*Disclosure:* Authors have nothing to disclose with regard to commercial support.

Abbreviations {#nc005}
=============

LCX

:   left circumflex

MV

:   mitral valve

CAG

:   coronary angiography

PCI

:   percutaneous coronary intervention

LVEF

:   left ventricle ejection fraction

ECG

:   Electrocardiography

1. Introduction {#s0005}
===============

The left circumflex (LCX) artery curves around the posterior mitral valve (MV) annulus, and this close proximity makes it susceptible to injury during MV surgery [@b0005]. Injury to the LCX artery can jeopardize the myocardium and expose patients to a considerable risk of mortality. LCX artery injury can transform low risk single valve surgery into higher double open-heart surgeries or emergency need for percutaneous coronary intervention (PCI) after cardiac surgery [@b0010], [@b0015], [@b0020], [@b0025], [@b0030], [@b0035], [@b0040], [@b0045], [@b0050], [@b0055], [@b0060], [@b0065], [@b0070], [@b0075], [@b0080], [@b0085], [@b0090], [@b0095], [@b0100], [@b0105], [@b0110], [@b0115], [@b0120]. Sporadic cases of this complication have been reported in the literature [@b0010], [@b0015], [@b0020], [@b0025], [@b0030], [@b0035], [@b0040], [@b0045], [@b0050], [@b0055], [@b0060], [@b0065], [@b0070], [@b0075], [@b0080], [@b0085], [@b0090], [@b0095], [@b0100], [@b0105], [@b0110], [@b0115], [@b0120], [@b0125], [@b0130], [@b0135], [@b0140], [@b0145], [@b0150], [@b0155], [@b0160]. Anatomical studies on the LCX artery proposed the left-dominant coronary circulation to be a risk factor due to the shortest distance recorded between the LCX artery and MV [@b0130], [@b0165], [@b0170], [@b0175]. In this article, we describe our experience with this complication and compare it to the previously reported cases in the literature.

2. Materials and methods {#s0010}
========================

We retrospectively analyzed all patients who underwent MV surgery in King Faisal Specialist Hospital (Riyadh, Saudi Arabia) between January 2000 and December 2016. Patients with postoperative complicated course who required coronary angiography (CAG) were identified. CAG reports and angiographic views were reviewed to identify patients with LCX injury or LCX occlusion. Electronic medical records and medical charts were used to extract variables into predesigned data sheets.

The variables extracted included: demographic data, cause of MV surgery, left ventricle ejection fraction (LVEF) at the baseline, postoperatively, and at the 6-months follow-up, coronary dominance pattern, electrocardiography (ECG) findings, treatment method, time between ischemia identification and treatment, and mortality rate at 30-days, 6-months, and 1-year follow-up. The data were analyzed using descriptive statistics and compared with the previous case reports. Data were expressed as mean ± standard deviation for continuous variables and as frequencies and percentages for categorical variables. The study was approved by the ethical committee at our institution.

3. Results {#s0015}
==========

Out of 1706 patients who underwent MV surgery during the assigned period, 95 (5.6%) underwent CAG shortly post-MV surgery, for suspicion of postoperative myocardial injury. Out of 1706 patients reviewed, nine (0.5%) were found to have LCX artery injury. The complication was associated with MV replacement (0.7%, 9/1313) but not MV repair (0.0%, 0/393). With the exception of one patient, the injured patients were females (88.9%). The mean age of the patients was 40.4 ± 14.2 years, ranging between 9 years and 56 years. The youngest patient was a female child with congenital heart disease (Shone complex). The etiology of MV disease was rheumatic heart disease in eight patients (88.9%).

