The porcine valve type predicts obstructive thrombosis beyond the first three postoperative months in bioprostheses in the aortic position

Early anticoagulation after aortic valve replacement with porcine bioprosthesis randomized control trial (ANTIPRO)

OBJECTIVES

Most evidence for anticoagulation (AC) in aortic bioprosthesis is centred on embolic events, bleeding and reintervention risk. The effect of AC on haemodynamics has not been previously assessed. Our hypothesis was that patients with early AC after aortic valve replacement (AVR) with porcine bioprosthesis have better haemodynamics at 1 year of follow-up.

METHODS

Prospective, randomized, open-label trial conducted at 2 cardiac surgery centres. All patients undergoing AVR with porcine bioprosthesis were consecutively recruited. The anticoagulated group received warfarin + aspirin and the non-anticoagulated (control) only aspirin. The primary outcome was mean gradient after 1 year of AVR and change in New York Heart Association class. Secondary outcomes were major and minor bleeding, embolic events and prosthetic leak.

RESULTS

Of 140 participants in the study, 71 were assigned to the anticoagulated group and 69 to the control group. The mean age of the overall population was 72.4 (SD: 7.1) years. Global EuroSCORE was 7.65 (SD: 5.73). At 1 year, the mean gradient was similar between both groups [18.6 (SD: 1.1 mmHg) and 18.1 (SD: 1.0 mmHg) in the control and anticoagulated groups, respectively, P = 0.701]. No differences in functional class at 3 months or 1 year were found among groups. No differences were found among groups in the secondary outcomes.

CONCLUSIONS

The addition of 3 months of oral AC to anti-aggregation treatment was not detected to affect bioprosthetic haemodynamics nor functional class at 1 year after AVR. Likewise, AC does not lead to the higher incidence of complications.

Structural analysis of regional transcatheter aortic valve underexpansion and its implications for subclinical leaflet thrombosis

Subclinical leaflet thrombosis has been increasingly recognized following transcatheter aortic valve replacement (TAVR). Determining the risk factors is vital in preventing clinical leaflet thrombosis and ensuring long-term value durability. Clinical data have indicated that regional stent under-expansion of transcatheter aortic valves (TAVs), particularly self-expanding devices, may be associated with an increased risk of subclinical leaflet thrombosis. This study aimed to determine the effects of regional TAV frame under-expansion on leaflet kinematics, leaflet structural characteristics, and explore its impact on the likelihood of leaflet thrombosis. In this study, mild and moderate regional frame under-expansion of a 26-mm CoreValve were examined using experimental testing and computational simulations. The results indicated that regional TAV frame under-expansion impairs leaflet kinematics and reduces the range of motion in leaflets with an angle less than 120°. The reduced range of motion can increase blood stasis on the surface of the TAV leaflets. The results also demonstrated that regional frame under-expansion induced localized high-stress regions in the leaflets close to the fixed boundary edge. The increased mechanical stress can lead to accelerated tissue degeneration. The study improves our understanding of the effects of regional stent under-expansion in TAVR. Post-procedural balloon dilatation of self-expanding TAVs can potentially be advantageous in reducing leaflet distortion and normalizing leaflet stress distribution. Large-scale, prospective, and well-controlled studies are needed to further investigate regional TAV frame under-expansion effects on subclinical leaflet thrombosis and long-term valve durability.

Bioprosthetic Aortic Valve Thrombosis and Literature Review

An 83-year-old gentleman with a history of 23-mm Hancock-II-bioprosthetic aortic valve (BAV) replacement ten-years prior presented with symptoms of dyspnea and lower extremity edema. During the preceding seven-years, he had been noted to have asymptomatic increased mean transvalvular gradients (MG; 36–50 mmHg) felt to be due to either early bioprosthetic degeneration, pannus formation, or patient–prosthesis mismatch. An echocardiogram at the time of symptom development demonstrated significant flow acceleration through the aortic valve, mild regurgitation, and severely increased MG (48 mmHg) with prolonged acceleration time (AT, 140 msec). A trial of warfarin anticoagulation resulted in dramatic improvement after only 6 weeks with laminar flow through the AV, near-total resolution of regurgitation, and a decrease in MG to 14 mmHg and AT to 114 msec. These findings strongly suggest that BAV thrombosis was the predominant mechanism responsible for the longstanding high MG. Our case highlights that BAV thrombosis should be considered in the differential of elevated gradients regardless of the age of prosthesis, and that a trial of warfarin anticoagulation may be beneficial even if elevated gradients have been present for a prolonged period. Valvular gradients are often abnormal long before a formal diagnosis; however, these may reverse quickly with anticoagulation therapy.

