settings

Anticoagulants have long been fundamental in preventing and treating thromboembolic disorders, with a recent shift of focus towards direct oral anticoagulants, thanks to their ease of use, efficacy, and safety. Despite these advancements, bleeding complications remain a major concern with any anticoagulant, highlighting the need for safer drugs. Factor XI (FXI) inhibitors have emerged as promising agents in this regard, offering a novel approach by targeting upstream factors in the coagulation system. Phase II trials have shown encouraging outcomes, indicating a reduced bleeding risk compared to that associated with traditional anticoagulants, particularly in the context of cardiovascular disease management when combined with antiplatelet therapy. However, the variability in findings and limited efficacy data call for a cautious interpretation pending insights from phase III trials. These trials are essential for validating the potential of FXI inhibitors to balance bleeding risk reduction and maintain anticoagulant efficacy. This review explores the pharmacology, potential indications, clinical data, and future directions of FXI inhibitors, providing a perspective on their evolving role in anticoagulant therapy. It also provides a detailed analysis of data from published clinical trials on FXI inhibitors in various indications. Preliminary data from ongoing trials are also outlined. As the field moves forward, a cautiously optimistic outlook can be expected, focusing on comprehensive data from phase III trials to define the role of FXI inhibitors in various clinical scenarios.

Predictors of Device-Related Thrombus After Left Atrial Appendage Occlusion: TED-F2 Score

Background

Left atrial appendage (LAA) occlusion (LAAO) is performed to prevent LAA thrombus in patients with atrial fibrillation (AF). The risk of device-related thrombus (DRT) on the atrial side of the LAAO device is approximately 4%. Identifying patients at high risk of DRT would enable closer surveillance and more-aggressive anticoagulation to prevent post-LAAO DRT-related stroke.

Methods

From the LAAO registry at The University of Kansas Medical Center, we identified patients who developed DRT. We chose 3 unmatched controls per DRT case from LAAO recipients without DRT. Predictor variables were obtained from transesophageal echocardiogram reports and/or images, transthoracic echocardiogram reports, and chart review. Implant depth was measured from the limbus of the left atrial ridge to the centre of the atrial aspect of the LAAO device, on a 45° transesophageal echocardiogram view.

Results

We identified 26 patients with DRT (aged 77.7 ± 9.7 years; 34.6% female) and selected 78 unmatched controls without DRT. Univariate predictors of DRT, comprising a novel TED-F2 score, included history of venous Thromboembolism (23.1% vs 5.1%, P = 0.01), an LAA Emptying velocity ≤ 20 cm/s (45.8% vs 18.9%, P = 0.01), an implant Depth > 2 cm (34.6% vs 12.8%, P = 0.02), and presence of AF rhythm at time of device implantation (50.0 % vs 11.5%, P = 0.0001). A TED-F2 score of ≥ 3 was very strongly associated with DRT-odds ratio 12.5 (95% confidence interval, 3.8-41.1, P < 0.0001).

Conclusions

We propose a novel risk score to predict development of DRT after LAAO, comprising history of venous Thromboembolism, LAA Emptying velocity ≤ 20 cm/s, implant Depth > 2 cm (1 point each), and an AF rhythm at implantation (2 points). A TED-F2 risk score of ≥ 3 identified patients who are at greatly elevated risk of developing DRT.

Antithrombotic Strategies After Transcatheter Aortic Valve Replacement in Patients Without an Indication of Oral Anticoagulants: A Network Meta-Analysis of Randomized Controlled Trials

Single-antiplatelet therapy (SAPT) has been a standard of care posttranscatheter aortic valve replacement with no clear evidence exist using direct oral anticoagulants (DOACs), vitamin K antagonists (VKA), or dual antiplatelet agents (DAPT); thus we aim to compare the safety and efficacy of the various antithrombotic strategies after transcatheter aortic valve replacement. We performed a network meta-analysis using a frequentist framework, pooling dichotomous outcomes using risk ratio (RR), and continuous data using mean difference, along with the corresponding 95% confidence interval (CI). Nine randomized controlled trials with 4193 patients were included, 567 patients were in the VKA group, 591 patients in the SAPT group, 1571 patients in the DAPT group, and 1464 patients in the DOACs group. Only DOAC showed a statistically significant higher risk of all-cause mortality [RR of 1.88 (95% CI: 1.07-3.28)] with no statistically significant difference between our arms in terms of mortality. For minor bleeding, DAPT had a significant higher risk with RR of 1.53 (95% CI: 1.04-2.25), while for major bleeding, DAPT and DOAC had a significant higher risk with RR of 2.36 (95% CI: 1.27-4.40) and 4.74 (95% CI: 2.05-10.92), respectively. There was no significant difference in terms of stroke and life-threatening bleeding. Moreover, only DOAC showed a significantly lower risk for valve thrombosis, when compared to other strategies [RR: 0.24 (95% CI: 0.13-0.46)]. Overall, SAPT had lower major bleeding events compared to other arms. There were no differences in the outcomes of stroke, myocardial infarction, or life-threatening bleeding outcomes. However, DOACs significantly reduced valve thrombosis compared to VKAs.

