Technical tips for Reducing the Risk of Atrioventricular Disruption
Following Mitral Valve Replacement
M.Marzban MD and P.Benharash MD
Mehrab Marzban, MD. Peyman Benharash,MD
Cardiovascular Outcomes Research Laboratories, Division of Cardiac
Surgery, David Geffen School of Medicine at UCLA, Los Angeles,
California
Corresponding author: Mehrab Marzban,MD
Email:MMarzban@mednet.ucla.edu
10833 Le Conte Ave.62-249 CHS
Los Angeles, CA 90095
Abstract
This report describes the effective measures in order to prevent the
devastating complication of AV groove disruption following mitral valve
replacement.
Ethics committee approval, consent statement and clinical trial
registration are not applicable for our study.
Introduction
Rupture of the Atrioventricular (AV) groove or in a broader sense, left
ventricular rupture is a n infrequent but often fatal complication of
mitral valve replacement. Treasure and colleagues were the first to
define this entity in 1973 in 7 patients. (1) In 1980, Cobb et al
described the complication as “transverse midventricular disruption.
“The authors also pointed out that a false aneurysm could be the end
result of an incomplete rupture. Although AV groove rupture was reported
in up to 14% of cases in the early years of valve replacement, refined
surgical techniques and lower profile prostheses have reduced its
incidence to 0.5-2% in modern series (2).
While the exact mechanism responsible for this complication was
initially unclear, several risk factors including redo operations,
severe annular calcification, advanced age, hemodialysis dependence, and
resection of posterior leaflet and apparatus, appear to increase the
likelihood of AV groove disruption. Preexisting intrinsic myocardial
disease, especially ischemia, rheumatic myocarditis, and infectious
processes have also been implicated. (3) Rupture is most commonly noted
in the operating room or in the early postoperative period and may be
often preceded by a period of systemic hypertension. There are several
reports of late presentation as a pseudo aneurysm of the left ventricle
or delayed rupture in the literature. (5) notwithstanding the favorable
outcomes of few investigators such as Tirone E. David (6), the fatality
of this complication appears to be in excess of 75%. (7). If rupture
occurs outside of the operating room, the chances of successful recovery
are negligible. Thus, every attempt should be made to prevent rupture
from happening. Below, we provide several technical considerations that,
in our experience, have reduced the risk of AV groove disruption.
Technique:
Exposure:
At first, it is essential to identify the high-risk patient based on the
preoperative evaluation. Every patient who has an MVR is a potential
candidate for AV groove complication and every effort should be made to
avoid it, but there is some extra caution which is required in high-risk
groups.
Good exposure
good exposure of the mitral valve is of paramount importance to avoid
this complication especially in patients who are obese or have barrel
chest when the LA is small and also in redo surgery. Pericardial
adhesion from the previous operation or rheumatic pancarditis may limit
heart mobility, in this situation, exposing the mitral valve, excising
the degenerated valve, and putting the annular sutures require excessive
traction on the annulus that may lead to subtle or obvious damage to the
ventricular wall. As a result, it is advisable to mobilize the heart
completely from pericardial adhesion. On the other hand, based on the
surgeon’s experience, a proper approach like the trans-septal approach
may be preferred to address the mitral valve.
.
Chordal sparing
Preservation of posterior leaflet and apparatus: Excision of posterior
leaflet and subvalvular apparatus has been suggested as a major
contributing factor for AV groove damage. (8) Thus it is prudent to
preserve the annulo-papillary continuity as much as possible. In some
occasions, due to severe mitral annular calcification, it is inevitable
to resect the posterior leaflet, even in this situation the papillary
muscles should be reattached to the corresponding posterior annulus
either directly by annular sutures or using artificial chordae. This
surgical tip leads to less impairment of left ventricular function and
minimizing the risk of ventricular rupture There are different methods
for annular decalcification based on the calcification severity and
extension, furthermore, the surgeon’s experience has a definitive role.
It can be a piecemeal or en bloc resection associated with annular
reconstruction using autologous or bovine pericardium. Either technique
needs a meticulous dissection, overzealous decalcification should be
avoided.
Undersizing the prosthesis
Another important measure is undersizing the prosthesis when the patient
is assumed to be at high risk for AV groove disruption. The oversized
prosthesis has been mentioned as a risk factor for the dreaded
complication of AV groove rupture (9) but, we put our step beyond that,
our recommendation is to undersizing the prosthesis to reduce the
pressure of the prosthesis cuff on the muscle fibers of the AV groove.
Interrupted pledgetted sutures
Despite several reports on the safety of continuous suture technique in
mitral valve replacement, we believe that continuous suturing has
potentially more risk of damage to the annulus due to the excessive
traction which is needed for suture placement especially if the exposure
is not optimal. Interrupted sutures provide more secure and reinforced
sutures in severe annular calcification.
Avoidance of inotrope and volume overload
Forceful contraction of the left ventricle against the rigid cuff of the
valve prosthesis has been implicated in the pathogenesis of AV groove
disruption following MVR. Most patients after MVR do not require
inotropic support and can be weaned from CPB without difficulty.
Unnecessary use of inotropes should be abandoned. Volume overload and
the chamber distention may contribute to muscle fiber separation in AV
groove and should be avoided.
Avoidance of heart massage or tapping on the heart for desiring
There are different methods to deair the heart chambers before the
termination of CPB. Some surgeons used to fill the heart while resuming
the ventilation and squeezing the heart whereas it has the potential to
damage the heart and should be discouraged after mitral valve
replacement.
Comment
Following these simple measures in 437 patients with mitral valve
replacement, luckily we did not encounter this dreaded complication.
References
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Intraoperative left ventricular rupture associated with mitral valve
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