Introduction
In this issue of the Journal, Jasinski and colleagues prospectively
evaluate the single-centre outcomes of aortic annular stabilisation
using either external annuloplasty (EA) or subcommisural annuloplasty
(SCA) in bicuspid aortic valve (BAV) repair for aortic regurgitation
(AR) alongside ascending aortic replacement1. 25
patients with type I BAV configuration that were assigned to each group
underwent post-operative echocardiographic follow-up at 1 and 3 years,
and morbidity and mortality outcomes were determined at 8 years. EA and
SCA had comparable influences on echocardiographic indices of
post-operative left ventricular reverse remodelling, and both techniques
achieved similar significant reductions in aortic regurgitant jet width.
However, a significant reduction in the aortic annulus diameter was only
observed with the EA approach (27.5 ± 3 mm pre-operatively vs 24.1 ± 2.6
mm post-operatively, p = 0.002), and not with SCA (27.7 ± 4.7mm
pre-operatively vs 25.8 ± 3.8mm post-operatively, p = 0.7). Furthermore,
EA resulted in lower mean trans-valvular gradients compared to SCA (7 ±
4.0 mmHg vs 12.6 ± 4.6 mmHg, p = 0.018). Whilst valvular re-operation
was not indicated in any patient during the 8-year follow-up period,
progression to grade ≥2 AR or trans-valvular gradient >20
mmHg was identified in 1/25 (4%) patients and 6/25 (24%) patients in
the EA and SCA groups, respectively. The authors propose that EA is
superior to SCA in terms of post-operative annular reduction,
trans-valvular flow gradient and freedom from AR.
BAV represents the commonest congenital cardiac abnormality affecting
1-2% of the general population2 and its association
with valvular dysfunction, infective endocarditis, and aortopathy with
proximal aortic aneurysm formation and a propensity for acute aortic
events renders it a considerable health burden3,4.
Furthermore, the incidence of AR in BAVs is greater than that in
tri-leaflet aortic valves. Although valve replacement is traditionally
considered the gold standard surgical management for severe AR,
prosthesis-related complications including thromboembolism, haemorrhage
and endocarditis, coupled with the cumulative risks of structural valve
deterioration and attendant re-operative surgery remain a major concern,
especially for younger patients. Survival after aortic valve replacement
has been reported at 50% at 10 years5.
Strategies for isolated aortic valve repair followed the introduction of
valve-sparing aortic root replacement procedures, first proposed as a
remodelling technique in 1983 by Yacoub6 and
subsequently with aortic valve reimplantation in 1992 by
David7 which were conceived to treat aortic root
dilatation without valve intervention. The aortic root complex,
comprising the aortic annulus, aortic valve leaflets, the sinuses of
Valsalva, and the sino-tubular junction, functions as a single
integrated unit, and AR may originate from the disruption of any of its
components8. Other pathologies causing AR therefore
include leaflet prolapse, leaflet perforation and annular dilatation.
Over the preceding two decades, a more profound understanding of the
functional anatomy of the BAV and the pathophysiological mechanisms
underlying AR, the implementation of standardised nomenclature to
describe the valvular defects encountered, ongoing refinements in
operative techniques and the development of a functional classification
of AR permitting a systematic approach to BAV
repair9,10, have contributed greatly to the
advancement of aortic valve reconstructive surgery. Recently, BAV repair
received a class 2b recommendation in the 2020 ACC/AHA valvular heart
disease management guidelines, when performed by an experienced
surgeon11.
Stabilisation of the aortic annulus is now well-established as a
fundamental principle during repair of regurgitant
BAVs12,13 for management of AR secondary to annular
dilatation in the absence of structural valve disease. Uncorrected
annular dilatation exceeding 25-29 mm is recognised as a predominant
risk factor for repair failure14. A variety of
surgical methods are available to stabilise the aortic annulus,
including an external polytetrafluoroethylene (PTFE)
suture13 or flexible annuloplasty ring to correct
ventriculo-aortic junction dilatation15, or internal
placement of a Cabrol stitch16 (subcommissural
annuloplasty, SCA), PTFE suture17 or rigid
annuloplasty ring18.
Due to the prevalence of functional aortic annular dilatation in
regurgitant BAVs, annular stabilisation is critical to the durability of
BAV repair. First described by Cabrol in 196616, SCA
is a relatively straightforward technique for aortic annular
stabilisation whereby a horizontal mattress suture is placed in the
subcommissural inter-leaflet triangle, reducing annular circumference
and improving leaflet coaptation. Initially a popular approach, SCA
produces asymmetric annular reduction only in the commissural zones of
the aortic annulus, predisposing the remaining annulus to future
dilatation requiring reintervention. Another potential drawback is that
SCA may generate an unequal distribution of stress on the repaired BAV
and risk recurrent AR19. This is further corroborated
by the inferiority of SCA in patients with a larger aortic annulus
compared to valve-sparing aortic root replacement, where the entire
annulus is reinforced with pledgetted sutures. Indeed, some studies have
highlighted SCA as a predictor of valve-related
reoperation20-22 in both tri-leaflet aortic valves and
BAVs, rendering the technique somewhat redundant. In contrast, EA
utilises a continuous mattress suture placed through the aortic wall
circumferentially around the entire aortic valve, passing through the
nadirs of the coronary sinuses and imbricating the aortic wall as the
suture is tensioned, thereby reducing the aortic annulus and promoting
leaflet coaptation. Care must be taken to avoid injury to the coronary
ostia. Rather than applying EA sutures, many groups now routinely
perform valve-sparing reimplantation23, where the
Dacron prosthesis provides complete annular stabilisation, although this
is more technically challenging than SCA.
In the only available study directly comparing EA and SCA, Ko and
colleagues analysed 20 patients with severe regurgitation in type I BAVs
undergoing external subannular aortic ring (ESAR) constructed from a
Dacron graft and 38 undergoing SCA19. They found that
ESAR afforded greater reductions in annular dimensions and
trans-valvular gradients than SCA, whilst both techniques resulted in
100% freedom from AR >grade 1 at a mean 9.2 ± 0.7 months
and 51.1 ± 38.5 months in the SCA and ESAR groups, respectively.
In the present study by Jasinksi and colleagues1, SCA
was performed using two braided 2/0 sutures with pledgets to narrow two
subcommissural triangles, whereas EA incorporated a line of interrupted
braided 2/0 sutures placed along the external perimeter of the aortic
annulus, buttressed by a Dacron strip. Several additional valve
preservation strategies were concomitantly employed, including prolapse
repair, raphe excision and pericardial patch reconstruction of the
aortic leaflets, although specific details are not provided, and their
influence on the observed valve repair outcomes cannot be elucidated
without additional analysis.
Nevertheless, Jasinski and colleagues are to be congratulated on the
excellent outcomes achieved in their series of patients undergoing BAV
repair with ascending aortic replacement. They have demonstrated good
medium-term durability with freedom from AR progression beyond grade 2
with both EA and SCA techniques at 35.1 ± 3.6 months, although this is
significantly better at 96% with EA, compared to SCA at 76%. EA also
provides lower trans-valvular flow velocities and gradients than SCA.
BAV repair with EA can be a safe and effective alternative to
conventional valve replacement, conditional on judicious patient
selection and the availability of surgical expertise for the geometric
and functional normalisation of all components of the aortic valve and
root. However, longer-term robustness of the repair with EA necessitates
extended follow-up.