Where is the common sense in aortic valve replacement? A review of hemodynamics and sizing of stented tissue valves

Functional performance of eight small surgical aortic valve bioprostheses: An in vitro study

OBJECTIVES

Selection of a surgical aortic valve bioprosthesis (SAV) model for treatment of aortic valve disease remains controversial. The aim of this study was to characterize the functional performance of eight SAV models in a standardized in vitro setting.

METHODS

The hydrodynamic performance of eight SAVs with labelled size 21 mm (Avalus™, Hancock® II, Mosaic® UltraTM, Perimount®, Perimount® Magna Ease, EpicTM Supra, Trifecta™ GT; Freestyle®) was investigated in a pulse duplicator. Transvalvular pressure gradients and effective orifice area (EOA) were recorded. The geometrical orifice area (GOA) and physical dimensions of the valves were determined, and new functional dimensions were introduced.

RESULTS

Mean pressure gradient (MPG) and EOA differed significantly between the analyzed SAVs. The Epic presented with the lowest EOA and highest MPG, while the Trifecta showed the highest EOA and the lowest MPG. We introduce a useful way to determine the minimal internal diameter and a new measure termed 'relative orifice area' to characterize a valve's performance.

CONCLUSIONS

SAVs showed significant differences in their hydrodynamic performance despite the same label size. This finding was related to the construction of the valves. We introduce a new measure that characterizes the functional performance of a valve model and size for treatment of an aortic annulus of a specific size. Our data emphasize that SAV selection should carefully be done using an individual patient approach and that future research is necessary to improve the current generation of SAVs.

Uniformity in bioprosthetic mitral valve sizing-When will we get there?

Much has changed since the introduction of surgical valve repair in the 1950s, from the introduction bioprosthetic valves to percutaneous approaches to valve repair. Yet, despite substantial advancements in bioprosthetic valve technology, there has been a lack of direct, independent comparison between bioprosthetic mitral valve devices, accompanied by a marked heterogeneity in approaches to the sizing and selection thereof. Wang et al. have hence endeavored to evaluate, head-to-head, the technical successes and biomechanical outcomes associated with three different bioprosthetic mitral valves (Epic; Abbott; Mosaic; Medtronic; Mitris Resilia; Edwards Lifesciences) in a porcine model, under standardized hemodynamic and anatomical conditions. With a robust experimental technique, they have made clear the heterogeneity in both sizing and biomechanical properties between bioprosthetic mitral valves, and have further emphasized the need for a uniform approach to the manufacturing and sizing of bioprosthetic valves.

The impact of patient-prosthesis mismatch on early and long-term survival after aortic replacement with the Edwards Perimount valve: A propensity score-matched analysis

BACKGROUND

To investigate the impact of severe patient-prosthesis mismatch (PPM) related to the Edwards Lifesciences Perimount (EP) bioprosthesis in the aortic position on early in-hospital outcomes and long-term survival.

METHODS

A total of 5964 consecutive patients underwent aortic valve replacement at the Bristol Heart Institute between 1998 and 2014, 2667 representing the cohort of this study received EP. PPM was defined severe as EOAi < 0.65 cm² /m² . To minimize bias, propensity score matching was conducted and two groups A and B (without and with severe PPM) of 320 patients with similar preoperative characteristics were matched. We assessed early in-hospital outcomes including CVA, re-exploration for bleeding, low cardiac output, wound infection, acute renal injury, length of hospital stay, and long-term survival for both groups in unmatched and matched populations.

RESULTS

In the unmatched analysis, 18.3% of patients had severe PPM. Severe PPM was not associated with increased in-hospital mortality (4.5% vs. 2.9%, respectively, p = .09) or any other early adverse outcomes except increased length of hospital stay (10.57 ± 8.2 vs. 11.7 ± 9.4, respectively, p = .01). Long-term survival differed significantly between groups at 2 and 8 years (91.8% vs. 91.4% and 60.5% vs. 55.7%, respectively, p = .02). Matched analysis showed no differences between the groups in early health outcomes and overall survival at 2 and 8 years was also similar (89.7% vs. 91% and 57.3% vs. 58%, group A vs. B, respectively p = .9).

CONCLUSION

Presence of PPM does not seem to affect early in-hospital outcomes or late survival when using EP in patients undergoing aortic valve replacement.

