Title : Long-term Outcomes Following Reoperations for Stentless
Aortic Valves.
Running Head : Reoperations for Stentless Valves.
Authors : Bindu Bittira MD, MSc1; Mohammed
Shurrab MD2; Stacey Santi3; Sarah
Grieve BA, BEd1; Derek J. MacDonald MD,
RPh1
Institutions and Affiliations :
1. Division of Cardiac Surgery, Department of Surgery, Health Sciences
North, Sudbury, Ontario, Canada.
2. Department of Cardiology, Health Sciences North, Sudbury, Ontario,
Canada.
3. Health Sciences North Research Institute, Sudbury, Ontario, Canada.
Key Words : aortic valve reoperation, survival, aortic valve
replacement, prosthetic valve endocarditis, stentless aortic valve.
Word Count : 3098
Address for correspondence :
Bindu Bittira, MD, MSc.
865 Regent St. South, Suite M-131
Sudbury Outpatient Centre, Health Sciences North
Sudbury, Ontario
P3E3Y9
Telephone: 705-671-5353
Fax: 705-671-5352
Email: bindubittira@sudburyheart.com.
AbstractBackground: There is limited data on the long-term outcomes in
patients who have undergone a reoperation following a failing stentless
aortic valve.Methods: Between 2006-2016, a retrospective analysis was
performed on 24 patients that underwent open aortic valve replacement
surgery for a failed stentless aortic valve prosthesis at Health
Sciences North, Sudbury, Ontario, Canada. The primary outcome was low
mortality from cardiac related deaths after 5 years.Results: All patients underwent an insertion of a Medtronic
Freestyle bioprosthesis implanted in the modified subcoronary technique
for their initial operation. The interval from the first operation to
the stentless redo surgery ranged from 6-13 years. Aortic valve
reoperation was performed for structural valve deterioration in 96% (n=
23) of the cases. Reoperations involved a removal of the stented valve
leaflets and stented valve-in-valve implantation in 20% (n= 5) of the
cases, with the remaining cases requiring complete removal of the
stentless prosthesis and aortic valve replacement. In those where a
complete removal of the stentless valve was possible (n=19), there was
no disruption of the native aortic root, and a 0% conversion to a
Bentall procedure. There was no intraoperative mortality. The 30-day and
10-year operative mortality was 4% and 16%, respectively.Conclusions: Redo surgery for failing stentless valves can be
done with relatively low-risk and with acceptable long-term outcomes
without resorting to root replacement techniques.Introduction:
The Freestyle Stentless Porcine Valve has been used since
19931 as a third generation porcine valve. Compared to
conventional stented bioprostheses, stentless valves provided better
hemodynamics with a larger effective orifice area with respect to their
valve size.2 This allowed for improved left
ventricular function secondary to left ventricular mass
regression3-5 and reduced incidences of
patient-prosthesis mismatch. However, despite the advantages,
historically the utilization of stentless valves has been controversial.
The benefits in hemodynamics have been negatively influenced by the
technical difficulty in implanting the valve, with a longer learning
curve and longer ischemic time.6 There are multiple
options for implanting a Freestyle valve, including the root inclusion
technique, an isolated complete subcoronary technique, or a full root
replacement.7As the use of the stentless valve gained popularity, it was reasonable
to accept that these valves would eventually degenerate, leading to
stentless valve reoperations. In addition to the technical difficulty of
implantation, reintervention is also widely regarded as a greater
surgical challenge. Over two decades at our center, Health Sciences
North, Sudbury, Ontario, over 300 Medtronic Freestyle stentless valves
were inserted. Many patients did return for reoperations. Prior to the
broad introduction of transcatheter aortic valve replacement (TAVR), all
patients returned to the operating room for reintervention. Subesequent
to 2016, with the introduction of catheter-based aortic valve
replacement in our center, valve-in-valve TAVR soon evolved as another
treatment option.8 This option, however, also
presented technical challenges, with the lack of radio-opaque markers to
guide trans-catheter valve implantation.
