Asian Cardiovasc Thorac Ann 2004;12:78-80
© 2004 Asia Publishing EXchange Ltd
Bilateral Isolated Coronary Ostial Stenosis Following Mediastinal Irradiation
Anand Sachithanandan, AFRCSI,
Alsir Ahmed, FRCS,
Hugh O’Kane, FRCS
Division of Cardiac Surgery, Royal Victoria Hospital, Belfast, Northern Ireland, UK
For reprint information contact: Anand Sachithanandan, AFRCSI Tel: 44 2890 240 503 Fax: 44 2890 894 918 Email: anandsachithanandan{at}yahoo.com Cardiac Surgery Unit, Royal Victoria Hospital, Belfast, Northern Ireland, UK.
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ABSTRACT
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Isolated coronary ostial narrowing is rare and may represent a separate disease entity from atherosclerotic coronary artery disease. The case of a 41-year-old female with no coronary risk factors who developed severe bilateral isolated coronary ostial stenosis following mantle radiotherapy for Hodgkin’s disease is described. She underwent urgent coronary artery bypass grafting and has remained well for 3 years.
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INTRODUCTION
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Coronary ostial disease is uncommon with a reported incidence of 0.13%–0.8% in patients undergoing coronary angiography, and it is usually associated with atherosclerosis of the coronary arteries elsewhere.1,2 Isolated coronary ostial narrowing is rare, the incidence is 0.07%–0.09% in patients undergoing angiography, and it may represent a specific disease entity.2 The etiology and pathogenesis of isolated coronary ostial disease which has a higher incidence in females remains uncertain.1 It may represent a lesion of the aortic wall that encroaches on the orifice of the coronary arteries, and thus can be considered to be separate anatomically from distal coronary artery disease (CAD). Excluding primary atherosclerosis, conditions implicated in this lesion include congenital abnormalities, syphilitic and Takayasu’s aortitis, homozygous familial hypercholesterolemia, fibromuscular dysplasia, iatrogenic stenosis from cannulation trauma when administering antegrade cardioplegia or during coronary angiography, and mediastinal radiation.1
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CASE REPORT
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A 35-year-old female presented with a short history of lethargy and "flu-like" symptoms. Examination revealed cervical and axillary lymphadenopathy. Chest radiography showed right hilar lymphadenopathy, and a thoracic computed tomography scan revealed extensive mediastinal lymphadenopathy. Cervical lymph node biopsy identified Reed-Sternberg cells, confirming nodular sclerosing Hodgkin’s disease. Chemotherapy was commenced for stage IIA supradiaphragmatic Hodgkin’s disease but the patient had a poor response and failed to complete her final cycle due to a profound thrombocytopenia. She subsequently responded well to a course of mantle radiotherapy (3,525 cGy in 21 fractions and a subsequent boosting dose of 400 cGy in 2 fractions) and showed no evidence of recurrence. She remained well until 6 years later at the age of 41 when she presented with exertional angina. Exercise stress testing demonstrated anterior and inferior ischemia. Coronary angiography (Figure 1
) revealed severe bilateral coronary ostial stenosis with normal disease-free vessels distally. Preoperative angiography (Figure 2) was performed to visualize both internal mammary arteries (IMA). The patient underwent urgent coronary artery bypass grafting (CABG) one month later. Bilateral IMA were harvested; the right IMA was used to bypass the proximal right coronary artery, and the left IMA was used to bypass the mid section of the left anterior descending coronary artery. Interestingly, both native coronary vessels were soft walled and disease free. The early postoperative recovery was complicated by hemodynamic instability and the patient was taken back to the operating room for additional CABG as there was concern about inadequate IMA blood flow. Reversed saphenous vein grafts were anastomosed to the circumflex and right coronary artery distal to the right IMA anastomosis. The patient was weaned off cardiopulmonary bypass with the aid of intraaortic counterpulsation, and extubated on postoperative day 4. Thereafter, she made good progress and was discharged home on postoperative day 9. She remained asymptomatic on review 3 years later.