Early Hemodynamics after Aortic Valve Replacement

Background and objectives: The aims of this study were to investigate changes in the hemodynamics associated with different types of aortic prostheses and to evaluate patient-prosthesis mismatch (PPM) at rest and after exercise. Materials and Methods: We retrospectively analyzed 150 patients who presented with indications for aortic valve replacement (AVR) with/without concomitant surgery from March 2019 to January 2020. The study population included 90 (60%) men and 60 (40%) women (mean age, 67.33 ± 10.22 years; range, 37-88 years). Echocardiography data such as peak and mean transprosthetic pressure gradients (Gmax, Gmean), velocity (V), effective orifice area (EOA), and indexed EOA (iEOA) were derived at rest and after exercise at baseline and before discharge. The study patients performed the six-minute walk test (6MWT) on the 5th-7th postoperative day. Results: Stented tissue valves showed excellent performance at rest and after exercise in comparison with mechanical valves, which showed favorable hemodynamics at rest only. At the time of discharge, moderate PPM was observed in 7/74 patients (9.5%) at rest and 5/98 (3.3%) patients after exercise. None of the patients showed severe PPM. EOA and iEOA were not significantly different between the groups. However, the stented group showed more pronounced changes in EOA and iEOA after exercise, whereas the changes in the mechanical valve group did not reach significance. Conclusions: In the early postoperative period, mechanical valves and stented valves showed favorable resting hemodynamics. The PPM rate measured after exercise was lower than that at rest.

Determinants of effective orifice area in aortic valve replacement: anatomic and clinical factors

Background

Obtaining adequate effective orifice area (EOA) in surgical aortic valve replacement (SAVR) is important to minimize pressure gradients across the prosthetic aortic valve (AV) and improve clinical outcomes. However, the predictors of EOA are unclear.

Methods

From July 2011 to March 2016, patients undergoing SAVR who were preoperatively evaluated using a computed tomography (CT) on the aortic root were enrolled. Indexed EOA (iEOA) was used as an indicator of prosthetic AV opening area. The aortic root parameters investigated were the annular diameter (max and min), annular perimeter, annular area, and maximal dimensions of the proximal ascending aorta. These variables were evaluated as predictors of EOA, and an individual surgeon was incorporated in analysis for verifying surgeon dependent factors.

Results

Among the 710 patients included in this study [age: 64.9±10.8 years; females: n=285 (40.1%)], 370 (52.1%) were implanted with bio-prosthesis. Mean prosthetic iEOA was 1.1±0.3 cm²/m². Univariable linear regression analysis showed that all indexed aortic root parameters (maximal and minimal annular diameters, annular perimeter, annular area, and sinus dimensions) were significantly associated with iEOA (P<0.001). Multivariable analysis showed that indexed aortic annular area, indexed maximal diameter of the Valsalva sinus, female sex, and bio-prosthesis, supra-annular type prosthesis and surgeon were significant and independent determinants of iEOA (adjusted R²=0.513, P<0.001).

Conclusions

Aortic annular area and Valsalva sinus diameter are independent determinants for iEOA measured by preoperative CT; surgeon-dependent factors are also significant determinants in SAVR.

Computed Tomography Annular Dimensions: A Novel Method to Compare Prosthetic Valve Hemodynamics

BACKGROUND

The Cardiac Surgical Societies Valve Labeling Task Force consensus document acknowledged inconsistent sizing and labeling of prosthetic heart valves. This study compared the labeled size, internal diameter, and hemodynamics of different surgical and transcatheter valve types implanted into the same size annulus, measured by preprocedural computed tomography (CT).

METHODS

Patients were retrospectively sorted into 3 CT annular diameter size groups: small (less than 23 mm), medium (23 to less than 26 mm), and large (26 mm or greater). Surgical valves were sorted into 4 categories based on tissue and design: (stentless porcine, standard stented bovine, wraparound stented bovine, and stented porcine). Comparisons were made within the surgical types and with a transcatheter valve. Echocardiograms were independently assessed and CTs were centrally measured.