Optimizing Anticoagulation in Valvular Heart Disease: Navigating NOACs and VKAs

BACKGROUND/OBJECTIVES

Non-vitamin K antagonist oral anticoagulants (NOACs) have demonstrated similar effectiveness and safety profiles to vitamin K antagonists (VKAs) in treating nonvalvular atrial fibrillation (AF). Given their favorable pharmacological profile, including the rapid onset and offset of action, fixed dosing, and predictable pharmacokinetics with a consistent dose-response relationship, reducing the need for frequent blood tests, researchers have investigated the potential of NOACs in patients with AF and valvular heart disease (VHD).

METHODS

Clinical trials, excluding patients with mechanical prosthetic valves or moderate/severe mitral stenosis, have shown the benefits of NOACs over VKAs in this population. However, there is a need for further research to determine if these findings apply to mechanical valve prostheses and NOACs.

RESULTS

Several ongoing randomized controlled trials are underway to provide more definitive evidence regarding NOAC treatment in moderate to severe rheumatic mitral stenosis. Importantly, recent trials that included patients with atrial fibrillation and bioprosthetic valves (also transcatheter heart valves) have provided evidence supporting the safety of NOACs in this specific patient population. Ongoing research aims to clearly define the specific scenarios where NOACs can be safely and effectively prescribed for various types of VHD, including moderate/severe mitral stenosis and mechanical valves.

CONCLUSIONS

The aim of this review is to accurately identify the specific situations in which NOACs can be prescribed in patients with VHD, with a focus centered on each type of valvulopathy.

Non-vitamin K versus vitamin K antagonist oral anticoagulants in surgical mitral valve repair or bioprosthetic valve replacement in the first three months after surgery

INTRODUCTION AND OBJECTIVES

Oral anticoagulation (OAC) with non-vitamin K antagonist oral anticoagulants (NOACs) after surgical mitral valve repair (MVR) or bioprosthetic valve replacement (BVR) in mitral position remains a controversial topic among the cardiovascular community, in particular in the early postoperative period. This study aimed to evaluate the efficacy and safety of NOACs in the first three months after MVR or mitral BVR compared to vitamin K antagonists (VKAs).

METHODS

This was a single-center retrospective study with prospectively collected peri-intervention outcomes between 2020 and 2021. Records were retrieved and all participants were contacted by telephone. Patients were divided into groups according to OAC strategy. The primary outcome was a composite of death, rehospitalization, myocardial infarction, stroke or transient ischemic attack, systemic embolism, mitral thrombosis, or bleeding during the first three months after surgery.

RESULTS

A total of 148 patients were enrolled, with a mean age of 65.5±12.2 years, 56.8% male. On discharge, 98 (66.2%) patients were on VKAs and 50 (33.8%) were on DOACs for at least three months. The primary outcome occurred in 22 (22.4%) patients in the VKA group and in three (6%) in the NOAC group (p=0.012), mainly driven by more bleeding events in the former. Independent predictors of the primary outcome were smoking (p=0.028) and OAC with VKAs at discharge, the latter predicting three times more events (p=0.046, OR 3.72, 95% CI 1.02-13.5).

CONCLUSIONS

NOACs were associated with fewer events, supporting their efficacy and safety during the first three months after surgical MVR or mitral BVR.

