Corresponding Author:
Prof GD Angelini, MD,MCh,FRCS, FMedSci
British Heart Foundation Professor of Cardiac Surgery,
Bristol Heart Institute
Bristol Royal Infirmary,
Upper Maudlin Street BS2 8HW
Bristol, UK
G.D.Angelini@bristol.ac.uk
Conflict of Interest : none
Funding: This work was supported by the British Heart
Foundation and the NIHR Biomedical Research Centre at University
Hospitals Bristol and Weston NHS Foundation Trust and the University of
Bristol.
Key words : Aortic Dissection, Root replacement, Limited root
repair
AbstractSignificant dilemma exists regarding management of the aortic root
pathology in acute aortic dissections. Several strategies for both
repair and replacement exist and there is a lack of clarity on the
superiority of one over the other. Important factors that influence
management strategies include involvement of the sinuses, competence of
the aortic valve, presence of Marfans syndrome and connective tissue
disorders, as well as availability of surgical expertise. The wide
variability in these factors makes it unlikely for any one technique to
be suitable for management of all aortic roots and the root pathology
has to be tailored to an individual patient.
Management of the aortic root pathology in acute aortic dissection
involving the thoracic aorta has been the subject of considerable
interest and controversy and the study by Percy et al examines the
strategies for this clinically relevant issue in a large nationwide
analysis. (1)
Percy et al in their study have divided these strategies broadly into
two groups- those where the aortic valve was spared and those where it
was replaced. However, the authors have not specified the various
interventions that fall under these two groups. For instance, aortic
valve replacement can be carried out separately with a supracoronary
replacement of the ascending aorta as well as a composite root
replacement. The former is a much simpler operation than a composite
root replacement, and it would be important to note if these patients
were treated as one and the same, as in both cases the aortic valve
would be replaced. Similarly, aortic valve repair group can potentially
include valve resuspension as well as valve sparing root replacements,
as in both cases the valve is spared but the two interventions are
technically at the two ends of the surgical expertise spectrum. Thus,
comparing outcomes under the headings of aortic valve repair or
replacement may lead to outcomes that are hard to be generalized. A more
clinically oriented way to group these patients would be to identify who
require a root replacement and those who do not. This can be followed by
an intra-group comparison of different techniques for root replacement
and those where no root replacement or limited repair can be carried
out.
A root replacement is indicated in the presence of gross dilatation or
destruction of the sinuses of Valsalva, Marfans Syndrome, annuloaortic
ectasia or presence of intimal tear in the aortic root with or without
involvement of the coronary arteries.(2,3) The root replacement can be
the more conventional composite root replacement (modified Bentall) with
a mechanical valve in situ or in younger patients, with essentially
normal aortic valves, the valve sparing techniques can be used (4,5).
The valve sparing root replacements can again be carried out using two
different techniques, aortic root remodeling technique (Yacoub)(6) or
the reimplantation technique (David)(7). Extensive comparisons have been
drawn between the composite aortic root replacement and valve- sparing
root replacement for management of the aortic root that has resulted in
several systematic reviews and meta-analysis, often with conflicting
observations.(8–12) A valve-sparing root replacement precludes the need
to take oral anti-coagulants, however composite valve-related
complications have been found to be similar among the two strategies(9)
Another study reported that the risk of endocarditis was lower with
valve-sparing techniques but it was associated with a higher rate of
reoperations compared with composite root replacements.(11) Others have
reported lower incidence of thrombo-embolic events and similar
durability of repair with both the strategies.(13)
Repair techniques can include several surgical strategies where both the
aortic valve and the sinuses (resuspension) are preserved, or the
sinuses are partially replaced (Uni Yacoub procedure). When the aortic
valves are normal, aortic regurgitation is essentially due to changes in
the aortic root anatomy and can be easily addressed by valve
resuspension which is a relatively simple, yet quite an effective
strategy. (14) Valve resuspension is carried out in conjunction with
repair of the dissected aortic root and several techniques have been
used to repair the dissected ascending aorta. This includes Teflon-felt
based repair techniques or glue-based techniques either in isolation or
in combination. The two well recognized Teflon based technique includes
formation of the “neo-media” and the “sandwich technique”. In the
neo-media technique Teflon-felt is inserted between the intima and the
adventitia thus replacing the dissected media. The alternative technique
is the sandwich technique where a Teflon-felt strip is placed
circumferentially along the inside and the outside of the aortic wall.
Gelatin-Resorcinol- Formaldehyde-(GRF) glue and Bioglue have been used
along with Teflon-felt repair as well as in in isolation to approximate
the aortic walls. Long-term durability of the aortic root repair is a
concern when GRF or Bioglue are used in isolation.(14) Uni-Yacoub is
another repair technique where the dissection involves only the
noncoronary sinus of Valsalva and limited excision of the sinus is
performed. (5) Depending on the repair technique there is significant
variability in outcomes. While the freedom from re-operation with the
“neo-media” and the “sandwich” technique has been reported to be
89% and 79% respectively at 15 years. (15,16), the 10-year freedom
from reoperation with GRF alone is only 69%.(17)
The question whether limited root repair in aortic dissections is
preferrable to root replacements has been examined by several studies.
The discussion around the choice of technique mainly focusses on two
considerations. Firstly, does a more extensive root replacement leads to
an increase in early mortality and in the longer term does it produce a
more durable repair? If it leads to a more durable repair, can increased
early mortality be an acceptable trade-off? Proponents of aortic repair
suggest that hospital mortality is of paramount importance and hence a
more conservative repair may be preferrable in most cases. (4,18)
However, it is increasingly been shown that more extensive root
replacement techniques do not increase the risk of early mortality.
(19–22) However, it must be borne in mind that most of these series are
reported from high volume centers and whether the results seen in these
studies are reproducible at all institutions remain questionable. On the
question of durability of repair while there is some evidence that root
repair results in an increase in the risk of reoperation(21) most
studies show no difference in durability in the longer term
(17,19,20,22) perhaps due to lower survival rates among these patients
compared with age- and gender-matched controls.(20) Thus, it becomes
obvious that in experienced hands root replacement does not pose any
additional risk, however, there is also no overwhelming evidence of it
being more durable than limited repair. So, experience with the
technique may be the key for a successful short-term outcome.
From a practical point of view the question that ought to be asked is-
when to replace the aortic root in an aortic dissection and when can we
leave it alone. Younger age, intimal tear involving the aortic root with
or without involvement of the coronaries , dilated aortic root
(>4.5cm), Marfans Syndrome are some of the indications
where more aggressive root replacement is mandatory. (3,17,20,22). When
a decision to replace the root has been taken the choice of the
technique of root replacement composite or valve-sparing, must be guided
by the pathology and the surgical experience. If root replacement is not
required, the next step is to assess if the aortic valve is incompetent
and/or diseased and resuspension or a separate aortic valve replacement
could be carried along with supra-coronary replacement of the ascending
aorta.
The conflicting results with the same technique highlights the
variabilities that exist in terms of extent of aortic damage, the type
of disease as well as the surgical expertise which may have a greater
impact on the outcome rather than the technique itself. Percy et al must
be congratulated for carrying out this clinically relevant study and
concluding that that “in selected cases’ repair can be carried out.
Management of the aortic root in aortic dissections is a complex problem
and generalizing a treatment option of either aortic root replacement or
repair would be erroneous. The management strategy must be
individualized considering the patient, the pathology, and the surgeon
expertise.