RESULTS

We analyzed 726 surgical and 923 transcatheter valve paired data sets. Among the various valve types implanted into the same size CT annulus, there were significant differences regarding size, internal diameter, and hemodynamics within all 3 size groups. Root enlargement procedures occurred in 1.2% with no differences across valve types or size groups. Transcatheter valve hemodynamics were similar to stentless valves and were significantly better than all stented valves. There was no difference in hemodynamics between the 2 bovine stented valve types, and stented porcine valves were inferior to all valve types.

CONCLUSIONS

This study documents that prosthetic heart valve sizing and labeling inconsistencies exist. Use of preoperative CT annular dimensions is the most accurate method to compare size, internal diameter, and hemodynamics of bioprosthetic aortic valves because it compares values among various valve types implanted into the same size annulus.

4D Flow MRI hemodynamic benchmarking of surgical bioprosthetic valves

PURPOSE

We exploited 4-dimensional flow magnetic resonance imaging (4D Flow), combined with a standardized in vitro setting, to establish a comprehensive benchmark for the systematic hemodynamic comparison of surgical aortic bioprosthetic valves (BPVs).

MATERIALS AND METHODS

4D Flow analysis was performed on two small sizes of three commercialized pericardial BPVs (Trifecta™ GT, Carpentier-Edwards PERIMOUNT Magna and Crown PRT®). Each BPV was tested over a clinically pertinent range of continuous flow rates within an in vitro MRI-compatible system, equipped with pressure transducers. In-house 4D Flow post-processing of the post-valvular velocity field included the quantification of BPV effective orifice area (EOA), transvalvular pressure gradients (TPG), kinetic energy and viscous energy dissipation.

RESULTS

The 4D Flow technique effectively captured the 3-dimensional flow pattern of each device. Trifecta exhibited the lowest range of velocity and kinetic energy, maximized EOA (p < 0.0001) and minimized TPGs (p ≤ 0.015) if compared with Magna and Crown, these reporting minor EOA difference s (p ≥ 0.042) and similar TPGs (p ≥ 0.25). 4D Flow TPGs estimations strongly correlated against ground-truth data from pressure transducers; viscous energy dissipation proved to be inversely proportional to the fluid jet penetration.

CONCLUSION

The proposed 4D Flow analysis pinpointed consistent hemodynamic differences among BPVs, highlighting the not negligible effect of device size on the fluidynamic outcomes. The efficacy of non-invasive 4D Flow MRI protocol could shed light on how standardize the comparison among devices in relation to their actual hemodynamic performances and improve current criteria for their selection.

Late clinical outcomes of aortic valve replacement with Carpentier-Edwards pericardial valves

Background

The present study aimed to compare the long-term clinical and hemodynamic outcomes of aortic valve replacement using Carpentier-Edwards Perimount (Perimount) or Perimount Magna (Magna) valves.

Methods

We enrolled 430 patients who underwent aortic valve replacements with Perimount (n=58) or Magna (n=372) valves [1998-2013]. Multivariable and inverse probability of treatment weight (IPTW) analyses were performed.

Results

Before IPTW analysis, the overall 8-year survival rate differed significantly between the groups [Perimount 90%±4% vs. Magna 76%±4%; P=0.02; hazard ratio (HR): 0.37 for the Perimount group; 95% confidence interval (CI): 0.17-0.83]. Multivariable analysis of the overall survival identified Perimount valve use as a protective factor (P=0.009; HR: 0.32; 95% CI: 0.14-0.75). Independent risk factors of overall survival were older age, male sex, higher preoperative left ventricular mass index, lower ejection fraction, lower aortic valve pressure gradient, and lower haemoglobin. After applying IPTW, overall survival was again found to be significantly longer in the Perimount group (P=0.04; HR: 0.43; 95% CI: 0.20-0.93). Event-free survival was also better in the Perimount group (P=0.006; HR: 0.38; 95% CI: 0.19-0.75). However, the Magna group had significantly lower aortic valve pressure gradients at one year and five years postoperative.

Conclusions

Although Magna use led to decreased aortic valve pressure gradients at follow-up, overall and event-free survival rates were significantly better with use of the Perimount valve. Additional and larger studies are needed to confirm these results.