Is There an Alternative Oral Anticoagulation to Vitamin-K-Antagonists for Patients with Mechanical Aortic Valve Replacement? - A Literature Review

Current guidelines exclusively recommend vitamin-K-antagonists (VKA) as anticoagulation for patients after mechanical aortic valve replacement due to the increased postoperative risk of valve thrombosis and thrombo-embolism. Strict and regular assessments are mandatory during VKA therapy to ensure a potent anticoagulatory effect within the desired range. From the patients' perspective, VKA are associated with relevant interactions and side effects reducing the quality of life and contributing to a high number of patients not achieving the optimal therapeutic target. Direct oral anticoagulants (DOAC) have replaced VKA therapy in the past for several indications, e.g., atrial fibrillation. However, it is still unclear if DOACs could replace VKA therapy in patients after mechanical aortic valve replacement. While the PROACT-Xa study did not show a sufficient anticoagulatory effect of apixaban plus aspirin compared to VKA therapy in patients after mechanical aortic valve replacement, the direct thrombin inhibitor dabigatran and the oral factor Xa inhibitors apixaban and rivaroxaban showed promising results in comparable patient cohorts in smaller studies and case reports. Factor Xa inhibitors were able to prevent thrombosis and thrombo-embolic events in patients after mechanical aortic valve replacement. Therefore, factor Xa inhibitors or factor XI inhibitors could provide a potent alternative to VKA for patients after a mechanical aortic valve replacement.

Efficacy and Safety of Non-Vitamin K Antagonist Oral Anticoagulants Compared with Vitamin K Antagonists in Patients with Atrial Fibrillation and Type 2 Valvular Heart Disease: A Systematic Review and Meta-Analysis

PURPOSE

This meta-analysis aimed to evaluate the efficacy and safety of non-vitamin K antagonist oral anticoagulants (NOACs) compared with vitamin K antagonists (VKAs) in patients with atrial fibrillation (AF) and type 2 valvular heart disease (VHD).

METHODS

We searched the PubMed, LILACS, and MEDLINE databases to retrieve, randomized controlled trials (RCTs) comparing NOACs and VKAs in patients with AF and type 2 VHD, excluding mitral stenosis (moderate to severe, of rheumatic origin) or mechanical heart valves. The efficacy outcomes assessed were stroke and systemic embolism (SE), while safety outcomes included major bleeding and intracranial hemorrhage (ICH).

RESULTS

Seven RCTs, including 16,070 patients with AF and type 2 VHD, were included. NOACs reduced the risk of stroke/SE (relative risk [RR], 0.75; 95% confidence interval [CI], 0.64-0.89; P = 0.0005), with no significant difference in major bleeding (RR, 0.88; 95% CI, 0.64-1.21; P = 0.43). The risk of ICH was reduced with NOACs (RR, 0.46; 95% CI, 0.27-0.77; P = 0.003). For patients with AF and bioprosthetic heart valve (five trials, 2805 patients), stroke/SE risks (RR, 0.65, 95% CI, 0.44-0.96) with NOACs were superior to VKAs. Major bleeding risks without ENVISAGE TAVI AF trial (RR, 0.53; 95% CI, 0.30-0.94; P = 0.03) with NOACs were superior to VKAs. The risks of ICH (RR, 0.61; 95% CI 0.34-1.09; P = 0.09) with NOACs were comparable to VKAs.

CONCLUSIONS

NOACs demonstrate efficacy and safety in patients with AF and type 2 VHD and reduce the risk of stroke/SE and ICH when compared with those with VKAs.

Acute lower-extremity arterial thrombosis with immune thrombocytopenia

We describe an acute lower-extremity arterial occlusion in a 30-year-old woman with immune thrombocytopenia and polycystic ovary syndrome. Thrombosis may be a complication of immune thrombocytopenia requiring careful management.

Mechanical valve thrombosis: Current management and differences between guidelines

