Invited Commentary

Abstract

Over the past decade, there has been intense research into the management of patients after aortic valve replacement (AVR). Historically, postoperative echocardiographic assessment was rarely routinely performed in the early term to midterm after surgical AVR (SAVR). With the advent of transcatheter AVR (TAVR), a more systematic postoperative assessment is performed, commonly including two transthoracic echocardiograms (TTEs) within 30 days of implantation. This has allowed physicians to concentrate on a more detailed postoperative assessment of the valve implant in terms of hemodynamics and leaflet mobility. Consequently, any abnormalities on TTE or clinical events, in particular thromboembolic stroke, would lead to more intense imaging tests (eg, transesophageal echocardiography or contrast-enhanced four-dimensional computed tomography [4DCT]). One key phenomenon that has been uncovered is subclinical leaflet thrombosis of both transcatheter and surgical bioprosthetic aortic valves. Although this was discovered incidentally after a CT scan in a patient suspected of a having neurologic event after TAVR, it opened our eyes to this interesting phenomenon [1Makkar R.R. Fontana G. Jilaihawi H. et al.Possible subclinical leaflet thrombosis in bioprosthetic aortic valves.N Engl J Med. 2015; 373: 2015-2024Crossref PubMed Scopus (728) Google Scholar]. Subsequently, the Assessment of Transcatheter and Surgical Aortic Bioprosthetic Valve Thrombosis and Its Treatment With Anticoagulation (RESOLVE) registry and the Subclinical Aortic Valve Bioprosthesis Thrombosis Assessed With 4D Computed Tomography (SAVORY) registry were established to collate data to evaluate the function of prosthetic aortic valves after SAVR or TAVR [1Makkar R.R. Fontana G. Jilaihawi H. et al.Possible subclinical leaflet thrombosis in bioprosthetic aortic valves.N Engl J Med. 2015; 373: 2015-2024Crossref PubMed Scopus (728) Google Scholar, 2Chakravarty T. Søndergaard L. Friedman J. et al.Subclinical leaflet thrombosis in surgical and transcatheter bioprosthetic aortic valves: an observational study.Lancet. 2017; 389: 2383-2392Abstract Full Text Full Text PDF PubMed Scopus (571) Google Scholar]. Although the rate of clinically relevant transcatheter leaflet thrombosis was reported to be less than 1% previously [3Latib A. Naganuma T. Abdel-Wahab M. et al.Treatment and clinical outcomes of transcatheter heart valve thrombosis.Circ Cardiovasc Interv. 2015; 8: e001779Crossref PubMed Scopus (221) Google Scholar, 4Trepels T. Martens S. Doss M. Fichtlscherer S. Schächinger V. Images in cardiovascular medicine. Thrombotic restenosis after minimally invasive implantation of aortic valve stent.Circulation. 2009; 120: e23-e24Crossref PubMed Scopus (42) Google Scholar], the RESOLVE and SAVORY registries and other reports have shown the incidence of subclinical leaflet thrombosis in TAVR to be between 4% and 14% [1Makkar R.R. Fontana G. Jilaihawi H. et al.Possible subclinical leaflet thrombosis in bioprosthetic aortic valves.N Engl J Med. 2015; 373: 2015-2024Crossref PubMed Scopus (728) Google Scholar, 2Chakravarty T. Søndergaard L. Friedman J. et al.Subclinical leaflet thrombosis in surgical and transcatheter bioprosthetic aortic valves: an observational study.Lancet. 2017; 389: 2383-2392Abstract Full Text Full Text PDF PubMed Scopus (571) Google Scholar, 3Latib A. Naganuma T. Abdel-Wahab M. et al.Treatment and clinical outcomes of transcatheter heart valve thrombosis.Circ Cardiovasc Interv. 