As shown in [Table 1](#t0005){ref-type="table"}, three patients (33.3%) underwent CAG prior to surgery as a routine procedure before open heart surgery for those who are at risk of coronary artery disease. The average preoperative LVEF was 48.8 ± 6.9%. The surgery done was redo MV replacement in four patients (44.4%) and primary MV replacement in the remaining patients. The time from LCX artery injury confirmation using CAG to revascularization either via PCI or bypass surgery varied between 2 hours and 72 hours. Postoperative CAG revealed evidence of total LCX artery occlusion in all patients. There was roughly similar distribution of left and right dominant coronary circulations (5 and 4 patients, respectively).Table 1Overview of patients reported with left circumflex artery injury during mitral valve surgery, KFSH, 2000--2016 (*n* = 9).Case No.SexAgePre-op CAGPre-op EFType of surgeryTime till reperfusion (h)ECGEchocardiography changesCoronary dominance Post-op CAGTreatment30-d mortality6-mo mortalityEF at 6 mo1F55Yes50MVR (Conform × valve 33/35)2.5NAAkinesia of inferiolateral wallRightCABGYesYes-2F44No55MVR (Mosaic \#29)\
TVR mosaic \#337Anterior ST depressionHypokinesia of lateral wallLeftCABGNoNo353F42No50MVR (ST Jude \#27) ring TV repair 3D \#322.5Inferior ST depressionHypokinesia of inferioposterio wallRightCABGYesYes-4F32No35MVR (Onyx 25/33)6Anterior ST depressionHyopkinesia of inferioposterior wallRightCABGNoNo255F9No55SAM resection and MVR (CM \# 23)72Inferior ST depressionHypokinesia of inferior wallLeftPCINoNo356M36No45Redo MVR (CM\#29)72Inferior ST elevationGlobal hypokinesiaLeftFailed CABG then PCIYesYes-7F49Yes55Redo MVR (ATS \# 27)\
TV repair Duran ring\#294Inferior ST elevationHypokinesia of inferioposterior wallRightCABGNoNo408F56Yes45Redo MVR (Apex \#31)8Anterior ST depressionGlobal hypokinesiaLeftPCINoNo459F41No55Redo MVR (CM\#29)\
TV repair MC3 ring2NAHypokinesia of inferiolateral wallLeftCABGNoNo35[^1]

As shown in [Table 1](#t0005){ref-type="table"}, [Table 2](#t0010){ref-type="table"}, the findings suggestive of myocardial ischemia due to LCX artery injury were documented on echocardiography as wall-motion abnormalities on echocardiography (100.0%), ST segment deviation (88.9%), electrical instability with ventricular tachycardia or ventricular fibrillation (66.7%). In three patients (33.3%), the complication manifested as cardiac arrest requiring resuscitation and in one patient (11.1%), extracorporeal membrane oxygenation (ECMO) was required. The injury was discovered intraoperatively in only one patient (11.1%), in whom transesophageal echocardiography showed hypokinesia of the lateral and inferior walls.Table 2Frequency of findings on patients with LCX artery injury post-MV surgery, KFSH, 2000--2016 (*n* = 9).Presentation findings suggestive of LCX artery injury post-MV surgery*N*%ECG changes with ST segment deviation888.9Electrical instability (ventricular fibrillation or ventricular tachycardia)666.7Regional wall motion abnormalities (postoperative echocardiography)9100.0Regional wall motion abnormalities (intraoperative transesophageal echocardiography)111.1Cardiac arrest333.3[^2]

For management, six patients (66.7%) had a second open-heart surgery performed to graft the vessel with saphenous vein graft and three patients (33.3%) had a PCI successfully restored antegrade blood flow to the occluded LCX artery ([Table 1](#t0005){ref-type="table"}). Patient 5, the youngest patient in our registry, underwent PCI at the age of 9 years. Patient 6 underwent PCI after a failed CABG, in which the LCX graft could not be placed due to extensive adhesions. Patient 8 successfully underwent PCI in which a drug-eluting stent was deployed into the LCX artery after multiple predilatation attempts with noncomplaint balloons ([Fig. 1](#f0005){ref-type="fig"}). The 30-day mortality was high (33.3%). Patients who survived the initial insult were alive at 6 months and 1 year later ([Table 1](#t0005){ref-type="table"}).Figure 1Successful percutaneous coronary stenting for patient with LCX injury post-MV surgery after multiple predilatation inflation attempts. LCX = left circumflex; MV = mitral valve. A; diagnostic angiogram, B; PTCA wire crossing the occlusion, C; angiogram post balloon dilation, D; angiogram post stent deployment.

4. Discussion {#s0020}
=============

We are reporting a total of nine patients with LCX injury post-MV surgery, the largest series up to date. Two cases were reported previously [@b0150], [@b0155]. LCX injury post-MV surgery is considered a rare complication, and only 42 cases reported in literature [@b0130]. Similarly, the overall incidence in this study was 0.5%.

The demography of our database is different from that of the cases reported in the literature, and this reflects the underlying etiology [@b0130]. Unlike Western countries, rheumatic etiology represents most valve diseases that require surgical treatment in Saudi Arabia [@b0180]. Of nine patients, eight were female, as rheumatic heart disease with mitral stenosis is more prevalent in females. The mean age of the patients was 40.4 ± 14.2 years, which is younger than the mean age reported in the literature and reflects a population with no ischemic heart disease risk factors [@b0130].

