Long-Term Clinical and Echocardiographic Follow-Up of the Freestyle Stentless Aortic Bioprosthesis

Interventional versus Surgical Treatment of Degenerated Freestyle Prosthesis

BACKGROUND

 Bioprosthetic stentless aortic valves may degenerate over time and will require replacement. This study aimed to evaluate early- and mid-term outcomes after isolated surgical redo aortic valve replacement (redo-SAVR) and transcatheter valve-in-valve implantation (TAVI-VIV) for degenerated stentless Freestyle bioprostheses.

METHODS

 We reviewed records of 56 patients at a single center. Overall, 37 patients (66.1%) received TAVI-VIV and 19 (33.9%) received redo-SAVR.

RESULTS

 Thirty-day survival was similar in both groups (100%). One-year survival was comparable between groups (97.3% in TAVI-VIV and 100% in redo-SAVR, p = 1.0). The difference in mid-term survival after adjusting for age and EuroScore II was not significant (p = 0.41). The incidence of pacemaker implantation after TAVI-VIV was higher than after redo-SAVR (19.4% vs. 0%, p = 0.08).

CONCLUSION

 The 30-day and 1-year survival rates after both procedures were outstanding, irrespective of baseline characteristics. Isolated redo-SAVR should be favored in young patients, as the pacemaker implantation rate is lower. TAVI-VIV for degenerated Freestyle prosthesis can be a method of choice in elderly patients and those with high operative risk.

The Longest Known Survival of a Patient With Bioprosthetic Aortic Valve Replacement: A 42-Year Follow-Up

Aortic valve replacement (AVR) is a frequently performed procedure for treating aortic valvulopathy. AVR involves replacing the damaged aortic valve with either a mechanical or a bioprosthetic valve. While many factors are involved when selecting between the two options, age and patient preference are the deciding factors at this point. Mechanical valves demonstrate long-standing durability that overlaps with the accompanied bleeding risk due to lifetime anticoagulant therapy, making them a more favorable choice for younger patients. Bioprosthetic valves are preferred for older patients as they show a reduced risk of thrombogenicity. However, bioprosthetic valves have a higher incidence of structural valve degeneration (SVD) than mechanical valves. Our case report focuses on a 76-year-old patient who had undergone an AVR with a bioprosthetic valve at the age of 33, which has still not demonstrated any valve deterioration. As the longest known case of bioprosthetic durability, this patient provides useful data for designing bioprosthetic valves more resistant to structural degeneration and thereby better suited to younger patients or those at higher risk of bleeding.

Structural abnormalities after aortic root replacement with stentless xenograft

OBJECTIVE

In complex and high-risk aortic root disease, the porcine Freestyle stentless bioprosthesis (Medtronic Inc, Minneapolis, Minn) is an important surgical treatment option. We aimed to determine prevalence and clinical effect of structural and functional abnormalities after full-root Freestyle implantation.

METHODS

Our cross-sectional 2-center study combined with clinical follow-up included 253 patients with full-root Freestyle bioprostheses implanted from 1999 to 2017. Patients underwent transthoracic echocardiography (TTE) and contrast-enhanced, electrocardiogram-gated 4-dimensional cardiac computed tomography (4DCT) at median age 70 (interquartile range, 62-75) years. After 4DCT, clinical follow-up continued throughout 2018. Median follow-up was 3.3 years before 4DCT and 1.4 years after.

RESULTS

We identified abnormalities in 46% of patients, including pseudoaneurysms (n = 32; 13%), moderate or severe coronary ostial stenosis (n = 54; 21%), and moderate-severe leaflet thickening or reduced leaflet motion (n = 51; 20%). TTE only identified 1 patient with pseudoaneurysm. After 4DCT, the unadjusted hazard ratio for surgical reintervention among patients with abnormal 4DCT was 4.2 (95% confidence interval, 1.2-15.3), in all, 10% required a reintervention. 4DCT abnormalities were associated with a statistically nonsignificant increased risk of death, stroke, or myocardial infarction (hazard ratio obtained using Cox proportional hazards regression analysis, 2.4; 95% confidence interval, 0.7-7.6). In all, 4.0% died, 3.6% had a myocardial infarction, and 2.0% had a stroke.

