Asian Cardiovasc Thorac Ann 2004;12:162-164
© 2004 Asia Publishing EXchange Ltd
Type B Dissection Complicated with Subacute Visceral Ischemia
Satoshi Yamashiro, MD,
Yukio Kuniyoshi, MD,
Kazufumi Miyagi, MD,
Toru Uezu, MD,
Katsuya Arakaki, MD,
Kageharu Koja, MD
Second Department of Surgery, School of Medicine, University of Ryukyus, Okinawa, Japan
For reprint information contact: Satoshi Yamashiro, MD Tel: 81 98 895 1168 Fax: 81 98 895 1422 Email: nigeka{at}med.u-ryukyu.ac.jp Second Department of Surgery, School of Medicine, Faculty of Medicine, University of Ryukyus, 207 Uehara, Nishihara, Okinawa 903-0215, Japan.
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ABSTRACT
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A 63-year old man presented with back pain and abdominal pain that worsened after eating. Contrast-enhanced computed tomography revealed type B aortic dissection. Arteriography 20 days after dissection revealed celiac trunk stenosis and the superior mesenteric artery did not arise from the true lumen. Saphenous vein bypass grafting from the right common iliac artery to the superior mesenteric and gastroduodenal arteries was performed. The postoperative course was uneventful and the abdominal symptoms completely disappeared.
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INTRODUCTION
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Although the results of surgical treatment for aortic dissection have improved because of advances in surgical techniques, the prognosis is still very poor, and the optimal therapeutic approach for dissection complicated by underperfusion has not been clearly established. Traditionally, graft revascularization of the affected aortic branch vessel or fenestration of the intimal flap have been the only alternatives.1,2 Despite the frequency of this problem, prioritization of treatment for ischemic complications in relation to management of the aortic dissection remains vague.3
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CASE REPORT
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A 63-year old man under medication for hypertension presented with chest pain radiating from the back to the epigastrium. Contrast-enhanced computed tomography revealed a type B dissecting aortic aneurysm that extended from the distal arch to the left renal artery and measured 40 mm in diameter at the thoracoabdominal aorta. The celiac trunk was dissected and the true lumen was compressed by a thrombosed false lumen, and the superior mesenteric artery (SMA) arose from the false lumen without thrombosis (Figure 1
). Intensive antihypertensive and negative inotropic medication was started and the pain disappeared. However, 7 days later, severe abdominal pain and fullness were experienced after eating. Contrast-enhanced computed tomography 8 days after dissection showed a partially thrombosed false channel and progression of the celiac trunk stenosis (Figure 2A). Arteriography at 20 days after dissection revealed celiac trunk stenosis (Figures 2B & 2C), and the SMA did not appear to arise from the true lumen; selective angiography showed its origin was in the false lumen (Figure 2D). Visceral ischemia due to low blood flow in the SMA and celiac artery was diagnosed. A laparotomy at 24 days after the onset of dissection showed that although there was abnormal flow in the SMA and gastroduodenal artery, there was no intestinal necrosis. Therefore, saphenous vein bypass grafting was performed from the right common iliac artery to the SMA and a celiac arterial branch (gastroduodenal artery) beyond the dissection (Figures 3A, 3B & 3C). The flow rate measured intraoperatively with an electromagnetic flowmeter (MFV-3200; Nihon Kohden, Tokyo, Japan) was 400 mL•min–1 in the SMA graft, and 420 mL•min–1 in the celiac artery graft. Moreover, flow rates and pressures in the target vessels were clearly increased: with the graft clamped, the SMA flow was 120 mL•min–1 which increased to 160 mL•min–1 when the graft was open; and celiac arterial flow increased from 130 to 380 mL•min–1 on opening the graft. With systemic blood pressure at 112/58 mmHg, the pressures in the SMA and celiac artery were 95/50 and 93/55 mmHg, respectively, with the grafts open, compared to 78/48 and 56/44 mmHg, respectively, with the grafts clamped. Arterial pulsation in the mesentery was seen to recover. The patient’s postoperative course was uneventful and the abdominal symptoms completely disappeared. Postoperative angiography revealed good perfusion of the vein grafts from the right common iliac artery (Figure 3D) to the SMA and gastroduodenal artery (Figures 3B & 3C). The patient remained well at follow-up 1 year later, but under careful observation given the possibility of expansion of the false lumen and stenosis or obstruction of the bypass grafts.
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Figure 1. Contrast-enhanced computed tomography showing a type B dissecting aneurysm that extended from the distal arch to the left renal artery, with a diameter of 40 mm in the thoracoabdominal aorta. The celiac trunk was dissected and compressed by the false lumen and the superior mesenteric artery arose from the false lumen without thrombosis (arrow).
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DISCUSSION
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Among patients with aortic dissection, those with peripheral vascular complications have the highest risk of death. The incidence of visceral ischemia and bowel infarction associated with aortic dissection has been reported to be between 3% and 5%.2 Although acute dissection leading to mesenteric ischemia or infarction is uncommon, the survival rate for patients with this complication is low, regardless of surgical or medical treatment.2 In patients with aortic dissection complicated by reduced blood flow in the SMA, Pinet and colleagues3 reported 23 deaths among 24 cases (96%). Of 59 patients with acute type B dissection treated in our institution, 5 (8.5%) had visceral ischemia, of whom 3 died despite both bowel resection and revascularization, due to multiorgan failure or descending aortic rupture. Only 2 patients who did not require bowel resection survived revascularization for visceral ischemia.
There are no definitive guidelines on blood pressure and flow rates to help the surgeon decide whether bowel resection should be performed in cases of visceral ischemic complications after revascularization of the affected aortic branch or fenestration. However, Beebe and colleagues4 reported that flow rates in the graft, measured at operation, often exceed 450 to 500 mL•min–1. In this case, graft flow rates at operation exceed 400 mL•min–1 and flow rates and pressure in the target vessels were clearly increased. Although it was unclear whether such flow rates were optimal for revascularization, we considered that bowel resection was unnecessary. The alleviation of intestinal ischemia and absence of intestinal necrosis at the time of operation were crucial factors in the survival of this patient. For patients treated for mesenteric ischemia, most institutions report hospital mortality of 5% to 7%, and 5-year survival rates of 50% to 71%.5,6 Although our patient remained well at follow-up 1 year later, careful observation is still needed because of potential dilatation of the aneurysm and stenosis or obstruction of bypass grafts. The severity and duration of visceral ischemia before intervention undoubtedly have an important impact on outcome and survival. This case demonstrates that prompt surgical relief of ischemia in major organs is important to save lives in cases of acute aortic dissection and ischemic complications.
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REFERENCES
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- Beebe HG, MacFarlane S, Raker EJ. Supraceliac aortomesenteric bypass for intestinal ischemia. J Vasc Surg
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- Johnston KW, Lindsay TF, Walker PM, Kalman PG. Mesenteric arterial bypass grafts: early and late results and suggested surgical approach for chronic and acute mesenteric ischemia. Surgery
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- Moawad J, McKinsey JF, Wyble CW, Bassiouny HS, Schwartz LB, Gewertz BL. Current results of surgical therapy for chronic mesenteric ischemia. Arch Surg
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