Transcatheter aortic valve replacement failure: déjà vu ou jamais vu?

Predictive Model for Thrombus Formation After Transcatheter Valve Replacement

PURPOSE

Leaflet thrombosis is a significant adverse event after transcatheter aortic valve (TAV) replacement (TAVR). The purpose of our study was to present a semi-empirical, mathematical model that links patient-specific anatomic, valve, and flow parameters to predict likelihood of leaflet thrombosis.

METHODS

The two main energy sources of neo-sinus (NS) washout after TAVR include the jet flow downstream of the TAV and NS geometric change in volume due to the leaflets opening and closing. Both are highly dependent on patient anatomic and hemodynamic factors. As rotation of blood flow is prevalent in both the sinus of Valsalva and then the NS, we adopted the vorticity flux or circulation (Г) as a metric quantifying overall washout. Leaflet thrombus volumes were segmented based on hypo-attenuating leaflet thickening (HALT) in post-TAVR patient's gated computed tomography. Г was assessed using dimensional scaling as well as computational fluid dynamics (CFD) respectively and correlated to the thrombosis volumes using sensitivity and specificity analysis.

RESULTS

Г in the NS, that accounted for patient flow and anatomic conditions derived from scaling arguments significantly better predicted the occurrence of leaflet thrombus than CFD derived measures such as stasis volumes or wall shear stress. Given results from the six patient datasets considered herein, a threshold Г value of 28.0 yielded a sensitivity and specificity of 100% where patients with Gamma < 28 developed valve thrombosis. A 10% error in measurements of all variables can bring the sensitivity specificity down to 87%.

CONCLUSION

A predictive model relating likelihood of valve thrombosis using Г in the NS was developed with promising sensitivity and specificity. With further studies and improvements, this predictive technology may lead to alerting physicians on the risk for thrombus formation following TAVR.

Reoperation After Transcatheter Aortic Valve Replacement: An Analysis of the Society of Thoracic Surgeons Database

OBJECTIVES

This study sought to report the largest series of patients receiving a surgical reoperation after transcatheter aortic valve replacement (TAVR) using the Society of Thoracic Surgeons (STS) Adult Cardiac Surgery Database.

BACKGROUND

TAVR has become an effective means of treating aortic stenosis. As TAVR is used in progressively lower-risk cohorts, management of device failure will become increasingly important.

METHODS

The STS Adult Cardiac Surgery Database was queried for patients with a history of prior TAVR undergoing surgical aortic valve replacement from 2011 to 2015. Observed-to-expected (O/E) mortality ratios were determined to facilitate comparison across reoperative indications and timing from index TAVR procedure.

RESULTS

A total of 123 patients met inclusion criteria (median age 77 years) with an STS Predicted Risk of Mortality of 4%, 4% to 8%, and >8% in 17%, 24%, and 59%, respectively. Median time to reoperation was 2.5 (interquartile range: 0.7 to 13.0) months, and the operative mortality rate was 17.1%. Common indications for reoperation included early TAVR device failures such as paravalvular leak (15%), structural prosthetic deterioration (11%), failed repair (11%), sizing or position issues (11%), and prosthetic valve endocarditis (10%). All pre-operative risk categories were associated with an increased O/E mortality ratio (Predicted Risk of Mortality <4%: O/E 5.5; 4% to 8%: O/E 1.7; >8%: O/E 1.2).

CONCLUSIONS

SAVR following early failure of TAVR, while rare, is associated with worse-than-expected outcomes as compared with similar patients initially undergoing SAVR. Continued experience with this developing technology is needed to reduce the incidence of early TAVR failure and further define optimal treatment of failed TAVR prostheses.

In vitro hemodynamic assessment of a novel polymeric transcatheter aortic valve

Transcatheter aortic valve replacement (TAVR) is a life-saving alternative to surgical intervention. However, the identification of features associated with poor outcomes, including residual paravalvular leakage (PVL), leaflet calcification, and subclinical leaflet thrombosis, are cause to be concerned about valve durablilty (Mylotte and Piazza, 2015a, 2015b; Dasi et al., 2017; Makkar et al., 2015; Kheradvar et al., 2015a). The aim of this study is to optimize the potential of a hyaluronan (HA) enhanced polymeric transcatheter aortic valve (HA-TAV) that has promised to reduce blood damage causing-turbulent flow while maintaining durability. HA-enhanced linear low-density polyethylene (LLDPE) leaflets were sutured to novel cobalt chromium stents, size 26 mm balloon expandable stents. Hemodynamic performance was assessed in a left heart simulator under physiological pressure and flow conditions and compared to a 26 mm Medtronic Evolut and 26 mm Edwards SAPIEN 3. High-speed imaging and particle image velocimetry (PIV) were performed. The HA-TAV demonstrated an effective orifice area (EOA) within one standard deviation of the leading valve, SAPIEN 3.The regurgitant fraction (RF) of the HA-TAV (11.23 ± 0.55%) is decreased in comparison the Evolut (15.74 ± 0.73%) and slightly higher than the SAPIEN 3 (10.92 ± 0.11%), which is considered trace regurgitation according to valve standards. A decreased number of higher principal Reynolds shear stresses were shown for the HA-TAV at each cardiac phase. The HA-TAV is directly comparable and in some cases superior to the leading commercially available prosthetic heart valves in in-vitro hemodynamic testing.

