Middle Aortic Syndrome - NCBI

Middle

Aortic Syndrome

Effectiveness and Durability of Complex Arterial Revascularization Techniques

LOUIS M. MESSINA, M.D. LINDA M. REILLY, M.D.

JERRY GOLDSTONE, M.D. WILLIAM K. EHRENFELD, M.D.

Middle aortic syndrome typically occurs as severe hypertension in young patients who have weak or absent femoral pulses and an abdominal bruit. It results from a diffuse narrowing of the distal thoracic and abdominal aorta, commonly involving the visceral and renal arteries. The clinical presentation, angiographic assessment, and surgical outcome of 10 patients (mean age: 19.5 years) who underwent one-stage revascularization for middle aortic syndrome were reviewed to determine the effectiveness and durability of one-stage revascularization techniques to relieve these complications. All patients were hypertensive (mean blood pressure: 176 mmHg); six (60%) had severe, poorly controlled hypertension, two of whom had previous failed operations for renovascular hypertension and one who presented with malignant hypertension and acute renal failure. Five patients had disabling myocardial insufficiency, only one of whom had documented coronary artery disease. Four patients had intermittent claudication. Aortography showed variable length high-grade midaortic stenosis, nine had visceral artery involvement, and eight had renal artery involvement. All patients underwent one-stage revascularization by a variety of autogenous and prosthetic techniques. The postoperative recovery was uncomplicated in eight of nine patients and was often associated with dramatic reduction in blood pressure. There was a single death from disruption of the thoracic anastomosis in a patient who had diffuse cystic medial necrosis of the aorta. Arterial biopsy in nine patients indicated evidence for both acquired and congenital origins of the midaortic stenosis. Late follow-up evaluation (mean: 4.1 years) showed normal growth and development, preservation of renal function, and relief of myocardial insufficiency in all patients. Seven patients (77%) are cured of their hypertension, and two (23%) have only mild hypertension. These results indicate that one-stage revascularization of patients with middle aortic syndrome can result in effective and durable relief of these severe life-threatening complications.

W

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'IDDLE AORTIC SYNDROME results from a diffuse narrowing of the distal thoracic or abdominal aorta commonly involving both the visceral

Presented at the 106th Annual Meeting of the American Surgical Association, Hot Springs, Virginia, April 24-26, 1986. Supported in part by the Pacific Vascular Research Foundation, San Francisco, California. Reprint requests: Ronald J. Stoney, M.D., Department of Surgery, Moffitt 488, University of California, San Francisco, CA 94143. Submitted for publication: May 13, 1986.

331

LINDA D. FERRELL, M.D. RONALD J. STONEY, M.D. From the Department of Surgery, University of California, San Francisco.

and renal arteries. This rare syndrome of unknown etiology typically occurs in young patients, usually in the second decade of life who are found to have severe hypertension, absent femoral pulses, and an abdominal bruit. Although the natural history of middle aortic syndrome is not known, the course of symptomatic patients treated medically has been documented in several series. Senning and Johansson' reported the fate of 32 patients, ten of whom died mostly from cerebral hemorrhage before age 34. In a large review of 89 patients, Onat and Zeren2 reported a mean age at death of 34 years in symptomatic patients. Forty-two of these patients developed hypertensive encephalopathy, most patients dying of congestive heart failure and stroke. This condition has many other synonyms, which include subisthmic coarctation, atypical coarctation, and abdominal coarctation. We chose to avoid the term coarctation, which connotes a vascular abnormality of congenital origin, in a specific location, and a characteristic presentation very early in life. In contrast, middle aortic syndrome describes a condition that almost certainly has multiple etiologies, is variable in its location and extent, and has a diverse clinical presentation. Although the incidence of this syndrome is quite rare, our experience and that of others3 suggests that it has been treated with greater frequency during the past 15 years. There are very few reports that document the results of modem surgical techniques in the treatment of this syndrome.31 In addition, since bypass techniques have been used almost exclusively, there has been very little histopathology available on which to determine concretely the etiology of this syndrome. We have now operated on ten of these patients, the first 13 years ago and, in addition, have histopathology available for examination in nine of these ten patients. The purpose of this report is to review

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Ann. Surg. * September 1986

tained in eight of the ten patients often within the first year after operation.