CONCLUSIONS

Structural and functional abnormalities of the aortic root are frequent after Freestyle implantation and TTE appears to be insufficient for follow-up. Abnormalities might be associated with increased risk of reintervention and potentially adverse clinical outcomes. Longer follow-up and larger study populations are needed to further clarify the clinical implications of abnormalities identified with 4DCT.

A systematic review on durability and structural valve deterioration in TAVR and surgical AVR

Mechanical valves and bioprosthetic heart valves are widely used for aortic valve replacement (AVR). Mechanical valves are associated with risk of bleeding because of oral anticoagulation, while the durability and structural valve deterioration (SVD) represent the main limitation of the bioprosthetic heart valves. The implantation of bioprosthetic heart valves is increasing precipitously due aging population, and the widespread use of transcatheter aortic valve replacement (TAVR). TAVR has become the standard treatment for intermediate or high surgical risk patients and a reasonable alternative to surgery for low risk patients with symptomatic severe aortic stenosis. Moreover, TAVR is increasingly being used for younger and lower-risk patients with longer life expectancy; therefore it is important to ensure the valve durability for long-term transcatheter aortic valves. Although the results of mid-term durability of the transcatheter heart valves are encouraging, their long-term durability remains largely unknown. This review summarises the definitions, mechanisms, risk factors and assessment of SVD; overviews available data on surgical bioprosthetic and transcatheter heart valves durability.

Two-year outcomes from the PARTNER 3 trial: where do we stand?

PURPOSE OF REVIEW

The PARTNER 3 trial was conducted to compare outcomes after transcatheter aortic valve replacement (TAVR) with a balloon-expandable valve and surgical aortic valve replacement (SAVR) in individuals at low surgical risk with aortic stenosis. Recently reported rates of death, stoke and valve thrombosis in the TAVR arm have raised concerns about the longevity of this intervention in low-risk individuals. It is incumbent on all members of the Heart Team to understand the potential consequences of these findings.

RECENT FINDINGS

TAVR was initially superior to SAVR at 1 year for a primary composite endpoint of death, stroke and rehospitalization. Results at 2 years now indicate noninferiority. Potential causative factors, comparisons with other transcatheter valves and implications for patients, providers and trainees are explored. Recommendations are additionally provided regarding TAVR and SAVR in individuals with aortic stenosis.

SUMMARY

Concerns regarding the longevity of TAVR in low-risk individuals notwithstanding, results from PARTNER 3 indicate that TAVR is at least noninferior to SAVR out to 2 years. Longer follow-up will be required to determine whether these newly founded concerns are justifiable.

Long-term survival after xenograft versus homograft aortic root replacement: Results from a prospective randomized trial

OBJECTIVE

The study objective was to investigate the long-term survival of patients undergoing xenograft versus homograft full root aortic valve replacement.

METHODS

A total of 166 patients requiring aortic valve surgery were randomized to undergo the Freestyle (Medtronic Inc, Minneapolis, Minn) bioprosthesis (N = 90) or a homograft (N = 76) full root aortic valve replacement between 1997 and 2005 in a single institution. Six patients randomly assigned to the homograft crossed over to the Freestyle bioprosthesis because of the unavailability of suitably sized homografts. All surgeons were required to adhere to the standard surgical technique for homograft root implantation previously described. Follow-up was 98.5% complete.

RESULTS

The mean age of the study population was 65 ± 8 years. Coronary artery bypass grafting was associated with root aortic valve replacement in 76 of 166 patients (46%, P = not significant between groups), and overall hospital mortality was 4.8% (8/166, P = not significant between groups). Median follow-up was 13.8 years (range, 0-21.8 years; 2033 patient-years). The Kaplan-Meier survival analysis showed that there was no significant difference in overall survival between the 2 arms at 5, 10, and 15 years. Twenty-year survival was 28.3% ± 5% for the Freestyle group versus 25.1% ± 5.7% for the homograft group (P = .90), which was comparable to the age- and sex-matched UK general population. The freedom from aortic valve reoperation at 20 years was comparable for the Freestyle group versus the homograft group (67.9% ± 8.8% vs 67.2% ± 10.3%, respectively; P = .74).

CONCLUSIONS

This is the first study to investigate the long-term survival of xenograft versus homograft full root aortic valve replacement from a prospective randomized trial. The observed 20-year overall survival and freedom from aortic valve reoperation serve as a benchmark for future studies on interventions for aortic valve disease in the elderly.