All foreign bodies inserted in the circulatory system are thrombogenic and require temporary or lifelong antithrombotic therapies to prevent thrombosis. The adequate level of anticoagulation during the first few months determines the long-term durability, particularly for mechanical prostheses, and also for biological valves. Suboptimal anticoagulation is the most frequent source of mechanical valve thrombosis (MVT). The patient's clinical presentation decides how mechanical prosthetic valve obstruction is managed. If the mechanical valve thrombosis is obstructive and the patient is in a critical condition with hemodynamic instability, an immediate surgical intervention should be performed. The thrombolytic treatment is an option for left mechanical valve thrombosis in patients who have high surgical risk and no contraindications and also for right heart valve thrombosis. In non-obstructive thrombosis on the mechanical valve, patients can be asymptomatic, requiring optimization of the anticoagulant treatment. Both obstructive and non-obstructive thrombus formed on the mechanical prosthesis can result in embolic events. If the thrombus persists following anticoagulant treatment, the recommended options include thrombolytic treatment or redo surgery. Pannus can also cause obstruction of the prosthesis for which surgical treatment is the only option. While these clinical scenarios may initially appear to have straightforward solutions in terms of surgery, thrombolysis, or effective anticoagulation, real-world clinical experience often proves more complex. For instance, a patient with some usual comorbidities and non-obstructive mechanical valve thrombosis, experiencing symptoms solely by repeated systemic embolizations, might undergo all three therapeutic options due to the unpredictable nature of MVT. Therefore, treatment indications can intersect both on the time axis and depending on the patient's clinical status and the expertise of the center where he is hospitalized. Moreover, the European and American guidelines show subtle but important differences. The aim of this review was to compare these differences, comment on recent studies and evidence gaps, propose a more pragmatic algorithm combining all current recommendations, and highlight important research directions for this disease that has dominated the cardiovascular landscape for more than five decades, but for which there have been no significant recent changes in management.

Outcomes of Patients with a Mechanical Heart Valve and Poor Anticoagulation Control on Warfarin

BACKGROUND

 Patients with a mechanical heart valve (MHV) require oral anticoagulation. Poor anticoagulation control is thought to be associated with adverse outcomes, but data are limited.

OBJECTIVE

 To assess the risks of clinical outcomes in patients with a MHV and poor anticoagulation control on warfarin.

METHODS

 We conducted a retrospective study of consecutive patients undergoing MHV implantation at a tertiary care center (2010-2019). Primary outcome was a composite of ischemic stroke, systemic embolism, or prosthetic valve thrombosis. Major bleeding and death were key secondary outcomes. We constructed multivariable regression models to assess the association between time in therapeutic range (TTR) on warfarin beyond 90 days after surgery with outcomes.

RESULTS

 We included 671 patients with a MHV (80.6% in aortic, 14.6% in mitral position; mean age 61 years, 30.3% female). Median follow-up was 4.9 years, mean TTR was 62.5% (14.5% TTR <40%, 24.6% TTR 40-60%, and 61.0% TTR >60%). Overall rates of the primary outcome, major bleeding, and death were 0.73, 1.41, and 1.44 per 100 patient-years. Corresponding rates for patients with TTR <40% were 1.31, 2.77, and 3.22 per 100 patient-years. In adjusted analyses, every 10% decrement in TTR was associated with a 31% increase in hazard for the primary outcome (hazard ratio [HR]: 1.31, 95% confidence interval [CI]: 1.13-1.52), 34% increase in major bleeding (HR: 1.34, 95% CI: 1.17-1.52), and 32% increase in death (HR: 1.32, 95% CI: 1.11-1.57).

CONCLUSION

 In contemporary patients with a MHV, poor anticoagulation control on warfarin was associated with increased risks of thrombotic events, bleeding, and death.

Evaluation and Management of Mechanical Heart Valve Dysfunction and Thrombosis

PURPOSE OF REVIEW

Dysfunction and thrombosis of mechanical heart valves, although uncommon, represents a challenge that requires multidisciplinary expertise for diagnosis and management. The aim of this review is to summarize strengths and weaknesses of diagnostic methods and therapeutic strategies for this uncommon but potentially life-threatening pathology.

RECENT FINDINGS

Expeditious diagnosis of mechanical valve thrombosis and exclusion of other diagnostic considerations, often with incorporation of multimodality imaging, can inform the best treatment strategy. Presentation of mechanical valve thrombosis can be asymptomatic or can include heart failure, life-threatening embolic events, or cardiogenic shock. Echocardiography, fluoroscopy and computed tomography are important in the evaluation of mechanical valve dysfunction. Therapeutic strategies for thrombosis include anticoagulation, systemic thrombolysis, and surgery. Choice of treatment depends on multiple factors including thrombus size, degree of valve dysfunction, clinical presentation, and available surgical expertise.