Limitations in the Assessment of Prosthesis-Patient Mismatch

Background Prosthesis-patient mismatch (PPM) after aortic valve replacement (AVR) may affect survival but data are conflicting. It is assessed by relating effective orifice area (EOA) to body surface area (EOAi). EOA is patient-specific as the result of flow-velocity times area at the individual patient's outflow tract levels (LVOTA) divided by trans-prosthetic flow velocity. However, some studies use projected EOAs (i.e., valve size associated EOAs from other patient populations) to assess how PPM affects outcome.

Methods We analyzed 76 studies addressing hemodynamic outcome and/or mortality after bioprosthetic AVR.

Results In 48 studies, projected or measured EOA for calculation of EOAi and PPM assessment was used (of which 25 demonstrated an effect on survival). We identified 28 additional studies providing measured EOA values and the corresponding Bernoulli's pressure gradients after AVR. Despite EOA being a patient-specific parameter, 77% of studies assessing a PPM impact on survival used projected EOAs. The 28 studies are providing measured EOA values and the corresponding Bernoulli's pressure gradients in patients after AVR showed a highly significant, linear relationship between EOA and Bernoulli's gradient. Considering this relationship, it is surprising that relating EOA to body surface area (BSA) (EOAi) is standard but relating pressure gradients to BSA is not.

Conclusion We conclude that the majority of studies assessing PPM have used false assumptions because EOA is a patient-specific parameter and cannot be transferred to other patients. In addition, the use of EOAi to assess PPM may not be appropriate and could explain the inconsistent relation between PPM and survival in previous studies.

Virtual medicine: Utilization of the advanced cardiac imaging patient avatar for procedural planning and facilitation

Advances in imaging technology have led to a paradigm shift from planning of cardiovascular procedures and surgeries requiring the actual patient in a "brick and mortar" hospital to utilization of the digitalized patient in the virtual hospital. Cardiovascular computed tomographic angiography (CCTA) and cardiovascular magnetic resonance (CMR) digitalized 3-D patient representation of individual patient anatomy and physiology serves as an avatar allowing for virtual delineation of the most optimal approaches to cardiovascular procedures and surgeries prior to actual hospitalization. Pre-hospitalization reconstruction and analysis of anatomy and pathophysiology previously only accessible during the actual procedure could potentially limit the intrinsic risks related to time in the operating room, cardiac procedural laboratory and overall hospital environment. Although applications are specific to areas of cardiovascular specialty focus, there are unifying themes related to the utilization of technologies. The virtual patient avatar computer can also be used for procedural planning, computational modeling of anatomy, simulation of predicted therapeutic result, printing of 3-D models, and augmentation of real time procedural performance. Examples of the above techniques are at various stages of development for application to the spectrum of cardiovascular disease processes, including percutaneous, surgical and hybrid minimally invasive interventions. A multidisciplinary approach within medicine and engineering is necessary for creation of robust algorithms for maximal utilization of the virtual patient avatar in the digital medical center. Utilization of the virtual advanced cardiac imaging patient avatar will play an important role in the virtual health care system. Although there has been a rapid proliferation of early data, advanced imaging applications require further assessment and validation of accuracy, reproducibility, standardization, safety, efficacy, quality, cost effectiveness, and overall value to medical care.

Hydrodynamic and Geometric Behavior of Two Pericardial Prostheses Implanted in Small Aortic Roots

Hydrodynamic performance of stented bioprostheses is far below that of the native valve. One of the reasons is that the internal diameter of the prosthesis is usually smaller than that of the native valve. However, other valve characteristics are also important in generating the pressure drop. We aimed to assess, in an ex vivo pulsatile mock loop, the hydrodynamic behavior of two bioprostheses, Trifecta and Mitroflow, to ascertain which geometric terms are limiting factors in hydrodynamic performance. At stroke volumes between 30 and 60 ml, Trifecta showed lower pressure drop, energy dissipation and valve resistance, and greater effective orifice area. This trend was overturned at higher stroke volumes, with Mitroflow slightly outperforming Trifecta. The geometric determinants were consistent with these results. Trifecta achieved its maximum opening area already at the lowest stroke volumes, featuring a divergent shape at the systolic peak. Mitroflow showed a complex opening pattern, featuring a convergent shape at the systolic peak for lower stroke volumes, while reaching its maximum opening area at higher stroke volumes, with a divergent shape. The two bioprostheses, although similar in design, displayed different biomechanical behaviors. The internal diameter of each bioprosthesis did not show to be strictly correlated with its hydrodynamic characteristics.