Midterm outcomes of subcoronary stentless porcine valve versus stented aortic valve replacement

INTRODUCTION

Stentless porcine xenografts are versatile bioprosthetic valves with the advantage of improved hemodynamics that mimic the function of the native aortic valve. However, these bioprostheses are challenging to implant in the subcoronary position.

METHODS

All consecutive patients who underwent a bioprosthetic aortic valve replacement (AVR) were included from our institutional database. Cox regression analysis was preformed to determine significant predictors for mid term mortality as well as all cause, cardiac, and heart failure readmission.

RESULTS

Patients in the subcoronary stentless group were older and more likely to be female and were likely to have a higher Society of Thoracic Surgery risk of mortality. Survival was superior in the stented AVR cohort at 30-days (96.4% vs 90.5%; P < .001), 1-year (90.5% vs 71.6%; P < .001), and 5-year (74.5% vs 56.9%; P < .001) follow up. Acute kidney injury (16.22% vs 5.22%; P < .001) and blood product transfusion (70.27% vs 44.0%; P < .001) were higher in the stentless group. Multivariable analysis revealed subcoronary stentless implantation as a significant independent risk factor for mortality (hazards ratio: 1.92 [1.35,2.72]; P < .001).

CONCLUSION

Stentless porcine xenograft implantation with the Freestyle bioprosthetic in the subcoronary position can be successfully performed in select patients, but its use is associated with increased perioperative morbidity and mortality affecting midterm outcomes. Individual patient selection and surgeon experience are important to ensure favorable outcomes.

Influence of Age on Longevity of a Stentless Aortic Valve

BACKGROUND

The longevity of a stentless valve in a younger population (20-60 years old) is unknown.

METHODS

From 1992 to 2015, 1947 patients underwent aortic valve/root replacement for aortic stenosis, insufficiency, root aneurysm, or aortic dissection with stentless bioprostheses (median size, 26 mm). At operation 105 patients were <40 years old, 528 were 40 to 59, 860 were 60 to 74, and 454 were ≥75 years. The data were obtained through chart review, administered surveys, and the National Death Index.

RESULTS

The 30-day mortality rate was 2.6%. During follow-up 807 patients (41%) died before reoperation, 993 (51%) were alive without reoperations because of deterioration, and 113 patients (5.8%) underwent reoperation for structural valve deterioration. After adjusting death and reoperation for non-structural valve deterioration causes as competing risks, the cumulative incidence of reoperation was significantly different between the younger groups (<40, 40-59) and the older groups (60-74, ≥75; P < .0001) but not inside the younger (<40 vs 40-59) or older (60-74 vs ≥75) group. The significant hazard ratio of reoperation for <40 versus ≥75 years of age was 12, <40 versus 60 to 74 was 4, 40 to 59 versus 60 to 74 was 3, and 40 to 59 versus ≥75 was 9 (P ≤ .01). The 10- and 15-year survival in the entire cohort was 53% and 29%, respectively.

CONCLUSIONS

The stentless aortic valve provides satisfactory durability as a conduit for aortic valve/root replacement for patients who prefer a bioprosthesis. However it should be judiciously considered for patients younger than 60 years because of an increased incidence of reoperation for structural valve deterioration.

Long-term results and durability of the CoreValve transcatheter aortic bioprosthesis: outcomes beyond five years

AIMS

The aim of this study was to determine the long-term outcomes of high-risk patients who underwent transcatheter aortic valve implantation (TAVI) with the third-generation CoreValve device, according to the 2017 EAPCI/ESC/EACTS definition of valve durability.

METHODS AND RESULTS

Between 2007 and 2013, 278 consecutive patients were enrolled in our prospective single-centre CoreValve registry (mean age 82±6 years, mean STS score 6.4±5.0%). The median follow-up of survivors was 6.8 years. The Cox proportional hazards model was used to identify independent predictors of HF rehospitalisation and all-cause mortality. Predictors of HF rehospitalisation were LVEF, MR and PVL at the last echocardiographic follow-up. The majority of patients were in NYHA Class I or II and showed mild/trivial paravalvular leak throughout follow-up. Mean pressure gradients remained stable over time. The overall crude cumulative incidences of structural valve deterioration and bioprosthetic valve failure were 3.6% and 2.5%, respectively.

