Anticoagulation therapy for the prevention of subclinical leaflet thrombosis after transcatheter aortic valve replacement: A comprehensive literature review and future directions

Leaflet thrombosis after transcatheter aortic valve replacement (TAVR) presents a significant challenge, leading to adverse clinical outcomes. Subclinical leaflet thrombosis (SLT) is increasingly recognized, and there is a growing concern about its role in clinical events and hemodynamic valve deterioration. Current recommendations for prophylactic anticoagulation or antiplatelet therapy following TAVR are primarily based on expert consensus rather than definitive evidence from randomized trials, resulting in a variety of antithrombotic strategies in clinical practice. While observational data suggest that prophylactic anticoagulation may be beneficial, clinical trial results are inconsistent, particularly for patients without an existing indication for OAC. Given the conflicting findings and potential safety concerns associated with prophylactic anticoagulation, further research is imperative. This review aims to summarize the existing literature on risk factors for SLT, preventive strategies, current recommendations, and future research directions to better understand the benefits and risks of prophylactic anticoagulation in this context.

Subclinical leaflet thrombosis and anticoagulation strategy following trans-catheter aortic valve replacement: A systematic review

Objective

Subclinical leaflet thrombosis (SLT) develops in 15% of patients undergoing trans-catheter aortic valve replacement (TAVR). TAVR is a procedure in which a faulty aortic valve is replaced with a mechanical one. An aortic valve replacement can be done with open-heart surgery; this is called surgical aortic valve replacement (SAVR). A significant problem is defining the best course of treatment for asymptomatic individuals with SLT post-TAVR, including the use of oral anticoagulation (OAC) in it.

Study design

Systematic review.

Method

The most pertinent published research (original papers and reviews) in the scientific literature were searched for and critically assessed using the online, internationally indexed databases PubMed, Medline, and Cochrane Reviews. Keywords like "Transcatheter valve replacement" and "Subclinical leaflet thrombosis" were used to search the papers. Selected studies were critically assessed for inclusion based on predefined criteria.

Results

The review examined the prevalence and characteristics of SLT after TAVR. To note, the incidence of SLT is seen to be higher in TAVR compared SAVR. Dual antiplatelet therapy, which is utilized in antithrombotic regimens post-TAVR, can possibly hasten SLT progression which could result in the impaired mobility of leaflets and the worsening of pressure gradients.

Conclusion

The use of dual antiplatelet drugs in routine antithrombotic therapy tends to accelerate initial subclinical leaflet thrombosis after TAVI, which results in a developing restriction of leaflet mobility and an increase in pressure differences.

A Mobile Thrombus Adhering to an Intra-Annular Self-Expanding Transcatheter Aortic Valve

An 81-year-old woman who had undergone transcatheter aortic valve implantation 3 months earlier underwent routine follow-up transthoracic echocardiography, which revealed a mobile thrombus adhering to the bioprosthetic valve. This thrombus differed in morphology from transcatheter aortic valve implantation valve thrombi commonly seen in daily practice.

Imaging of Bioprosthetic Valve Dysfunction after Transcatheter Aortic Valve Implantation

Transcatheter aortic valve implantation (TAVI) has become the standard of care in elderly high-risk patients with symptomatic severe aortic stenosis. Recently, TAVI has been increasingly performed in younger-, intermediate- and lower-risk populations, which underlines the need to investigate the long-term durability of bioprosthetic aortic valves. However, diagnosing bioprosthetic valve dysfunction after TAVI is challenging and only limited evidence-based criteria exist to guide therapy. Bioprosthetic valve dysfunction encompasses structural valve deterioration (SVD) resulting from degenerative changes in the valve structure and function, non-SVD resulting from intrinsic paravalvular regurgitation or patient-prosthesis mismatch, valve thrombosis, and infective endocarditis. Overlapping phenotypes, confluent pathologies, and their shared end-stage bioprosthetic valve failure complicate the differentiation of these entities. In this review, we focus on the contemporary and future roles, advantages, and limitations of imaging modalities such as echocardiography, cardiac computed tomography angiography, cardiac magnetic resonance imaging, and positron emission tomography to monitor the integrity of transcatheter heart valves.

