Intravascular lithotripsy-assisted balloon angioplasty to facilitate transfemoral transcatheter aortic valve implantation in a patient with coral reef aorta

Abstract

This case describes the management of a woman in her 70s with severe symptomatic aortic stenosis and concomitant severe stenosis of the suprarenal abdominal aorta due to ‘coral reef’ calcification of the aortic wall and lumen (CRA). Due to her religious beliefs as a Jehovah’s Witness regarding the use of blood products, she rejected the option of surgical aortic valve replacement. Transfemoral (TF) delivery of a transcatheter aortic valve was challenged by the presence of CRA. A successful TF transcatheter aortic valve implantation (TAVI) was achieved by the treatment of the CRA with intravascular lithotripsy-assisted angioplasty, followed by delivery and deployment of a self-expanding TAVI valve.

Background

Coral reef aorta (CRA) is a rare pathology characterised by dense exophytic intraluminal calcification located primarily in the suprarenal and juxtarenal aorta. Patients are most commonly diagnosed above the age of 50 years. Clinically, patients typically present with one or a combination of the following: resistant renovascular arterial hypertension, intermittent claudication and chronic mesenteric ischaemic symptoms.

The pathophysiological process of CRA is poorly understood. Although patients with CRA have typical risk factors predisposing to atherosclerosis, the severe calcified masses found in patients with CRA suggest an alternative diagnosis other than atherosclerosis alone.¹ Immunohistochemistry analysis of the calcifications in CRA has shown low levels of calcification inhibitors fetuin-A, uncarboxylated matrix Gla protein and osteoprotegerin, suggesting that a deficiency of these molecules may be playing a pathophysiological role.² In a German registry of 80 patients with CRA, no association between CRA and aortic valvular pathology has been reported.³ A single case of CRA in a patient with severe aortic stenosis (AS) has been reported and was managed with transapical delivery of the transcatheter aortic valve implantation (TAVI) valve.⁴

CRA is primarily treated with surgical aortic reconstruction with endarterectomy and bypass grafting to the affected visceral arteries. Endovascular therapy for CRA has been reported in recent case publications.^{5 6}

Lithotripsy was initially developed in the 1980s for the treatment of renal calculi. In the last decade, intravascular lithotripsy (IVL) has found application in the treatment of calcific disease in the coronary and peripheral vascular circulation.^{7 8} IVL is delivered by lithotripters which are mounted along the central lumen of a semicompliant angioplasty balloon. Pulses of sonic pressure waves emitted by lithotripters are transmitted through the diluted contrast in the balloon inflated to low pressure (typically four atmospheres), which opposes the wall of the diseased artery. The effect of sonic waves is to cause direct stress with compression and decompression of the lesion, causing the calcium to fracture. This leads to more effective acute luminal gain with a reduced risk of intimal and medial dissection in the wall of the artery.⁹ The use of IVL as a treatment option for CRA has not been previously reported

Case presentation

This woman in her 70s presented with progressive shortness of breath. She described bilateral intermittent claudication and had poorly controlled hypertension, despite being compliant with four antihypertensive medications.

Her medical history included coronary artery disease, hypertension, hyperlipidaemia, ischaemic stroke and paroxysmal atrial fibrillation. She had no history of smoking. A CT of her abdominal aorta documented the presence of an area of dense calcification with associated severe stenosis involving the abdominal aorta just proximal to the origin of the renal arteries (figure 1).

Figure 1.

CT with contrast of the aorta showing coral reef aorta. (A) Coronal view of the abdominal aorta showing severely calcified suprarenal stenosis. (B) Sagittal view of the abdominal aorta showing severely calcified suprarenal aorta at the level of L1 vertebrae. White arrow indicates origin of the superior mesenteric artery.

Her current medications included bumetanide 1 mg once a day, spironolactone 25 mg once a day, losartan 100 mg once a day, amlodipine 10 mg once a day and doxazosin XL 4 mg once a day.

On examination, she had a 3/6 ejection systolic murmur and an absent second heart sound, consistent with severe AS.

The patient met with a cardiothoracic surgeon to discuss the option of conventional surgical aortic valve replacement (SAVR), which would be the standard of care for this relatively young patient at low surgical risk. Because of her religious beliefs as a Jehovah’s Witness, she rejected the option of SAVR due to the concern about the use of blood replacement products. She was referred for evaluation of percutaneous options to manage her severe AS.

