Use of Endovascular Stent-Graft Repair for Type B Aortic Dissection in Polycystic Kidney Disease

ABSTRACT: Aortic dissection (AD) is a life-threatening medical urgency with autosomal-dominant polycystic kidney disease (ADPKD) being one of its major risk factors. Even though endovascular stent-graft repair has better outcomes in complicated Type B AD, its use in a patient with ADPKD has not been reported previously. This case involves a 44-year-old female with a history of ADPKD, hypertension and chronic low back pain presented with severe pain in the interscapular region. She was diagnosed with Type B AD by a computed tomographic (CT) scan of her chest and was managed medically. She was readmitted 9 days after discharge with worsening pain due to the proximal extension of AD. She was treated, with endovascular stent-graft repair sealing the dissection flap with significant subsequent reduction of the false lumen index and symptoms. We are reporting the first case of a complicated Type B AD in a patient with ADPKD managed with endovascular stent-graft repair.

J INVASIVE CARDIOL 2010;22:E171–E174

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Aortic dissection (AD) is considered the most common life-threatening condition involving the aorta,¹ with an estimated incidence of 3–8 cases per 100,000 people.^2–4 Only 10% of patients with acute proximal (Type A) dissection and 40% with acute distal (Type B) dissection are expected to live after 1 year, making it a highly lethal condition.^1–4 Systemic hypertension is found to be the most common predisposing factor for this condition and is found in 3 out of 4 patients with AD.² Several other factors are known to increase the risk of developing this complication including atherosclerosis, connective tissue disorders, iatrogenic injuries and pregnancy.⁵ Although dissection of the aorta is an acute event, in most cases, an underlying chronic generalized disease affecting the media wall predisposes patients to this phenomenon.¹⁰ Autosomal polycystic kidney disease (ADPKD) is one such risk factor characterized by several vascular abnormalities including thoracic and abdominal aortic dissection. Even though early onset of hypertension in patients with ADPKD is blamed for this increased risk, studies also noted changes in the vascular connective tissue due to altered expression of polycystin, which may increase the risk of AD.^6,7 A Type A dissection, if untreated, bears a mortality rate of 1–2% per hour, up to 50–74% within the first 2 weeks,^8,9 making any endovascular approach experimental and anecdotal for localized pathologies in patients unfit for surgery.¹⁰ Type B dissections, on the contrary, have much better survival rates of 89% in medically treated patients at 1 month.^2,11 But surgical or endovascular stent-graft repair is pursued in patients with a complicated dissection.¹² In this article, we report the first case (to the best of our knowledge) of a complicated Type B aortic dissection in a patient with ADPKD being managed by endovascular stent-graft repair followed by a review of literature. Case Report. A 44-year-old Caucasian female presented to the emergency room with sudden onset of excruciating pain in the interscapular region. She denied any similar episodes in the past and was not involved in any strenuous activities at the time of onset. She had mild shortness of breath, but denied any palpitations. She had a history of ADPKD (evident from her family history), hypertension and spinal stenosis causing chronic low back pain. Risk factor evaluation revealed smoking and noncompliance with medications. No history of premature coronary artery disease in the family. She admitted that she was off her anti-hypertensive medications and was found to have a blood pressure of 184/110 on admission. Physical examination was otherwise unremarkable. Initial workup included a computed tomographic (CT) scan of the chest with contrast, which revealed a Type B aortic dissection originating just distal to the take off of the left subclavian artery (Figures 1A and 1B) and terminating at the celiac trunk (Figures 2A and 2B). The patient was medically managed in an intensive care setting and discharged on day 12 post admission in stable condition. Nine days later, she was readmitted for worsening posterior interscapular pain. The patient was noted to have normal blood pressure during her second admission, with no changes in physical examination. A CT scan of the chest with contrast revealed retrograde extension of the dissection into her proximal left subclavian artery, slightly increased aortic diameter at the origin of the left subclavian, with possible pseudoaneurysm formation versus worsened intramural hematoma with increased false lumen