Preface

This book presents some of the advances that have occurred in the diagnosis and management of aortic valve disease over the last 50 years for healthcare personnel involved in the care of infants, children, and adults with aortic valve abnormalities.

The book is divided into seven sections. Section 1 introduces the book. In the introductory chapter, I review the normal anatomy of the aortic valve apparatus, the prevalence of different types of aortic valve diseases and ascending aortic aneurysm, and topics not adequately dealt within the other chapters in the book, including clinical features, echocardiographic diagnosis, and aortic valve surgery other than valve replacement.

In Section 2 on the pathology of the aortic valve, Dr. Abdumadjidov Khamidulla Amanullaevich and Urakov Shukhrat Tukhtaevich address issues associated with acquired heart disease in Chapter 2. The author identifies these issues as an assortment of pathological abnormalities that develop during the life of a patient. Because there is already a high prevalence of rheumatic heart disease in the developing regions of the world, the added burden of aortic valve disease is substantial. The prevalence of aortic valve disease in the elderly in the author's region (Republic of Uzbekistan) is estimated to be greater than 10%. Aortic stenosis (AS) is more prevalent, with aortic insufficiency (AI) coming second. The chapter includes excellent illustrations of the surgical anatomy of the aortic valve, including surgical photographs and pathologic specimens. The chapter concludes that acquired aortic valve disease is of high scientific and practical importance in the region.

In Chapter 3, Dr. Freiholtz et al. review the relationship of aortic valve phenotypes to ascending aortic aneurysms (AAAs). They state that the bicuspid aortic valve (BAV) is a major risk factor for the development of AAA. There appear to be different mechanisms for aneurysm development in bicuspid vs. tricuspid aortic valves (TAVs). The authors assert that AAA associated with BAV is pathologically distinct from that associated with TAV. They go on to describe molecular mechanisms of AAA in both these groups; BAV aortopathy is associated with endothelial instability and endocardial-to-mesenchymal transition, presumably embryonic in origin, whereas TAV aortopathy manifests medial degeneration, inflammation, and fibrosis.

In Section 3 on the technique of transcatheter aortic valve replacement, Dr. Ali Yasar Kilinc and Mustafa Ucar, in Chapter 4, discusses the technique of transcatheter aortic valve replacement (TAVR) with a focus on current approaches. Since the description of TAVR by Cribier in 2002, it has been increasingly used to treat calcific AS in the elderly. The author classifies the types of available transcatheter aortic valves into selfexpandable valves and balloon-expandable valves. He then names and characterizes each of them as well as reviews details of the technique of the procedure.

In Section 4 on the management of AS, I discuss, in Chapter 5, transcatheter interventions in the management of congenital aortic valve stenosis. I review the procedure of balloon aortic valvuloplasty (BalAV) and its results. BalAV offers good relief of aortic valve obstruction and serves as a substitute for surgery. It is considered a favored option in the management of AS in all age groups, namely, fetuses, neonates, infants, children, adolescents, and young adults. However, BalAV in elderly patients with calcific AS offers only temporary relief of aortic valve obstruction. While there is conclusive data for the provision of pressure gradient relief both acutely and at follow-up as well as deferral of any surgery after BalAV, the development of AI at long-term follow-up is an important drawback of this procedure. Notwithstanding the issue of AI, BalAV is presently believed to be a therapeutic procedure option in the treatment of valvar AS in pediatric and young adult patients. Methodical follow-up to identify the reappearance of aortic obstruction and the development of substantial AI is suggested.

In Chapter 6, Dr. Shah et al. address catheter-based therapies in the management of patients with severe AS. They detail the indications and contraindications for aortic valve replacement and discuss pre-procedural work-up. They also present a detailed description of the available devices (both balloon-expandable and self-expanding valves) for TAVR. This is followed by a discussion of the techniques of the TAVR procedure, followed by a review of post-procedure management.

In Chapter 7, Dr. Navaratnarajah et al. describe valve-in-valve TAVR (ViV-TAVR) to address recurrence following a prior surgical aortic valve replacement (SAVR) or TAVR. Repeat SAVR or ViV-TAVR are the available options. The authors compare these options and conclude that ViV-TAVR shows better short-term mortality, but that both procedures have similar mortality rates at mid-term. ViV-TAVR is also associated with higher rates of patient–prosthesis mismatch, post-procedural AI, and elevated transvalvular gradients. Given the limitations of these meta-analysis studies, the authors recommend randomized control studies. They conclude that ViV-TAVR is preferred at most institutions around the world and that ViV-TAVR is a safe and effective treatment option to address failed bioprosthetic aortic valves, however, they suggest retaining the repeat SAVR strategy.