Mechanical Valves: Past, Present, and Future-A Review

The mechanical valve was first invented in the 1950s, and since then, a wide variety of prostheses have been developed. Although mechanical valves have outstanding durability, their use necessitates life-long treatment with anticoagulants, which increases the risk of bleeding and thromboembolic events. The current guidelines recommend a mechanical prosthetic valve in patients under 50-60 years; however, for patients aged 50-70 years, the data are conflicting and there is not a clear-cut recommendation. In recent decades, progress has been made in several areas. First, the On-X mechanical valve was introduced; this valve has a lower anticoagulant requirement in the aortic position. Second, a potential alternative to vitamin K-antagonist treatment, rivaroxaban, has shown encouraging results in small-scale trials and is currently being tested in a large randomized clinical trial. Lastly, an innovative mechanical valve that eliminates the need for anticoagulant therapy is under development. We attempted to review the current literature on the subject with special emphasis on the role of mechanical valves in the current era and discuss alternatives and future innovations.

Design and Rationale for the Direct Oral Anticoagulant Apixaban in Left Ventricular Assist Devices (DOAC LVAD) Study

Implantable left ventricular assist device (LVAD) therapy is used to improve quality of life, alleviate symptoms and extend survival rates in patients with advanced heart failure. Patients with LVADs require chronic anticoagulation to reduce the risk of thromboembolic complications, and they commonly experience bleeding events. Apixaban is a direct oral anticoagulant that has become first-line therapy for patients with nonvalvular atrial fibrillation and venous thromboembolism; however, its safety in patients with LVADs has not been well characterized. The evaluation of the hemocompatibility in the DOAC LVAD (Direct Oral Anti-Coagulant apixaban in Left Ventricular Assist Devices) trial is a phase 2, open-label trial of patients with LVADs who were randomized to either apixaban or warfarin therapy. Patients randomized to apixaban will be started on a dosage of 5 mg twice daily, whereas those randomized to warfarin will be managed at an International Normalized Ratio goal of 2.0-2.5. All patients will be treated with aspirin at 81 mg daily. We plan to randomize and follow as many as 40 patients for 24 weeks to evaluate the primary outcomes of freedom from death or hemocompatibility-related adverse events (stroke, device thrombosis, bleeding, aortic root thrombus, and arterial non-CNS thromboembolism). The DOAC LVAD trial will establish the feasibility of apixaban anticoagulant therapy in patients with LVADs. Clinicaltrials.gov: NCT04865978.

On-X aortic valve replacement patients treated with low-dose warfarin and low-dose aspirin

OBJECTIVES

To assess if warfarin targeted to international normalized ratio (INR) 1.8 (range 1.5-2.0) is safe for all patients with an On-X aortic mechanical valve.

METHODS

This prospective, observational registry follows patients receiving warfarin targeted at an INR of 1.8 (range 1.5-2.0) plus daily aspirin (75-100 mg) after On-X aortic valve replacement. The primary end point is a composite of thromboembolism, valve thrombosis and major bleeding. Secondary end points include the individual rates of thromboembolism, valve thrombosis and major bleeding, as well as the composite in subgroups of home or clinic-monitored INR and risk categorization for thromboembolism. The control was the patient group randomized to standard-dose warfarin (INR 2.0-3.0) plus daily aspirin 81 mg from the PROACT trial.

RESULTS

A total of 510 patients were enroled at 23 centres in the UK, USA and Canada. Currently, the median follow-up duration is 3.4 years, and median achieved INR is 1.9. The primary composite end point rate in the low INR patients is 2.31% vs 5.39% (95% confidence interval 4.12-6.93%) per patient-year in the PROACT control group, constituting a 57% reduction. Results are consistent in subgroups of home or clinic-monitored, and high-risk patients, with reductions of 56%, 57% and 57%, respectively. Major and total bleeding are decreased by 85% and 73%, respectively, with similar rates of thromboembolic events. No valve thrombosis occurred.

CONCLUSIONS

Interim results suggest that warfarin targeted at an INR of 1.8 (range 1.5-2.0) plus aspirin is safe and effective in patients with an On-X aortic mechanical valve with or without home INR monitoring.

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.

Treatment options for isolated aortic valve insufficiency: a review

Aortic insufficiency (AI) is a valvular disease with increasing prevalence in older patients. The modern era provides numerous options for the management of AI which is explored here. Traditional interventions included aortic valve replacement with either mechanical or bioprosthetic aortic valves. While the former is known for its durability, it has grown out of favor due to the potential complications of anticoagulation. The preference for bioprosthetic valves is thus on the rise, especially with the advancements of transcatheter technology and the use of valve-in-valve therapy. Surgical options are also no longer limited to replacement but include complex techniques such as those required for aortic valve repair, Ozaki neocuspidization, Ross procedure and valve-sparring aortic root repair. Transcatheter options for the management of AI are not commercially available currently; however, preliminary data from ad-hoc trials, showed promising results and potential use of transcatheter technology in a variety of patients with pure AI.