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Figure 1. Coronary angiograms illustrating bilateral severe isolated ostial disease: (A) right coronary ostial stenosis; (B) left coronary ostial stenosis.
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DISCUSSION
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Mediastinal irradiation is a common treatment modality for several malignant tumors including Hodgkin’s disease. Depending on the dose of radiation and field of exposure, secondary radiation-induced damage may occur to various structures. The heart is susceptible to radiation injury; pericardial disease, valvular dysfunction, restrictive cardiomyopathy, conduction abnormalities, myocardial fibrosis, and CAD may all follow chest irradiation.3 Coronary artery stenosis may be due to intimal proliferation and fibrosis from radiation-induced damage of the capillary endothelial wall. A peculiar feature of postradiation CAD is the high incidence of ostial or proximal lesions, presumably because these are in the radiation field, with relative sparing of the main arteries.4 Microscopically, radiation-induced lesions differ from atherosclerotic lesions; there is diffuse fibrosis of all wall layers, loss of smooth myocytes in the media, and few lipid deposits. However, irradiation and elevated cholesterol levels can act synergistically to enhance the tendency towards atherosclerosis. It has been suggested that irradiation damages the arterial endothelium which is then repaired by platelet aggregation and fibrin deposition, and subsequently by fibrosis and collagenization.3
Radiation-induced CAD must be considered in any patient undergoing mediastinal irradiation with a dose of 30 Gy or more.5 With more patients treated by radiotherapy now surviving their thoracic malignancies, an increasing young population may be susceptible to early onset CAD. Regular surveillance should be performed in such individuals to detect the insidious onset of CAD despite the absence of classic coronary risk factors. Improved techniques to reduce myocardial exposure to radiotherapy include cardiac shielding, hyperfractionation, altering the depth of fields, and utilizing CT scanning to deliver the calculated tumor dose more precisely.6 Treatment of radiation-induced CAD includes percutaneous transluminal coronary angioplasty and CABG. Angioplasty is often limited by technical considerations in patients with ostial lesions, and the possibility of associated mediastinal fibrosis would preclude emergency CABG in cases of failed angioplasty. Thus, elective CABG is the best option and it also facilitates more complete revascularization in these relatively young patients. Surgical ostial angioplasty is another option but the potential for progression of disease distally would favor a more definitive CABG procedure. The choice of conduit to revascularize the heart may be limited by radiation damage to the IMA. Preoperative angiography to assess the patency of the IMA is essential in planning the operative strategy, as in this case. Alternative investigations include transthoracic B-mode imaging and Doppler-derived blood flow measurements. We recognize that use of bilateral IMA could theoretically increase the risk of impaired sternal wound healing, especially following chest irradiation, however, in view of this patient’s age, we elected to use both IMA because of their superior long-term patency. Intraoperatively, both conduits exhibited good flow, and on angiography, appeared to be unaffected by the previous radiotherapy. Little is known about the effect of radiation on the vascular reactivity of IMA but this might explain the volatile early postoperative course in our patient. It could be argued that a single graft would suffice for an isolated left ostial lesion, but we consider that placing two grafts at the left side of the heart is warranted when it is technically feasible to bypass the circumflex system, thereby minimizing any potential problem due to inadequate IMA blood flow in the perioperative period.
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REFERENCES
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- Barner HB, Naunheim KS, Kanter KR, Fiore AC, McBride LR, Pennington DG, et al. Coronary ostial stenosis. Eur J Cardio-thorac Surg
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- Applefield MM, Wiernik PH. Cardiac disease after radiation therapy for Hodgkin’s disease: analysis of 48 patients. Am J Cardiol
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- Withers HR. Biological basis of radiation therapy for cancer. Lancet
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ABSTRACT
INTRODUCTION
