Cutting edge research on transcatheter aortic valve implantation: moving indications, complications, and current outcomes

For the podcast associated with this article, please visit https://academic.oup.com/eurheartj/pages/Podcasts. The management of valvular heart disease has seen an impressive change over the last decade. The development of transcatheter aortic valve implantation or TAVI has attracted a lot of interest and stimulated research not only in the further development of this novel technique, but also as regards1,2 the pre-interventional assessement and follow-up care and outcomes3–5 of such patients. This Focus Issue is therefore devoted to this topic, beginning with ‘The year in cardiology 2017: valvular heart disease’ by Lars Sondergaard and colleagues from the Rigshospitalet in Copenhagen, Denmark.6 The authors remind us that the new joint European Society of Cardiology and European Association of Cardiothoracic Surgeons guidelines on the management of valvular heart disease was published in 2017.7 Of note, these guidelines are presented in a new format, are more focused, and are linked to the upcoming ESC Textbook of Cardiovascular Medicine. The main changes concern the role of TAVI, indications for surgery, as well as medical therapy. The guidelines present a new concept of Heart Valve Centres with recommended requirements, including multidisciplinary teams with competencies in various interventions and diagnostic techniques for valvular heart disease, the availability of important collaborative services, standardized processes, and recording of performance data. Some of changes in the latest guidelines are highlighted in this article. Initially, TAVI was primarily considered in patients deemed unsuitable for surgery.8 Due to the impressive success of TAVI, patients at lower surgical risk have been increasingly considered.9 This raises the question of to what extent TAVI indications should be expanded, a topic that is addressed in a timely review entitled ‘Transcatheter aortic valve implantationin lower-risk patients:whatis the perspective?’ by Giuseppe Tarantini and colleagues from the Università degli Studi di Padova in Italy.10 Increased operator experience, technical advances in the new generation of TAVI valves, and excellent results after implantation have led to the expansion of indications for TAVI as an alternative to surgical aortic valve replacement in intermediate-risk subjects. It appears timely, therefore, to examine the role of TAVI in low-risk patients, currently the objective of on-going randomized trials. This review summarizes current knowledge on TAVI in low- to intermediate-risk patients, and discusses its potential advantages and pitfalls in this clinical setting. The impact of the number of procedures and increased experience with complications and today’s in-hospital mortality of patients undergoing TAVI is further analysed in the Fast Track entitled ‘Outcome after transvascular transcatheter aortic valve implantation in 2016’ by Helge Möllmann and colleagues from the St. Johannes Hospital in Dortmund, Germany.11 More than 15 000 TAVI procedures were performed in 2016 in Germany. Interestingly, post-procedural complications declined within the last years, including new pacemaker implantations and vascular complications. Thus, in 2016, the overall in-hospital mortality rate after TAVI averaged 2.6%, which is for the first time numerically below that of surgical aortic valve replacement at 2.9%. Importantly, in-hospital mortality was significantly lower after TAVI than after surgical valve replacement in the very high-, in the high-, and in the intermediate-risk groups, and equalled that of surgical aortic valve replacement in low-risk patients. Thus, these impressive results are likely to contribute to a redefinition of the standard of care of patients with aortic stenosis in the future. Life-threatening complications necessitating emergent cardiac surgery may occur during TAVI. In their manuscript entitled ‘Incidence and outcomes of emergent cardiac surgery during transfemoral transcatheter aortic valve implantation (TAVI):insightsfrom the European Registry on Emergent Cardiac Surgery during TAVI (EuRECS-TAVI)’, Holger Eggebrecht and colleagues from the Cardioangiological Center Bethanien in Frankfurt, Germany analysed the risks and outcomes of patients needing emergent cardiac surgery during or immediately after TAVI in a real-world multicentre registry involving 27 760 patients.12 Of these, 0.76% of patients required emergent cardiac surgery. The risk of emergent cardiac surgery declined from 2013 (1.07%) to 2014 (0.70%), but remained stable subsequently. Leading causes for emergent cardiac surgery were left ventricular perforation by the guidewire and annular rupture. Immediate mortality of transfemoral TAVI patients requiring emergent surgery was 35% (Figure 1). Overall in-hospital mortality was 46%, and was highest with annular rupture (62%). Independent predictors of in-hospital mortality following emergent surgery were age above 85 years, annular rupture, and immediate emergent surgery. One-year survival of the 114 patients surviving the in-hospital period was only 40%. These important findings are further discussed in an Editorial by Craig Smith from the College of Physicians and Surgeons of Columbia University in New York.13 Different types of complications necessitating emergent cardiac surgery and their temporal trends in the 2013–2016 period (from Eggebrecht H, Vaquerizo B, Moris C, Bossone E, Lämmer J, Czerny M, Zierer A, Schröfel H, Kim W-K, Walther T, Scholtz S, Rudolph T, Hengstenberg C, Kempfert J, Spaziano M, Lefevre T, Bleiziffer S, Schofer J, Mehilli J, Seiffert M, Naber C, Biancari F, Eckner D, Cornet C, Lhermusier T, Philippart R, Siljander A, Cerillo AG, Blackman D, Chieffo