Intravascular Ultrasound Imaging and Percutaneous Intervention in a Patient with Post-Mitral Valve Replacement Circumflex Corona

Iatrogenic damage to coronary arteries is a previously described, but uncommon, complication of mitral valve surgery. The circumflex artery, due to its anatomical proximity to the mitral valve annulus, is at particular risk for surgical trauma when mitral valve surgery is performed. Although it is a classically described complication of this type of operation, there are few published reports of this potentially fatal complication in the surgical literature. Post mortem data from the early 1960s demonstrated that circumflex coronary artery occlusion was the cause of death in 3 of 178 mitral valve replacements.¹ Fatal circumflex artery damage was again described in 1982, when a patient demonstrated electrocardiographic evidence of myocardial infarction (MI) soon after mitral valve replacement.² Post mortem examination in these cases revealed an MI in anatomic proximity of an accidentally sutured circumflex coronary artery. Mitral valve repair/reconstruction has also been implicated in causing damage to the circumflex coronary artery.³ The proximity of the circumflex coronary artery to the mitral valve annulus is partly determined by coronary dominance.⁴ Cornu’s study of post mortem specimens with a left or balanced/co-dominant coronary artery distribution showed that the circumflex artery could be situated as little as 1 mm away from the mitral valve annulus. In certain locations along the path of the circumflex coronary artery, the vessel was actually in contact with the mitral valve apparatus.⁵ In this case report, we describe a patient who developed an acute anterolateral MI immediately following mitral valve replacement surgery. Emergent cardiac catheterization demonstrated subtotal occlusion of a large, dominant circumflex artery. The mechanism of the occlusion was elucidated by intravascular ultrasound (IVUS) imaging, and treatment of the lesion was successfully performed by percutaneous transluminal coronary angioplasty (PTCA) and stent implantation. Case Report. A 76-year-old man was admitted for elective mitral valve replacement because of severe mitral regurgitation (MR) secondary to a ruptured chordae tendinae. Pre-operative coronary angiography demonstrated no angiographically significant obstructive disease in a left dominant coronary circulation. Left ventriculography confirmed severe mitral regurgitation. One week subsequent to the catheterization, elective replacement of the valve was performed with a 33 mm St. Jude mechanical valve. Intra-operatively, the mitral valve annulus was noted to be extremely large, and the use of purse-string suturing was necessary to achieve adequate tissue apposition. Peri-operative transesophageal echocardiography demonstrated good left ventricular function with resolution of the MR, and the patient was weaned from cardiopulmonary bypass uneventfully. However, after returning to the intensive care unit, the patient developed ventricular ectopy and arterial hypotension. An emergent electrocardiogram demonstrated 3 mm ST elevation in the inferolateral leads and ST depression in the anterior precordial leads, suggesting the possibility of an acute inferoposterolateral MI (Figure 1). The patient was transferred emergently to the cardiac catheterization laboratory, where coronary angiography demonstrated subtotal occlusion of the large dominant mid circumflex artery (Figure 2). Based on this finding, we were concerned about the possibility of a suture mishap with compression of the circumflex artery. An IVUS study was performed to provide additional anatomic information prior to a final decision on the patient’s clinical management. The subtotal occlusion was crossed using a Choice PT wire and IVUS imaging was performed using a 2.5 French Atlantis SR 40 Mhz catheter. The lesion was found to be a tubular, rather than focal, narrowing of the circumflex artery, suggesting that the vessel lumen was compromised due to tissue traction as opposed to suture mishap. As can be seen in Figure 2, there was anatomic proximity of the mitral valve apparatus and the partial occlusion in the mid circumflex coronary artery. The tubular lesion had a luminal diameter of 1.4 mm in a vessel with a media-media diameter of almost 4.5 mm. After conferring with the surgeon regarding the therapeutic options of redo cardiac surgery with bypass grafting of the circumflex coronary artery, versus possible stenting of the target lesion, we decided to proceed with percutaneous intervention as the less invasive therapeutic approach. As the compliance of this lesion was unknown, we decided to initially test the target site with a low-pressure balloon inflation to determine whether subsequent stent implantation was feasible. A 4.0 x 20 mm Scimed Rx balloon catheter was advanced across the lesion and was inflated for 1 minute at a low pressure of 4 atmospheres (atm). Since there was full balloon expansion at this low pressure, we believed that this lesion was compliant and could be successfully treated with stent implantation. Post-PTCA IVUS imaging confirmed that there was significant improvement in the luminal diameter at the target site. Stent implantation was then performed, utilizing a 4.5 x 20 mm Scimed Express stent deployed at 10 atm for 40 seconds. Repeat balloon inflation with a noncompliant 4.5 x 15 mm NC Monorail catheter at 10 atm for 40 seconds achieved an excellent result, with 0% residual stenosis and TIMI grade 3 flow. Post-intervention IVUS imaging demonstrated an excellent luminal diameter and full stent apposition at the lesion site (Figure 3). Discussion. Although circumflex coronary artery occlusion is a classically described surgical complication of mitral valve surgery, it is an unusual sequela with few references in the surgical literature. Most published cases have been post mortem diagnoses following a fatal outcome. In this patient’s case, immediate diagnosis of this serious complication was established by electrocardiogram and angiography. The precise mechanism of the obstructive lesion in the circumflex artery was determined with IVUS imaging, which indicated a lesion morphology most consistent with tissue traction, as opposed to suture mishap. After considering the options of redo surgery with bypass grafting of the circumflex coronary artery versus percutaneous coronary intervention, cautiously performed balloon angioplasty at low inflation pressures demonstrated a compliant lesion at the area of subtotal occlusion, allowing for successful intracoronary stent implantation. The patient has been clinically asymptomatic for 7 months following surgery. This case is an example of how IVUS imaging, in concert with low-pressure balloon inflation, can provide useful information to clarify the mechanism of iatrogenic coronary artery occlusion post mitral valve replacement as well as guide treatment with stent implantation.