Further steps in the TAVI revolution

Download the Issue @ a Glance podcast Subscribe to the EHJ Podcast In an ageing society, aortic stenosis becomes an increasingly important condition.1,2 Transcatheter aortic valve implantation (TAVI) has revolutionized the treatment of this elderly and often frail patient population, but the indication for this novel procedure is still under debate.3 Recently, the indication for TAVI was expanded based on the results of randomized controlled trials.4 Thus, the question ‘TAVI or no TAVI: identifying patients unlikely to benefit from transcatheter aortic valve implantation’ as discussed by Josep Rodés-Cabau and colleagues from the Heart & Lung Institute at Laval University in Quebec, Canada, becomes daily practice of Heart Teams. Newer device iterations are delivering lower peri- and early post-procedural complication rates in patients with aortic stenosis, who were otherwise deemed too high risk for conventional surgical valve replacement.5 Yet beyond the post-procedural period, a considerable portion of current TAVI recipients fail to derive a benefit from TAVI, because they die either shortly after implantation of the valve or due to lack of clinical and functional improvement. With increasing possibilities, considerable interest now lies in better identifying factors likely to predict futility post-TAVI. Implicit in this are the critical roles of frailty, disability, and a multimorbidity patient assessment. TAVI risk scores, and combining such scores along with frailty parameters and the presence of specific organ failure, may provide a more accurate and holistic assessment of potential TAVI-related futility. The transcatheter valve technology pipeline started as simple balloon valvuloplasty for the treatment of stenotic heart valves6 and has evolved since 2002 either to repair or to replace heart valves percutaneously with multiple devices.7 In another review ‘The transcatheter valve technology pipeline for treatment of adult valvular heart disease’, Hans R. Figulla and colleagues from the University of Jena in Germany discuss the currently available technology and its application and provide a glimpse into the near future.8 So far all guidelines recommend surgical back-up in centres performing TAVI procedures;9,10 however, such an approach has been challenged by certain centres. In the FAST TRACK clinical research paper entitled ‘Outcomes of transfemoral transcatheter aortic valve implantation at hospitals with and without on-site cardiac surgery department: insights from the prospective German aortic valve replacement quality assurance registry (AQUA) in 17 919 patients’, Holger Eggebrecht and colleagues from the Cardioangiological Center Bethanien in Frankfurt, Germany provide the first data on this hotly debated issue, i.e. whether performing transcatheter aortic valve implantation at hospitals with only a cardiology department but no cardiac surgery on-site might be safe in spite of the recommendations of current Guidelines.11 To that end, they analysed data from the prospective German Quality Assurance Registry on Aortic Valve Replacement involving 17 919 patients with a German Aortic Valve score 2.0 of 5.6 ± 5.8% and a logistic EuroSCORE I of 21.1 ± 15.4% who underwent transfemoral TAVI. Overall, 7.4% underwent TAVI at hospitals without on-site cardiac surgery. Patients in non-cardiac surgery hospitals were slightly older and had more co-morbidities. Predicted mortality risks also were higher in patients at non-cardiac surgery sites. Complications, including strokes and in-hospital mortality, were similar in both groups. Matched-pair analysis of 555 patients in each group with an identical German Aortic Valve score confirmed similar rates of intraprocedural complications, strokes, and in-hospital mortality. Thus, although patients undergoing TAVI at hospitals without an on-site cardiac surgery department were at higher risk, major complications and in-hospital mortality were not different, suggesting the feasibility and safety of Heart Team-based TAVI at non-cardiac surgery sites. These provocative findings will obviously need confirmation in future studies and are discussed critically in an Editorial by Alec Vahanian from the Hôpital Bichat in Paris, France.12 Based on randomized trials, transcatheter aortic valve replacement is now well established in the treatment of high- and intermediate-risk as well as inoperable patients with severe aortic stenosis. To date, there is a paucity of adjudicated, prospective data evaluating outcomes with transcatheter aortic valve replacement with newer generation devices and in lower risk patients. In a second FAST TRACK clinical research paper entitled ‘Early clinical and echocardiographic outcomes after SAPIEN 3 transcatheter aortic valve replacement in inoperable, high-risk, and intermediate-risk patients with aortic stenosis’, Susheel K. Kodali and colleagues from the Columbia University Medical Center in New York report early outcomes of a large, multicentre registry of 583 high surgical risk or inoperable and 1078 intermediate-risk patients undergoing transcatheter aortic valve replacement with the next-generation SAPIEN 3 transcatheter heart valve.13 All patients received transcatheter aortic valve replacement with the SAPIEN 3 system mainly via the transfemoral, i.e. 87%, or the transapical or transaortic routes, i.e. 13%. The rate of 30-day all-cause mortality was 2% in high-risk/inoperable patients and 1% in intermediate-risk patients, while cardiovascular mortality was 1.4% and 0.9%, respectively. In high-risk/inoperable patients, the 30-day rate of major/disabling stroke was as low as 0.9%, while major bleeding was 14%, major vascular complications 5%, and requirement for permanent pacemaker 13%. In intermediate-risk patients, the 30-day rate of major/disabling strokes was 1%, major bleeding 11%, major vascular complications 6%, and requirement for permanent pacemaker 10%. Mean overall Kansas City Cardiomyopathy Questionnaire score increased from 48 to 68 and from 55 to 74 in high-risk/inoperable patients and intermediate risk patients, respectively. Overall, paravalvular regurgitation at 30 days was none or trace in 56% of