In Chapters 8 and 9, Di Pietro et al. and Jiménez-Rodríguez et al. and their associates review the risk of stroke during TAVR and state that prevention is better than cure. Strokes are linked with high mortality with an impact on cognitive function. Cerebral embolic protection devices (CEPDs) may help capture the embolic debris and their use appears to be safe and effective for decreasing the risk of stroke. The authors classify CEPDs as deflectors (TriGUARD, Embrella, Point-Guard, and ProtEmbo) and filters (Sentinel, Emboliner, and Emblok). They describe the use of some of these devices and conclude that use of CEPDs is a novel strategy for preventing strokes during TAVR and that they help decrease the frequency of disabling strokes.

In Chapter 10, Dr. Zotov et al. review the surgical treatment of aortic valve disease in patients who also have atrial fibrillation (AF). The authors state the incidence of AF is much higher (4% to 30%) in patients with severe AS than in the general population and that AF adversely affects long-term survival. The authors review the surgical and transcatheter procedures to treat AF that have been developed over the years. They present two options in the management of these patients, namely, a complete

MAZE-IV operation and a non-MAZE procedure (pulmonary vein isolation, boxlesion, and their variations). Then they describe the operative procedure in detail. They assert that performing ablation of the arrhythmogenic substrate during aortic valve surgery does not adversely affect in-hospital mortality and does not increase the length of hospital stay. Accordingly, it is recommended that these procedures should be performed in all patients diagnosed with AS and AF. The authors propose an original approach of combined treatment of AS and arrhythmia using the Perceval-S suture-less valve and the Gemini-S clamp ablator.

In Section 5 on the management of AI, Dr. Velagapudi et al. review transcatheter therapies for AI in Chapter 11. AI is classified into stages A through D according to its severity. The author states that stage D AI with severe symptoms is a Class I indication for SAVR. TAVR may be used on an off-label basis for patients who are at a prohibitive risk for SAVR. He then enumerates challenges for TAVR in patients with AI, namely, lack of calcification of valve leaflets and perivalvular apparatus dilatation, which may compromise optimal anchorage of the valve prosthesis with the consequent risk of valve embolization and perivalvular leak. Oversizing the valve by 10%–15% (but no more than 20%) may overcome some of these difficulties. Current data indicate satisfactory results for off-label use of Medtronic Evolut and Edwards Sapien 3. Results of clinical trials with specially designed JenaValve to address TAVR for native AI are awaited. The author suggests cautious selection of AI subjects for off-label use of TAVR until the results of randomized control trials become available.

In Section 6 on surgical therapy for BAV syndrome, Milewski et al., in Chapter 12, review current therapeutic strategies to address BAV syndrome. Patients with BAV exhibit a range of aortic valvar and ascending aortic and aortic root aneurysmal pathology. This varying pathology requires designing different surgical techniques to develop a tailored approach to BAV syndrome. The authors review embryologic and genetic bases for BAV syndrome with associated aortic aneurysms. They also describe genetic syndromes associated with BAV. Then, they discuss issues related to surveillance of BAV syndrome depending upon symptomatology and magnitude of pathology. Then they review evidence-based surgical therapeutic strategies including aortic valve repair, replacement of the aortic valve, and replacement of supra-coronary ascending aorta, Bentall procedure, and valve-sparing aortic root reimplantation. The authors conclude that BAV syndrome manifests aortic valvar disease (AS and AI) and ascending aortic and aortic root aneurysms. This varying spectrum of pathologies mandates the development of individualized approaches to manage these conditions.

Finally, in Section 7 on patient perspective, Dr. Hutchens, who had TAVR, describes his perspective as a patient in Chapter 13. He was in touch with several patients who either had TAVR or are being considered for TAVR. Most of these patients were concerned about the high cost and safety of the procedure, their longevity after TAVR, and the longevity of the replaced aortic valve. Dr. Hutchens points to improved quality of life after TAVR. He also presents his life-long story of his aortic valve problems. He concludes with the hope that his story of heart valve experience will be of comfort to future patients and physicians.

The last five decades have witnessed a great many advances in the diagnosis and management of aortic valve disease, which resulted in increased survival of neonates, infants, children, and adults with diseases of the aortic valve. This book discusses

some of these advances and is a useful resource on diagnostic and therapeutic methods for healthcare professionals in providing quality care to their patients with aortic valve and aortic root diseases.

> **P. Syamasundar Rao, MD, DCH, FAAP, FACC, FSCAI** Children's Heart Institute, Children's Memorial Hermann Hospital and McGovern Medical School, University of Texas Health Sciences Center at Houston, Houston, TX, USA

Section 1 Introduction