First Ex Vivo Animal Study of a Biological Heart Valve Prosthesis Sensorized with Intravalvular Impedance

IntraValvular Impedance (IVI) sensing is an innovative concept for monitoring heart valve prostheses after implant. We recently demonstrated IVI sensing feasible in vitro for biological heart valves (BHVs). In this study, for the first time, we investigate ex vivo the IVI sensing applied to a BHV when it is surrounded by biological tissue, similar to a real implant condition. A commercial model of BHV was sensorized with three miniaturized electrodes embedded in the commissures of the valve leaflets and connected to an external impedance measurement unit. To perform ex vivo animal tests, the sensorized BHV was implanted in the aortic position of an explanted porcine heart, which was connected to a cardiac BioSimulator platform. The IVI signal was recorded in different dynamic cardiac conditions reproduced with the BioSimulator, varying the cardiac cycle rate and the stroke volume. For each condition, the maximum percent variation in the IVI signal was evaluated and compared. The IVI signal was also processed to calculate its first derivative (dIVI/dt), which should reflect the rate of the valve leaflets opening/closing. The results demonstrated that the IVI signal is well detectable when the sensorized BHV is surrounded by biological tissue, maintaining the similar increasing/decreasing trend that was found during in vitro experiments. The signal can also be informative on the rate of valve opening/closing, as indicated by the changes in dIVI/dt in different dynamic cardiac conditions.

Clinical outcomes of the ACURATE neo2 transcatheter heart valve: a prospective, multicenter, observational, post-market surveillance study

BACKGROUND

The next-generation ACURATE neo2 transcatheter aortic valve was designed for simplified implantation and to mitigate the risk of paravalvular leak (PVL) compared to the earlier device.

AIMS

To collect clinical outcomes and device performance data, including echocardiography and 4-dimensional computed tomography (4D-CT) data, with the ACURATE neo2 transcatheter heart valve in patients with severe aortic stenosis (AS).

METHODS

ACURATE neo2 PMCF is a single-arm, multicentre study of patients with severe AS treated in routine clinical practice. The primary safety endpoint was all-cause mortality at 30-days. The primary imaging endpoint was hypo-attenuated leaflet thickening (HALT), measured by core laboratory-adjudicated 4D-CT at 30 days. Secondary endpoints included VARC safety endpoints, procedural success, and evaluation of valve performance via core laboratory-adjudicated echocardiography.

RESULTS

The study enrolled 250 patients at 18 European centres (mean age: 80.8 years; 63.6% female; mean STS score: 2.9±2.0%); 246 (98.4%) were successfully treated with ACURATE neo2. The 30-day rates for mortality and disabling stroke were 0.8% and 0%, respectively. The new permanent pacemaker implantation rate was 6.5%. HALT >50% was present in 9.3% of patients at 30 days. Valve haemodynamics improved from baseline to 30 days (mean aortic valve gradient: from 47.6±14.5 mmHg to 8.6±3.9 mmHg; mean aortic valve area: from 0.7±0.2 cm2 to 1.6±0.4 cm2). At 30 days, PVL was evaluated as none/trace in 79.2% of patients, mild in 18.9%, moderate in 1.9%, and severe in 0%.

CONCLUSIONS

The study results support the safety and efficacy of TAVI with ACURATE neo2 in patients in routine clinical practice.

Innovative IntraValvular Impedance Sensing Applied to Biological Heart Valve Prostheses: Design and In Vitro Evaluation

Subclinical valve thrombosis in heart valve prostheses is characterized by the progressive reduction in leaflet motion detectable with advanced imaging diagnostics. However, without routine imaging surveillance, this subclinical thrombosis may be underdiagnosed. We recently proposed the novel concept of a sensorized heart valve prosthesis based on electrical impedance measurement (IntraValvular Impedance, IVI) using miniaturized electrodes embedded in the valve structure to generate a local electric field that is altered by the cyclic movement of the leaflets. In this study, we investigated the feasibility of the novel IVI-sensing concept applied to biological heart valves (BHVs). Three proof-of-concept prototypes of sensorized BHVs were assembled with different size, geometry and positioning of the electrodes to identify the optimal IVI-measurement configuration. Each prototype was tested in vitro on a hydrodynamic heart valve assessment platform. IVI signal was closely related to the electrodes' positioning in the valve structure and showed greater sensitivity in the prototype with small electrodes embedded in the valve commissures. The novel concept of IVI sensing is feasible on BHVs and has great potential for monitoring the valve condition after implant, allowing for early detection of subclinical valve thrombosis and timely selection of an appropriate anticoagulation therapy.