FIG. 1. Typical angiographic appearance of middle aortic syndrome. Tight midaortic stenosis, high-grade renal artery stenoses, and superior mesenteric artery (top arrow) and celiac artery occlusion (bottom arrow).

the clinical presentation and angiographic assessment, surgical outcome, and histopathology of these ten patients in order to determine the effectiveness and durability of our operative techniques to relieve the life-threatening complications of middle aortic syndrome.

Patients and Materials

The records of all patients who underwent revascularization procedures for middle aortic syndrome at Moffitt Hospital, University of California Medical Center, San Francisco, were reviewed. Pertinent preoperative data obtained from the records included presenting symptoms and signs, electrocardiograms, chest radiographs, blood urea nitrogen and creatinine levels, and results of angiography. The surgical record and postoperative course in these patients were reviewed to determine the nature of the operation performed, its attendant complications, and the early outcome. All biopsy materials were reviewed by an experienced vascular pathologist. Follow-up was obtained in all patients. This included examination by the operative surgeon as well as by the referring physician. Postoperative angiograms were ob-

Results Ten patients, eight females and two males, with a mean age of 19.5 years (range: 8-34 years), underwent one-stage revascularization for middle aortic syndrome. One patient who had neurofibromatosis and mental retardation was the only patient known to have a congenital abnormality. Upon clinical presentation, all patients were found to be hypertensive, with a mean blood pressure of 176 mmHg (range: 140-260 mmHg), despite aggressive medical treatment. Six patients (60%) had severe, poorly controlled hypertension, including two who had previous failed operations for hypertension and one who presented with malignant hypertension and acute renal failure. Five patients had evidence of myocardial insufficiency characterized by exertional angina and shortness of breath in three, recurrent pulmonary edema in one, and dyspnea on exertion in another. Only one of these patients had documented coronary artery disease. The preoperative chest radiograph and electrocardiograms further documented the severity of the hypertension in these patients. Six of the nine patients in whom electrocardiograms were available for review showed left ventricular hypertrophy. In addition to the findings of hypertrophy, three had evidence of ischemia: one patient had an old inferior and anterior myocardial infarction, another had inferior ischemia, and the third had nonspecific ST segment and T wave changes. Two of the nine preoperative chest radiographs showed cardiomegaly. Only one patient had impaired renal function before operation. She presented with malignant hypertension, acute anuric renal failure, and obtundation. She had a prior history of stroke at age 16. Four of the ten patients had lower limb claudication. Preoperative angiography showed a variable length, high-grade midaortic stenosis usually extending from just above the celiac artery to just below the renal artery in all patients (Fig. 1). In eight patients there were renal artery stenoses, which were bilateral in seven. These stenoses were usually confined to the orifice. Three patients had multiple renal arteries. The visceral arteries were abnormal in nine patients. Typically, there was either a high-grade stenosis with postenotic dilatation or an occlusion. All the patients who had visceral artery involvement had a characteristic huge meandering artery (Fig. 1). Two patients had small branch renal artery aneurysms. One patient had a left-sided vena cava. All patients underwent a one-stage revascularization by a left thorocoabdominal, retroperitoneal approach in eight, a median sternotomy and transabdominal midline approach in one, and a transabdominal midline approach alone in another. The aortic obstruction was relieved by patch enlargement in one patient, by thorocoabdominal

MIDDLE AORTIC SYNDROME

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TABLE 1. Revascularization Techniques for Middle Aortic Syndrome Reconstruction Age

Aorta

Autograft Origin

Renal

8

DacronO patch aortoplasty Thoracoabdominal bypass graft

Right common, internal, external iliac arteries Right external iliac artery

Retrograde aortic bilateral renal bypass Left renal artery reimplantation into bypass graft Hepato-right renal bypass via arterial autograft Antegrade aortic bilateral renal artery bypass

16

11

34 26 17

28 17

15

24

Thoracoabdominal bypass graft Thoracoabdominal bypass graft Thoracoabdominal bypass graft Infra SMA aortic replacement graft

Aortoiliac bifurcation

Antegrade aortic bilateral renal bypass Resection L renal aneurysm Aortic graft-left renal artery bypass

Ascending aortic to infrarenal aortic Dacron bypass graft Thoracoabdominal bypass graft Thoracoabdominal bypass graft

Reimplantation right renal artery Aortic bilateral renal artery Dacron bypass grafts Transaortic bilateral renal endarterectomy

