Suprarenal Aortic Occlusion Due to Coral Reef Calcification: Successful Endovascular Management Assisted by Intravascular Lithotripsy and Visceral Protection

Introduction

Coral reef aorta (CRA) is a rare disease of severe calcification of aorta causing significant stenosis of the abdominal aorta, which may lead to visceral ischemia, renovascular hypertension, and claudication. Management of these patients is complex and presents a conundrum as most of these patients have associated heart failure, hypertension and varying degrees of renal dysfunction. Unyielding dense calcification was considered a contra indication for endovascular treatment, and most of these patients have been managed by open surgical thrombo-endarterectomy (TEA) or bypass. Open surgical procedures have been shown to carry a high reintervention rate and mortality. Intravascular lithotripsy (IVL) has been seldom used in these patients as dedicated large lithotripsy balloon for the aorta is not available. This is the first case to demonstrate the use of IVL coupled with stenting and distal embolic protection safely in the treatment of CRA involving suprarenal visceral aorta.

Case Report

A 72-year-old frail women presented with 5 months history of bilateral gluteal and leg claudication. She was diabetic and hypertensive for over 12 years. She has had 2 episodes of acute left ventricular failure and pulmonary oedema needing ventilatory support in the last 2 years. She had breathlessness on exertion and recurrent angina. Her blood pressure was poorly controlled though she was on 4 antihypertensives. Her renal function had progressively worsened and her serum creatinine level was 1.5 mgm/dL. Her lower limb pulses were not felt. Her blood pressure was 220/110 mm hg in the upper limbs. Her ankle-brachial index was 0.51 and 0.49 on the right and left, respectively.

Echocardiogram (ECHO) showed a hypokinetic left ventricle (LV), poor ejection fraction of 35% with severe pulmonary artery hypertension. A noncontrast computed tomography (CT) abdomen (Figure 1) done showed a circumferentially calcified aorta with coral reef calcification causing occlusion of the aorta between the coeliac and superior mesenteric (SMA) arteries. Coronary angiogram revealed 70% stenosis of the right coronary artery and 50% stenosis of left anterior descending artery. Contrast aortogram done at the same time showed complete occlusion of the aorta at the level of celiac artery. There were extensive collaterals reforming the SMA and the lower aorta. Coeliac artery and left renal artery (LRA) had ostial narrowing. An accessory lower polar LRA was also noted. Right renal artery was normal (Figure 2A–C). In view of her poor cardiac condition, she was planned for endovascular repair of the aortic stenosis under local anesthesia and sedation. However, all preparations needed for a major aortic surgery were done.

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Figure 1.

Noncontrast computed tomography of abdominal aorta showing dense calcification occluding the suprarenal aorta.

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Figure 2.

(A) Contrast aortogram showing total occlusion of aorta at the level of celiac artery. Celiac artery shows osteal stenosis. (B) Extensive collaterals reforming superior mesenteric artery which reforms the distal aorta. (C) Infrarenal aortogram showing total occlusion of suprarenal aorta. Right renal artery is normal. Left renal artery shows osteal stenosis.

Left brachial and bilateral femoral accesses were taken. Diagnostic aortogram showed large coral reef calcium causing celiac origin stenosis and complete aortic occlusion. Superior mesenteric was reformed by collaterals which reformed the aorta. There was pressure gradient of 100 mm Hg across the stenosis (Figure 6A). Aortic lesion was crossed with a 0.035 Radifocus guidewire (Terumo) from above and snared from the right femoral access. The right renal artery was cannulated from the left femoral access with a 0.014 Command wire (Abbott vascular), and a 5 mm SpiderFX filter (Medtronic) was deployed in the proximal renal artery. Superior mesenteric was also cannulated through the same access and a 7 mm × 20 mm balloon was inflated to occlude the ostium and proximal SMA. The aortic stenosis was first predilated with 4 × 40 mm Mustang balloon (Boston Scientific Corporation) and then a 7 × 60 mm shockwave IVL balloon (Shockwave Medical, Fremont, CA, USA) was deployed to deliver 270 pulses in 9 cycles (Figure 3). The pressure gradient was measured after every 3 cycles, and lithotripsy was stopped when no further fall was noticed. A self-expandable nitinol 14 × 40 mm Sinus XL (Optimed) bare metal stent was deployed across the stenosis from proximal to the celiac artery and landing just above the renal arteries (Figure 4A and B). Post stenting, a peak pressure gradient of 45 mm Hg was noticed. Hence, the stent was postdilated with an Atlas gold 12 × 40 mm balloon (Bard) (Figure 4A and B). Completion angiogram showed normal flow in the coeliac, SMA, and both renal arteries (Figures 4C and 5A). At this stage, there was equalization of pressures across the stenosis (Figure 6A–C). Patient made an uneventful recovery and was discharged after 48 hours. Pedal pulses became palpable. At 6 months follow-up her blood pressure had stabilized and her antihypertensives were reduced to a single drug. Her renal function had improved (serum creatinine improved from 1.5 to 1.2 mgm/dL) and postoperative ECHO showed improvement in the LV function (ejection fraction improved from 35% to 45%).

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Figure 3.