After careful consideration, it was felt that the best option for TAVI would involve transfemoral (TF) access for TAVI valve delivery, with the goal of minimising the bleeding risk in a patient in whom avoidance of blood products was critical. The TF approach necessitated the treatment of the CRA to facilitate delivery of the TAVI valve. Because of the dense calcification at the site of stenosis, the option of IVL-assisted balloon angioplasty was deemed appropriate.

Investigations

Transthoracic echocardiogram showed severe AS of a tricuspid aortic valve with peak and mean gradients of 75 mm Hg and 52 mm Hg, respectively. The ejection fraction was normal (figure 2).

Figure 2.

Transthoracic echocardiogram prior to transcatheter aortic valve implantation (TAVI). (A) Severely calcified aortic valve shown in parasternal long-axis view. (B) Doppler ultrasound of aortic valve showing peak gradient of 75 mm Hg across the aortic valve prior to TAVI.

A dedicated CT TAVI documented the following:

1. Aortic valve annulus with an area of 406.6 mm², perimeter of 72.4 mm, and minimal and maximal diameters of 20.5 mm×24.9 mm, respectively (figure 3).

2. Good calibre iliofemoral arteries bilaterally, with no calcification or tortuosity.

3. Severe aortic calcification and luminal narrowing at the level of the superior mesenteric artery consistent with the diagnosis of CRA (figure 1).

Figure 3.

Dimensions of native aortic annulus before transcatheter aortic valve implantation.

Differential diagnosis

In this case, the diagnosis of CRA is not in doubt. This patient had all the classical characteristics of CRA based on the patient’s age, medical background and findings on imaging.

Idiopathic midaortic syndrome is a non-artherosclerotic, non-inflammatory disease that can cause concentric and tubular stenosis of the abdominal aorta in the same location as the patient in this report. However, this is typically a paediatric diagnosis, and stenosis in these patients is not calcified.^{10 11}

Treatment

The procedure was performed in the catheterisation laboratory under conscious sedation.

Sheaths were placed in the right and left common femoral arteries (CFAs) and the right common femoral vein.

The site of CRA in the suprarenal aorta was sequentially dilated with a 5 mm×40mm conventional non-compliant balloon, with a 7mm×60mm M5-IVL Shockwave balloon (Shockwave Medical) and finally with a 10 mm×60 mm conventional non-compliant balloon (figure 4). Subsequent angiography showed a good angiographic result (figure 4).

Figure 4.

Intravascular lithotripsy (IVL)-assisted angioplasty of coral reef aorta (CRA) in the abdominal aorta. (A) A prior aortogram showing the CRA before IVL-assisted angioplasty. White circle highlights the CRA. B. Inflation of 7mm×60mm M5-IVL Shockwave IVL balloon. (C) Inflation of 10 mm×60 mm conventional peripheral balloon. (D) Aortogram after IVL-assisted angioplasty. White circle highlights the CRA.

A 26 mm Evolut PRO TAVI valve (Medtronic) was then delivered through the area of CRA with minimum difficulty to the level of the native aortic valve and was deployed under fluoroscopic guidance (figure 5). The valve’s implant depth was approximately 7 mm.

Figure 5.

Deployment of self-expanding valve. (A) Partial deployment of transcatheter aortic valve implantation (TAVI) valve. (B) Complete deployment of TAVI valve.

The valve delivery system and sheath in the right CFA were removed, and closure of the arteriotomy was achieved using suture-mediated closure with no immediate periprocedural complications.

Outcome and follow-up

An echo on day 1 after procedure documented a normally functioning TAVI valve with peak and mean gradients of 18 mm Hg and 10 mm Hg, respectively, and no paravalvular leak.

On the first day after TAVI, the patient developed sinus bradycardia with associated left bundle branch block (LBBB) and first-degree heart block. She then had paroxysms of atrial fibrillation (PAF) with ventricular rates up to 120/min (figure 6). Given her baseline bradycardia and conduction disease after TAVI, it was decided to proceed with insertion of a permanent pacemaker (PPM) to deal with her bradycardia and allow the addition of a beta-blocker to help treat her PAF. The PPM was inserted on day 5 after TAVI. She was discharged on day 6 after TAVI.

Figure 6.

ECGs after transcatheter aortic valve implantation procedure. (A) Sinus bradycardia 56 beats per minute with left bundle branch block (LBBB) and first-degree heart block. (B) Atrial fibrillation 97 beats per minute with LBBB.

At 6 months after the procedure, her dyspnoea had resolved and an echocardiogram showed a normally functioning TAVI valve with minimal gradients and no paravalvular leak. She reported a decrease in severity of her intermittent claudication, and a 24-hour blood pressure monitor showed a mean blood pressure of 127/70 mm Hg.