Aortic endarterectomy

Visceral

Aortoceliac artery

interposition graft

Aortic graftSMA bypass

Aortic bifurcation graft to celiac and SMA Transaortic visceral endarterectomy

SMA = superior mesenteric artery.

bypass in eight, and by endarterectomy in one (Table 1). All patients underwent complete renal revascularization. This was accomplished by a combination of autogenous and prosthetic techniques depending on the age and growth potential of the patient as well as the size of the renal arteries (Table 1). The aortoiliac segment or a part of it were used for the autogenous renal grafts, and the resulting deficit in vascular continuity was replaced with a prosthetic bypass graft.7'8 Visceral artery revascularization was achieved by bypass grafting in three and endarterectomy in one. One patient died from the sequellae of a suture line disruption of her thoracic anastomosis in the recovery room. Although she was resuscitated and successfully repaired, she suffered irreversible cerebral ischemia. The postmortem showed diffuse aortic cystic medial necrosis. The postoperative recovery was uncomplicated in the remaining nine patients and was often associated with dramatic reduction in blood pressure. Nine patients underwent biopsy of an involved vessel. Aortic biopsy was performed in seven patients, and an additional renal biopsy was available in six of these seven patients. The other two patients had biopsies of various branches of the aorta. Aortic biopsy revealed chronic inflammatory aortitis in two patients (Fig. 2). One patient

had severe transmural atherosclerosis with calcification and fibrosis; biopsy of the renal and celiac artery in the same patient showed myointimal fibrosis and medial calcification. The microscopic findings in this patient suggested "burned-out" inflammation. Two had evidence of advanced atherosclerosis. Both of these patients were young women ofAsian descent. One had features of Takayasu's syndrome, i.e., involvement of multiple branches of the aortic arch. Cystic medial necrosis was identified only in the one patient who died. One patient had an unusual "medial degeneration" and areas of intimal atherosclerosis. Two patients had myointimal hyperplasia in aortic branches, although neither had an aortic biopsy. Late follow-up (mean: 4.1 years, range: 6 months-13 years) was available in all nine survivors. Seven were cured of their hypertension, and two had only mild hypertension. Remarkably, no patient had symptoms of myocardial insufficiency. The patient with documented coronary artery disease had unstable angina and underwent successful aortocoronary bypass grafting before correction of her middle aortic syndrome. All patients have normal renal function. Growth and development in the very young patients has proceeded normally. One patient has had an uneventful pregnancy and delivered a normal term

infant.

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FIGS. 2A and B. A, left. Aortic biopsy showing adventitial fibrosis (top), intimal thickening (bottom), and focal

chronic inflammation. Arrow shows internal elastic membranes separating media and intima. B, right. Higher power of adventitia, showing inflammatory cell infiltrate, increased vascularity.

Follow-up angiography was available in seven patients. All grafts were patent and without significant stenosis except for the following findings. One patient has stable aneurysmal changes in the arterial autograft used for aortorenal bypass 13 years ago. A second patient had an early occlusion of a small lower pole renal artery graft. Lastly, one patient underwent arteriography for persistent hypertension. He had originally undergone bilaterial renal artery saphenous vein grafts at another hospital at 7 years

of age. More recently, because ofintractable hypertension and a follow-up angiogram that showed an occluded right aortoiliac graft and aneurysmal degeneration of the left graft, we performed an arterial autograft between the common hepatic and right renal artery as well as reimplantation of the left renal artery into a thorocoabdominal bypass graft. He developed hypertension approximately 7 months after this procedure, and an arteriogram revealed an unsuspected celiac artery stenosis arising from his

FIGS.

3A and B. Postoper-

ative

angiogram showing proximal (A, left) and distal (B, right) anastomosis of thorcoabdominal

bypass.


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midaortic disease. Since the hepatorenal reconstruction depended on normal antegrade perfusion, aortoceliac artery Dacron® bypass was performed (Fig. 3). He is now normotensive 10 years later on no medication. Discussion

