Early transcatheter valve prosthesis degeneration and future ramifications

Early Detection of Risk of Neo-Sinus Blood Stasis Post-Transcatheter Aortic Valve Replacement Using Personalized Hemodynamic Analysis

Background

Despite the demonstrated benefits of transcatheter aortic valve replacement (TAVR), subclinical leaflet thrombosis and hypoattenuated leaflet thickening are commonly seen as initial indications of decreased valve durability and augmented risk of transient ischemic attack.

Methods

We developed a multiscale patient-specific computational framework to quantify metrics of global circulatory function, metrics of global cardiac function, and local cardiac fluid dynamics of the aortic root and coronary arteries.

Results

Based on our findings, TAVR might be associated with a high risk of blood stagnation in the neo-sinus region due to the lack of sufficient blood flow washout during the diastole phase (e.g., maximum blood stasis volume increased by 13, 8, and 2.7 fold in the left coronary cusp, right coronary cusp, and noncoronary cusp, respectively [N = 26]). Moreover, in some patients, TAVR might not be associated with left ventricle load relief (e.g., left ventricle load reduced only by 1.2 % [N = 26]) and diastolic coronary flow improvement (e.g., maximum coronary flow reduced by 4.94%, 15.05%, and 23.59% in the left anterior descending, left circumflex coronary artery, and right coronary artery, respectively, [N = 26]).

Conclusions

The transvalvular pressure gradient amelioration after TAVR might not translate into adequate sinus blood washout, optimal coronary flow, and reduced cardiac stress. Noninvasive personalized computational modeling can facilitate the determination of the most effective revascularization strategy pre-TAVR and monitor leaflet thrombosis and coronary plaque progression post-TAVR.

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.

Cardiac surgery following transcatheter aortic valve replacement

OBJECTIVES

The objective of this study was to retrospectively analyse surgical outcomes of patients undergoing secondary cardiac surgery after initial transcatheter aortic valve replacement (TAVR).

METHODS

Between December 2012 and February 2020, a total of 41 consecutive patients underwent cardiac surgery after a TAVR procedure at our institution. Patients who underwent emergency operations due to periprocedural complications such as ventricular rupture and TAVR dislocation were excluded from this study (n = 12). Thus, 29 patients were included in the analysis. Data are presented as medians (25th-75th quartiles) or as absolute numbers (percentages).

RESULTS

The median age was 76 years (68-80); 58.6% were men. The median time to a secondary conventional procedure was 23 months (8-40), with 8 patients requiring surgical intervention within the first year post TAVR. The indications for secondary conventional procedures were prosthesis endocarditis (n = 15), prosthesis degeneration or dysfunction (n = 7) and progression of valvular, aortic or coronary artery disease (n = 7). Surgical redo aortic valve replacement was performed in 24 patients (82.8%). No complications involving the aortic root or the aortomitral continuity were observed. The operative mortality was 10.3%. Extracorporeal life support was required in 3 patients (10.3%) for a median duration of 3 days (3-3 days). No adverse cerebrovascular events were observed postoperatively. Postoperatively, 4 patients (13.8%) required a pacemaker and 7 patients (24.1%) required renal replacement therapy. Overall survival at 1 year was 83.0%.

CONCLUSIONS

Conventional cardiac surgical procedures following TAVR are feasible with reasonable results and a low complication rate.

Effect of stent crimping on calcification of transcatheter aortic valves

OBJECTIVES

Although many challenges related to the acute implantation of transcatheter aortic valves have been resolved, durability and early degeneration are currently the main concerns. Recent reports indicate the potential for early valve degeneration and calcification. However, only little is known about the underlying mechanisms behind the early degeneration of these valves. The goal of this study was to test whether stent crimping increases the risk for early calcification.

METHODS

Stented valves that were crimped at 18-Fr and 14-Fr catheter and uncrimped controls were exposed to a standard calcifying solution for 50 million cycles in an accelerated wear test system. Subsequently, the leaflets of the valves were imaged by microcomputed tomography (micro-CT) followed by histochemical staining and microscopic analyses to quantify calcification and other changes in the leaflets' characteristics.