Atrial Fibrillation and Outcomes After Transcatheter or Surgical Aortic Valve Replacement (from the PARTNER 3 Trial)

The prognostic impact of preexisting atrial fibrillation or flutter (AF) in low-risk patients with severe aortic stenosis treated with transcatheter (TAVR) or surgical aortic valve replacement (SAVR) remains unknown. In this sub-analysis of the PARTNER 3 trial of patients with severe aortic stenosis at low surgical risk randomized 1:1 to TAVR versus SAVR, clinical outcomes were analyzed at 2 years according to AF status. Among 948 patients included in the analysis (452 [47.7%] in the SAVR vs 496 [52.3%] in the TAVR arm), 168 (17.6%) patients had AF [88/452 (19.5%) and 80/496 (16.1%) treated with SAVR and TAVR, respectively]. At 2 years, patients with AF had higher unadjusted rates of the composite outcome of death, stroke or rehospitalization (21.2% vs 12.9%, p = 0.007) and rehospitalization alone (15.3% vs 9.4%, p = 0.03) but not all cause death (3.8% vs 2.6%, p = 0.45) or stroke (4.8% vs 2.6%, p = 0.12). In adjusted analyses, patients with AF had a higher risk for the composite outcome of death, stroke or rehospitalization (hazard ratio [HR] 1.80, 95% confidence interval [CI] 1.20-2.71, p = 0.0046) and rehospitalization alone (HR 1.8, 95% CI 0.12-2.9, p = 0.015), but not death or stroke. There was no interaction between treatment modality and AF on the composite outcome (Pinter = 0.83). In conclusion, preexisting AF in patients with severe AS at low surgical risk was associated with increased risk of the composite outcome of death, stroke or rehospitalization at 2 years, irrespective of treatment modality.

Early cost-utility analysis of tissue-engineered heart valves compared to bioprostheses in the aortic position in elderly patients

OBJECTIVES

Aortic valve disease is the most frequent indication for heart valve replacement with the highest prevalence in elderly. Tissue-engineered heart valves (TEHV) are foreseen to have important advantages over currently used bioprosthetic heart valve substitutes, most importantly reducing valve degeneration with subsequent reduction of re-intervention. We performed early Health Technology Assessment of hypothetical TEHV in elderly patients (≥ 70 years) requiring surgical (SAVR) or transcatheter aortic valve implantation (TAVI) to assess the potential of TEHV and to inform future development decisions.

METHODS

Using a patient-level simulation model, the potential cost-effectiveness of TEHV compared with bioprostheses was predicted from a societal perspective. Anticipated, but currently hypothetical improvements in performance of TEHV, divided in durability, thrombogenicity, and infection resistance, were explored in scenario analyses to estimate quality-adjusted life-year (QALY) gain, cost reduction, headroom, and budget impact.

RESULTS

Durability of TEHV had the highest impact on QALY gain and costs, followed by infection resistance. Improved TEHV performance (- 50% prosthetic valve-related events) resulted in lifetime QALY gains of 0.131 and 0.043, lifetime cost reductions of €639 and €368, translating to headrooms of €3255 and €2498 per hypothetical TEHV compared to SAVR and TAVI, respectively. National savings in the first decade after implementation varied between €2.8 and €11.2 million (SAVR) and €3.2-€12.8 million (TAVI) for TEHV substitution rates of 25-100%.

CONCLUSIONS

Despite the relatively short life expectancy of elderly patients undergoing SAVR/TAVI, hypothetical TEHV are predicted to be cost-effective compared to bioprostheses, commercially viable and result in national cost savings when biomedical engineers succeed in realising improved durability and/or infection resistance of TEHV.