CONCLUSIONS

Although overall mortality was high in this elderly patient cohort, the CoreValve bioprosthesis showed good durability at seven-year follow-up.

Long-term Transcatheter Aortic Valve Durability

Transcatheter aortic valve implantation (TAVI) has become the standard of care for high-risk and inoperable surgical patients and a valid alternative to surgery for low- and intermediate-risk patients with severe, symptomatic aortic stenosis. It is increasingly being used for younger, lower-risk patients, so it is important to ensure the durability for long-term transcatheter aortic valves. The lack of standard definitions of structural valve degeneration (SVD) had made comparison among studies on prosthetic valve durability problematic. The 2017 standardised definitions of SVD by the European Association of Percutaneous Cardiovascular Intervention), the European Society of Cardiology and the European Association for Cardio-Thoracic Surgery, and the 2018 definitions by the Valve In Valve International Data group, has generated an increased uniformity in evaluations. This article examines the potential mechanisms and rates of SVD of transcatheter bioprostheses and the role of redo TAVI as a treatment option.

Structural valve deterioration of bioprosthetic aortic valves: An underestimated complication

OBJECTIVES

Structural valve deterioration (SVD) remains a major bioprosthesis-related complication, as recently described for the Mitroflow valve (models LX and 12A) (LivaNova, London, United Kingdom). The real incidence of the SVD risk remains unclear, often due to methodologic pitfalls by systematically using the Kaplan-Meier estimator and/or the Cox model. In this report, we propose for the first time a precise statistical modeling of this issue.

METHODS

Five hundred sixty-one patients who underwent aortic valve replacement with the aortic Mitroflow valve between 2002 and 2007 were included. We used an illness-death model for interval-censored data. Median follow-up was 6.6 years; 103 cases of SVD were diagnosed.

RESULTS

The 4-year and 7-year SVD cumulative incidences after the first anniversary of surgery were 15.2% (95% confidence interval, 11.9-19.1) and 31.0% (95% confidence interval, 25.8-37.2), respectively. Female gender, dyslipidemia, chronic obstructive pulmonary disease, and severe patient-prosthesis mismatch were significant risk factors of SVD. The occurrence of SVD was associated with a 2-fold increase in the risk of death.

CONCLUSIONS

Appropriate statistical models should be used to avoid underestimating the SVD complication associated with worse long-term survival.

Long-term outcome of cryopreserved allograft for aortic valve replacement

OBJECTIVE

The most efficient surgical approach to severe aortic valve disease in the young adult is still debated: cryopreserved aortic allograft offers excellent hemodynamic and avoid anticoagulation, but long-term durability is influenced by structural valve deterioration (SVD). This study aimed to describe long-term results of aortic allografts and to identify factors influencing long-term durability.

METHODS

From January 1993 to August 2010, 210 patients underwent aortic allograft replacement via the free-hand subcoronary implantation technique (N = 55) or root replacement with coronary reimplantation (N = 155). Clinic and echocardiographic follow-up was updated to April 2016.

RESULTS

Overall mortality and cardiac mortality occurred in 80 (38.1%) and 64 (30.5%) patients, respectively. Reoperation was required in 69 cases (32.8%), whereas SVD required reoperation in 57 cases (27.1%). No early endocarditis occurred, whereas late endocarditis occurred in 4 patients. The free-hand technique seems to be associated with improved left ventricular remodeling compared with the root-replacement technique, and smaller allograft size represents a predictor of reoperation independently on the surgical technique used. In the overall population, there were 44 women of childbearing age, and 37 patients remained pregnant during the follow-up of the study. No differences were found in the clinical outcomes among women who had children and who did not.

CONCLUSIONS

Cryopreserved allograft is a valid option, especially in complex infective endocarditis and in women of childbearing age. A careful choice of allograft size and implantation technique can reduce the risk of SVD.