Factor XI Inhibitors: A New Horizon in Anticoagulation Therapy

Anticoagulation therapy has undergone significant evolution, marked by the emergence of direct oral anticoagulants with distinct advantages. Despite these advancements, challenges persist in managing residual thrombotic and bleeding risks, particularly among vulnerable populations. The pursuit of alternative drugs has honed in on factor XI/XIa inhibitors. This comprehensive review delves into several key aspects regarding this new target: (i) the role of factor XI in the coagulation cascade; (ii) the genetic evidence and pathophysiologic rationale supporting factor XI inhibition as a therapeutic target; (iii) an exploration of the various types of factor XI/XIa inhibitors currently under investigation; (iv) potential applications of these medications, spanning thromboprophylaxis after orthopedic surgery, stroke prevention in atrial fibrillation, secondary prevention after acute coronary syndrome, non-cardioembolic stroke, thromboprophylaxis after foreign material implantation, end-stage renal disease, and patients with cancer; and (v) an overview of ongoing studies, recent findings, and the future trajectory of research into these drugs.

Early Intervention in Asymptomatic Aortic Stenosis: What Are We Waiting For?

Aortic stenosis (AS) contributes to significant cardiovascular morbidity and mortality worldwide, and the natural history from symptoms to ventricular decompensation, heart failure, and death has been well documented. For more than 2 decades, technologies including imaging and biomarkers have shown a promising ability to detect myocardial damage associated with AS before symptoms arise. Current treatment guidelines rely heavily on symptoms or ventricular decompensation as triggers for aortic valve intervention. There is increasing appreciation of the relationship between myocardial damage due to AS before the emergence of symptoms, and a number of published randomised trials suggest a benefit to early intervention in asymptomatic AS, with additional trials actively enrolling. Future treatment paradigms may incorporate early detection of ventricular damage by noninvasive new technologies as triggers for asymptomatic intervention. Enthusiasm for early aortic valve replacement should be tempered by consideration of the competing risks of early valve intervention, but an increasing preponderance of evidence continues to suggest that earlier intervention in AS is warranted.

When Direct Oral Anticoagulants Should Not Be Standard Treatment: JACC State-of-the-Art Review

For most patients, direct oral anticoagulants (DOACs) are preferred over vitamin K antagonists for stroke prevention in atrial fibrillation and for venous thromboembolism treatment. However, randomized controlled trials suggest that DOACs may not be as efficacious or as safe as the current standard of care in conditions such as mechanical heart valves, thrombotic antiphospholipid syndrome, and atrial fibrillation associated with rheumatic heart disease. DOACs do not provide a net benefit in conditions such as embolic stroke of undetermined source. Their efficacy is uncertain for conditions such as left ventricular thrombus, catheter-associated deep vein thrombosis, cerebral venous sinus thrombosis, and for patients with atrial fibrillation or venous thrombosis who have end-stage renal disease. This paper provides an evidence-based review of randomized controlled trials on DOACs, detailing when they have demonstrated efficacy and safety, when DOACs should not be the standard of care, where their safety and efficacy are uncertain, and areas requiring further research.

Association of sex with major bleeding risks in sub-Saharian anticoagulated patients with mechanical heart valves: A cohort study from the Khartoum Emergency Salam Centre

BACKGROUND

Rheumatic heart disease (RHD) with mechanical heart valve (MHV) replacement is common in Africa. However, MHV requires lifelong anticoagulation that could have a particular impact in women in reproductive age.

METHODS

We report data of a prospective observational cohort study conducted between August 2018 and September 2019 in MHV patients in the Salam Centre for Cardiac Surgery built in Khartoum by Emergency, an Italian Non-Governmental Organization, to evaluate bleeding risk, its associated determinants, and the impact of lifelong anticoagulation in fertile women.

