Role of the femorofemoral crossover graft in acute lower limb ischemia due to acute type B aortic dissection

Abstract

Acute limb ischemia due to type B aortic dissection is rare and continues to be a management challenge. A case series is presented here with the aim of assessing the outcomes of treatment with a femorofemoral crossover graft with or without thoracic stent graft insertion. This is a combined retrospective and prospective review of nine cases of acute lower limb ischemia secondary to acute type B aortic dissection. The presenting features, radiological findings, treatment and outcomes were reviewed. Five patients had a femorofemoral crossover graft (FFXO) alone, two an FFXO with a thoracic stent graft and the eighth a thoracic and iliac stent. The other case was initially treated conservatively but subsequently required an FFXO. The mean follow-up was 16 (3–51) months. A further two thoracic stents were placed during the follow-up period. Thus five out of nine patients (56%) required aortic stenting. This series suggests that an FFXO is a reliable treatment for acute limb ischemia due to type B aortic dissection. However, these patients are often complex with ischemia in other vascular beds and are at risk of subsequent aneurysmal dilation.

Keywords

aortic dissection lower limb ischemia femorofemoral crossover aortic stent graft

Introduction

Acute thoracic dissection usually presents in the early 60s¹ and is still regularly a fatal disease despite modern high dependency care and the relatively young age of the patients. Acute aortic dissection is currently defined as a dissection presenting within two weeks of onset and is said to be complicated if, among other features, end organ (including limb) ischemia is present. The commonly used Stanford classification describes a type A dissection when the tear originates from the ascending aorta or the arch, and a type B when the tear originates distal to the origin of the left subclavian artery.

When and how to best treat the acute dissection, particularly the acute type B dissection, are difficult questions. The presence of an ischemic leg in these cases adds another layer of complexity. Acute limb ischemia is rare in aortic dissection and for this reason it is and will continue to be very difficult to obtain level 1 or 2 evidence regarding treatment of these patients. Therefore a review of the cases of acute limb ischemia secondary to type B dissection seen by a tertiary referral aortic centre was undertaken with the aim of assessing treatment outcomes.

Materials and methods

A combined retrospective (2002–2008) and prospective (2009) study of acute limb ischemia in acute type B dissection was undertaken. A prospectively maintained database of thoracic stent graft cases was interrogated for those treated who had acute lower limb ischemia associated with a thoracic dissection. To identify those who did not undergo endovascular treatment the hospital's PACS (Picture Archiving and Communication System) was used to find all cases of computed tomography (CT) diagnosed dissection. Request forms for the relevant CT scans were then screened for cases with acute limb ischemia.

Nine patients presented with acute type B dissection and acute lower limb ischemia during the study period (for example, see figure 1). The presenting features, radiological findings, treatment and outcomes were reviewed.

Figure 1

Type B dissection (white arrow) in patient 4

Results

Of the nine patients, eight had unilateral leg ischemia. All had a preceding history of high blood pressure. Eight were men. The mean age at presentation was 55.8 presented with chest or interscapular pain. Three also had renal infarcts, one a splenic infarct, one a cerebral infarct and one paraplegia (see Tables 1 and 2).

Table 1

Presenting features

Patient	Sex	Age at presentation	History hypertension	Ischemicleg	Chest/back pain atpresentation	Associated ischemia
1	M	40	Yes	Right	Chest pain radiating to back	Occluded right renal artery
2	M	62	Yes	Left	Chest pain	No
3	M	53	Yes	Right	Chest pain radiating to back	No
4	M	69	Yes	Right	Chest pain radiating to back	No
5	M	44	Yes	Left	Chest pain radiating to back	No
6	M	44	Yes	Right	Chest pain radiating to back	Left renal and splenic infarcts
7	M	78	Yes	Left	Chest pain radiating to back	No
8	F	41	Yes	Right	Low back pain	Left basal ganglia infarct
9	M	62	Yes	Bilateral	No	Paraplegia, occluded right renal artery