Multimodality Imaging of Complications of Cardiac Valve Surgeries

Replacement with a prosthetic heart valve (PHV) remains the definitive surgical procedure for management of severe cardiac valve disease. PHV dysfunction is uncommon but can be a life-threatening condition. The broad hemodynamic and pathophysiologic manifestations of PHV dysfunction are stenosis, regurgitation, and a stuck leaflet. Specific structural abnormalities that cause PHV dysfunction include prosthetic valve-patient mismatch, structural failure, valve calcification, dehiscence, paravalvular leak, infective endocarditis, abscess, pseudoaneurysm, abnormal connections, thrombus, hypoattenuating leaflet thickening, and pannus. Multiple imaging modalities are available for evaluating a PHV and its dysfunction. Transthoracic echocardiography is often the first-line imaging modality, with additional modalities such as transesophageal echocardiography, CT, MRI, cine fluoroscopy, and nuclear medicine used for further characterization and establishing a specific cause. The authors review PHVs and the role of imaging modalities in evaluation of PHV dysfunction and illustrate the imaging appearances of different complications. Online supplemental material is available for this article. ^©RSNA, 2019.

Clinical Valve Thrombosis and Subclinical Leaflet Thrombosis Following Transcatheter Aortic Valve Replacement: Is There a Need for a Patient-Tailored Antithrombotic Therapy?

Transcatheter aortic valve replacement (TAVR) has become an established therapeutic option for patients with symptomatic, severe aortic valve stenosis at increased surgical risk. Antithrombotic therapy after TAVR aims to prevent transcatheter heart valve (THV) thrombosis, in which two different entities have to be recognized: clinical valve thrombosis and subclinical leaflet thrombosis. In clinical valve thrombosis, obstructive thrombus formation leads to an increased transvalvular gradient, often provoking heart failure symptoms. Subclinical leaflet thrombosis is most often an incidental finding, characterized by a thin layer of thrombus covering the aortic side of one or more leaflets; it is also referred to as Hypo-Attenuating Leaflet Thickening (HALT) as described on multi-detector computed tomography (MDCT) imaging. This phenomenon may also affect leaflet motion and is then classified as Hypo-Attenuation affecting Motion (HAM). Even in case of HAM, the transvalvular pressure gradient remains within normal range and does not provoke heart failure symptoms. Whereas, clinical valve thrombosis requires treatment, the clinical impact and need for intervention in subclinical leaflet thrombosis is still uncertain. Oral anticoagulant therapy protects against and resolves both clinical valve thrombosis and subclinical leaflet thrombosis; however, large-scale randomized clinical trials studying different antithrombotic strategies after TAVR are still under way. This review article summarizes the currently available data within the field of transcatheter aortic valve/leaflet thrombosis and discusses the need for a patient tailored antithrombotic approach.

Thrombo-embolic prevention after transcatheter aortic valve implantation

Transcatheter aortic valve implantation (TAVI) has emerged as a valuable treatment alternative to surgical aortic valve replacement among patients with symptomatic aortic stenosis at increased surgical risk. The rapid technological evolution from early to current-generation TAVI systems with low-profile delivery catheters, bioprosthetic valves with proven midterm durability, and improved positioning and retrieval features have made important contributions to the widespread clinical use of this minimal invasive therapy. Although peri-procedural and long-term thrombotic and bleeding events after TAVI remain a relevant concern, the optimal antithrombotic strategy and duration to mitigate these risks remain unclear. This review provides an overview of recent insights in this field, and highlights current and future antithrombotic trials focusing on optimizing outcomes in patients undergoing TAVI.

Transcatheter aortic valve thrombosis: the relation between hypo-attenuated leaflet thickening, abnormal valve haemodynamics, and stroke

Aims

The presence of hypo-attenuated leaflet thickening (HALT) and/or reduced leaflet motion on multi-detector row computed tomography (MDCT) has been proposed as a possible marker for early transcatheter aortic valve thrombosis. However, its association with abnormal valve haemodynamics on echocardiography (another potential marker of thrombosis) and clinical outcomes (stroke) remains unclear. The present study evaluated the prevalence of HALT on MDCT and abnormal valve haemodynamics on echocardiography. In addition, the occurrence of ischemic stroke and/or transient ischemic attack (TIA) was assessed.