RESULTS

We studied 3647 patients (median age 25.1 years; 53.9% female). During follow-up [median time 1.1 (0.1-1.2) years], we recorded 85 major bleedings (rate 2.16 × 100 pt-years), Major bleedings occurred more frequently among women (64/85 cases, 75.3%; rate 3.0 × 100 pt-years), compared to men (21/85 cases, 24.7%; rate 1.16 × 100 pt-years) (RR 2.6; 95% CI 1.6-4.5; p = 0.0001). Multivariate analysis was performed to identify variables associated with major bleeding, and female sex was the only risk factor significantly associated, whereas aspirin treatment and higher INR target showed a non-significant trend for higher bleeding risk. Thirty-two/85 (37.6%) of major bleedings were metrorrhagias. When we calculate the incidence of major bleedings after the exclusion of gynecological events, no sex differences in the bleeding risk were found (HR 1.3, 95% CI 0.8-2.3; p = 0.3).

CONCLUSIONS

Bleeding risk of young MHV patients on oral anticoagulant therapy is higher among women, mainly due to metrorrhagia. Women in the reproductive life are at high risk for gynecological bleeding when treated with anticoagulants.

Optimal management of cardiac surgery patients using direct oral anticoagulants: recommendations for clinical practice

OBJECTIVES

Literature is scarce on the management of patients using direct oral anticoagulants (DOACs) undergoing elective, urgent and emergency surgery. Therefore, we summarize the current evidence and provide literature-based recommendations for the management of patients on DOACs in the perioperative phase.

METHODS

A general literature review was conducted on the pharmacology of DOACs and for recommendations on the management of cardiac surgical patients on DOACs. Additionally, we performed a systematic review for studies on the use of direct DOAC reversal agents in the emergency cardiac surgical setting.

RESULTS

When surgery is elective, the DOAC cessation strategy is relatively straightforward and should be adapted to the renal function. The same approach applies to urgent cases, but additional DOAC activity drug level monitoring tests may be useful. In emergency cases, idarucizumab can be safely administered to patients on dabigatran in any of the perioperative phases. However, andexanet alfa, which is not registered for perioperative use, should not be administered in the preoperative phase to reverse the effect of factor Xa inhibitors, as it may induce temporary heparin resistance. Finally, the administration of (activated) prothrombin complex concentrate may be considered in all patients on DOACs, and such concentrates are generally readily available.

CONCLUSIONS

DOACs offer several advantages over vitamin K antagonists, but care must be taken in patients undergoing cardiac surgery. Although elective and urgent cases can be managed relatively straightforwardly, the management of emergency cases requires particular attention.

Evolving technology: the TRIFLO tri-leaflet mechanical valve without oral anticoagulation: a potential major innovation in valve surgery

The aortic valve is the most frequently diseased valve and aortic stenosis (AS) is the most prevalent valvular heart disease in developed countries. The diseased native aortic valve can be replaced by either a biological or mechanical valve prosthesis. The main concerns relate to durability, the need for oral anticoagulants and the incidence of complications related to this medication. Experimental, computational and biomolecular blood flow studies have demonstrated that the systolic forward flow but also the reverse flow phase at the end of the systole and leakage during the diastolic phase is mainly responsible for platelet activation and thrombosis. Better design of mechanical prosthetic heart valves must ensure smooth closing during flow deceleration and must eliminate high-shear hinge flow during diastole to prevent life-threatening thrombosis. A novel tri-leaflet valve should combine the favorable hemodynamics and the durability of existing mechanical heart valves and eliminate the less favorable characteristics, including the extremely rapid closing. In this paper, we discuss some issues of current mechanical heart valve prostheses and present a new valve design with the potential for significant innovation in the field. The TRIFLO Heart Valve, is a rigid, three-leaflet central flow heart valve prosthesis consisting of an alloyed titanium housing, and three rigid polymer (PEEK) cusps. This valve has a physiological operating mode. During the forward flow phase, the intraventricular pressure opens the leaflets so that blood can freely flow through with little obstruction, and with the deceleration of the blood flow, the leaflets close early and smoothly, minimizing blood flow regurgitation, blood cell damage, and activation of the coagulation cascade. Pre-clinical studies have shown pretty favorable results and a first-in-man study should start very soon.