RESULTS

Heavily calcified regions were found over the stent-crimped leaflets compared to uncrimped controls, particularly around the stent's struts. Micro-CT studies measured the total volume of calcification in the uncrimped valves as 77.31 ± 1.63 mm3 vs 95.32 ± 5.20 mm3 in 18-Fr and 110.01 ± 8.33 mm3 in 14-Fr stent-crimped valves, respectively. These results were congruent with the increase in leaflet thickness measured by CT scans (0.44 ± 0.07 mm in uncrimped valves vs 0.69 ± 0.15 mm and 0.75 ± 0.09 mm in 18-Fr and 14-Fr stent-crimped valves, respectively). Histological studies confirmed the micro-CT results, denoting that the percentage of calcification in uncrimped leaflets at the valve's posts was 5.34 ± 3.97 compared to 19.97 ± 6.18 and 27.64 ± 13.17 in the 18-Fr and 14-Fr stent-crimped leaflets, respectively.

CONCLUSIONS

This study concludes that stent-crimping damage is associated with a higher level of passive leaflet calcification, which may contribute to early valve degeneration.

TAVI-thick on technology but thin on evidence

Transcatheter aortic valve implantation (TAVI) has emerged as one of the most popularly deployed interventional innovations of recent times. After addressing the inoperable and high-risk patients, it is application is being extended to intermediate and low-risk category. There is some disquiet about the strength of evidence on which the clinical application is based. Durability and pacemaker requirement are also areas of concern. This review highlights the areas of concern on these aspects. There is also a need to address these deficiencies in future trials and also bring updated database reports in the public domain.

TAVR Vs. SAVR in Intermediate-Risk Patients: What Influences Our Choice of Therapy

PURPOSE OF REVIEW

To determine what influences patients and physicians to choose between transcatheter aortic valve replacement (TAVR) or surgical aortic valve replacement (SAVR) in intermediate-surgical-risk patients with severe, symptomatic aortic stenosis.

RECENT FINDINGS

Advances in transcatheter valve technology, techniques, and trials demonstrating non-inferiority compared to surgical aortic valve replacement (SAVR) have led to expanded eligibility of transcatheter aortic valve replacement (TAVR) to both intermediate-risk patients in clinical practice and low-risk patients in pivotal trials. Since lower-risk individuals tend to be younger and good operative candidates, concerns of valve durability, procedure-related morbidity, and patient survivability require careful consideration. Results from the PARTNER II intermediate risk trials and SURTAVI trials have given us insight into the benefits and potential risks of both treatment modalities. In this article, we review the brief yet remarkable history of TAVR and discuss its role in the treatment of intermediate-surgical-risk patients.

Transcatheter aortic valve replacement in intermediate and low risk patients-clinical evidence

The encouraging results of the PARTNER 2 (Placement of AoRtic TraNscathetER Valves 2) trial led to the approval of transcatheter aortic valve replacement (TAVR) in intermediate-surgical-risk patients. Recently, the SURTAVI (SUrgical Replacement and Transcatheter Aortic Valve Implantation) investigators demonstrated the feasibility of TAVR with self-expanding valves in intermediate-risk patients. The focus has now shifted to clinical trials comparing TAVR to surgery in low-surgical-risk populations with a goal to expand TAVR to all-risk patients. However, low-surgical-risk patients continue to be acceptable candidates for surgical aortic valve replacement, with proven outcomes over many decades. Although new data has emerged showing feasibility of TAVR in young patients with bicuspid valves, with newer generation TAVR valves there will be minimal tolerance for adverse outcomes in the low risk category. To expand the reach of TAVR into low-surgical-risk patients, important questions about valve durability, leaflet thrombosis, higher rates of paravalvular leak and permanent pacemakers (PPM) will need to be addressed. However, as TAVR technology continues to evolve, it seems to be just a matter of time before TAVR establishes itself as a modality for aortic valve replacement regardless of surgical risk.

Review of Major Registries and Clinical Trials of Late Outcomes After Transcatheter Aortic Valve Replacement

The results of the Placement of AoRtic TraNscathetER Valves (PARTNER) 2 trial established the feasibility of transcatheter aortic valve replacement (TAVR) for intermediate surgical risk patients. The expansion of TAVR into the low-risk patient population will largely depend on its durability outcomes due to the high life expectancy in low-risk patients. Long-term follow-up results from low-risk clinical trials will take several years to be reported. Given this, we performed a systematic review of current long-term data to provide further insights into TAVR durability and long-term patient survival. We searched MEDLINE, Embase, Google Scholar, BIOSIS, and major conference abstracts for TAVR studies with follow-up of at least 4 years. Abstracts were retrieved and independently reviewed for eligibility. Final studies were selected irrespective of the type of TAVR valve, route of vascular access, or surgical risk profile. A total of 12 studies met the inclusion criteria. We reviewed data from these studies with emphasis on long-term survival and echocardiographic findings.