An in vitro evaluation of turbulence after transcatheter aortic valve implantation

BACKGROUND

This study aimed at assessment of post-transcatheter aortic valve (TAV) replacement hemodynamics and turbulence when a same-size SAPIEN 3 (Edwards Lifesciences Corp, Irvine, Calif) and Medtronic Evolut (Minneapolis, Minn) were implanted in a rigid aortic root with physiological dimensions and in a representative root with calcific leaflets obtained from patient computed tomography scans.

METHODS

TAV hemodynamics were studied by placing a SAPIEN 3 26-mm and an Evolut 26-mm in rigid aortic roots and representative root with calcific leaflets under physiological conditions. Hemodynamics were assessed using high-fidelity particle image velocimetry and high-speed imaging. Transvalvular pressure gradients (PGs), pinwheeling indices, and Reynolds shear stress (RSS) were calculated.

RESULTS

(1) PGs obtained with the Evolut and the SAPIEN 3 were comparable among the different models (10.5 ± 0.15 mm Hg vs 7.76 ± 0.083 mm Hg in the rigid model along with 13.9 ± 0.19 mm Hg vs 5.0 ± 0.09 mm Hg in representative root with calcific leaflets obtained from patient computed tomography scans respectively); (2) more pinwheeling was found in the SAPIEN 3 than the Evolut (0.231 ± 0.057 vs 0.201 ± 0.05 in the representative root with calcific leaflets and 0.366 ± 0.067 vs 0.122 ± 0.045 in the rigid model); (3) higher rates of RSS were found in the Evolut (161.27 ± 3.45 vs 122.84 ± 1.76 Pa in representative root with calcific leaflets and 337.22 ± 7.05 vs 157.91 ± 1.80 Pa in rigid models). More lateral fluctuations were found in representative root with calcific leaflets.

CONCLUSIONS

(1) Comparable PGs were found among the TAVs in different models; (2) pinwheeling indices were found to be different between both TAVs; (3) turbulence patterns among both TAVs translated according to RSS were different. Rigid aortic models yield more conservative estimates of turbulence; (4) both TAVs exhibit peak maximal RSS that exceeds platelet activation 100 Pa threshold limit.

Transcatheter aortic valve implantation: where are we now?

Transcatheter aortic valve implantation (TAVI) was first used in clinical practice in 2002. Since 2002, there has been a rapid increase in TAVI activity in patients with symptomatic severe aortic stenosis. This has been supported by systematic randomized data comparing TAVI against the gold standard treatment for the last 50 years’ surgical aortic valve replacement. TAVI is now currently a recommended therapeutic intervention in the treatment of severe aortic stenosis patients who are deemed either high risk or inoperable. The indications for TAVI continue to expand. Within this review we will focus on the current guidelines for TAVI, the evidence for it, the complications of TAVI, postprocedure care, the technology available to clinicians now and finally the future perspectives for TAVI.

Clinical Bioprosthetic Heart Valve Thrombosis After Transcatheter Aortic Valve Replacement: Incidence, Characteristics, and Treatment Outcomes

OBJECTIVES

The aim of this study was to determine the incidence, characteristics, and treatment outcomes of patients diagnosed with clinical transcatheter heart valve thrombosis.

BACKGROUND

Limited data exists on clinical or manifest transcatheter heart valve thrombosis. Prior studies have focused on subclinical thrombosis.

METHODS

A retrospective analysis was conducted of prospectively collected data from a single-center registry that included 642 consecutive patients who underwent transcatheter aortic valve replacement between 2007 and 2015 (305 patients had self-expanding valves; balloon-expandable, n = 281; mechanically expanding, n = 56). Long-term oral anticoagulation (OAC) was indicated in 261 patients, while 377 patients received dual-antiplatelet therapy post-procedure. All patients underwent scheduled clinical and echocardiographic follow-up.