Hypo-attenuated leaflet thickening after Perceval sutureless bioprosthesis implantation

Modern multi-slice computed tomography (CT) has increased the detection of hypo-attenuated leaflet thickening (HALT). Furthermore, HALT's impact on transcatheter or surgical biological aortic valve (AV) prostheses has attracted attention. However, few reports on HALT in sutureless bioprostheses exist. Herein, we report a case of early structural valve deterioration due to HALT after AV replacement (AVR) with a Perceval bioprosthesis, which improved after anticoagulation therapy. A 79-year-old man admitted to our hospital with paroxysmal atrial fibrillation (PAF) during hemodialysis was also diagnosed with AV stenosis and, coronary artery disease, and PAF. He underwent AVR, coronary artery bypass grafting, and left atrial appendage resection. Although the postoperative course was uneventful with dual antiplatelet therapy, postoperative enhanced CT revealed HALT with reduced leaflet motion, and echocardiography showed an increased transvalvular pressure gradient. After using warfarin with target prothrombin time-international normalized ratio of 2-2.5 and/or heparin with target activated partial thromboplastin time of 45-60 s, the HALT disappeared with an improved transvalvular pressure gradient without any thromboembolic events.

Subclinical leaflet thrombosis after transcatheter aortic valve implantation: no association with left ventricular reverse remodeling at 1-year follow-up

Hypo-attenuated leaflet thickening (HALT) of transcatheter aortic valves is detected on multidetector computed tomography (MDCT) and reflects leaflet thrombosis. Whether HALT affects left ventricular (LV) reverse remodeling, a favorable effect of LV afterload reduction after transcatheter aortic valve implantation (TAVI) is unknown. The aim of this study was to examine the association of HALT after TAVI with LV reverse remodeling. In this multicenter case-control study, patients with HALT on MDCT were identified, and patients without HALT were propensity matched for valve type and size, LV ejection fraction (LVEF), sex, age and time of scan. LV dimensions and function were assessed by transthoracic echocardiography before and 12 months after TAVI. Clinical outcomes (stroke or transient ischemic attack, heart failure hospitalization, new-onset atrial fibrillation, all-cause mortality) were recorded. 106 patients (age 81 ± 7 years, 55% male) with MDCT performed 37 days [IQR 32-52] after TAVI were analyzed (53 patients with HALT and 53 matched controls). Before TAVI, all echocardiographic parameters were similar between the groups. At 12 months follow-up, patients with and without HALT showed a significant reduction in LV end-diastolic volume, LV end-systolic volume and LV mass index (from 125 ± 37 to 105 ± 46 g/m2, p = 0.001 and from 127 ± 35 to 101 ± 27 g/m2, p < 0.001, respectively, p for interaction = 0.48). Moreover, LVEF improved significantly in both groups. In addition, clinical outcomes were not statistically different. Improvement in LVEF and LV reverse remodeling at 12 months after TAVI were not limited by HALT.

The impact of hypo-attenuated leaflet thickening on haemodynamic valve deterioration following transcatheter aortic valve replacement

BACKGROUND

Hypo-attenuated leaflet thickening (HALT) may occur following transcatheter aortic valve replacement (TAVR), however, it remains unclear if HALT is a predictor of haemodynamic valve deterioration (HVD).

AIM

To determine the impact of HALT on the occurrence of HVD.

METHODS

We prospectively evaluated 186 patients for the presence of HALT at a median of 6 weeks following TAVR (Interquartile-range [IQR] 4-12 weeks). HALT depth and area were measured. HVD encompassed any of the following: mean gradient ≥20 ​mmHg with an increase in gradient ≥10 ​mmHg from baseline, Doppler velocity index reduction ≥0.1 or new moderate-to-severe valvular regurgitation. Routine echocardiograms at discharge, one month and annually, were assessed by echo-cardiologists that were blinded to the HALT status.

