Discussion
The present study tries to address the important question whether it is
still reasonable to undertake a re-sternotomy for AVR in patients with
patent CABG in the era of transcatheter valve therapy.
The reported mortality of re-sternotomy is 6-20% (5-7). Mayo Clinic
reported 8% early mortality for conventional redo biological valve
replacements over 20 years in a mixed series of aortic and mitral valve
replacements. New York Heart Association functional class (hazard ratio,
2.1; 95% confidence interval, 1.06-4.3; P = 0.03) and prior CABG
(hazard ratio, 3.5; 95% confidence interval, 1.2-10.9; P = 0.03) were
independent predictors of early death (8). Survival at 5 and 10 years
was 63% and 34% respectively. Patients with the combination of prior
CABG and New York Heart Association functional class III or IV accounted
for 46% of early deaths.
Our in-hospital mortality of 7.8% compares favourably with these
results. We divided our patients into 2 subgroups based on the premise
that group 1 (isolated AVR with re-sternotomy and no other concomitant
cardiac procedure) have the option of TAVI. They can potentially avoid a
risky and complex operation and have a reduced hospital stay and quicker
recovery.
The in-hospital mortality in group 2 was almost twice that of group 1
(10.2%, group 2 versus 5%, group 1, p=0.247). Although, this did not
reach statistical significance, a concomitant procedure does add to the
complexity of surgery and increases risk.
These mortality rates are still remarkably high compared to isolated
first time AVR with mortality of 0.5-1.9% (9-12). In addition to the
hazard of surgery itself, there may also be the additional hazard
associated with long standing ischemic heart disease in combination with
aortic valve disease. Our analysis showed that the long-term survival of
patients undergoing first time isolated AVR approaches that of an
age-matched general population whereas it lags behind significantly
after a re-sternotomy AVR in patients with previous surgical myocardial
revascularisation.
Attempts to dissect and control LIMA increases risk of injury and
operative mortality (13,14). Patent LIMA in a perfused heart bloodies
the operative field with inconvenience of stitching on a beating heart.
In conjunction with moderate to deep hypothermia on a fibrillating
heart, this technique has been considered safe and avoids injury to LIMA
(15,16). Systemic hyperkalaemia with adjunctive hypothermia, for
diastolic arrest is a safe proposition, to avoid injury to LIMA when
dissection is difficult due to adhesions.
Pre-sternotomy institution of cardiopulmonary bypass through peripheral
cannulation is considered a safe strategy to manage any catastrophic
bleeding. It decreases myocardial injury and complication rates, blood
and blood product usage, hospital stay and hospital costs (17). In this
analysis, our numbers may have been too small for estimation of the
effects of LIMA injury and pre-sternotomy institution of cardiopulmonary
bypass.
TAVI now provides a safe option for isolated AVR in patients with a
hostile chest. These include previous multiple sternotomies, sternal
infections and mediastinitis, prior irradiation, elderly, frail
patients, calcified aorta/root. TAVI allows a shorter hospital stay and
a lower postoperative morbidity rate compared to re-sternotomy (18,19).
Stortecky et al reported that in elderly, high-risk patients after prior
CABG, conventional AVR and TAVI are comparable treatment options.
All-cause mortality was 2.5% in both groups and major adverse cardiac
and cerebrovascular event rates were comparable (7.5% TAVI vs 17.5%
S-AVR, p = 0.311) after 30 days. TAVI had a higher rate of permanent
pacemaker implantation (30% vs 0%, p < 0.001) and grade II
residual aortic regurgitation in 14%. Incidence of cerebrovascular
events was 7.5% in SAVR vs 2.5% in TAVI (p = 0.61).
Patent grafts can also provide protection in cases of low coronary
ostial heights especially for high profile transcatheter valves. There
remain concerns for high paravalvular leak rates, permanent pacemaker
implantation, sub-valvular leaflet thrombosis, need for anticoagulation
and long-term durability of transcatheter valves (20-22).
There is a significant economic burden with re-sternotomies due to
longer ventilation times, intensive care and hospital stay and need more
intensive tests and treatments like inotropic support, hemofiltration,
invasive and non-invasive ventilator support and intra-aortic balloon
pumps. Our analysis did not evaluate the cost burden of these
procedures. No direct cost comparisons are available between
re-sternotomies and TAVI. With increasing TAVI volumes, greater operator
experience and decreasing costs, TAVI remains an attractive option in
this group of difficult surgical patients.
Best practice recommendations now include discussions in the Heart Valve
Team to ensure the most appropriate procedure in terms of technical
feasibility, safety and durability. Frail and comorbid patients may
benefit from a less invasive intervention, however, in case of
concomitant diseases, a complete treatment with a complex conventional
surgical operation should not be avoided despite relatively high initial
comorbidity.