Comparison of the Performance of a Sutureless Bioprosthesis With Two Pericardial Stented Valves on Small Annuli: An In Vitro Study

BACKGROUND

Aortic valve replacement has evolved recently with the development of the sutureless bioprosthesis. One such valve is the Perceval bioprosthesis, which is built by mounting leaflets of bovine pericardium to a thin stent; this approach has the potential to provide an excellent fluid dynamic performance. We undertook an in vitro study to compare the hydrodynamic performance of the sutureless bioprosthesis with two standard pericardial stented bioprostheses (Crown and Magna).

METHODS

Tests were conducted using a mock loop, testing on two sizes of the three prostheses. The prosthesis sizes were chosen to house the valves in porcine aortic roots with a native annulus diameter of 19 mm (n = 6) or 21 mm (n = 6). The stroke volume ranged from 25 mL to 105 mL at a simulated heart rate of 70 beats per minute.

RESULTS

Mean pressure drop and energy loss rose with increasing stroke volume in all of the valves tested (p < 0.001), with the sutureless valve showing the lowest values for both variables (p < 0.001). Effective orifice area values were stable across the stroke volume intervals and were larger in the sutureless valves (p < 0.001).

CONCLUSIONS

All of the valves tested provided good fluid dynamic performances. The sutureless bioprosthesis provided the best performance with the least hindrance to flow behavior. From the hydrodynamic perspective, the sutureless prosthesis may present an advance in the evolution of bioprostheses, ensuring low gradients and potential for low incidence of patient-prosthesis mismatch even in small annuli.

Challenges in valve-in-valve therapy

At present, the majority of surgical heart valves (SHVs) implanted are bioprosthetic valves. Over time however, these are prone to structural deterioration, which may manifest as valvular stenosis, regurgitation or a combination of the two. Re-operation is the current standard of care for these patients but this itself carries a significant risk of mortality and morbidity. As a natural extension of transcatheter aortic valve implantation (TAVI), now an evidence based solution for severe aortic stenosis in high-risk patients, valve-in-valve (VIV) therapy is evolving into an alternative option in selected patients with structural biological valvular deterioration in all four-valve positions. The first of these VIV procedures was performed in Germany in 2007, for failing aortic valve prosthesis and later, reported in other positions. As with any novel emerging therapy, there is a learning curve to the procedure and the operator must be aware of the potential challenges. In this review we describe some of these challenges with the aim of providing awareness as well as guidance on attaining a successful outcome.

Reliability, Agreement, and Presentation of a Reference Standard for Assessing Implanted Heart Valve Sizes by Multidetector-Row Computed Tomography

The implanted prosthetic heart valve (PHV) size is vital for the evaluation of suspected PHV dysfunction and in case of reoperation or valve-in-valve transcatheter approaches. The labeled size is not always known, and discrepancies exist between manufacturers' labeled sizes and true sizes. Reproducible methods for noninvasive PHV size assessment are lacking. We determined the reliability and agreement of PHV size measurements using multidetector-row computed tomography (MDCT) and provide reference values of MDCT measurements compared with manufacturer specifications. In vitro, 15 different PHV types in available sizes (total n = 63) were imaged. In vivo, available MDCT acquisitions of patients with PHVs were retrospectively gathered in 2 centers, and 230 patients with 249 PHVs were included. Inner valve area and area-derived diameter were measured in all PHVs. For mechanical PHVs, the inner diameter was also measured. Data were analyzed using the intraclass correlation coefficient and Bland-Altman plots and related to manufacturer specifications. Measurements could be obtained for all PHV types, except the Björk-Shiley (n = 7) because of severe valve-related artifacts hampering the image quality. Intrarater and interrater reliability was excellent for biological and mechanical PHVs (intraclass correlation coefficients ≥0.903). Agreement was good for all measurements with an overall maximal mean difference (95% confidence interval) of -2.61 mm(2) (-37.9 to 32.7), -0.1 mm (-1.1 to 1.0), and 0 mm (-0.4 to 0.3) for valve area, area-derived diameter, and inner diameter, respectively. MDCT reliably discriminated consecutive PHV sizes as labeled by the manufacturer because the absolute ranges for the measurements never overlapped. In conclusion, MDCT allows assessment of the implanted PHV size with excellent reliability and agreement and can discriminate between PHV sizes for contemporary prostheses. MDCT can be used to noninvasively identify the manufacturer-labeled PHV size.

