Iatrogenic occlusion of the left circumflex artery due to mitral valve repair surgery : a not well-known , but potentially fatal complication

Mitral valve surgery has become an increasingly common procedure for patients with mitral valve disease. Iatrogenic coronary artery lesion has been reported as an uncommon and potentially fatal complication of mitral valve surgery. Its diagnosis must be considered during perioperative care, and coronary angiography helps in deciding the best therapeutic strategy. In the present clinical report, we describe a patient with iatrogenic occlusion of the left circumflex artery after surgery for mitral valve replacement due to rheumatic disease.


BACKGROUND
In Brazil, heart valve disease represents a significant fraction of the total number of patient hospitalizations for cardiovascular disease.Unlike developed countries, in Brazil rheumatic fever is the main etiology of heart valve diseases and is responsible for up to 70% of cases. 1 Surgical treatment of valvular heart disease, in the situations foreseen by the gui delines, modifies the natural course of the disease, enabling reverse remodeling of heart chambers, recovery of ventricular function and remission of symptoms. 1atrogenic coronary artery lesion during mitral valve surgery has been reported as a rare and potentially severe complication, due to the proximity of the left circumflex artery (LCx) to the posterior segment of the mitral valve annulus.
Several mechanisms suggest that coronary artery injuries are related to direct le sion to a vessel by surgical suture or due to distortion of the surrounding tissue, resul ting in dynamic, functional stenosis or occlusion of the artery. 2

2
This potentially fatal complication should be considered and promptly recognized during the perioperative period of repair or replacement of the mitral valve in order to re duce morbidity and mortality.

CASE REPORT
In February 2017, a 60yearold female patient with a history of rheumatic fever during childhood, percutaneous mitral valvuloplasty performed in 1991, permanent atrial fibrillation, presenting with symptomatic mitral stenosis (MS) and tricuspid regurgitation (TR) was scheduled for elective mitral valve replacement and tricuspid valve repair.
The preoperative transthoracic echocardiogram showed severe MS, with a rheumatic characteristics; a thickened tri cuspid valve with leaflet coaptation failure, causing severe TR; pulmonary artery systolic pressure of 45mmHg; preserved left ventricular systolic function; right ventricu lar systolic dysfunction, and left atrial enlargement.Preo perative coronary angiography did not reveal obstructive lesions (Figure 1).
The surgery was performed by median sternotomy, with cannulation of the ascending aorta and inferior and superior vena cava, extracorporeal circulation (EC), clam ping of the ascending aorta, and cardioplegic solution in fusion.The mitral valve showed rheumatic features, with severe stenosis due to fusion of commissures.The anterior and posterior leaflets were resected and a 29 mm mechani cal prosthesis was implanted in addition to left atrial appen dage closure.Tricuspid valve repair was attempted, but was unsuccessful.We then opted for the implantation of a 31 mm biological prosthesis.The intraoperative transesophageal echocardiogram showed a satisfactory surgical result.
EC and clamping time were 158 and 125 minutes, res pectively.Junctional heart rhythm was observed at EC weaning, requiring use of epicardial pacemaker and vasoac tive drugs.After the surgical procedure, the patient was transferred to the postoperative care unit, and the elec trocardiogram showed a junctional rhythm with ST seg ment elevation in DII, DIII, aVF, V5, V6, V7 and V8 upon admission (Figure 2).
The patient was referred for tcoronay angiography, which revealed occlusion in the proximal segment of the LCx and we decided to perform a primary coronary an gioplasty.The left main coronary artery was catheterized with a JL 3.5, 6F guiding catheter, and a 0.014" PT Flo ppy® guidewire (Boston Scientific, Marlborough, USA) was introduced beyond the occlusion.The stenosis was predilated using 2.0×10 mm Pantera PRO® and 2.5×8 mm Pantera LEO® balloons (Biotronik, Berlin, Germany), under high pressures.A conventional 2.75×28 mm Mul tiLink stent (Abbott Vascular, Illinois, USA) was deployed in the proximal segment of LCx under 12 atmospheres.During the stent release, a waist in the balloon was evident at the site of the stricture.The procedure was completed with instent postdilation with a noncompliant Pantera LEO® 3.0×12 mm balloon, under 26 atmospheres.A satis factory angiographic result was achieved, with a residual lesion of 30% (Figure 3).The subsequent postoperative period went uneventful, with gradual weaning of vasoac tive drugs and no episodes of angina or new electrocar diographic changes.
The 8month followup showed a satisfactory surgical procedure result and absence of symptoms related to coro nary artery injury.

DISCUSSION
The left circumflex artery runs through the left atrio ventricular groove and is in close relation with the poste rior portion of the mitral valve ring.LCx lesion associated with mitral valve replacement or annuloplasty is rare, and its incidence ranges from 0.5 to 1.8%. 24natomical studies have documented that the distance between the mitral annulus and the LCx can be only 1 mm.This very close distance between the structures has been described in the anterior commissure area, indicating that the proximal segment of the LCx is at a higher risk of iatro genic injury during mitral valve surgery. 5,6he risk of LCx injury is higher when the artery ana tomy shows left dominance or codominance. 5,7,8here are several mechanisms of coronary injury, such as artery entrapment due to suture involvement, arterial obliteration due to suture through the arterial lumen, co ronary perforation, thrombosis due to endothelium lacera tion, vascular distortion caused by tissue retraction leading to dynamic or fixed occlusion, external compression by the annuloplasty ring, laceration of the artery resulting in lo calized hemorrhage or subintimal hematoma causing ex trinsic compression of the LCx. 2,5,9e possibility of iatrogenic LCx injury should always be highly suspected, for it is essential to immediately indicate coronary angiography to detect the location of injury and to help determine the best therapeutic strategy.

CONCLUSION
Although uncommon, the iatrogenic lesion of the left circumflex artery should be considered as the etiology of acute coronary syndrome in the immediate postoperative period of mitral valve repair or replacement.Early recog nition of this complication helps to determine the best treat ment to restore coronary blood flow and to reduce morbi dity and mortality of patients.

SOURCES OF FINANCING
None.