The objective of this study was to evaluate the short- and long-term
outcomes of patients who underwent a stentless valve reoperation at our
center, including their perioperative outcomes, operative mortality, and
long-term survival following aortic valve reoperation following an
initial implantation of a Medtronic Freestyle stentless valve.Material and Methods:Study Approval and Design:
This study was approved by the Institutional Review Board at Health
Sciences North (Sudbury, Ontario) and was in compliance with Health
Insurance Portability and Accountability Act regulations. Operative
reports and medical records were reviewed by a single cardiac surgeon
(BB) to confirm that these patients all had received a Medtronic
Freestyle stentless valve (Medtronic Inc., Minneapolis, MN, USA) for
their initial operation and had received a reoperation for a failed
stentless valve. Long-term survival was obtained through medical record
review and supplemented with telephone calls with 100% follow-up of all
patients. All reoperations for stentless valves were performed by the
same team of cardiac surgeons (BB and DJM).Patient Selection:From 2006-2016, all consecutive patients (N=24) who underwent open
reoperative aortic valve replacement (AVR) for a failing stentless valve
were enrolled in this study.Operative Technique:
In all cases, surgery was performed via redo median sternotomy. Prior
cannulation of the femoral artery or subclavian artery was used only
when the right ventricle was in close proximity to the posterior table
of the sternum. Cardiopulmonary bypass, with standard ascending aortic
cannulation, the aortic arch or femoral artery and the right atrium or
femoral vein, was used with systemic hypothermia of
320C. Myocardial protection was achieved with
intermittent antegrade cold blood cardioplegia. All concomitant
procedures were performed according to standard techniques.
Intraoperatively, the size of the stentless valve inserted in the first
operation often determined whether a valve-in-valve technique would be
feasible. We found that larger stentless valves (size 25 or greater)
often allowed for an adequately sized stented valve to be inserted after
removal of the torn leaflet tissue and the pannus in the left
ventricular outflow tract (LVOT). When the stentless valve was of a
smaller size (size 23 or smaller), meticulous removal of the entire
valve was necessary before an appropriately sized valve was inserted. In
our practice, this decision to proceed with complete removal of the
stentless valve , or perform a valve-in-valve was often made
intraoperatively. Factors such as the amount of calcification of the
stentless casing (particularly in the area of the noncoronary sinus, the
quality of the native tissue, the proximity of the subcoronary suture
line to the ostium of the coronaries, and the annular size of the
stentless bioprosthesis played a role in this decision. Additionally, if
the patient had significant comorbidities and the perceived length of
time required on cardiopulmonary bypass to completely explant the entire
stentless valve was considered too lengthy, we would choose a more
conservative, quicker surgical strategy such as a valve-in-valve
implant.
When the stentless was particularly adherent to the native root, we
found that starting the removal in the area of the non-coronary sinus
was the most forgiving strategy. If the wrong tissue plane between the
stentless valve and the native aortic root was entered here, a
pericardial or bovine patch repair of the root could be performed more
easily than in other areas of the disrupted root. Stentless extraction
was typically a lengthy process, requiring great care and patience to
preserve the integrity of the native aortic root, and with strict
adherence to myocardial protection. Fine Penfield dissectors were
employed for much of this process and supported with sharp dissection
when necessary. Great caution was used in the subcoronary areas where
the margin of the stentless bioprosthesis was extremely intimate with
the ostium of the coronary arteries. Removal of the stentless valve in
this area often left a ridge or flap of tissue near the inferior margin
of the main coronary artery. In such instances this area was reinforced
with several 7-0 prolene sutures.
When a surgical valve-in-valve technique was performed, 4-0 Ethibond
pledgeted sutures were used, and the fragile tissue of the remaining
porcine annulus was avoided. In these instances the native aortic
annulus was covered by the stentless sewing cuff and therefore not
visible. Sutures were placed just below the inferior margin of the cuff
and exited through the stentless valve sewing ring ensuring good
anchoring of the stented prosthesis that was being implanted.
Maintenance cold blood cardioplegia at 8-12 degrees Celsius was given
selectively into the coronary ostia at twenty-minute intervals for the
duration of the procedure.Statistical Analysis:
Descriptive statistics were computed for the study cohort. Continuous
variables were summarized by reporting the median and ranges.
Categorical variables were reported as N (%) in frequency tables.Results:
All patients (n=24) received a Freestyle Aortic Root Bioprosthesis for
their initial operation due to disease from aortic valve pathology. All
patients had their initial stentless surgery performed by the same
surgeon at the Sudbury Regional Hospital, Sudbury, Ontario. All patients
had their initial valve inserted with the modified subcoronary
implantation technique.
Preoperative status and comorbidities of the patients are outlined in
Table 1. The stentless valve required reoperation on average after 9.8
years, with aortic insufficiency as the mode of failure in all cases
except one. Intraoperative examination of the stentless valve and the
aortic root revealed a linear tear at or near the base of one of the
leaflets. The leaflets, although demonstrating remarkably little
calcification, were extremely brittle with minimal traction or
manipulation.