Hemodynamic comparison between Trifecta and freestyle aortic valve during exercise in patients with small aortic root

BACKGROUND

Patients with a small aortic annulus, that is ≤ 23 mm, constitute a challenge for the surgeon, because they are at high risk of patient-prosthesis mismatch. Stentless valves provide better hemodynamic performance at rest and during exercise than stented valves, and are advocated in this group of patients. A new-generation stented valve, the Trifecta (St. Jude), has recently become available with improved hemodynamics. The aim of this study was to compare the hemodynamic performance of Freestyle (Medtronic) and Trifecta at rest and during exercise in patients with a small aortic annulus.

METHODS

From September 2012 to September 2014, 22 patients with a native aortic annulus ≤ 23 mm underwent ergometric stress testing one year after aortic valve replacement with either a Trifecta (12 patients) or a Freestyle (10 patients) bioprosthesis as part of a randomized study.

RESULTS

The mean gradient at rest was 6.0 ± 2.3 mmHg for Trifecta and 4.3 ± 3.5 for Freestyle (p = 0.213). The mean gradient at peak of exercise was 9.7 ± 3.4 mmHg for Trifecta and 7.4 ± 5 mmHg for Freestyle (p = 0.243). No significant differences were found between the two prostheses regarding other hemodynamic parameters: effective orifice area, velocity index, and performance indexes.

CONCLUSION

Both the stented Trifecta and stentless Freestyle prostheses provide excellent hemodynamic results during physical stress in patients with a small aortic annulus. Our study confirms that Trifecta implantation results in low gradients at rest and during exercise and that the performance of Trifecta is similar to that of a stentless valve.

Valve-in-valve procedure: importance of the anatomy of surgical bioprostheses

Transcatheter aortic valve implantation is an accepted and established alternative to surgical aortic valve replacement for patients with severe symptomatic aortic valve stenosis and multiple comorbidities that would make open surgery a high-risk option. It has also evolved as a suitable treatment option for degenerative surgical heart valve disease, with considerable experience in the aortic and mitral positions. To enable a successful procedure, avoiding malposition, valve embolization and coronary obstruction, clinicians should be familiar with the design, fluoroscopic appearances and implantation technique of the degenerated surgical bioprosthetic valve in situ, as well as its compatibility with currently available transcatheter valves.

Comparing aortic root replacements: porcine bioroots versus pericardial versus mechanical composite roots: hemodynamic and ventricular remodeling at greater than one-year follow-up

BACKGROUND

Stentless porcine bioroots and pericardial composite roots were developed as prostheses that avoid the anticoagulation necessary for mechanical composite roots. Data on the hemodynamics of all root replacements are lacking and questions remain regarding comparative performance.

METHODS

This study evaluated patients receiving a stentless porcine bioroot, a pericardial, or a mechanical composite root at a single institution from January 2000 to December 2008. All patients underwent preoperative, postoperative and greater than 1-year echocardiograms. All root replacements were performed for aortic insufficiency or aneurysm. Median follow-up was 3.3 years (1 to 8 years).

RESULTS

There were no significant differences in preoperative left ventricular ejection fraction, aortic valve peak gradient, mean gradient, left ventricular end diastolic diameter, and left ventricular end systolic diameter. Postoperative peak and mean gradients in mechanical composite roots were significantly higher than stentless porcine bioroots. At greater than 1 year, stentless porcine bioroots had significantly lower peak and mean gradients than both mechanical composite roots and pericardial composite roots. The end diastolic diameter was also significantly smaller in stentless porcine bioroots at greater than 1 year than mechanical composite roots.

CONCLUSIONS

All prostheses resulted in favorable hemodynamic and ventricular remodeling. Stentless porcine bioroots had the lowest gradients at greater than 1 year of all root replacements, with significantly better ventricular remodeling when compared with mechanical composite roots. Pericardial roots also had favorable hemodynamics and ventricular remodeling, suggesting that they are a viable alternative.