Table 2

Dissection characteristics

Patient	Stanford classification	Vessel luminal origin*	Iliac involvement in dissection	Aortic diameter (mm)^†
1	B	C false	No contrast RCIA	R = 37.3
		S true	Dissection flap to distal LCIA	A = 39.9
		RR occluded		D = 35.8
		LR n/a		C = 30.2
				Re = 21.8
2	B	C false	Occluded RCIA	R = 37.8
		S true	Flap to proximal L CIA	A = 36.6
		RR true		D = 36.5
		LR false		C = 33.3
				Re = 28.8
3	B	C true	Flap to both proximal CIA	R = 39.9
		S true		A = 34.3
		RR true		D = 40.0
		LR both		C = 32.0
				Re = 27.3
4	B	C true	Flap to both CIA	R = 39.0
		S true		A = 37.6
		RR true		D = 37.0
		LR false		C = 26.1
				Re = 24.0
5	B	n/a	n/a	n/a
6	B	C false	Flap to right EIA, left IIA	R = 44.0
		S true		A = 41.0
		RR true		D = 37.9
		LR false		C = 24.0
				Re n/a
7	B	C both	Flap into RCIA and RIIA	R = 37.4
		S both	LCIA occluded	A = 35.1
		RR false		D = 51.0
		LR false		C = 32.0
				Re = 24.9
8	B	C true	Flap into both CIA	R = 35.0
		S true		A = 41.6
		RR true		D = 31.7
		LR false		C = 27.2
				Re = 21.6
9	B	C true	Both EIAS	R = 43.5
		S true		A = 44
		RR true		D = 35
		LR false		C = 30
				Ee = 34

n/a, data not available; CIA, common iliac artery; EIA, external iliac artery; IIA, internal iliac artery

*C = co-eliac, S = superior mesenteric artery, RR = right renal, LR = left renal

^†R = root, A = ascending/arch, D=descending, C = level of co-eliac axis, Re = level renal arteries

Eight legs were immediately threatened by the degree of ischemia and required urgent intervention. Five had a femorofemoral crossover alone, two a femorofemoral crossover with a thoracic stent graft (see Figure 2) and the eighth a thoracic and iliac stent (see Table 3). The remaining case was initially treated conservatively as he (patient 3) presented with intermittent loss of pulses in the affected leg and the ischemia fully resolved during admission. However, the patient developed very short distance claudication after discharge and underwent a femorofemoral crossover electively three months later.

Figure 2

Successful stent graft insertion (arrow) in patient 11

Table 3

Treatment and outcomes

Patient	Initial treatment leg ischemia	Initialtreatmentaorticdissection	Outcome of initial treatment	Subsequentaortictreatment	Outcome ofsubsequenttreatment	Lengthfollow up
1	FFXO	Nil but had right renal stent	Ongoing left buttock claudication (contralateral side) and erectile dysfunction	Nil		9 months
2	FFXO			Stent graft for TAA at 1 year (with carotid subclavian bypass)		33 months
3	Nil	Nil	Short distance claudication	FFXO at 3 months Arch and root repair at 1 year	Subdural hematoma, chest sepsis, necrotic gallbladder, died 16 months postpresentation	16 months
4	FFXO		Occluded at 3 months but asymptomatic			3 months
5	Left iliac stent	Thoracic stent graft	Claudicating at 41 months	Redo aortic valve replacement at 2 years		51 months
6	FFXO (redo 48 hours later)	Thoracic stent graft	Multiorgan failure			10 months
6	FFXO (redo 48 hours later)	Thoracic stent graft	Died 10 months
7	FFXO			Thoracic stent graft 6 months, extension at 10 months	Groin hematoma required evacuation. Infected groin seroma	12 months
8	FFXO					3 months
9	FFXO	Thoracic stent graft	Acute tubular necrosis			5 months
9	FFXO	Thoracic stent graft	Chest infection
			At 5 months, renal function improved, mobile with sticks, right leg neuropathic pain

FFXO, femorofemoral crossover graft; TAA, thoracic aortic aneurysm

The mean follow-up was 16 months with a range of 3–51 months. In addition to the three thoracic stents undertaken acutely, a further two thoracic stents were placed during the follow-up period. Thus 56% (5/9) of patients required stent insertion during the study period.