Biological aortic valve replacement: advantages and optimal indications of stentless compared to stented valve substitutes. A review

Controversy still surrounds the optimal biological valve substitute for aortic valve replacement. In light of the current literature, we review advantages and optimal indications of stentless compared to stented aortic bio-prostheses. Recent meta-analyses, prospective randomized controlled trials and retrospective studies comparing the most frequently used stentless and stented aortic bio-prostheses were analyzed. In the present review, the types and implantation techniques of the bio-prosthesis that are seldom taken into account by most studies and reviews were integrated in the interpretation of the relevant reports. For stentless aortic root bio-prostheses, full-root vs. sub-coronary implantation offered better early transvalvular gradients, effective orifice area and left ventricular mass regression as well as late freedom from structural valve deterioration in retrospective studies. Early mortality and morbidity did not differ between the stentless and stented aortic bio-prostheses. Early transvalvular gradients, effective orifice area and regression of left ventricular hypertrophy were significantly better for stentless, especially as full-root, compared to stented bio-prostheses. The long-term valve-related survival for stentless aortic root and Toronto SPV bio-prosthesis was as good as that for stented pericardial aortic bio-prostheses. For full-root configuration this survival advantage was statistically significant. There seems to be not one but different ideal biological valve substitutes for different subgroups of patients. In patients with small aortic root or exposed to prosthesis-patient mismatch full-root implantation of stentless bio-prostheses may better meet functional needs of individual patients. Longer follow-ups on newer generation of stented bio-prostheses are needed for comparison of their hemodynamic performance with stentless counterparts especially in full-root configuration.

Current indications for stentless aortic bioprostheses

The best aortic prostheses have been debated for decades. The introduction of stentless aortic bioprostheses was aimed at improving hemodynamics and potentially the durability of aortic bioprostheses. Despite the good short- and long-term outcomes after implantation of stentless aortic bioprostheses, their use remains limited owing to the technically demanding implantation techniques. Nevertheless, stentless aortic bioprostheses might be of special benefit in certain indications, where they could be a valuable addition to the surgical armamentarium.

Ascending Aortic Replacement and Sutureless Valve in a Failed Stentless Aortic Prosthesis: A Bailout Option

Aortic valve replacement with a Perceval sutureless bioprosthesis is a viable rescue option for a failed aortic stentless prosthesis. However, a dilated sinotubular junction and ascending aorta are reported as a contraindication for this technique. We describe an aortic sutureless valve implantation in a patient with a dilated ascending aorta and small aortic root after Dacron graft replacement of the ascending aorta in a failed aortic stentless bioprosthesis.

Perceval S Valve Solution for Degenerated Freestyle Root in the Presence of Chronic Aortic Dissection

Aortic root replacement with porcine xenograft is a valuable treatment option in acute aortic dissection, but conduits are often prone to degeneration. Reoperation is still associated with high operative mortality, and it usually requires root removal and repetition of the Bentall procedure, or a less radical option limited to valve replacement. We describe two cases of Freestyle root degeneration in patients with chronic aortic dissection, in whom we performed a valve-in-valve procedure with the Perceval S prosthesis (Sorin Group, Saluggia, Italy).

Stentless bioprostheses: a versatile and durable solution in extensive aortic valve endocarditis

OBJECTIVES

Infective endocarditis of the aortic valve with local aortic root destruction requires radical resection of infected tissues and subsequent reconstruction of periannular structures and the left ventricular outflow tract (LVOT). Homografts or stentless bioprostheses are recommended for use in this specific patient group. The Freestyle stentless bioprosthesis is a porcine aortic root prosthesis, which approaches the surgical versatility of the homograft, but has the advantage of ready availability and uniform quality. We assessed clinical and echocardiographic outcome following the use of this prosthesis in extensive aortic valve endocarditis.

METHODS

Between June 2000 and December 2014, 55 Freestyle prostheses were implanted for aortic valve endocarditis involving the root in 54 patients (74% male). The mean age at operation was 61 ± 13 years. The mean EuroSCORE II was 20.1 ± 13.5. Twenty-nine (54%) patients had prosthetic valve endocarditis. The median follow-up time after surgery was 3.5 years, ranging from 0 to 15 years.

RESULTS

Early and late mortality were 11% (6 patients) and 14% (7 patients), respectively. Estimated overall survival at 1 and 5 years was 83 and 70%, respectively. There was no survival difference between patients with native or prosthetic valve endocarditis. One patient underwent reoperation for recurrent endocarditis 2.3 years after the initial procedure. No other prosthesis failure occurred. At a median follow-up of 3.3 years, mean gradient over the prosthesis was 4.3 ± 2.3 mmHg. No patient had more than mild aortic regurgitation.