Middle aortic syndrome is a rare clinical entity that may result in life-threatening complications secondary to severe hypertension. There are few published reports that document the results of modem surgical treatment. Our results in a series of ten patients indicate that one-stage revascularization by combination of prosthetic and autogenous techniques can relieve the severe hypertension and its attendant complications found in these patients. The surgical management ofpatients with middle aortic syndrome requires a unique approach in each individual patient. We believe that all patients who have symptomatic renovascular hypertension should undergo operative correction. The timing of surgery depends on the severity of the hypertension and the age of the patient. Although it is preferable to postpone surgery until the patient has reached his full growth potential, the presence of severe intractable hypertension requires immediate surgery independent of the age of the patient to avoid the complications of stroke and heart failure and their sequellae. Careful preoperative angiography is essential for planning a successful operative strategy. This includes multiple oblique views of the renal arteries and a lateral aortogram to determine the status of the remainder of the visceral vessels. The renal artery stenoses are often short ostial lesions that are signalled by the presence of a dilated distal artery. The incidence of visceral artery involvement in our patients (9 of 10 patients) is much higher than that in most other reports. We believe that this higher incidence is not due to patient selection but rather the routine use of lateral aortography. Determination of visceral artery involvement is important if alternative means of renal artery vascularization are to be considered. We believe that one-stage revascularization is the procedure of choice for most patients. Because these patients have severe hypertension, the most important goal of the operation is the restoration of renal blood blow to relieve the hypertension.5 The surgical approach depends largely on the presence of direct renal artery or visceral artery involvement. Thus, patients who have either renovascular hypertension and/or lower limb claudication on the basis of a tight midaortic stenosis without branch involvement can have effective relief by simple thoracic aortic to abdominal aortic bypass (Fig. 4) or patch aortoplasty. Patients who have involvement of the major aortic branches require more complex repairs. Relief of the aortic constriction by either patch aortoplasty or bypass are complementary options. Patch aortoplasty is a techinque applicable to the very young patient

FIG. 4. Postoperative angiogram showing thoracoabdominal bypass and reimplantation of left renal artery into the graft. Right renal artery revascularized by an arterial autograft between the common hepatic artery and right renal artery. Celiac stenosis was relieved by a Dacrons inter-

position graft.

who requires revascularization for severe hypertension, which leaves the possibility of thoracoabdominal aortic bypass at an older age after the patient is physically mature. An important consideration in the performance of an aortic bypass is the site of the proximal anastomosis. The single death in our series occurred in a young woman who underwent a proximal anastomosis to a descending thoracic aorta that was later found to have diffuse cystic medial necrosis. She suffered suture line disruption in the immediate postoperative period. This consideration prompted us to choose the ascending aorta as the site of proximal anastomosis in a later patient in whom we suspected an abnormal descending thoracic aorta (Fig. 5). The options for renal artery reconstruction are multiple and include autogenous arterial or venous grafts, prosthetic grafts, patch angioplasty, and autotransplantation. Our approach has been to reserve arterial autografts in the renal position for the very young patient who has small vessels and has not reached his full growth potential. Prosthetic grafts are employed in the older patient who has reached physical maturity, as the larger vessels with post stenotic dilatation are easily reconstructed by an antegrade graft. The indications for visceral artery revascularization are less well defined. Although chronic abdominal pain thought to be secondary to chronic visceral ischemia was

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only one of whom had documented coronary artery disease, have had complete relief of these symptoms. Except for the patient who had documented coronary artery disease, we believe the remainder of the patients had myocardial insufficiency on the basis of severe hypertension

FIG. 5. Illustration of the revascularization of a patient who was suspected to have had a diffusely diseased descending thoracic aorta before operation. Graft is brought from the ascending aorta through the diaphragm posteriorly, tunneled beneath the pancreas, and attached distally to the infrarenal aorta. The superior mesenteric and left renal arteries are re-

vascularized by Dacron4 interposition grafts.

apparently common when the syndrome was first described,9 it was not seen in our patients. Four patients underwent visceral artery revascularization (Table 1). As previously described, one was required to relieve a celiac artery stenosis in a patient who underwent hepatorenal bypass. Another was performed because the bowel appeared ischemic at the completion of the operation. Two were performed prophylactically. The effectiveness of the relief of the hypertension achieved by these operations was evidenced by cure of the hypertension in seven patients and significant improvement in the remaining two. Four patients who had evidence of myocardial insufficiency before operation,