Two deaths occurred during follow-up (patients 3 and 6). Patient 4 developed a subdural hematoma resulting from spinal drainage after an elective arch and root repair one year after initial presentation. He developed chest sepsis and died 16 months postpresentation. Patient 6 had a thoracic stent inserted acutely and developed multiorgan failure resulting in death 11 months later. No patient required major amputation. One developed buttock claudication on the donor side of the femorofemoral crossover graft, one crossover occluded but the patient remained asymptomatic (see Table 3).

Discussion

Acute lower limb ischemia is a common vascular surgical emergency. Approximately three quarters of cases are due to embolization and the majority of the remainder due to in situ thrombosis.² Acute thoracic dissection is an unusual cause but should always be considered in the differential diagnosis. Chest pain is common in acute dissection but not universal. In this study 8/9 (89%) had chest pain on presentation: the IRAD (International Registry of Acute Aortic Dissections) investigators have reported that 79% of acute type A dissections and 63% of acute type B have chest pain.¹ Indeed, one study has shown that those presenting with lower limb ischemia are less likely to have chest and back pain.³ Therefore the classical symptoms of dissection cannot be relied upon for diagnosis. Limb ischemia in acute type B aortic dissection has a reported incidence of 6–7.5%.^3,4

Stroke, peripheral neurological deficit, mesenteric and renal malperfusion are significantly more common in those with acute limb ischaemia (ALI) than without. Nineteen percent of those with ALI in dissection had clinical symptoms or signs of visceral ischemia but 30% had CT imaging demonstrating visceral ischemia.³

The presence of acute limb ischemia increases the mortality of acute type B dissection: the mortality is nearly three times as high for those with ALI than for those without (31% compared with 11.9%). ALI is an independent factor significantly associated with death and those with ALI are more likely to suffer a myocardial infarction or acute renal failure while in hospital.³

The question then arises as to how the acute limb ischemia should be treated, and how and when the dissection itself should be managed.

The two main treatment options for Type B dissections are medical management and endovascular stent graft insertion, the latter having all but replaced open surgical repair of the descending aorta due to the high in-hospital mortality (31%) of descending thoracic aortic replacement.¹ Aortic fenestration is a third possible treatment and will be discussed later.

The current management of the uncomplicated type B dissection is not guided by level 1 evidence. However, a randomized controlled trial comparing medical and endovascular stent grafts, the ADSORB trial is in progress and may provide helpful information.⁵ Meanwhile, the IRAD data have demonstrated a 10.7% 30-day mortality for medical of acute Type B dissections.¹ Mortality may continue to decrease as high-dependency care and tailored antihypertensive treatment become increasing available. At present, most uncomplicated Type B acute dissections are probably best managed medically with aggressive blood pressure control in a high-dependency setting.

In contrast, the acute complicated dissection requires more invasive therapy. In the case of ALI, the options are treating the dissection itself with the aim of correcting lower limb perfusion or treating the ALI itself and monitoring the aortic dissection (if, of course, there is no other emergent reason the treat the dissection such as aortic enlargement).

No published series of aortic stent graft insertion for the acute type B dissection with ALI alone currently exist, no doubt due to rarity of the disease and the relatively recent arrival of thoracic stent grafting in dissection. This is certainly the experience in our unit. Despite being a tertiary referral unit with a large endovascular program, less than 1% of thoracic stent grafts inserted over a seven-year period were in cases of acute type B dissection with ALI. Therefore, the best available analogies are probably drawn from the management of the acute complicated type B dissection in general. Jing-Dong has published the results of thoracic stent graft insertion for 30 cases of acute complicated type B aortic dissection. Four of the 30 (13%) had malperfusion of one or more vascular beds. There was one retrograde dissection and rupture (although the proximal sealing zone was ‘ballooned’ in this procedure), one lymph leak, one transient renal impairment and one fatal liver failure. The mortality was 7% over a mean follow-up of 12 months.⁶ Ehrlich reports a series of 32 thoracic stent graft insertions for acute complicated type B dissections. Eighteen also needed visceral stent insertion to correct malperfusion. The in-hospital mortality was 12%, with a one-year survival of 81% and a five-year survival of 76%. Again the authors report one retrograde dissection.⁷ The EUROSTAR database reveals an 11.7% 30-day mortality for endovascular repair of the complicated type B acute dissection.⁸