RESULTS

LT prevalence was 17.7% (33/186). HVD was present in 8.6% (16/186) at a median follow-up of 2 years (IQR 1-3); two required valve re-intervention and five required anticoagulation. HALT was the only independent predictor of HVD on multivariate analysis (OR 33.3, 95%CI 7.4-125). Patients with HALT were more likely to develop HVD, require repeat valve intervention and have higher trans-valvular gradients at up to 3-year follow-up. Patients with HALT had a median cumulative thickness of 2.9 ​mm (IQR 1.9-4.7) and area of 64.2 ​mm² (IQR 40.9-91.6). Thresholds for HALT in predicting HVD were a cumulative depth of 2.4 ​mm (Specificity 94.1%, Sensitivity 75.0%, AUC ​= ​0.87) and cumulative area of 28 ​mm² (Specificity 92.2%, Sensitivity 81.3%, AUC ​= ​0.86).

CONCLUSION

HALT is an independent predictor of HVD, which exhibits specific depth and area thresholds to predict HVD. CT following TAVR may determine patients at risk of HVD.

Usefulness of Antiplatelet Therapy After Transcatheter Aortic Valve Implantation

The rationale for dual antiplatelet therapy (DAPT) after transcatheter aortic valve implantation (TAVI) is to facilitate endothelialization of metallic struts of the transcatheter heart valve and to prevent thrombosis that could lead to thromboembolic events. Based on expert consensus, current societal guidelines recommend DAPT for 1 to 6 months after TAVI with weak evidence. Although the pivotal TAVI trials mandated this regimen, the evidence for the efficacy of DAPT to prevent transcatheter heart valve thrombosis is limited to 3 small trials and a handful of observational studies. Multiple coronary trials have demonstrated that DAPT is associated with increased bleeding in comparison with single antiplatelet therapy, especially in elderly patients. TAVI patients are predominantly elderly and frequently have risk factors that predispose them to bleeding. Herein, we summarize the evidence for antiplatelet therapy after TAVI and explore the theoretical benefit of DAPT to prevent thromboembolic events versus the risk of increased bleeding.

Clinical predictors and sequelae of computed tomography defined leaflet thrombosis following transcatheter aortic valve replacement at medium-term follow-up

BACKGROUND

The clinical predictors and sequelae of leaflet thrombosis (LT) following transcatheter aortic valve replacement (TAVR) is still unclear. Therefore, our aim was to determine the clinical predictors and sequelae at mid-term follow-up of computed tomography (CT)-defined LT following TAVR.

METHODS AND RESULTS

We performed a prospective evaluation with a 320-multislice CT following TAVR for the presence of LT, defined as hypo-attenuated leaflet thickening (HALT). Four-dimensional CT image-rendering was performed to determine the presence of reduced leaflet motion (RELM). 172 patients [89 (51.7%) male, mean age 82.8 ± 5.7 years] treated with commercially available TAVR device (Lotus 54%, CoreValve 32% and Sapien 3 14%) were included, with median CT-scan at 6.0 weeks post-TAVR. Prevalence of HALT was 14.0% (24 cases) and RELM was 9.8% (17 cases). On multivariate analysis, patients with HALT were less prescribed oral anticoagulation (OAC) (OR 9.9), received larger TAVR prostheses (OR 5.7) and higher rates of moderate-severe para-valvular regurgitation (PVR) (OR 16.3). There was no difference in clinical outcomes at a median follow-up of 2.3 years. Patients with RELM had significantly higher transvalvular gradients after discharge when compared to those without RELM.

CONCLUSIONS

Absence of OAC, large TAVR prostheses and moderate-severe PVR were predictors for LT. Transvalvular gradients were higher in patients that developed RELM but not HALT. Further studies are warranted to determine the long-term impact of LT on TAVR durability. Prevalence of different sub-types of CT-defined LT (HALT and RELM) and the clinical predictors of developing LT following TAVR. CT computed tomography, HALT hypo-attenuated leaflet thickening, LT leaflet thrombosis, RELM reduced leaflet motion, TAVR transcatheter aortic valve replacement.