diameter (Figure 3). An aortic and four- vessel angiogram confirmed the proximal extension of the dissection and showed normal carotid and vertebral arteries. The dissection flap extended distally to end just proximal to the celiac trunk. There was normal perfusion of the celiac, superior mesenteric and renal arteries via the true lumen. The iliac arteries also were filling via the true lumen. A distal aortic focal dissection just above the iliac bifurcation was noted. The aorta measured 37 mm in maximum diameter just distal to the left subclavian artery. Distally, the aorta had normal dimensions for the most part We considered the situation to be a complicated Type B dissection, thus the patient was evaluated for endovascular stent-graft repair. The extension of the dissection flap into the left subclavian artery warranted extending the stent graft proximal to the origin of the left subclavian artery. Subsequently, a left carotid-to-left subclavian bypass was performed the day prior to the planned stent-graft repair. The following day, she was taken back to the operating room where she had a lumbar drain catheter placed to monitor intraspinal pressure during and following the procedure; general anesthesia was induced, a 10 mm Dacron conduit size was sutured into the right common iliac artery via the retroperitoneal approach and was tunneled subcutaneously out of the right groin to facilitate delivery of the stent graft device. A Gore TAG stent-graft device size 34 mm x 15 cm (W.L.Gore & Associates, Flagstaff, Arizona) was positioned just distal to the origin of the left common carotid artery after placing a diagnostic catheter into the left common carotid artery to secure access to the vessel. The TAG device was deployed to extend approximately 10 cm distal to the left subclavian artery. The rest of the dissection flap was left uncovered distally. The stent graft was postdilated using the Tri-Lobe balloon catheter (W.L.Gore) designed for maintaining flow during balloon inflation. The final angiogram showed excellent proximal and distal positioning of the graft, with normal flow within the left common carotid artery as well as the left carotid to subclavian bypass (Figure 4). The iliac conduit was taken down. The patient had remarkable improvement post operatively. She rarely required any pain killers and remained neurologically intact. Subsequently, the lumbar drain was removed. She had an uneventful post-operative course, and was discharged on post operation day five. Five months later, she remained pain free and clinically stable. CT of her chest and abdomen was repeated one month post operatively and showed reduction of aortic diameter, false lumen index (false lumen diameter/whole lumen diameter) 33 from 0.59 to 0.16 and stable findings with no evidence of reentry or endoleak (Figures 5A and 5B). A head CT angiography showed no evidence of cerebral aneurysm. Discussion. AD is a life-threatening condition demanding early diagnosis and prompt treatment.¹³ It is known to occur twice as frequently in men as in women.² Multiple risk factors have been attributed to AD including hypertension. ADPKD is one such important risk factor noted to predispose patients to an increased incidence of AD. ADPKD is a relatively common systemic disorder with predominant renal manifestations, but is also associated with the liver, pancreas, blood vessels, or a combination of these sites.^28,29 Its incidence is being reported to be as high as 1 in 400, or up to 1,000 individuals in the U.S.²⁷ ADPKD is caused by mutations in PKD1 in 85–90% of affected individuals, the rest being caused by mutations in PKD2. Polycystin, a protein expressed by these genes, is found altered in the arterial wall smooth muscle cells, suggesting the generic role of ADPKD in vascular pathology.³⁰ The association of ADPKD with berry and abdominal aortic aneurysms, vertebral artery dissections, in addition to thoracic aortic dissections, suggests a defect in the structural integrity of the vascular wall.²⁴ One autopsy series revealed that thoracic aortic dissection was seven times more common in patients with ADPKD compared to the normal population.²⁵ Studies of animal models using mutated PKD1 allele also resulted in early embryonic death secondary to vascular leaks and massive hemorrhage, supporting the importance of polycystin in vascular integrity.²⁶ Histological studies on excised aortas in several patients with AD in ADPKD revealed cystic medial necrosis, which is characteristic of Marfans and Ehler Danlos syndromes.