Fibromuscular Dysplasia of the Superficial Femoral Artery<br />

Most obstructions in femoral artery are due to atherosclerotic occlusive disease. Fibromuscular dysplasia (FMD) is most prevalent in the renal, carotid, and iliac arteries and its known cause of renal artery stenosis. FMD exists in multiple vascular beds in 28% of affected patients.¹ FMD is currently defined as an idiopathic, segmental, noninflammatory and nonatherosclerotic disease of the musculature of arterial walls, leading to stenosis of small- and medium-sized arteries.² The lesions may become symptomatic as a result of flow reduction, embolic phenomena, dissection or aneurysmal degeneration.
Atherosclerosis generally occurs at the origin or proximal portion of the artery in older patients with typical cardiovascular risk factors. In contrast, FMD occurs in the middle or the distal arterial segments in younger patients with several or no cardiovascular risk factors.³ Involvement of the superficial femoral artery in FMD is uncommon.⁴ This article describes a case of a young patient with intermittent claudication due to femoral artery occlusion from FMD.

Case Report. A 32-year-old hispanic male presented with a 4-month history of intermittent claudication of the right lower extremity and a short and disabling walking distance. The patient also had a non-healing right leg ulcer for the past 4 months. He did not complain of rest pain, shortness of breath, palpitations, pedal edema or chest pain. He did not smoke. The patient was diagnosed with deep-vein thrombosis (DVT) 4 months prior, involving the superficial femoral veins in both lower extremities. A workup for a hypercoagulable state was negative. The patient was started on coumadin for DVT. He was also diagnosed with cellulitis of both lower extremities 4 months previously and was treated with intravenous antibiotics. On physical examination, his temperature was 97.6º F, his heart rate was 73/minute and his blood pressure was 117/63. The patient’s heart and lung examination was normal and his peripheral pulses were palpable. Electrocardiography showed normal sinus rhythm and no ST-T wave changes. The patient’s cholesterol panel and chemistry were normal. Duplex arterial ultrasound of the lower extremities showed a mid-to-distal stenosis of the superficial femoral artery (SFA) on the right side. Peripheral angiography was performed and is described below.
Procedure. Using modified Seldinger technique, a 6 Fr sheath was placed in the left femoral artery. Peripheral angiography was performed using A 5 Fr Omniflush catheter (AngioDynamics, Inc., Queensbury, New York), which was introduced over a 0.035 inch x 180 cm Glidewire (Terumo, Japan). The 5 Fr Omniflush catheter was replaced by a 5 Fr Glidecath angled taper catheter (Boston Scientific Corp., Natick, Massachusetts). Peripheral angiography showed FMD of the right SFA (Figure 1), with spontaneous dissections and post stenosis aneurysmal dilatation of the SFA (Figure 2). The 6 Fr arterial sheath was replaced by a 7 Fr x 45 cm Pinnacle sheath (Terumo, Japan). The lesion was crossed using a 0.014 inch x 300 cm Whisper wire (Guidant Corp., Santa Clara, California). Percutaneous transluminal angioplasty (PTA) of the right SFA was performed using a 6.0 mm x 100 mm Savvy balloon (Cordis Europa, The Netherlands), followed by a Sterling 7.0 mm x 100 mm balloon (Boston Scientific) (Figure 3). Successful revascularization was achieved (Figure 4) after PTA of the superficial femoral artery. The renal angiogram was essentially normal (Figure 5). The patient was started on aspirin 81 mg daily and continued on coumadin for DVT, and was discharged home the next day. Two months later, he started to have intermittent claudication of the left lower extremity. The patient underwent bilateral lower-extremity angiography and was found to have FMD of the proximal left SFA (Figure 6). An over-the-wire Synergy PTA balloon (Boston Scientific) was used in the left SFA, and successful revascularization was achieved post PTA (Figure 7). Furthermore, 3-month follow-up angiography showed a patent right SFA without any stenosis or FMD (Figure 8), and the patient’s right leg ulcer was completely healed.