and increased afterload. The patient who presented in acute oliguric renal failure had return of normal renal function following thoracoabdominal aortic bypass. In spite ofthe very high prevalence of renal artery disease and renovascular hypertension in patients with middle aortic syndrome, to our knowledge this is the first report of a patient with documented acute renal insufficiency. The follow-up of these patients (mean: 4.1 years) indicates that the results were durable. Seven of the nine survivors remained cured of their hypertension, and the remaining two continued to have only mild hypertension. Renal function has remained normal in all patients. The only significant problem detected on postoperative angiography was an unsuspected celiac artery stenosis in a patient who became hypertensive after hepatorenal bypass. This illustrates two important points in the management of these patients. First, careful lateral aortography should be performed before either a hepatorenal or splenorenal bypass is undertaken. Second, revascularization of patients with middle aortic syndrome results in very effective relief of their hypertension, and all patients who develop postoperative hypertension should undergo immediate repeat angiography. The etiology of middle aortic syndrome has been the subject of considerable controversy, most authors attempting to develop a single hypothesis to explain all of the reported cases. The controversy centers around whether this syndrome is a congenital or an acquired condition. An early report by Maycock'0 suggested that middle aortic syndrome was a congenital lesion that resulted from failure of fusion of the paired dorsal aortae during the fourth week of gestation. This hypothesis was further supported by the clinical observation by Graham et al.,3 who noted a very high incidence of multiple renal arteries. The paired dorsal aortae fused at approximately the same time that the multiple renal branches to the metanephros recede, leaving only a single renal artery. In addition to this evidence, support for the congenital hypothesis comes from the known association of middle aortic syndrome with a number of congenital syndromes,"l-'4 including neurofibromatosis, rubella, infantile hypercalcemia, and tuberous sclerosis. Support for the acquired hypothesis'5 '6 comes largely, although not exclusively,6"17-'9 from reports from India and Asia. It holds that middle aortic syndrome is secondary to a localized aortitis resulting in segmental stenosis ofthe aorta that is often complicated by atherosclerosis. 17 Sen et al.9 reported a clinicopathologic study of 16 patients with middle aortic syndrome. Many of them also had tuberculosis, and evidence for aortitis was found in each

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patient. Daimon and Kitamura"6 report the findings of nonspecific aortitis in 14 of26 patients with middle aortic syndrome. These authors believe that middle aortic syndrome represents a variant of Takayasu's aortitis. In fact, Lande'7 reports that re-evaluation of the pathology of the original case reported by Maycock shows unequivocal evidence of aortitis. Our review of the histopathology obtained in nine of the ten patients indicates that middle aortic syndrome results from a number of distinct etiologies of both congenital and acquired origin. Two patients had evidence of chronic inflammatory aortitis, and one had findings of atherosclerosis and a "burned out" aortitis. Three patients had evidence of atherosclerosis, which could represent a generalized response to arterial wall injury of either an acquired or congenital cause. Another patient was found to have extensive cystic medial necrosis. Although typically one notes aneurysmal changes with this disease, this is not the first report of the association of cystic medial necrosis and middle aortic syndrome."9 Finally, one patient had a picture of peculiar medial degeneration. The extended outlook for these patients is uncertain. Our follow-up results at a mean of 4.1 years following single stage complex revascularization techniques for patients with middle aortic syndrome have resulted in effective relief of their hypertension and offer an excellent prospect for a cure of this life-threatening lesion. The durability of these prosthetic aortic bypasses and autogenous or prosthetic aortic branch reconstructions will be the ultimate determinant oftheir quality and length oflife. The high flow in the vascular beds reconstructed in these patients should favor prolonged patency, allowing these patients the opportunity for a full, healthy life. Acknowledgment We thank Richard Aleguas for preparation of the manuscript.

DISCUSSION

DR. MICHAEL E. DEBAKEY (Houston, Texas): I would like to commend Dr. Messina and his associates on bringing this matter to our attention, but I do have some concern about the use of the term "middle aortic syndrome," largely because when I first saw it on the program and before I read the abstract, I was not sure what it meant. The significance of that statement lies in the fact that the term will be recorded in the medical archives, particularly in the indexing sources, and it will be difficult to retrieve the references to this syndrome by those who wish to review previous reports on this condition. In the past, traditionally, this syndrome has been referred to as coarctation, and in the medical journals you will find references to subischemic coarctation or coarctation of the abdominal aorta, which is the term we used in our first publication and our first presentation in 1959. At that time, we had 21 cases, and in a review of previous publications, we pointed out that much of the earlier direct attack on this condition was concerned with resection and homograft replacement. I think Glenn performed the first bypass in 1952, using the splenic artery. That, of course, did not completely resolve the problem, but it did improve circulation to the abdominal aorta. Following those who had preceded us with this problem, in our initial experience with our first patient in 1953, we also performed resection

