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.