The role of four-dimensional computed tomography in transcatheter aortic valve replacement prosthesis endocarditis with concurrent leaflet thrombosis: a case report

Background

Transcatheter aortic valve replacement (TAVR) is becoming increasingly utilized for the treatment of severe aortic valvular heart disease. Infective endocarditis of TAVR is rare but associated with higher mortality and morbidity. The potential for leaflet thrombosis following TAVR is also becoming increasingly recognized. Diagnosis of these conditions on echocardiography can be challenging due to prosthesis artefact.

Case summary

An 84-year-old man with a previous transcatheter aortic valve replacement presented with a febrile illness and bacteraemia. Transthoracic and transoesophageal echocardiography demonstrated high transvalvular gradients with features of prosthesis endocarditis, though leaflet morphology could not be fully assessed due to prosthesis artefact. Four-dimensional computed tomography revealed hypo-attenuated leaflet thickening with reduced leaflet motion, consistent with prosthesis leaflet thrombosis. The patient was successfully treated with antibiotics and anticoagulation, with resolution of the infection and normalization of the transvalvular gradient after 6 weeks.

Discussion

Echocardiography should be the first-line investigation for assessing leaflet morphology in suspected prosthetic valve endocarditis or leaflet thrombosis but its accuracy may be limited by artefact. Our case highlights that four-dimensional computed tomography provides further evaluation of prosthesis leaflet morphology/motion, providing valuable diagnostic information.

Early detection of transcatheter heart valve dysfunction

Introduction: Transcatheter aortic valve implantation therapy is spreading rapidly, representing the standard of care in inoperable and high-risk patients, and a valid alternative in intermediate- and low-risk patients with severe symptomatic aortic stenosis. In this subset, the development and validation of noninvasive, quantitative, in vivo imaging modality, to monitor possible valve dysfunction is mandatory, in order to plan timely therapeutic interventions before the onset of symptoms.Areas covered: The implantation of transcatheter heart valves (THV) is increasing rapidly. As a consequence, THV dysfunction will become a major cause of cardiovascular morbidity after TAVI. Emergency repeat aortic valve replacement surgery is associated with a high rate of mortality compared with elective repeat surgery. In this context, early detection of THV dysfunction is therefore highly desirable. The review aims to examine the different diagnostic method to early detect THV dysfunction.Expert opinion: Most promising innovations in the diagnosis of early detection of THV dysfunction are evaluated, and the future outlook is explored. Waiting for upcoming evidence about the utility of CT, CMR, and PET on early detection of THV dysfunction, tailoring echocardiogram follow-up based on patients' characteristics is the desirable approach.

Transcatheter Bioprosthetic Aortic Valve Dysfunction: What We Know So Far

Transcatheter aortic valve replacement (TAVR) is an established alternative to surgical valve replacement for patients with severe aortic stenosis (AS) and increased surgical risk. On the basis of the favorable outcomes of recent randomized clinical trials conducted in intermediate and low risk populations, TAVR is expected in the near future to be offered to patients not only at lower surgical risk, but also with longer life expectancy. In this particular subset, the long-term durability of the bioprosthetic valve is of critical importance. The European Association of Percutaneous Cardiovascular Interventions (EAPCI), the European Society of Cardiology (ESC), and the European Association for Cardio-Thoracic Surgery (EACTS) recently introduced standardized criteria to define structural valve deterioration (SVD) and valve failure of transcatheter and surgical aortic bioprosthesis-this with the aim to generate uniformity in data reporting in future studies assessing long-term durability of aortic bioprosthesis. On this background, the aim of this article is to review the definition, incidence and predictors of transcatheter bioprosthetic valve dysfunction, including structural and non-structural valve deterioration (SVD/NSVD), valve thrombosis, and endocarditis.