^24,31,32 Hypertension is another important factor associated with patients with ADPKD, which may contribute to the risk of developing an AD. It occurs in 59% of patients with ADPKD, even before the onset of renal insufficiency²² at least 10 years earlier than in the general population,²³ requiring multiple medications to achieve control. The initial admission of our patient revealed high blood pressure due to poor compliance with her multiple medications, but her second admission was marked with normal blood pressures. Management of AD has been an area of constant debate. Immediate surgical repair has been a general consensus in patients with ascending aortic dissection,¹³ but the optimal treatment strategy for patients with AD confined to the descending aorta remains controversial.³ Current practices warrant medical management with tight blood-pressure control as the primary method of managing AD Type B, leaving surgery only for evolving complications (unrelenting pain, progressive aortic dilatation, malperfusion syndromes or imminent rupture).³ Medical management alone has an established benchmark, which is tough to surpass or even match by endovascular stent-graft treatment in uncomplicated cases.¹² However, complicated acute Type B AD has a very poor outcome requiring surgery or endovascular intervention on an urgent basis.¹⁵ Even in the absence of a randomized, controlled trial to determine the benefits of endovascular stent-graft placement over surgical treatment, several studies and meta-analyses indicate a more favorable neurological outcome and survival rate with this approach in patients with complicated Type B AD.¹⁴ The concept of endovascular stent-graft placement is intended to occlude the proximal entry tear and thereby promote thrombosis of the false lumen and aortic remodeling.¹⁸ This course of treatment is based on a clinical observation that patients who develop false-lumen thrombosis have better prognoses.¹⁹ A recent retrospective study reiterated the potential of the endovascular approach even in chronic Type B dissections, permitting gradual aortic remodeling or even complete resolution of the false lumen, as in our case report.³³ Thoracic reentry causing retrograde perfusion of the false lumen and endoleak pose a potential immediate complication in endovascular stent grafting, which can be avoided by monitoring with transesophageal echocardiography post closure of the main entry site.¹³ A strict imaging follow up including a delayed acquisition after the arterial phase is mandatory to detect false-lumen expansion and rupture from regular flow and slow-flow endoleak.^20,21 Assessment of changes in true and false lumen indices before and after endovascular repair (at a fixed location like the carina) can be considered an adjunctive method in the objective measurement of aortic remodeling post procedure.³³ The true- lumen index (TLi) is a defined as the ratio of true the lumen diameter to the whole lumen diameter.³³ An ideal TLi to achieve would be one, or close to one. The false-lumen index (FLi) is calculated in a similar manner, and an ideal FLi to achieve would be zero or close to it.³³ Although primary medical therapy may improve hospital survival in an uncomplicated Type B AD, it has not changed the long-term survival rates.¹⁶ Eventually, most of the deaths in these patients are related to late complications of AD (new dissection, rupture of a weak false channel or aneurysmal changes leading to rupture) or comorbid conditions.¹⁷ In our case report, the initial episode was attributed to the patient’s uncontrolled hypertension and the risk associated with ADPKD as the cause of AD. Our patient was managed medically with strict blood-pressure control, however, a worsening clinical course with development of a complicated Type B AD (persistent pain and retrograde extension of the AD into the left subclavian artery) warranted the need for endovascular stent repair as an optimal treatment. Conclusion. Patients with ADPKD are at increased risk for AD. Medical management with strict blood-pressure control and pain management are mandatory. Close follow up and monitoring for development of complications can be life-saving since timely intervention can be provided. To our knowledge, this is the first report demonstrating endovascular stent-graft repair for Type B AD in a patient with polycystic kidney disease.

References

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From the †University of Miami / JFK Medical Center, and ‡Daniel Heart and Vascular Center, P.A, Boca Raton, Florida. The authors report no conflicts of interest regarding the content herein. Manuscript submitted January 12, 2010, provisional acceptance given January 19, 2010, final version accepted January 26, 2010. Address for correspondence: George K. Daniel, MD, FACC, FSCAI, Daniel Heart and Vascular Center, P.A, 1601 Clint Moore Rd, Suite 100, Boca Raton, FL 33487. E-mail: gdanielmd@gmail.com