Discussion. FMD is a nonatherosclerotic angiopathy that has remained an enigma since its original description in 1938.⁵ The etiology contributing to FMD has been the subject of much speculation. Although a variety of genetic, mechanical and hormonal factors have been proposed, the cause of FMD remains unknown and is probably multifactorial.^6,7 Harrison and McCormack attempted to establish a uniform terminology for fibrous and fibromuscular nonatherosclerotic lesions.⁸ They classified arterial disease histopathologically into one of several types based on the site of principle involvement within the arterial wall: intima, media or adventitia. The association between FMD and diseases such as ankylosing spondylitis, scleroderma and Reiter’s syndrome may suggest that an autoimmune process plays a part in the etiology of some cases. Mural ischemia by compromised vasa vasorum or popliteal artery entrapment may also contribute to the formation of dysplastic arteries. Experimental studies lend credence to this theory.⁹ The gold standard for diagnosing FMD is angiography, but this invasive procedure is only performed on patients in whom it is clinically indicated to proceed with revascularization during the same procedure. In regard to specific angiographic appearances, FMD has been described as showing a localized “string-of-beads”, which is caused by areas of relative stenosis alternating with small aneurysms. The diameters of the aneurysms exceed the normal diameter of the artery. In cases with focal and tubular FMD stenosis, differential diagnoses are atherosclerotic or inflammatory arterial diseases, vascular Ehlers-Danlos and Williams’ syndromes, and Type 1 neurofibromatosis. FMD lesions are typically truncal or distal, as opposed to atherosclerotic stenoses, which are mostly ostial or proximal. Most patients with FMD are young and present few or no risk factors for atherosclerosis and no aortic plaques. Dissection is also recognized as an angiographic manifestation of this disorder.⁹
These angiographic characteristics are only visible at an early stage and could not be demonstrated in the patients who had total occlusions. Fibromuscular dysplasia continues to have an unclear natural history in the asymptomatic patient. Symptomatic lesions usually present as either renovascular hypertension or carotid lesions that embolize and cause transient ischemic attacks or stroke. Percutaneous angioplasty has been demonstrated to be effective in treating renal and other arterial FMD, and has become the dominant mode of treatment of renal FMD at most institutions. The mechanism by which balloon angioplasty enlarges the arterial lumen in FMD involves stretching the arterial wall, which results in separation of the intima from the media, fracture of the media and stretching of the adventitia beyond its elastic recoil. Subsequent changes include smooth muscle cell necrosis, fibrosis, and some degree of neointima formation.¹⁰ Routine placement of stent following balloon angioplasty in successfully recanalized artery is not necessary. Stenting should be reserved for failed angioplasty cases with refractory stenosis or flow-limiting dissection. Surgical revascularization such as bypass should be reserved for complex and complete occlusion lesions that could not be crossed with a wire.
In conclusion, this report demonstrates the need to consider FMD, and not just atherosclerosis, as a possible cause of occlusive disease of the SFA in young patients with intermittent claudication. As was the case here, FMD of the SFA can be easily treated with balloon angioplasty in most cases, whereas stents and bypass graft surgery should be used selectively.

Acknowledgements. The authors wish to express their appreciation to Diago Guzman for his assistance with the angiographic images.

References

1. Luscher TF, Keller HM, Imhof HG, et al. Fibromuscular hyperplasia: Extension of the disease and therapeutic outcome; Results of the University Hospital Zurich Cooperative Study on Fibromuscular Hyperplasia. Nephron 1986;44(Suppl 1):109–114.
   
2. Plouin PF, Perdu J, Batide-Alanore AL, et al. Fibromuscular dysplasia-review. Orophanet J Rare Dis 2007;2:28.
   
3. Slovut DP, Olin JW. Current concepts in fibromuscular dysplasia. N Engl J Med 2004;350:1862–1871.
   
4. Van den Dungen JJ, Boontje AH, Oosterhuis JW. Femoropoplitial arterial fibrodysplasia. Br J Surg 1990:77:396–399.
   
5. Leadbetter WF, Burkland CE. Hypertension in unilateral renal disease. J Urol 1938:39:611–615.
   
6. Stanley JC, Gewertz BL, Bove EL, et al. Arterial fibroplasia, histopathologic character and current etiologic concepts. Arch Surg 1975;110:561–566.
   
7. Rushton AR. The genetics of fibromuscular dysplasia. Arch Int Med 1980;140:233–236.
   
8. Harrison EG, McCormack LJ. Pathological classification of renal arterial disease in renovascular hypertension. Mayo Clin Proc 1971;46:161–167.
   
9. Palubinskas AI, Perloff D, Newton TH. Fibromuscular hyperplasia: An arterial dysplasia of increasing clinical importance. Am J Radiol 1966;98:907–913.
   
10. Kerlan RK. Angioplasty. In: LaBerge JL (eds). Interventional Radiology Essentials. Philadelphia: Lippincott William & Wilkins, 2000.