Antithrombotic Therapy in Transcatheter Aortic Valve Replacement

Transcatheter aortic valve replacement (TAVR) has recently emerged as an effective alternative to medical treatment or surgical aortic valve replacement in all symptomatic patients with severe aortic stenosis and high or prohibitive risk and in intermediate risk when transfemoral access is feasible. Patients undergoing TAVR are often at high risk for either bleeding or cerebrovascular complications, or both, so adjuvant antithrombotic therapies are commonly used before, during and after the procedure. Today, there is no clear evidence on the best antithrombotic regimen in this context. In this review, we will try to go through the mechanisms involved in bleeding and embolic complications and we will discuss the current points of antithrombotic treatment in patients during and after TAVR, with or without oral anticoagulation (OAC) indication.

Impact of Antithrombotic Regimen and Platelet Inhibition Extent on Leaflet Thrombosis Detected by Cardiac MDCT after Transcatheter Aortic Valve Replacement

The impact of antithrombotic regimen and platelet inhibition extent on subclinical leaflet thrombosis (SLT) detected by cardiac multidetector computed tomography (MDCT) after transcatheter aortic valve replacement (TAVR) is not well established. Hypoattenuation affecting motion (HAM) has been proposed as a surrogate marker of SLT, and is characterized by hypoattenuated leaflet thickening (HALT) and concomitant reduction in leaflet motion (RELM). We sought to investigate (i) the prevalence of HAM and HALT after TAVR detected by MDCT, (ii) the predictors of SLT, (iii) the impact of oral anticoagulant (OAC) and platelet inhibition extent assessed by platelet reactivity index vasodilator stimulated phosphoprotein (PRI-VASP) and closure time adenosine diphosphate (CT-ADP) on SLT. Of 187 consecutive patients who underwent TAVR from 1 August 2017 to 31 March 2018, 90 of them had cardiac CT at relevant follow-up. Clinical, biological, echocardiographic, procedural characteristics and treatments were collected before, at discharge, and 1 year after TAVR. P2Y₁₂ platelet inhibition extent and primary haemostasis disorders were investigated using platelet PRI-VASP and CT-ADP point-of-care assays. Eighty-five post-TAVR CTs out of 90 were ranked for clarity and assessed with sufficient diagnostic quality. HAM was evidenced in 13 patients (15.3%) and HALT in 30 patients (35%). Procedural characteristics, including aortic valve calcium score, annulus size, or procedural heparin regimens, were equivalent between groups. Likewise, no impact of P2Y₁₂ inhibition (PRI-VASP) nor primary haemostasis disorders (CT-ADP) on SLT could be evidenced. No impact of SLT on valve deterioration evaluated by transthoracic echocardiography (TTE) and clinical events could be established at 12 months follow-up. By multivariate analysis, lack of oral anticoagulant therapy at discharge (HR 12.130 CI 95% (1.394-150.582); p = 0.028) and higher haemoglobin levels were evidenced as the sole independent predictors of SLT. In four patients with HAM, MDCT follow-up was obtained after initiation of OAC therapy and showed a complete regression of HAM. SLT was evidenced in a sizeable proportion of patients treated by TAVR and was mainly determined by the lack of oral anticoagulant therapy. Conversely, no impact of platelet inhibition extent on SLT could be evidenced.

A Novel Sensorized Heart Valve Prosthesis: Preliminary In Vitro Evaluation

Background: Recent studies have shown that subclinical valve thrombosis in heart valve prosthesis (HVP) can be responsible for reduced leaflet motion detectable only by advanced imaging diagnostics. We conceived a novel sensorized HVP able to detect earlier any thrombus formation that may alter the leaflets motion using an electric impedance measurement, IntraValvular Impedance (IVI). Methods: For IVI measurement, dedicated electrodes are embedded in the structure of the HVP to generate a local electric field that is altered by the moving valve leaflets during their cyclic opening/closing. We present preliminary in vitro results using a first prototype of sensorized mechanical heart valve connected to an external impedance measurement system. The prototype was tested on a circulatory mock loop system and the IVI signals were recorded during both normal dynamics and experimentally induced altered working of the leaflets. Results: Recordings showed a very repetitive and stable IVI signal during the normal cyclic opening/closing of the HVP. The induced alterations in leaflet motion were reflected in the IVI signal. Conclusions: The novel sensorized HVP has great potential to give early warning of possible subclinical valve thrombosis altering the valve leaflet motion, and to help in tailoring the anticoagulation therapy.