1. Introduction
Severe symptomatic aortic stenosis (AS) is associated with a poor prognosis when managed with medical therapy alone [1]. Until recently, severe symptomatic AS has been traditionally treated with surgical aortic valve replacement (SAVR) with better outcomes than medical therapy alone [2-4]. Trans-catheter aortic valve replacement (TAVR) is superior to best medical therapy alone in severe symptomatic AS patients who are deemed inoperable [5,6]. Indeed TAVR has revolutionised the treatment of patients with severe symptomatic AS, offering a less invasive alternative to surgery. TAVR is now a well-established alternative to SAVR for the management of patients with severe symptomatic AS who are at high or moderate surgical risk [7-12]. Recent evidence demonstrates similar efficacy with TAVR comparable to surgery in low surgical risk patients as well [13,14]. There’s also an ongoing trial for TAVR in severe asymptomatic AS patients, which if positive will increase the already growing population of patients eligible for TAVR [15]. This cumulative evidence has resulted in the exponential rise of TAVR procedures. In 2015 TAVR procedures were estimated to be around 300 000 per year worldwide by the year 2025 [16]. This estimate is likely to increase further with the emergence of recent TAVR data from randomised controlled trials.
Correct sizing of the TAVR device which is determined by aortic annulus size is imperative for procedural success. This is pivotal for avoiding paravalvular aortic regurgitation (PVAR) post TAVR, coronary obstruction and aortic root trauma. Under sizing in particular is associated with PVAR [17-19]. All grades of PVAR are associated with worse outcomes whether it is at least moderate PVAR, [20-22] or even mild PVAR [23]. Multi-slice computed tomography (MSCT) is now considered the gold standard for the measurement of the aortic annulus to determine TAVR device sizing [24-29]. Two dimensional (2D) and three-dimensional (3D) transesophageal echocardiography (TEE) has previously been shown to generally underestimate the annulus size and hence TEE is not as widely accepted as MSCT for the aortic annular sizing for TAVR device [30-34].
However in some patients, MSCT might not be feasible such as those with well documented anaphylaxis to iodinated contrast or those with chronic kidney disease (CKD). Moreover, TAVR is commonly considered in elderly patients who often have CKD and are at a higher risk of contrast induced nephropathy (CIN). In these instances where MSCT might not be ideal, 3D TEE is a reasonable imaging modality for aortic annulus sizing to determine TAVR device sizing, especially with recent improvements in 3D TEE technology that address previous pitfalls. The off-label use of newer commercially available software (Q-lab MVQ software version 8.1; Philips Medical Imaging, Andover, MA) normally designed to track the mitral annulus has been described in this setting for 3D TEE semi-automated aortic annulus sizing with good success [35-36].
The aim of our study was to determine the accuracy of aortic annulus sizing using (i) manual 3D TEE and (ii) more recent 3D semi-automated TEE annular detection software in patients undergoing TAVR procedures who had already undergone pre-planning MSCT in measuring annular measurements. In addition we sought to assess the reproducibility of these 3D TEE methods.