CONCLUSIONS

The Freestyle stentless bioprosthesis is a valuable option to reconstruct the LVOT after debridement in extensive aortic valve endocarditis. It is readily available with a versatility and clinical outcome comparable with that of homografts. Although early mortality remains considerable in this high-risk group of patients, late survival is good with low rates of recurrence of endocarditis, immediate local control and good haemodynamic performance on echocardiography.

Long Term Outcomes Following Freestyle Stentless Aortic Bioprosthesis Implantation: An Australian Experience

BACKGROUND

The Freestyle stentless bioprosthesis (FSB) has been demonstrated to be a durable prosthesis in the aortic position. We present data following Freestyle implantation for up to 10 years post-operatively and compare this with previously published results.

METHODS

A retrospective cohort analysis of 237 patients following FSB implantation occurred at five Australian hospitals. Follow-up data included clinical and echocardiographic outcomes.

RESULTS

The cohort was 81.4% male with age 63.2±13.0 years and was followed for a mean of 2.4±2.3 years (range 0-10.9 years, total 569 patient-years). The FSB was implanted as a full aortic root replacement in 87.8% patients. The 30-day all cause mortality was 4.2% (2.0% for elective surgery). Cumulative survival at one, five and 10 years was 91.7±1.9%, 82.8±3.8% and 56.5±10.5%, respectively. Freedom from re-intervention at one, five and 10 years was 99.5±0.5%, 91.6±3.7% and 72.3±10.5%, respectively. At latest echocardiographic review (mean 2.3±2.1 years post-operatively), 92.6% had trivial or no aortic regurgitation. Predictors of post-operative mortality included active endocarditis, acute aortic dissection and peripheral vascular disease.

CONCLUSIONS

We report acceptable short and long term outcomes following FSB implantation in a cohort of comparatively younger patients with thoracic aortic disease. The durability of this bioprosthesis in the younger population remains to be confirmed.

Echocardiographic Assessment of Heart Valve Prostheses

Patients submitted to valve replacement with mechanical or biological prosthesis, may present symptoms related either to valvular malfunction or ventricular dysfunction from other causes. Because a clinical examination is not sufficient to evaluate a prosthetic valve, several diagnostic methods have been proposed to assess the functional status of a prosthetic valve. This review provides an overview of echocardiographic and Doppler techniques useful in evaluation of prosthetic heart valves. Compared to native valves, echocardiographic evaluation of prosthetic valves is certainly more complex, both for the examination and the interpretation. Echocardiography also allows discriminating between intra- and/or peri-prosthetic regurgitation, present in the majority of mechanical valves. Transthoracic echocardiography (TTE) requires different angles of the probe with unconventional views. Transesophageal echocardiography (TEE) is the method of choice in presence of technical difficulties. Three-dimensional (3D)-TEE seems to be superior to 2D-TEE, especially in the assessment of paravalvular leak regurgitation (PVL) that it provides improved localization and analysis of the PVL size and shape.

The freestyle aortic bioprosthesis: a systematic review

BACKGROUND

The Medtronic Freestyle bioprosthesis (FSB) provides an alternative to other prostheses for both aortic valve and aortic root surgery. This paper is a systematic review of the post-operative outcomes in patients with aortic valve and/or aortic root disease following FSB implantation.

METHODS

Electronic databases were searched for primary analysis, prospective randomised studies comparing the FSB with an alternative aortic prosthesis were included. Additionally, case series that included data for at least 100 individual operated patients were used for secondary analysis.

RESULTS

Among three identified randomised studies, 199 FSB cases were compared with homografts, and stented and an alternative stentless bioprosthesis. The FSB showed comparable hospital mortality (4.5% vs. 5.3%) and eight-year actuarial survival (80±5.0% versus 77±6.0%) with the homograft (respectively) and comparable reduction in left ventricular mass index relative to other prosthesis types. Over 6000 individual patients were included in the selected 15 case series. Weighted mean operative mortality, neurological event rate and five-year actuarial survival was 5.2%, 5.5% and 77.8%, respectively.

CONCLUSION

The FSB performed comparably against alternative prostheses regarding in-hospital mortality, long-term survival and reduction in left ventricular mass index. Included case series demonstrated robust post-operative outcomes in both the short and long term.

