Left Main Coronary Artery Stenosis following Surgical Valve Replacement: Changing Valvular into Ischemic Heart Disease

ABSTRACT: Left main stem coronary artery (LMSCA) stenosis after surgical aortic valve replacement (AVR) is a rare but potentially lethal complication. Among the different possible causes, antegrade cardioplegia for direct coronary perfusion seems to be the most significant and prevalent. Here we discuss two cases of late presentation of iatrogenic coronary ostial stenosis following valve replacement surgery. Both cases were successfully treated with percutaneous intervention and stent implantation. Left main stem coronary artery (LMSCA) stenosis after surgical valve replacement is a rare but severe complication, with ominous consequences that may require early intervention. We report on two cases of severe LMSCA stenosis that occurred several months after surgical valve replacement, both confirmed by means of coronary angiography and treated with percutaneous coronary intervention (PCI) and stent implantation. Case Reports Case 1. A 58-year-old male with hypertension, type II diabetes mellitus and hypercholesterolemia as cardiovascular risk factors was affected by symptomatic severe aortic stenosis and referred to our hospital for aortic valve replacement. His preoperative electrocardiogram (ECG) showed sinus rhythm and left ventricular hypertrophy. An echocardiogram confirmed the severity of the stenosis (mean aortic gradient of 48 mmHg and a maximum gradient of 68 mmHg) with a moderate grade III regurgitation); his left ventricular function was normal. Coronary artery angiography showed no significant coronary artery lesions (Figure 1A). Surgical intervention consisted of aortic valve replacement with a mechanical Omnicarbon nº 21 prosthesis. To perform the intervention, antegrade cardioplegia was used, with direct cannulation of the coronary ostia (cardiopulmonary bypass time, 79 minutes; aortic clamp time, 57 minutes). The postoperative period evolved without complications, and the patient was discharged 8 days after surgery on medical treatment with ACE-inhibitors, statins, oral anticolagulation (INR 2.89) and oral hypoglycemic agents. Three months after the intervention, the patient began experiencing progressive angina pectoris with episodes of chest pain at rest. The physical examination showed a systolic aortic murmur with an audible click, and no signs of heart failure were detected. The ECG did not show any change, and the enzymatic curve was negative. An echocardiogram confirmed the correct function of the aortic prosthesis. Coronary angiography was performed (Figure 1B) and showed severe stenosis of the LMSCA. In the same setting, PCI was performed, with implantation of a drug-eluting stent (Figure 1C), and no complications. The patient was discharged on medical therapy with aspirin 100 mg, clopidogrel 75 mg and oral anticoagulation with acenocumarol. Case 2. A 73-year-old female without cardiovascular risk factors was affected by severe mitral and aortic stenosis and was referred to our center for surgical valve replacement. The preoperative ECG showed sinus rhythm and negative T-waves in the inferior leads. The echocardiogram confirmed the severe aortic stenosis with a maximal gradient of 69 mmHg and a mean gradient of 50 mmHg; severe mitral stenosis was confirmed as well, with a mean gradient of 12 mmHg. The patient’s ventricular function was normal. Coronary angiography did not detect any significant coronary artery lesions (Figure 2A). The surgical intervention consisted of aortic and mitral valve replacement with Omnicarbon nº 19 and Omnicarbon no. 25 prostheses, respectively. Antegrade cardioplegia was used, with direct cannulation of the coronary ostia (CPB time, 140 minutes; clamp time, 101 minutes). The postoperative period evolved without complications and the patient was discharged 6 days after the intervention on treatment with furosemide and oral anticoagulation. Forty-five days after surgery, the patient returned to our center with resting chest pain and ECG changes in the anterior leads (ST-segment depression). The echocardiogram showed the correct function and position of both prostheses. The coronary angiography (Figure 2B) showed a severe stenosis of the LMSCA and no significant lesion of the right coronary ostium. A drug-eluting stent was implanted during the same procedure (Figure 2C ). The patient was discharged on therapy with aspirin 100 mg, clopidogrel 75 mg daily and acenocumarol. Discussion. We reported two cases of late presentation of iatrogenic coronary ostial stenosis following valve replacement surgery. Both cases were treated with percutaneous intervention and stent implantation. Iatrogenic coronary ostial stenosis following aortic valve replacement (AVR) is a rare but potentially lethal complication. Stenosis of the LMSCA and ostium of the right coronary artery after AVR was first described by Roberts and Morrow in 1967, and the incidence of this complication has been estimated to be between 1% and 5% in