If the initial aim is to treat the limb ischemia only, two main options exist: surgical bypass of the occluded vessel and aortic fenestration. In our series, eight of nine cases were of unilateral lower limb ischemia. This is reflected in other studies⁹ although in Henke's series most (22/28: 79%) were bilateral.³ In the unilateral cases, a femorofemoral crossover graft should correct the limb ischemia and has the advantages of being a quick procedure which is important in dissection in order to allow for stable blood pressure control and can be carried out in units without access to endovascular facilities around the clock. In the series reported here, seven of the nine patients had a femorofemoral crossover graft which resolved the acute limb ischemia in all cases.

The intimomedial flap of the dissection can be fenestrated to allow luminal and therefore vessel reperfusion. Both surgical and endovascular methods have been reported. One series of 18 patients undergoing either thoracic surgical fenestration or infrarenal surgical fenestration and aortic replacement reported an in-hospital mortality of 22%. Ten of these patients had ALI and three also required FFXO despite the fenestration procedure.¹⁰ Surgical fenestration is therefore a high-risk procedure and does not reliably correct distal ischemia.

Endovascular fenestration with or without aortic or iliac bare stent insertion has an early mortality rate of 8.3–13.6%^9,11 and also does not reliably correct limb ischemia, with 13 – 22% having ongoing ischemia requiring treatment such as axillobifemoral bypass grafts.^9,11,12 Therefore fenestration was not felt to be a suitable treatment option for the patients in the series presented here.

Endovascular stent graft of a type B dissection does not guarantee reperfusion of the lower limbs: in our study three of those who had stent grafts also had a femorofemoral crossover graft or iliac stent, although the insertion of a stent graft did convert the lower limb ischemia of patient 11 from bilateral to unilateral, thus allowing the use of a FFXO. However, it does have the advantage of treating the primary entry tear and preventing aortic dilation in the stented aorta.

This is important as one of the key concerns in the acute aortic dissection is progressive aortic expansion, leading to an increasing risk of aortic rupture. Following endovascular fenestration with or without bare stent insertion, the aorta will continue to expand.^11,12 The same must be true of those treated with FFXO or axillobifemoral bypass grafting alone. Certainly of the six patients in our group of nine who did not undergo primary surgical or stent graft repair of the dissection, two developed significant aneurysmal dilation of the affected part of the aorta which required intervention during the follow-up period. Therefore of our nine patients, five had a thoracic stent graft for their type B dissection either urgently or during follow-up. Fifty-six percent of those in this study with ALI and dissection therefore ultimately underwent treatment of the primary dissection. Although the treated area of aorta can continue to expand after stent insertion, this is uncommon.^13,14 Therefore, serious consideration should be given to treating the primary dissection at presentation when ALI is present. As a minimum, close observation of the aorta with regular imaging is needed to detect dilation and allow for treatment before the aorta ruptures.

Endovascular stent grafting of the thoracic aorta is, of course, not without its complications which have to be taken into account when deciding the best treatment for each individual with acute aortic dissection and ALI. Stenting the thoracic aorta carries a stroke risk of just under 2% and a paraplegia rate of just under 1%.^8,15 Retrograde dissection into the ascending aorta is a very real concern and has a reported rate of 2% in the acute dissection.¹⁵

Conclusion

This series suggests that a femorofemoral crossover graft is a reliable and simple treatment for the limb ischemia. However, these patients often have ischemia in other vascular beds and have a real risk of aneurysmal change. Such cases should therefore be treated in, or discussed with, a vascular unit capable of thoracic stent grafting and undergo regular aortic imaging.

Footnotes

Conflicts of interest: None.

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