CIRCUMFLEX ARTERY LESION
MV repair can be associated to the danger of CX injury (direct damage by
sutures), due to the close spatial relationship between the CX and the
mitral annulus. The artery is involved in the great majority of the
cases in its proximal portion, close to the anterolateral commissure or
P1, where the distance between the artery and the annulus is the
shortest [11]. Patients with larger CX diameter seem to be more
exposed to this complication, as the distance to the annulus reduces
[12]. Another mechanism is CX distortion, where the CX is attracted
toward the annulus when a misplaced stitch is tied causing severe flow
reduction till functional occlusion (Figure 2). In this case the CX has
to be far from the annulus, but other contributing factors have to be
present, as the atrial wall has to be enough stiff and resistant to move
the CX toward the annulus without tearing.
Spatial relationship between the CX and the mitral annulus have been
widely studied. Most of the reports showed that the CX is closer to the
annulus in presence of left dominance or codominance, but, according to
Pessa et al. [13], independently from the dominance, the proximal CX
can be as close as 1 mm to the mitral annulus at the level of the
anterolateral commissure. These data were confirmed by Caruso et al.
[14], who found that 66.7% of the patients considered at high risk
(mean distance CX-annulus <3 mm) had right dominance. However,
Kishimoto et al. [15] found that the distance CX-annulus is 3 mm or
less in 25% of the patients overall, but in presence of a left coronary
dominance the percentage rose to 75%, whereas the prevalence was more
or less similar in patients with left co-dominance (26%) or right
dominance (17%).
This complication is potentially lethal and immediate recognition and
treatment are mandatory to avoid the sequelae of a lateral acute
myocardial infarction. Surgeons must suspect CX injury or kinking in
presence of ventricular arrhythmias, difficult weaning from CPB,
inferolateral hypo- or akinesia, or EKG signs of myocardial ischemia.
Better information can be provided by direct echocardiographic analysis
of the CX course, where the presence of aliasing or no flow is able to
make evident the lesion [16]. When there is no suspicion in OR, in
Intensive Care Unit arrhythmias, EKG changes or hemodynamic instability
are indications for urgent coronary catheterization, as angioplasty can
immediately restore the flow. If the point of injury cannot be crossed,
urgent surgery is mandatory. It consists in direct revascularization of
the occluded vessel or in partial/total removal and re-implantation of
the ring, in the area of the anterolateral commissure and P1, passing
the stitches as close as possible to the leaflet. Not always the
consequences are immediately evident, but the complication can be
diagnosed even after days [17], months [18-19] or years
[20-21]. In a review of the literature, where cases of MV
replacement were included, 7% of the patients had a diagnosis after 30
days from surgery.
The prevalence of iatrogenic lesions of the CX during MV repair is not
well known. Only a few papers checked systematically the preoperative
relationships between the CX and the annulus, reporting the results and
the surgical outcome. Caruso et al., in 95 consecutive patients, showed
that in 25% of the patients the distance CX-annulus was <3 mm
[14]. In these patients the stitches were not passed in the
dangerous area. Nevertheless, 1 patient (1.1%) experienced CX
obstruction, immediately corrected replacing a rigid ring with a
flexible one [22]. Ender et al. used TEE to visualize the CX in 110
cases. Three patients (2.7%) experienced CX injury and successfully
underwent surgical or percutaneous correction [16]. In other similar
series the prevalence was 1.9% [23] and 1.8% [24], higher than
reported in other experiences (0.15% [25] to 0.3% [17]).
The real problem is the time from CX lesion to revascularization, from
which the extension of lateral infarction and the clinical outcome
depends. When the complication is treated before leaving the OR, results
are uniformly good, but when the treatment is performed after a coronary
angiography, the mortality is around 10%, but the consequences on the
LV function can be serious. Coutinho et al. reported 6 cases where only
1 case was treated in OR successfully. All the other cases had a
coronary angiography and delayed treatment. One patient was transplanted
after 10 days, 3 were discharged with a low ejection fraction (1 had a
redo 2 years later due to severe MR and huge posteroinferior aneurysm)
and 1 was reoperated on after 5 years for severe MR with depressed LV
function.