337 References

1. Senning A, Johansson L. Coarctation of the abdominal aorta. J Thorac Cardiovasc Surg 1960; 40:517-523. 2. Onat T, Zeren E. Coarctation of the abdominal aorta: review of 91 cases. Cardiologia 1969; 54:140-157. 3. Graham LM, Zelenock GB, Erlandson EE, et al. Abdominal aortic coarctation and segmental hypoplasia. Surgery 1979; 86:519-529. 4. Hallett JW, Brewster DC, Darling RC, O'Gara PT. Coarctation of the abdominal aorta: current options in surgical management. Ann Surg 1980; 191:430-437. 5. Scott WH, Dean RH, Boerth R, et al. Coarctation ofthe abdominal aorta: pathophysiologic and therapeutic considerations. Ann Surg 1979; 189:746-757. 6. DeBakey ME, Garrett HE, Howell JF, Morris GC. Coarctation of the abdominal aorta with renal arterial stenosis. Ann Surg 1967; 5:830-843. 7. Stoney RJ, De Luccia N, Ehrenfeld WK, Wylie EJ. Aortorenal arterial autografts. Arch Surg 1981; 116:1416-1422. 8. Wylie EJ, Stoney RJ, Ehrenfeld WK, Effeney DJ. Manual of Vascular Surgery, Vol. 2. New York: Springer-Verlag, 1986. 9. Sen PK, Kinare SG, Engineer SD, Parulkas GB. The middle aortic syndrome. Br Heart J 1963; 25:610-618. 10. Maycock Wd'A. Congenital stenosis of the abdominal aorta. Am Heart J 1937; 13:633-646. 11. Halpern M, Currarino G. Vascular lesions causing hypertension in neurofibromatosis. N Engl J Med 1965; 273:248-252. 12. Riemenschreider TA, Emmanouilides GC, Hirose F, Luide LM. Coarctation of the abdominal aorta in children: report of the cases and review of the literature. Pediatrics 1969; 44:716-726. 13. Siassi B, Klyman G, Emmanouilides GC. Hypoplasia of the abdominal aorta associated with the rubella syndrome. J Dis Child 1970; 120:476-479. 14. Flynn PM, Robinson MB, Stapelton FB, et al. Coarctation of the aorta and renal artery stenosis in tuberous sclerosis. Pediatric Radiol 1984; 14:337-339. 15. Inada K, Shimizu J, Kobayashi T, et al. Pulseless disease and atypical coarctation of the aorta. Arch Surg 1962; 84:306-311. 16. Daimon S, Kitamura K. Coarctation of the abdominal aorta. Jpn Heart J 1964; 5:562-573. 17. Lande A. Takayasu's arteritis and congenital coarctation of the descending thoracic and abdominal aorta: a critical review. Am J Roentgenol 1976; 127:227-233. 18. Holter AR, Bassett JE. Takayasu's arteritis and atypical coarctation: the same disease. Minn Med 1983; 66:355-357. 19. Brust AA, Howard JM, Bryant MR, Godwin JT. Coarctation of the abdominal aorta with stenosis of the renal arteries and hypertension. Am J Med 1959; 27:793-802.

and homograft replacement. Later, however, we began to use the bypass principle, particularly as it related to the need to restore circulation to the renal arteries, because most ofthe patients we encountered had renal artery stenosis in association with coarctation of the lower thoracic and abdominal aorta. As Dr. Messina indicated, some patients with this syndrome do not have renal artery stenosis, and the lesions also vary considerably. I would like to show you a few examples of our own experience, which now comprises more than 60 cases, with results that I think are comparable to those of Dr. Messina, which I think were quite good. (Slide) This slide is from our second presentation of 26 cases (in the original article we had 16 cases). It shows how we progressed from using homograft replacement to bypass with Dacron" grafts. One patient had endarterectomy associated with bypass, but most patients had thoracoabdominal bypasses with additional bypass grafts to the renal arteries. (Slide) This slide shows some of the variations-a very well-localized area in the lower descending thoracic and upper abdominal aorta. There was no need for correction of renal artery stenosis since this was not present, so the bypass corrected the problem quite well. Twenty-two years later, the patient remains asymptomatic, and the aortogram shows the Dacron graft functioning well. (Slide) This patient, a 34-year-old white woman, had complete occlusion of the descending thoracic aorta but little or no involvement of the