Methods and results

A total of 434 patients (mean age 80 ± 7 years, 51% male) who underwent transcatheter aortic valve replacement (TAVR) were evaluated. Transcatheter valve haemodynamics were assessed on echocardiography at discharge, 6 months, and thereafter yearly (up to 3 years post-TAVR). The presence of HALT and/or reduced leaflet motion was assessed on MDCT performed 35 days [interquartile range 19-210] after TAVR in 128 of these 434 patients. Possible TAVR valve thrombosis was defined by mean transvalvular gradient ≥20 mmHg and aortic valve area (AVA) ≤1.1cm2 on echocardiography or by the presence of HALT or reduced leaflet motion on MDCT. The occurrence of ischemic stroke/TIA at follow-up was recorded. HALT and/or reduced leaflet motion was present in 12.5% of 128 patients undergoing MDCT, and was associated with a slightly higher mean transvalvular gradient (12.4 ± 8.0 mmHg vs. 9.4 ± 4.3 mmHg; P = 0.026) and smaller AVA (1.49 ± 0.39 cm2 vs. 1.78 ± 0.45 cm2, P = 0.017). Only one patient with HALT on MDCT revealed abnormal valve haemodynamics on echocardiography. At 3-year follow-up, abnormal valve haemodynamics on echocardiography were observed in 3% of patients. HALT on MDCT and abnormal valve haemodynamics on echocardiography were not associated with increased risk of ischemic stroke/TIA.

Conclusion

On MDCT, 12.5% of patients showed HALT or reduced leaflet motion, whereas only one of these patients had abnormal valve haemodynamics on echocardiography. Neither HALT nor increased transvalvular gradient were associated with stroke/TIA.

Early Prosthetic Valve Dysfunction Due to Bioprosthetic Valve Thrombosis: The Role of Echocardiography

OBJECTIVES

The purpose of this study was to review the institutional practice of surveillance transthoracic echocardiography (TTE) for diagnosing early prosthetic valve dysfunction (PVD).

BACKGROUND

Bioprosthetic valve thrombosis (BPVT) is an important cause of PVD, and guidelines do not recommend routine TTE during the first 5 years after valve implantation.

METHODS

The authors performed a retrospective case-control study of all suspected (imaging diagnosis) or confirmed (histopathological diagnosis) cases of BPVT from January 1997 through December 2016. Patients were matched 1:2 (age, sex, prosthesis position) to patients whose prostheses were explanted because of structural failure (SF). PVD was defined as a 50% increase above baseline gradient at valve implantation and classified as early (≤5 years) or late (>5 years) after implantation.

RESULTS

There were 94 BPVT (51 suspected, 43 confirmed) and 188 SF cases; patient age 61 ± 9 years; men 61 (65%). The prosthesis positions were aortic 56%; mitral 26%; tricuspid 15%; and pulmonary 3%. Early PVD was more common in the BPVT versus SF group: 83 of 94 (88%) versus 20 of 188 (11%) (p < 0.001). Time from implantation to PVD was shorter for BPVT than SF: 26 months (interquartile range [IQR]: 12 to 43 months) versus 74 months (IQR: 48 to 102 months) (p < 0.001). At the initial PVD diagnosis, 81% of BPVT and 90% of SF patients were asymptomatic. However, BPVT patients had rapid symptomatic deterioration, requiring intervention sooner after PVD diagnosis: 6 months (IQR: 4 to 7 months) versus 51 months (IQR: 22 to 55 months) (p < 0.001).

CONCLUSIONS

Most patients with PVD due to BPVT were asymptomatic at initial diagnosis, which was made based on routine surveillance TTE, often performed before 5 years. BPVT, an acute disease process, requires timely diagnosis because patient conditions rapidly deteriorate. Further studies are needed to determine whether routine surveillance TTE should be considered for patients with bioprosthetic valves to identify pre-symptomatic features of BPVT in order to provide effective, appropriate therapy.