RESULTS

The overall incidence of clinical valve thrombosis was 2.8% (n = 18). No patient on OAC developed thrombosis. Of the detected thrombosis cases, 13 patients had balloon-expandable, 3 had self-expanding, and 2 had mechanically expanding valves. Thrombosis occurred significantly more often with balloon-expandable valves (odds ratio: 3.45; 95% confidence interval: 1.22 to 9.81; p = 0.01) and following valve-in-valve procedures (odds ratio: 5.93; 95% confidence interval: 2.01 to 17.51; p = 0.005). Median time to diagnosis of valve thrombosis was 181 days. The median N-terminal pro-brain natriuretic peptide level was 1,318 pg/ml (interquartile range: 606 to 1,676 pg/ml). The mean transvalvular gradient and valve area were 34 ± 14 mm Hg and 1.0 ± 0.46 cm², respectively. Computed tomography showed hypoattenuating areas with reduced leaflet motion. Initiation of OAC resulted in significant reduction of transvalvular gradient and clinical improvement. No deaths were related to valve thrombosis.

CONCLUSIONS

Clinical transcatheter heart valve thrombosis is more common than previously considered, characterized by imaging abnormalities and increased gradients and N-terminal pro-brain natriuretic peptide levels. It occurred more commonly after balloon-expandable transcatheter aortic valve replacement and valve-in-valve procedures. OAC appeared to be effective in the prevention and treatment of valve thrombosis. Randomized control trials are needed to define optimal antithrombotic therapy after transcatheter aortic valve replacement.

On the Mechanics of Transcatheter Aortic Valve Replacement

Transcatheter aortic valves (TAVs) represent the latest advances in prosthetic heart valve technology. TAVs are truly transformational as they bring the benefit of heart valve replacement to patients that would otherwise not be operated on. Nevertheless, like any new device technology, the high expectations are dampened with growing concerns arising from frequent complications that develop in patients, indicating that the technology is far from being mature. Some of the most common complications that plague current TAV devices include malpositioning, crimp-induced leaflet damage, paravalvular leak, thrombosis, conduction abnormalities and prosthesis-patient mismatch. In this article, we provide an in-depth review of the current state-of-the-art pertaining the mechanics of TAVs while highlighting various studies guiding clinicians, regulatory agencies, and next-generation device designers.

Incidence, Predictors, and Mid-Term Outcomes of Possible Leaflet Thrombosis After TAVR

OBJECTIVES

This study sought to clarify the incidence and predictors of hypoattenuated leaflet thickening (HALT) and mid-term outcomes after transcatheter aortic valve replacement.

BACKGROUND

HALT detected on multidetector computed tomography (MDCT) scanning raised concerns about possible subclinical leaflet thrombosis.

METHODS

We studied 70 of 100 consecutive patients from a single-center registry who underwent implantation with the Edwards SAPIEN-XT device. MDCT results, echocardiographic data, and laboratory findings obtained at the 6-month and 1-year follow-ups were analyzed.

RESULTS

Of 70 patients, MDCT scans revealed HALT in 1 patient (1.4%) at discharge, 7 (10.0%) at 6 months, and 10 (14.3%) at 1 year post-transcatheter aortic valve replacement cumulatively. The degree of leaflet immobility correlated with the HALT area on 4-dimensional MDCT (r = 0.68) on the basis of data from 10 patients. HALT was associated with male sex (70% vs. 25%; p = 0.008) and larger sinus of Valsalva (31.0 ± 2.0 mm vs. 28.6 ± 2.6 mm; p = 0.005). HALT was found in 3 of 49 patients with a 23-mm bioprosthesis and in 7 of 21 patients with a 26-mm bioprosthesis (6.1% vs. 33.3%; p = 0.006). D-dimer levels were significantly increased in the HALT group at the 6-month (2.3 μg/ml [interquartile range (IQR): 2.1 to 6.1 μg/ml] vs. 1.1 μg/ml [IQR: 0.8 to 2.2 μg/ml]; p = 0.002) and 1-year (2.7 μg/ml [IQR: 1.7 to 4.8 μg/ml] vs. 1.2 μg/ml [IQR: 0.9 to 2.1 μg/ml]; p = 0.006) follow-ups, despite no differences at discharge. The pressure gradient was decreased in the HALT group at the 1-year follow-up (8.3 ± 0.8 mm Hg vs. 11.1 ± 4.9 mm Hg; p = 0.005). After detecting HALT, additional anticoagulation therapy was not administered. Clinical outcomes, including all-cause mortality (0% vs. 1.7%; p = 1.00) and stroke (0% vs. 0%; p = 1.00), were similar between the groups.

CONCLUSIONS

HALT with reduced leaflet motion was not rare but usually subclinical. Valve hemodynamics and mid-term outcomes were uneventful even without additional anticoagulant therapy in our limited number of cases. Male sex, larger sinus and bioprosthesis size, and elevated D-dimer levels during follow-up were associated with this phenomenon.