There were no serious adverse events which occurred during
re-sternotomy. All five patients who underwent the valve-in-valve
technique received a biological tissue valve. 37.5 % (N=9) of patients
required a concomitant procedure, predominantly coronary artery bypass
grafting. Surgical variables and characteristics are outlined in Table
2.
In patients where the stentless valve was explanted (N=15), the root was
preserved in 100% of cases, with no need for a conversion to a Bentall
procedure. Of the 24 patients who underwent this procedure, 10 received
mechanical valves and 14 received a stented aortic prosthesis. In 5 of
these patients, the stentless leaflets were removed, and the new valve
was sutured to the native annulus (valve-in-valve technique). Urgent
surgeries were required in 20.8% (n= 5) of the cases, mostly due to
hemodynamic compromise or endocarditis. Mean cross-clamp time was 156
minutes. 30- day outcomes revealed no post-operative myocardial
infarctions, or strokes, with only one patient suffering from new onset
renal failure.
Hospital length of stay averaged 7.5 days. The single in-hospital
mortality was an immunocompromised patient presenting with
Staphylococcus aureus endocarditis involving the Freestyle valve.
Intraoperatively, the valve was successfully explanted, however the
patient required a concomitant repair of a ventricular septal defect,
reconstruction of the left ventricular outflow tract, and concomitant
coronary artery bypass grafting to the left anterior descending artery.
The patient had a significantly lengthy cardiopulmonary bypass run, with
post-operative coagulopathy and left ventricular dysfunction,
necessitating mediastinal re-exploration twice. The patient subsequently
expired on post-operative day 5 of multi-system organ failure.
Follow-up at 2 months post-operatively and then once annually was
performed. All patients had improved functional status with all in NYHA
Functional Classes I-II. None of the valve-in-valve patients had a
measurable paraprosthetic leak and two of the patients ultimately
required re-interventions on their replaced aortic valves. One patient
had a TAVR procedure performed eightt years later, and one patient
underwent a third sternotomy with a tissue aortic valve replacement.
Procedural outcomes are detailed in Table 3.
The 5-year mortality was 4% (n=1), who was the in-hospitality mortality
identified above. The 10-year mortality was 16.7% (n=4). Causes of
death included two patients with acute renal failure and encephalopathy,
and one patient with Staphylococcus aureus endocarditis and acute renal
failure.
The 10-year all-cause mortality was 33% (n=8). Of these 4 deaths, 2
were secondary to metastatic cancers and 2 were listed as death
secondary to multi-system organ failures.Comment:
In this study, we summarized a retrospective review of a single surgical
team’s experience of reoperative surgery for failing, predominantly
regurgitant, stentless valves. The primary findings of the study are as
follows. The 30-day mortality was 4% (1/24) for all patients, and the
long-term cardiac 10-year mortality was 16% (4/24) for all patients.
The primary operative method involved complete explantation of the
stentless xenograft, without incurring any damage to the root
necessitating the need for a complete root replacement. In their own
retrospective series, Borger and colleagues9 reported
an operative mortality of 11% with 63% of patients requiring aortic
root replacements, despite specifically attempting to preserve the
pre-existing native aortic root. In a similar study, Boning and
colleagues10 reported a 21% (5/24) 30-day operative
mortality following their stentless reoperations, which was higher than
the 4% operative mortality in their patients who had a stented aortic
valve reoperation.
Our only early mortality was in a patient who had an active infection of
their stentless valve, highlighting the further complexity in removing
not only the stentless valve, but adjacent structures which were
involved in the infectious process. In our hands, while all attempts
were made to completely remove the stentless valve, if annular
dimensions were adequate in an otherwise relatively higher risk patient,
a stented valve was implanted within the stentless casing.
Similar to other centres8, our reoperative approach to
stentless valves has evolved over the years, with the potential role for
valve-in-valve TAVR in this particular setting. However, several
difficulties and potential complications still have to be considered
with this approach: the initial implantation technique of the stentless
valve, the bulky nature of the leaflet tissue, lack of annular
calcification, device malpositioning due to lack of anatomic markers to
guide landing zones and coronary obstruction.11-13Future studies will need to analyze the long term impact of
valve-in-valve TAVR prior to committing to this approach for stentless
reoperations as a primary approach.