**1. Introduction**

Aortic regurgitation (AR) is defined as retrograde blood flow across the aortic valve (AV) during diastole. A normal AV is tricuspid, whereas a bicuspid aortic valve could accelerate the degenerative process leading to aortic stenosis (AS) or AR. According to Framingham Heart study, AR was observed in 13% of men (n = 1326) and 8.5% of women (n = 1539) using echocardiography data [1].

AR may be acute or chronic. While acute severe AR (e.g., with type A aortic dissection) is a surgical emergency, chronic AR progresses gradually, requiring serial imaging and appropriate therapy when it becomes severe. There are several etiologies of AR. Diseases of aortic valve leaflets, aortic root, annulus, or ascending aorta may result in AR. AR is subdivided into four clinical stages (A to D) elaborated in **Table 1** [2–4]. Stage D signifies severe symptomatic AR, and surgical aortic valve replacement (SAVR) is a class I indication per 2020 American College of Cardiology (ACC)/American Heart Association (AHA) [3]. Asymptomatic patients


*AR = aortic regurgitation, AV = aortic valve, CW = continuous wave, EROA = effective regurgitant orifice area, LV = left ventricle, LVEF = left ventricle ejection fraction, LVOT = left ventricle outflow tract, PHT = pressure half time, RF = regurgitant fraction, RVol = regurgitant volume, VCW = vena contracta width.*

#### **Table 1.**

*Clinical stages of chronic aortic regurgitation.*

*Transcatheter Therapies for Aortic Regurgitation: Where Are We in 2023? DOI: http://dx.doi.org/10.5772/intechopen.112679*

with severe AR and left ventricular ejection function (LVEF) < 55% (stage C2) also qualify for SAVR if no other cause of left ventricle (LV) dysfunction is identified [3]. Symptomatic patients with severe AR have 10–20% annual mortality if left untreated. A study by Dujardin et al. demonstrated a mortality rate of 34 ± 5% at ten years in patients (n = 246) with moderate to severe AR [5]. They also had higher morbidity at ten years follow-up (47 ± 6% heart failure and 62 ± 4% AV surgery). A prospective study of valvular heart disease in Europe demonstrated that 7.8% of patients with severe AR qualifying for aortic valve replacement (AVR) had no intervention due to high peri-operative risk [6, 7]. Such patients may benefit from transcatheter aortic valve replacement (TAVR) after carefully assessing procedural safety and feasibility. In contrast to AS, TAVR is challenging in AR due to the dilation of the perivalvular apparatus and lack of annular/leaflet calcification, compromising the optimal anchorage of the bioprosthesis. The potential complications include improper valve seal, paravalvular leak (PVL), valve embolization, and malalignment or malposition of the bioprosthetic valve [8, 9]. This chapter discusses transcatheter therapies for chronic native valvular AR.