the patients, mild in 41%, moderate in 3%, and severe in only 0.1%. Mean gradients among patients with paired baseline and 30-day or discharge echocardiograms decreased from 46 mmHg at baseline to 11 mmHg at 30 days, while aortic valve area increased from 0.7 cm2 to 1.7 cm2. Thus, the SAPIEN 3 transcatheter heart valve system was associated with low rates of 30-day mortality and major or disabling strokes, as well as excellent echocardiographic outcomes including very low rates of moderate or severe paravalvular regurgitation and significant improvement in quality of life. Axial and sagittal oblique reconstructions of a contrast-enhanced retrospectively electrocardiogram-gated post-transcatheter aortic valve implantation computed tomography angiography of an 80 year-old female (A and B) revealing subtle early hypo-attenuated thickening of the acoronary leaflet of an SAPIEN 3 prosthesis. Due to the clinical circumstances, the patient was only continued on single-antiplatelet therapy with aspirin. After 3-month follow-up computed tomography angiography revealed progression with up to 5 mm thickening of the non-coronary and additionally the right coronary cusp with restricted leaflet motion (C and D, Supplementary material online, Video S1). The patient received a modified therapy with a combination of clopidogrel and phenprocoumon. Following further 3-month repeat computed tomography angiography showed almost complete disappearance of the hypo-attenuated thickening and resolution of leaflet rigidity (E and F, Supplementary material online, Video S2). (From Pache G, Schoechlin S, Blanke P, Dorfs S, Jander N, Arepalli CD, Gick M, Buettner H-J, Leipsic J, Langer M, Neumann F-J, Ruile P. Early hypo-attenuated leaflet thickening in balloon-expandable transcatheter aortic heart valves. See pages: 2263–2271). Short- and long-term valve function after transcatheter valve implantation is still being debated. Leaflet thrombosis14,15 and dysfunction16 have been recently described. In the third clinical research paper, entitled ‘Early hypo-attenuated leaflet thickening in balloon-expandable transcatheter aortic heart valves’, Gregor Pache et al. from the University Heart Centre in Freiburg-Bad Krozingen, Germany evaluated the frequency of early hypo-attenuated leaflet thickening of the SAPIEN 3 transcatheter aortic valve, also known as ‘S3’, in 249 patients (Figure 1).17 Of those, 156 consecutive patients underwent ECG-triggered dual-source computed tomography angiography a median of 5 days after implantation. The prosthesis was assessed for hypo-attenuated leaflet thickening. Apart from heparin, peri-interventional antithrombotic therapy consisted of aspirin alone in 29% or aspirin plus clopidogrel in 71% of the patients. Hypo-attenuated leaflet thickening was found in 10% of the patients. None of the baseline and procedural variables was associated with hypo-attenuated leaflet thickening, nor was there an association with antithrombotic regimens, either peri-interventionally or at the time of computed tomography. Also, hypo-attenuated leaflet thickening was not associated with clinical symptoms, but a small, albeit significant, difference of ∼3 mmHg in mean pressure gradient at the time of computed tomography angiography was noted. Full anticoagulation led to almost complete resolution of hypo-attenuated leaflet thickening in patients with follow-up computed tomography angiography. Pache et al. conclude that irrespective of the antiplatelet regimen, early hypo-attenuated leaflet thickening occurs in 1 out of 10 patients undergoing transcatheter aortic S3 implantation and is clinically unapparent and reversible by full anticoagulation. In a thought-provoking Editorial, Jeroen J. Bax from the Leiden University Medical Center in The Netherlands puts these findings into clinical context.18 In spite of all the successes of TAVI, aortic valve surgery remains an important and well-evaluated treatment option for patients with aortic stenosis. The fourth clinical research paper ‘Aortic valve surgery and survival in patients with moderate or severe aortic stenosis and left ventricular dysfunction’ by Zainab Samad and colleagues from Duke University in Durham, North Carolina determined the frequency of aortic valve surgery with or without coronary artery bypass grafting among patients with moderate/severe aortic stenosis and left ventricular systolic dysfunction, and its relationship to survival.19 The Duke Echocardiographic Database involving 132 804 patients was queried for patients with mean gradient ≥25 mmHg and/or peak velocity ≥3 m/s and left ventricular systolic dysfunction as reflected by a left ventricular ejection fraction ≤50%. A total of 1634 patients had moderate or severe aortic stenosis by mean gradient criteria. Overall, 26% of the patients with moderate aortic stenosis and 48% of the patients with severe aortic stenosis underwent aortic valve surgery within 5 years of the qualifying echo. A total of 53% of the patients died up to 5 years following index echo. Aortic valve surgery was associated with a higher 5-year survival amongst patien with moderate and severe aortic stenosis whether classified by aortic valve area or mean gradient criteria. Overall, aortic valve surgery with or without coronary artery bypass grafting, compared with medical therapy, was associated with significantly lower mortality and a hazard ratio of 0.49. Compared with coronary artery bypass grafting alone, coronary artery bypass grafting plus aortic valve surgery was associated with a markedly better survival and a hazard ratio of 0.18. The authors therefore conclude that in patients with moderate or severe aortic stenosis and left ventricular systolic dysfunction, mortality is substantial and, among those selected for surgery, aortic valve surgery with or without coronary artery bypass grafting is associated with higher survival. Research is required to understand factors contributing to current practice patterns and the possible utility of transcatheter approaches in this high-risk cohort. The editors hope that readers of this issue of the European Heart Journal will find it of interest to them.

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