Aortic regurgitation after transcatheter aortic valve implantation: mechanisms and implications

In recent years, transcatheter aortic valve implantation (TAVI) has become an established treatment option for selected high-risk patients with severe aortic stenosis (AS). Favorable results with regard to both hemodynamics and clinical outcome have been achieved with transcatheter valves. Aortic regurgitation (AR) remains a major concern after TAVI. Echocardiography is the imaging modality of choice to assess AR in these patients due to its wide accessibility and low cost. Mostly mild residual AR has been observed in up to 70% of patients. However, as even a mild degree of AR has been associated with a decreased survival up to two years after TAVI, accurate evaluation and classification of AR is important. AR in transcatheter valves can be divided into three types according to different pathophysiological mechanisms. Besides the well-known transvalvular and paravalvular forms of regurgitation, a third form termed supra-skirtal has recently been observed. A thorough understanding of AR in transcatheter valves may allow to improve device design and implantation techniques to overcome this complication. The aim of this review is to provide an overview of the three types of AR after TAVI focussing on the different pathophysiological mechanisms.

Structural valve deterioration after aortic valve replacement with Medtronic freestyle stentless porcine aortic root bioprostheses

The Medtronic freestyle aortic root bioprosthesis (Medtronic, Inc., Minneapolis, MN, USA) is a stentless valve with an effective orifice area that is larger than that observed on other bioprostheses. However, there have been sporadic reports of structural valve deterioration (SVD), such as aortic root wall rupture, leaflet tearing, and pseudoaneurysm formation. We report five cases of SVD of freestyle aortic root bioprostheses. doi: 10.1111/jocs.12235 (J Card Surg 2014;29:22-25)

Reoperation for failure of freestyle bioprosthesis using an Edwards intuity valve

We report the first case of a successful implantation of the new Edwards Intuity rapid-deployment bioprosthesis in a 50-year-old man with acute failure of a Freestyle Medtronic root with severe aortic regurgitation and massive calcification of the root and both coronary buttons.

Current status and future perspectives of prosthetic valve selection for aortic valve replacement

Aortic valve abnormality is the most frequent form of valvular heart disease. Notably, aortic stenosis in the elderly population has been increasingly common. Aortic valve replacement (AVR) using prosthetic valve has been still believed as a gold standard surgical intervention for various types of diseased aortic valve. The numerous reports and studies evaluating the clinical outcomes and durability of prosthesis were revealed, however, prosthesis selection for AVR is still debated. In twenty-first century, paradigm shift of prosthesis preference might be emerged from mechanical valves to bioprosthesis due to the development of the technology. Moreover, transcatheter aortic valve implantation accelerated among the worldwide trends. It could be developed having the potential to reduce the mortality and morbidity associated with high-risk traditional AVR. After the current guidelines for the management of patients with valvular heart disease, we should consider the valve choice in various patients' profile setting. This review summarizes the current status of prosthesis selection and future perspectives of ideal aortic valve intervention, including minimal invasive care.

Effect of electrical stimulus parameters on the development and propagation of action potentials in short excitable fibres

Intracellular action potentials (IAPs) produced by short fibres in response to their electrical stimulation were analysed. IAPs were calculated on the basis of the Hodgkin-Huxley (1952) model by the method described by Joyner et al. (1978). Principal differences were found in processes of activation of short (semilength L less than 5 lambda) and long fibres under near-threshold stimulation. The shorter the fibre, the lower was the threshold value (Ithr). Dependence of the latency on the stimulus strength (Ist) was substantially non-linear and was affected by the fibre length. Both fibre length and stimulus strength influenced the IAP amplitude, the instantaneous propagation velocity (IPV) and the site of the first origin of the IAP (and, consequently, excitability of the short fibre membrane). With L less than or equal to 2 lambda and Ithr less than or equal to Ist less than or equal to 1.1Ithr, IPV could reach either very high values (so that all the fibre membrane fired practically simultaneously) or even negative values. The latter corresponded to the first origin of the propagated IAP, not at the site of stimulation but at the fibre termination or at a midpoint. The characters of all the above dependencies were unchanged irrespective of the manner of approaching threshold (variation of stimulus duration or its strength). Reasons for differences in processes of activation of short and long fibres are discussed in terms of electrical load and latency. Applications of the results to explain an increased jitter, velocity recovery function and velocity-diameter relationship are also discussed.