A, Kahlert P, Czerwinska-Jelonkiewicz K, Szymanski P, Landes U, Kornowski R, D’Onofrio A, Kaulfersch C, Søndergaard L, Mylotte D, Mehta RH, De Backer O, on Behalf of European Registry on Emergent Cardiac Surgery during TAVI (EuRECS-TAVI). Incidence and outcomes of emergent cardiac surgery during transfemoral transcatheter aortic valve implantation (TAVI): insights from the European Registry on Emergent Cardiac Surgery during TAVI (EuRECS-TAVI). See pages 676–684). There are limited data on coronary obstruction following TAVI inside failed aortic bioprostheses. In a research paper entitked ‘Incidence, predictors, and clinical outcomes of coronary obstruction following transcatheter aortic valve replacement for degenerative bioprosthetic surgical valves: insights from the VIVID Registry’, Danny Dvir and colleagues from St Paul’s Hospital in Vancouver, Canada aimed to determine the incidence, predictors, and clinical outcomes of coronary obstruction in TAVI procedures.14 A total of 1612 procedures from the Valve-in-Valve International Data Registry were evaluated. The virtual transcatheter valve to coronary ostium distance was determined. Clinically evident coronary obstruction was present in 2.3% of the patients. Coronary obstruction was more common in stented bioprostheses with externally mounted leaflets or stentless bioprostheses than in stented bioprostheses with internally mounted leaflets. Valve to coronary ostium distance was shorter in coronary obstruction patients (3.2 mm) than in controls (6.3 mm). Stentless or stented bioprosthesis with externally mounted leaflets had an odds ratio of 7.7 for coronary obstruction. Using computed tomography (CT) data, a shorter valve to coronary ostium distance predicted this complication with an optimal cut-off level of 4 mm. Coronary obstruction was associated with a high 30-day mortality of 53% compared with 4% in controls. Thus, coronary obstruction following valve-in-valve TAVI is a life-threatening complication that occurred more frequently in patients with prior stentless or stented bioprostheses with externally mounted leaflets and in those with a short valve to coronary ostium distance. The clinical implications of these findings are put into context in an Editorial by Bernard Iung from the Bichat Hospital in Paris, France.15 Myocardial fibrosis occurs in response to mechanical, inflammatory,16,17 and ischaemic injuries to the heart muscle and has an impact on outcomes.18,19 In a final manuscript entitled ‘Reappraising myocardial fibrosis in severe aortic stenosis:an invasive and non-invasive study in 133 patients’, Thomas Alexander Treibel and colleagues from the Heart Hospital Imaging Centre, University College London Hospitals in London, UK investigated myocardial fibrosis in 133 patients with severe aortic stenosis using invasive biopsy, and non-invasive cardiovascular magnetic resonance with late gadolinium enhancement and extracellular volume fraction quantification.20 Intra-operative left ventricular biopsies were obtained. Myocardial fibrosis occurred in three patterns: (i) thickened endocardium with a fibrotic layer; (ii) subendomyocardial microscopic scars; and (iii) diffuse interstitial fibrosis. The collagen volume fraction was higher than in controls and in endocardium-containing samples with a decreasing collagen volume fraction gradient from the subendocardium. Late gadolinium enhancement correlated with collagen volume fraction, but not extracellular volume fraction (Figure 2). However, both correlated with N-terminal pro-brain natriuretic peptide and high-sensitivity troponin T. A high extracellular volume fraction was also associated with worse left ventricular remodelling, left ventricular ejection fraction, and functional capacity. Combining high extracellular volume fraction and late gadolinium enhancement better identified patients with adverse left ventricular remodelling, blood biomarkers, and histological parameters, and worse functional capacity than each parameter alone. Thus, myocardial fibrosis in severe aortic stenosis is complex. A combined, multiparametric approach with extracellular volume fraction and late gadolinium enhancement allows best stratification according to the response of the myocardial collagen matrix, findings that are further discussed in an Editorial by Robert Manka and Alexander Gotschy from the University Hospital Zurich in Switzerland.21 Aortic stenosis, myocardial hypertrophy, and fibrosis by imaging and biopsy. Four exemplar patients showing continuous-wave Doppler (maximum velocities >4 m/s; Column 1), short axis cine stills demonstrating degrees of left ventricular hypertrophy (Cine; Column 2), matching late gadolinium enhancement images (LGE, Column 3), matching extracellular volume fraction (ECV, Column 4), myocardial biopsy stained with picrosirus red [collagen volume fraction (CVF), Column 5]. Patient A has minimal LVH, no LGE, an ECV of 28.4%, and minimal biopsy subendocardial fibrosis (CVF 4.6%). Patient B has concentric LVH, patchy non-infarct LGE, an ECV of 29.9%, and moderate biopsy fibrosis (CVF 19.3%). Patient C has concentric LVH, widespread non-infarct LGE, an ECV of 36.5%, and severe biopsy fibrosis (CVF 24.5%). Patient D has mild concentric LVH, subtle subendocardial LGE (white arrow), an ECV of 24.5%, thickened endocardium, and subendocardial scarring. Scale bars (Columns 2–4) equal 5 cm (from Treibel TA, López B, González A, Menacho K, Schofield RS, Ravassa S, Fontana M, White SK, DiSalvo C, Roberts N, Ashworth MT, Díez J, Moon JC. Reappraising myocardial fibrosis in severe aortic stenosis: an invasive and non-invasive study in 133 patients. See pages 699–709). The editors hope that readers of this issue of the European Heart Journal will find it of interest.

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