Aortic Valve Bioprostheses: Leaflet Immobility and Valve Thrombosis

Leaflet immobility and valve thrombosis have been reported with both transcatheter and surgical aortic valve bioprostheses. The relationships between these abnormalities and their incidence, time course, clinical significance, predisposing factors, optimal imaging modality, and current therapeutic options remain uncertain but are rapidly evolving. Four-dimensional computerized tomographic imaging has been determined to have the highest sensitivity in studies evaluating leaflet immobility and valve thrombosis. Echocardiography is also used during surveillance, but it appears to be less sensitive. The definitive diagnosis of valve thrombosis is based on a combination of diagnostic 4-dimensional computerized tomographic imaging findings, resolution of imaging abnormalities, and elevated transcatheter gradients with anticoagulation or surgical or pathological confirmation. Uncertainty about the incidence and clinical significance of the findings is the basis of 2 US Food and Drug Administration-approved studies comparing transcatheter and surgical aortic valve replacement with a subset undergoing surveillance 4-dimensional computerized tomographic imaging. Given the expansion of transcatheter aortic valve procedures, including potentially lower-risk patients, the resolution of these uncertainties is critical.

Course of early subclinical leaflet thrombosis after transcatheter aortic valve implantation with or without oral anticoagulation

BACKGROUND

After transcatheter aortic valve implantation, early leaflet thickening, presumably reflecting thrombus, has recently been described on computed tomography angiography (CTA) in ~10% of the patients. We sought to investigate the impact of the antithrombotic regimen on the course of leaflet thickening.

METHODS

The study comprised 51 patients with leaflet thickening. Based on the time period, patients without an established indication for anticoagulation were put on phenprocoumon plus clopidogrel for at least 3 months or on dual antiplatelet therapy with aspirin and clopidogrel. Follow-up CTAs were evaluated for leaflet restriction, assessed by four-point-grading score, and maximal thickness.

FINDINGS

The anticoagulation and the dual antiplatelet therapy group comprised 29 and 22 patients, respectively. After a median of 86 days, we obtained follow-up CTAs in 22 patients on anticoagulation and in 16 patients on dual antiplatelet therapy. Leaflet thickening progressed in 11 on dual antiplatelet therapy, but always regressed onanticoagulation. The course of leaflet restriction and maximal thickness was significantly different between the two groups (P < 0.001): in the dual antiplatelet therapy group, maximal thickness increased by a mean of 1.37 ± 1.67 mm (P = 0.005) and leaflet restriction score by a median 1[quartiles 0;2] (P = 0.013), whereas in the anticoagulation group, maximal thickness regressed by 2.57 ± 1.52 mm (P < 0.001) and leaflet restriction score decreased by 1[-4;0] (P = 0.001). After a median of 91 days after discontinuation of anticoagulation, CTA performed in ten patients revealed a significant recurrent increase in leaflet restriction score and maximal thickness (P = 0.023, P = 0.007). In the entire cohort, changes in leaflet restriction correlated significantly with changes in transvalvular pressure gradients (r = 0.511, P < 0.001).

INTERPRETATION

The course of leaflet restriction was fundamentally different depending on the presence or absence of anticoagulation, with consistent regression under phenprocoumon, but mostly progression under antiplatelet therapy alone. Changes in leaflet restriction were associated with changes in transvalvular pressure gradients.

Complementary role of cardiac CT in the assessment of aortic valve replacement dysfunction

Aortic valve replacement is the second most common cardiothoracic procedure in the UK. With an ageing population, there are an increasing number of patients with prosthetic valves that require follow-up. Imaging of prosthetic valves is challenging with conventional echocardiographic techniques making early detection of valve dysfunction or complications difficult. CT has recently emerged as a complementary approach offering excellent spatial resolution and the ability to identify a range of aortic valve replacement complications including structural valve dysfunction, thrombus development, pannus formation and prosthetic valve infective endocarditis. This review discusses each and how CT might be incorporated into a multimodal cardiovascular imaging pathway for the assessment of aortic valve replacements and in guiding clinical management.