2015; 8: e001779Crossref PubMed Scopus (221) Google Scholar] Importantly, leaflet thrombosis and decreased leaflet mobility are usually not apparent on TTE, and gradients across the valve are typically within the normal range. Therefore, transesophageal echocardiography and 4DCT are the only accurate imaging modalities to diagnose subclinical leaflet thrombosis. The treatment of subclinical leaflet thrombosis remains controversial. Although some investigators have advocated that the treatment of clinically significant leaflet thrombosis with warfarin or other novel oral anticoagulant agents is warranted [1Makkar R.R. Fontana G. Jilaihawi H. et al.Possible subclinical leaflet thrombosis in bioprosthetic aortic valves.N Engl J Med. 2015; 373: 2015-2024Crossref PubMed Scopus (728) Google Scholar, 2Chakravarty T. Søndergaard L. Friedman J. et al.Subclinical leaflet thrombosis in surgical and transcatheter bioprosthetic aortic valves: an observational study.Lancet. 2017; 389: 2383-2392Abstract Full Text Full Text PDF PubMed Scopus (571) Google Scholar, 3Latib A. Naganuma T. Abdel-Wahab M. et al.Treatment and clinical outcomes of transcatheter heart valve thrombosis.Circ Cardiovasc Interv. 2015; 8: e001779Crossref PubMed Scopus (221) Google Scholar, 4Trepels T. Martens S. Doss M. Fichtlscherer S. Schächinger V. Images in cardiovascular medicine. Thrombotic restenosis after minimally invasive implantation of aortic valve stent.Circulation. 2009; 120: e23-e24Crossref PubMed Scopus (42) Google Scholar], there is no clear evidence to suggest that anticoagulation is the correct treatment to decrease thromboembolic events in patients with subclinical leaflet thrombosis [5Yanagawa B. Mazine A. Bhatt D.L. et al.Subclinical bioprosthetic aortic valve thrombosis: clinical and translational implications.Curr Opin Cardiol. 2017; 32: 137-146Crossref PubMed Scopus (13) Google Scholar]. Furthermore, with the average age of a patient undergoing TAVR remaining in the 80s, routine anticoagulation may lead to untoward bleeding complications. In their eloquent study reported in this issue of The Annals of Thoracic Surgery, Basra and colleagues [6Basra S.S. Gopal A. Hebeler K.R. et al.Clinical leaflet thrombosis in transcatheter and surgical bioprosthetic aortic valves by four-dimensional computed tomography.Ann Thorac Surg. 2018; 106: 1716-1726Abstract Full Text Full Text PDF PubMed Scopus (20) Google Scholar] have taken a “for cause” subgroup of patients who had a clinical event after SAVR or TAVR and performed further interrogation of the bioprosthesis with 4DCT. Basra and colleagues [6Basra S.S. Gopal A. Hebeler K.R. et al.Clinical leaflet thrombosis in transcatheter and surgical bioprosthetic aortic valves by four-dimensional computed tomography.Ann Thorac Surg. 2018; 106: 1716-1726Abstract Full Text Full Text PDF PubMed Scopus (20) Google Scholar] noted that ∼31% patients who underwent TAVR and ∼33% of those who underwent SAVR were found to have leaflet thrombosis. Although these numbers seem high, it should be noted that this is a highly selective group of patients with a high suspicion for leaflet abnormalities. Of specific interest, and surprisingly, there was no difference between the TAVR and SAVR recipients, and in this group of patients with a high suspicion for leaflet abnormalities, ∼70% did not have leaflet thrombosis by 4DCT. In summary, leaflet thrombosis is a multifactorial process and is incompletely understood. This study highlights that we may be just at the tip of the iceberg in terms of leaflet thrombosis in patients undergoing AVR. As a medical community, we should refrain from changes in anticoagulation management that are based on anecdotal observations (especially in patients with subclinical leaflet thrombosis). We should await the multiple prospective clinical trials that are under way to assess this important phenomenon and for testing safety and effectiveness of different anticoagulation regimens after TAVR or SAVR. Clinical Leaflet Thrombosis in Transcatheter and Surgical Bioprosthetic Aortic Valves by Four-Dimensional Computed TomographyThe Annals of Thoracic SurgeryVol. 106Issue 6PreviewThe incidence of leaflet thrombosis after transcatheter aortic valve replacement (TAVR) with active surveillance by four-dimensional computed tomography (4DCT) ranges from 7% to 14%. The incidence of leaflet thrombosis when 4DCT is performed for clinical and echocardiographic indications is unknown. Full-Text PDF