Atrial fibrillation and stroke prevention: 25 years of research at EP Europace journal

Stroke prevention in patients with atrial fibrillation (AF) is one pillar of the management of this common arrhythmia. Substantial advances in the epidemiology and associated pathophysiology underlying AF-related stroke and thrombo-embolism are evident. Furthermore, the introduction of the non-vitamin K antagonist oral anticoagulants (also called direct oral anticoagulants) has clearly changed our approach to stroke prevention in AF, such that the default should be to offer oral anticoagulation for stroke prevention, unless the patient is at low risk. A strategy of early rhythm control is also beneficial in reducing strokes in selected patients with recent onset AF, when compared to rate control. Cardiovascular risk factor management, with optimization of comorbidities and attention to lifestyle factors, and the patient's psychological morbidity are also essential. Finally, in selected patients with absolute contraindications to long-term oral anticoagulation, left atrial appendage occlusion or exclusion may be considered. The aim of this state-of-the-art review article is to provide an overview of the current status of AF-related stroke and prevention strategies. A holistic or integrated care approach to AF management is recommended to minimize the risk of stroke in patients with AF, based on the evidence-based Atrial fibrillation Better Care (ABC) pathway, as follows: A: Avoid stroke with Anticoagulation; B: Better patient-centred, symptom-directed decisions on rate or rhythm control; C: Cardiovascular risk factor and comorbidity optimization, including lifestyle changes.

DOACs in the Anticoagulation of Mechanical Valves: A Systematic Review and Future Perspectives

Valvular heart disease is a common disease often necessitating valve replacement. Mechanical heart valves (MHVs) are often used in younger patients because of their longer durability. Their main disadvantage is the need for lifelong anticoagulation. Warfarin is considered a standard treatment, but it is far from perfect. Direct oral anticoagulants (DOACs) are a new and more patient-friendly alternative to warfarin when anticoagulation is required, but have not yet been approved for the indication of mechanical valves.

EVIDENCE ACQUISITION

A literature search of Pubmed, Embase, Web of Science (Core Collection), and Cochrane Library (from inception to May 2023) was performed using a search string that was well defined and not modified during the study. An extensive overview of the search terms used in each database can be found in the Appendix. Only prospective clinical trials were included in this review. A total of 10 publications were included in this review.

RELEVANCE TO CLINICAL PRACTICE

This systematic review summarizes the different types of DOACs and their possible use in the anticoagulation of mechanical valves. We aim to propose future directions in anticoagulation research for mechanical valves.

CONCLUSIONS

DOAC use in MHVs has been halted due to the failure of both dabigatran and apixaban in two major clinical trials. However, rivaroxaban was successful in two small clinical trials. Ample research is still needed to explore new valve designs as well as new anticoagulation targets.

Unresolved issues in the use of direct acting oral anticoagulants

INTRODUCTION

Currently approved direct oral anticoagulants (DOACs) target thrombin or coagulation factor Xa. Administered in fixed doses without routine laboratory monitoring, DOACs have simplified the approach to oral anticoagulation, when previously the choice was limited to vitamin K antagonists (VKAs).

AREA COVERED

We discuss a) unresolved issues related to optimal use of DOACs and b) new developments including the potential for FXIa inhibitors to be effective and safer anticoagulants.

EXPERT OPINION

By simplifying oral anticoagulation, DOACs have facilitated the uptake of anticoagulation. The DOACs are approved for stroke prevention in atrial fibrillation and for the prevention and treatment of venous thromboembolism, and their indications are expanding to include the prevention of atherothrombosis. DOACs have now replaced vitamin K antagonists (VKAs) for most indications, but not all. DOACs are inferior to VKAs for patients with mechanical heart valves, left ventricular assist device, rheumatic atrial fibrillation, and those with antiphospholipid syndrome, and their safety and efficacy are uncertain in some populations (e.g. advanced renal and liver disease). Impediments to use include concerns for bleeding and cost. The newly developed FXIa and FXIIa inhibitors have the potential to be safer than current anticoagulants, but phase 3 trials are needed to confirm their clinical efficacy and safety.

Anticoagulant Therapy for Mechanical Heart Valves - Unmet Need Persists

Direct oral anticoagulants such as apixaban or dabigatran have revolutionized anticoagulant treatment. These drugs, which specifically inhibit either factor Xa or thrombin, respectively, are at least as effective as vitamin K antagonists (e.g., warfarin) in patients with atrial fibrillation or venous thromboembolism and have important safety advantages that include reduced risks of intracranial hemorrhage, fatal bleeding, and all-cause mortality.1-3 They are also much easier to use because they are given in a fixed dose without routine laboratory monitoring of the anticoagulant effect and dose adjustment in the individual patient.