Discussion

This case outlines the successful percutaneous treatment of a patient with a rare combination of CRA causing severe stenosis of the suprarenal abdominal aorta and severe symptomatic AS. The management was made more challenging by the patient’s religious beliefs as a Jehovah’s Witness, which resulted in her refusal to accept the risk of transfusion of blood products. Despite being a low-risk candidate for SAVR, this consideration resulted in her refusing the option of SAVR after discussion with a surgeon. As a result, we sought to offer a TAVI procedure to deal with her AS and deliberated over the optimal access site for delivery of the TAVI valve, given that the presence of a CRA made TF access impossible without some form of interventional treatment.

A variety of alternative access sites other than the TF route are available for TAVI delivery, including central (ie, transapical (TA), transaortic) or peripheral (ie, transsubclavian (TS), transaxillary (TAx) or transcaval (TCV)) options. Among the central access sites, the TA site had traditionally been dominant and was the primary alternative access site in the early experience with TAVI.¹² Among the peripheral access sites, the TS/TAx access site is dominant and has emerged as the favoured alternative access site in contemporary practice.¹³ These alternate access sites (other than the TCV strategy) would avoid the suprarenal abdominal aorta for TAVI valve delivery and were technically feasible in this patient. The TCV option was of no value because the connection between the inferior vena cava and abdominal aorta is typically created at the level of the infrarenal aorta below the level of the CRA in the suprarenal aorta.

A large body of data supports TF TAVI based on superior clinical outcomes associated with the TF access site, most notably reduced rates of mortality and stroke compared with non-TF TAVI.¹² In addition, TF TAVI is associated with a reduced risk of significant bleeding, transfusion and the need for conversion to surgery to deal with major valve or vascular complications from TAVI.^{12 14 15} The latter considerations seemed particularly pertinent to our patient.

Following a synthesis of the clinical situation presented, we felt the optimal strategy for our patient was to attempt revascularisation of the segment of CRA in the suprarenal abdominal aorta to facilitate delivery of the TAVI valve from the femoral artery access site. Given the densely calcified nature of the CRA-associated stenosis, treatment with IVL-assisted angioplasty that has specifically been developed to deal with highly calcified arterial lesions seemed a reasonable decision. The application of IVL-assisted angioplasty in the abdominal aorta does represent an off-label use of the device, with approved use currently applying to large peripheral vessels (ie, iliac and femoral) and coronary arteries.^{16 17} In this case, the IVL-assisted angioplasty of the CRA was successful in creating a lumen sufficient for TAVI valve delivery and was not associated with injury or dissection to the aortic wall.

The choice of TAVI valve used in this case was heavily influenced by the presence of CRA. The use of a self-expanding TAVI valve as opposed to a balloon-expandable valve was favoured. With a self-expanding valve, the metallic stent frame of the valve is entirely covered by a capsule until deployment at the site of the native aortic valve, allowing for a smoother transit through the calcified segment of CRA. In contrast, the balloon-expandable valve leaves the stent frame exposed during delivery through the suprarenal aorta, increasing the chance of interaction with the calcified segment of CRA, particularly at the proximal margin of the stent frame. The Evolut PRO valve’s optimal implantation depth is between 3 mm and 5 mm.¹⁸ A greater implantation depth increases the valve’s surface contact with the interventricular septum and proximity to the atrioventricular node, which increases the risk of conduction disease.¹⁹ The implantation depth seen in this case likely contributed to the development of the LBBB and the need for pacemaker.

This case underscores the complexity of decision-making sometimes encountered in the management of patients with severe AS. The advent of TAVI has represented a major paradigm shift in patient management and has greatly enhanced our ability to offer treatment in unusual clinical circumstances. An individualised approach to care addressing each of the unique challenges encountered is critical in achieving optimal clinical outcomes.

Learning points.

• Coral reef aorta in the abdominal aorta is a rare vascular disease process characterised by dense calcification causing stenosis in the suprarenal and juxtarenal abdominal aorta. This condition would usually preclude a transfemoral (TF) approach to transcatheter aortic valve implantation (TAVI).

• A TF approach to TAVI in this case was strongly favoured due to the lower risk of bleeding and need for surgical conversion.

• Intravascular lithotripsy-assisted angioplasty of the abdominal aorta and use of a self-expanding TAVI valve resulted in successful TF delivery and deployment of the TAVI valve with a good clinical outcome.