A major difference between our data and previously reported cases is the pattern of coronary dominance. Our patients showed roughly similar distribution of left and right dominant coronary circulations. This was generally inconsistent with the findings from anatomical studies and reported cases in the literature [@b0115], [@b0130], [@b0165], [@b0170], [@b0175]. In these cases, left-dominant circulation was more prevalent and tended to be a risk factor for LCX artery injury during MV surgery [@b0130]. The LCX artery curves in close proximity to posterior MV annulus and the distance was measured in several anatomical studies. Three of these studies confirmed a pattern of a short distance (average, 3.99 mm) between the LCX artery and the posterior mitral annulus in hearts with left-dominant coronary circulations [@b0115], [@b0170], [@b0175]. However, an anatomical study performed by Pessa et al. [@b0165] found this small distance can be recorded in right-dominant circulation negating the findings observed in other studies and supporting our results. Occlusion of nondominant LCX artery might not cause major hemodynamic compromise and it can be underreported in literature. This might account for the difference in the pattern of coronary dominance noted in our patients than the ones reported earlier.

Therefore, the performance of CAG to determine the pattern of coronary dominance prior to every MV surgery does not necessarily preclude the possibility of LCX artery injury. With advancements in cardiac imaging and improved spatial resolution of cardiac computed tomography (CT), the distance between the MV and the LCX artery can be accurately measured prior to surgery [@b0065], [@b0185]. However, this raises the question of whether cardiac CT prior to every MV surgery is cost effective given the low incidence of this complication. The mechanism of injury could be related to suture going around or through the artery, tissue retraction, artery laceration, or external compression from the valve implanted [@b0115].

If the prevention of this complication is not feasible, then early diagnosis is crucial. The main presenting feature of this complication was ST changes on routine postoperative ECG. However, a high index of suspicion is required to initiate further investigations and therapy since these patients can rapidly deteriorate. Three patients in this series rapidly progressed to cardiac arrest. In one patient, regional wall-motion abnormalities were observed on intraoperative transesophageal echocardiography. Ender et al. [@b0190] studied the patency of the LCX artery on transesophageal echocardiography during minimally invasive MV surgery. This is an interesting aspect as early changes might be noted during surgery, and therapy can be initiated during the same setting. The time from ischemia detection to therapy varied in our patients. In general, this time should be as short as possible to prevent myocardial damage. Therefore, performing the surgery in a hybrid room might be beneficial to reduce the reperfusion time and allow CAG to be done in the same setting.

In our study, the 30-day mortality was high (33.3%). Patients who survived the acute insult remained alive at 6 months and 1 year, however some of them developed reduced left-ventricular function on echocardiography ([Table 1](#t0005){ref-type="table"}). The average deterioration was 14.2%, ranging between 0% and 20%.

Our therapeutic approach was to try to establish the coronary flow to the injured LCX artery surgically or percutaneously as soon as possible. The decision which option to follow was according to interventionist and cardiac surgeon judgment. There is a lack of consensus about what is the best approach to treat this situation. The traditional concept is to shorten ischemia time to avoid mortality and morbidity. We propose the percutaneous approach as the first option to spare the patients from undergoing open-heart surgery for a second time, and it is faster to establish coronary blood flow. In our patients, PCI was associated with slightly lower deterioration of LVEF at 6 months (10.0%) compared with open-heart surgery (16.3%) but similar mortality (33.3% in both).

4.1. Limitations {#s0025}
----------------

The main limitation of our study is the small number of patients studied, which is related to the low incidence of this complication during MV surgery. This should be considered when interpreting our findings. Worldwide registries are needed to assemble all such cases and to find better strategies to predict and treat this complication.

5. Conclusion {#s0030}
=============

The LCX artery curves around the posterior mitral annulus, which makes it susceptible to injury during MV surgery. In our study, the overall incidence was very low (0.5%) with roughly similar distribution of left and right dominant coronary circulations. A high index of suspicion is required to diagnose this injury. ECG monitoring of ischemic changes and intraoperative transesophageal echocardiography to detect regional wall-motions abnormalities can allow for early detection and timely therapy.

5.1. Impact on daily practice {#s0035}
-----------------------------

Increasing awareness of the possibility of LCX artery injury during MV surgery is mandatory for the early detection and prompt treatment of this complication, which carries a high risk of mortality. Percutaneous therapy can provide early and successful restoration of blood flow.

Peer review under responsibility of King Saud University.

[^1]: CABG = coronary artery bypass grafting; CAG = coronary angiography; ECG = electrocardiography; EF = ejection fraction; F = female; KFSH = King Faisal Specialist Hospital; M = male; MVR = mitral valve replacement; PCI, percutaneous coronary intervention; TV = tricuspid valve; TVR, tricuspid valve replacement; SAM, Sub-Aortic membrane; ATS, bileaflet prosthetic valve developed by ATS Medical; Inc., CM, Carbomedics valve; MC, Edwards MC annuloplasty ring (Edwards LifeScience, Irvine, CA, USA); NA, not available.

[^2]: ECG = electrocardiography; KFSH = King Faisal Specialist Hospital; LCX = left circumflex artery; MV = mitral valve.