different series.1–6 This complication may occur in both proximal coronary arteries with predominance of the LMSCA.1 A pathological feature is the intimal fibrous thickening in the aortic root and proximal coronary artery1 along with mucinous degeneration and hyaline degeneration,7 but no evidence of atherosclerosis. Cardioplegia is the most common procedure for accomplishing asystole and myocardial preservation during cardiac surgery. It consists of infusing an iced (4º C) solution of dextrose, potassium chloride and other ingredients into the coronary circulation via specialized cannulae. When the solution is introduced into the aortic root, it is called antegrade cardioplegia; when introduced into the coronary sinus, it is called retrograde cardioplegia. When the aortic valve is severely pathological and aortic valve replacement is needed, then cardioplegia is administered with direct coronary artery cannulation. Retrograde cardioplegia is preferred, especially when coronary artery disease is known or suspected, to ensure total myocardial perfusion. However, the latter method alone may not be effective in the entire myocardium due to the coronary sinus anatomy. Therefore, the best route for cardioplegia administration to achieve cardioprotection during valve surgery is still under debate.8,9 Of note, aortic valve prosthesis and the consequent turbulent flow are considered causes of aortic root and coronary ostial fibrosis, which may lead to coronary ostial stenosis.10,11 Furthermore, as reported by Wikelman,12 a genetic predisposition may exist, as 70% of the population with severe LMSCA ostial stenosis presented with the genotype apolipoprotein E (allel ε4), compared with the 10–15% in the control group. The ε4 allel might predispose patients to a pathologically increased response of proliferative repair mechanisms after arterial injury. Among the aforementioned causes, antegrade cardioplegia for direct coronary perfusion seems to be the most significant and prevalent. Two different presentation patterns exist: early presentation in the immediate postoperative period, and late presentation, at 3–6 months after surgery, when the most common clinical feature is progressive exertional angina. In a recent report on an acute LMSCA dissection,13 selective antegrade cardioplegic perfusion was administered to a patient who underwent surgery for severe aortic valve stenosis. The dissection induced by the cardioplegia catheter caused myocardial infarction and the patient ultimately died due to heart failure.13 Funada and colleagues14 described three cases of late presentation of iatrogenic coronary artery lesions after AVR. Two cases were detected by multidetector computed tomography (MDCT) before angiography. MDCT and virtual histology suggested fibrous tissue formation in the lesions, suggesting that they may be distinct from conventional atherosclerosis. All three patients successfully underwent PCI and stenting. Several clinical implications must be considered. Which is the best treatment in this clinical situation? Currently, PCI is not routinely recommended for treating unprotected LMS disease, although it can be used in carefully selected patients in the absence of other options.15 In such carefully selected cases, coronary stenting of unprotected LMSCA stenosis is a safe and effective alternative to bypass surgery. Further clinical studies are needed. In our two cases, PCI was successfully performed, as was the case by Funada and coworkers; while in other previously reported cases, when the operators were less experienced, coronary artery bypass grafting was chosen.16,17 Patients with a mechanical valve prosthesis receive chronic oral anticoagulation therapy. A drug-eluting stent would be the best option when considering the fibrotic reaction as a physiopathological mechanism in the development of a late-presenting coronary ostial iatrogenic lesion. However, the optimal antiplatelet treatment for patients on long-term oral anticoagulation undergoing PCI with stenting is currently undefined.18 This must be taken into account when considering drug-eluting stent implantation. Conclusion. Although these cases are indeed rare, given the thousands of valve replacement procedures performed every year, the physician should be aware of this potential complication in patients who experience chest pain several months after valve surgery.

Author Affiliations: From the Interventional Cardiology Unit, Department of Cardiology, Sant Pau University Hospital, Barcelona, Spain. The authors report no conflicts of interest regarding the content herein. Manuscript submitted July 11, 2008, provisional acceptance given July 31, 2008, and final version accepted August 5, 2008. Address for correspondence: Manel Sabaté MD, PhD, Interventional Cardiology Unit, Department of Cardiology, Sant Pau University Hospital, Barcelona, Spain. E-mail: msabatet@santpau.cat

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J INVASIVE CARDIOL 2009;21:e9–e11

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