Intravascular lithotripsy balloon across the aortic stenosis (white arrow). SpiderFX embolic protection device in the right renal artery (blue arrow). Balloon occlusion of superior mesenteric artery (black arrow).

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Figure 4.

(A) Showing poststenting dilatation of the aorta with 12-mm balloon. Balloon occlusion of superior mesenteric (SMA) and embolic protection filter in the right renal artery can be seen. (B) 14 × 40 mm Sinus XL stent deployed in the suprarenal aorta across the visceral arterial origins. (C) Completion aortogram showing satisfactory dilatation of aorta, good flow in visceral and renal vessels and complete disappearance of collaterals.

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Figure 5.

(A) Completion aortogram showing both the renal arteries. (B) Filter in the renal artery showing atheromatous debris.

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Figure 6.

(A) Simultaneous supra and infrarenal aortic pressures (preintervention). Pressure gradient 100 mm Hg. (B) Simultaneous supra and infrarenal aortic pressures (after intravascular lithotripsy [IVL] and stenting). Pressure gradient 45 mm Hg. (C) Simultaneous supra and infrarenal aortic pressures after balloon dilatation of the stent. Pressure equalized.

Discussion

Atherosclerotic occlusive disease of the aorta usually affects the infrarenal aorta, including the bifurcation, and extends into the iliac arteries. Coral reef aorta is a rare calcifying stenotic disease of the juxta renal and suprarenal aorta. In 1984, Qvarfordt et al ¹ reported their experiences with 9 patients who had eccentric, heavily calcified polypoid lesion, originating from the posterior surface of the suprarenal aorta which was rock-hard, irregular, gritty, and had whitish luminal surface. He named this “coral reef aorta.” Since then, many case reports and reviews have been published.^2,3

The cause and pathogenesis of CRA is still uncertain. Calcification of a fibrin-platelet thrombus, repetitive injury to the aortic endothelium, and secondary aortic amyloidosis have all been suggested as possible causes. Takayasu’s aortoarteritis as well as tubercular aortitis have also been considered as possible etiological factors.

Schlieper et al ⁴ reported low levels of calcification inhibitors, such as fetuin-A and uncarboxylated matrix GLA protein (ucMGP), in the serum of patients with CRA.

This condition is slightly more common in women. In a large single-center experience, intermittent claudication was seen in 40.0% of patients, renovascular hypertension in 44.3% of patients, and long-term visceral ischemia in 24.3% of patients. ² Distal embolization has also been reported.

The treatment of choice has been open transaortic TEA and transaortic TEA of the aortic branches.^2,3 The aortic segment is opened longitudinally over the involved segment, and the calcified plaque is removed. A bypass can be done if the lesion extends too far into the visceral and/or renal arteries. If the quality of the aortic wall after TEA is not healthy, prosthetic aortic replacement is necessary.

After elective aortic TEA, mortality of 11.6% and reintervention rate of 15.9% has been reported. ²

Owing to the location of the lesion and the involvement of the renal and visceral vessels, these lesions were considered unsuitable for balloon angioplasty or stent placement. ³

Endovascular therapy using a bare metal stent and a self-expanding stent graft (SESG) for CRA was performed recently in the infrarenal segment. ⁵ However, they may not be fully expandable and have a risk of late recoiling.

Balloon expandable stent grafts have been successfully used in infrarenal CRA. ⁶ There has been only one case report of endovascular repair for a para visceral aortic occlusion using parallel stent grafts.7

The peripheral IVL system (Shockwave Medical, Inc., Fremont Calif) modifies intimal and medial calcium via pulsatile sonic pressure waves. The IVL system transforms electric energy into pulsatile sonic pressure waves causing microfractures in calcified plaques which make the vessel more compliant to yield to simple balloon dilatation. Angioplasty can be performed with lower pressures minimizing arterial dissection and enhancing vessel compliance. The safety and usefulness of the IVL system on calcified lower limb arterial stenosis has been evaluated in various studies. ⁸

Intravascular lithotripsy has been successfully used in the treatment of calcific access vessels during thoracic endovascular aortic repair (TEVAR), endovascular aortic repair (EVAR), and transcatheter aortic valve intervention. ⁹

Chag et al ¹⁰ reported on the use of IVL along with another plain balloon in treating an infrarenal aortic coral reef coupled with renal artery stenting. However, the use of IVL in suprarenal CRA has not been reported so far.

Even though distal embolization has not been reported with IVL, we used a filter in the renal artery because this patient already had compromised renal function. Since the LRA was small and had stenosis at origin, embolic protection device was placed in the right renal artery which was normal. There was atheromatous debris in the filter at the end of the procedure (Figure 5B). To protect the SMA from possible dissection balloon occlusion at origin was done during IVL and angioplasty. Post procedure, SMA and both renal arteries were well perfused. Although the proximal aorta measured 16 mm in diameter, we deployed only a 14 mm stent and post dilated it with a 12 mm balloon because we did not want to dilate the aorta to its full diameter to avoid rupture.

This is the first documented successful case of aortic dilatation and stenting for suprarenal aortic occlusion due to coral reef calcification using IVL and visceral protection device.