Discussion

Narrowing of the abdominal aorta was first identified by Quain in 1848, but the term “middle aortic syndrome” was created by Sen et al.^{Reference Sen, Kinare, Engineer and Parulkar4} in 1963 after observing 16 patients with Takayasu’s arteritis and active tuberculosis. Now, the term “midaortic syndrome” refers to all obstructive lesions of the midaorta, regardless of their cause.

As with aortic coarctation, high upper extremity blood pressure, low lower extremity blood pressure, and weak femoral pulses are common clinical findings. Hypertension has been detected in nearly every case. In our patient, on physical examination, blood pressure was high in the upper extremities and both femoral pulses were weak.

Severe middle aortic syndrome causes major morbidity and mortality. Approximately half of untreated middle aortic syndrome cases lead to hypertensive encephalopathy, congestive heart failure, and stroke, which have less than 20% survival after age 40. The management of middle aortic syndrome is challenging, and it necessitates a multidisciplinary approach. Medical management of hypertension has been generally ineffective.^{Reference D’Souza, Tsai and Silver5} In order to achieve sufficient blood pressure management and reverse or avoid end-organ damage, invasive intervention is often required. In addition, studies have shown that symptoms such as intestinal ischemia and claudication develop more frequently in patients who received only antihypertensive treatment than those who undergo invasive treatment, but medical treatment is recommended for the stabilisation of the patient before intervention.^{Reference D’Souza, Tsai and Silver5}

Surgical and endovascular procedures are the two forms of invasive interventions. Surgical treatment is the oldest, most common, and well-known technique. Thoracoabdominal aortic bypass, interposition aortic graft, and patch angioplasty are the most using surgical options for middle aortic syndrome. Even though many surgical studies report excellent clinical outcomes, surgery is technically difficult with more potential risks as opposed to percutaneous interventional approaches. Surgical bypass using conduits is hard and complicated, and the tube graft will need to be replaced later, particularly if the patient has not reached full growth at the time of the initial surgical treatment.^{Reference Kim, Vakili and Ramos-Gonzalez6} For this reason, the surgical procedure requires frequent repetitions in children.

Interventional endovascular therapy consists of balloon dilatation or stent implantation. Balloon angioplasty seemed initially as an acceptable alternative treatment to surgery because it was less invasive and required short hospitalisation, but it is limited by unsatisfactory results due to significant vessel recoil, especially in hypoplastic and fibrotic stenoses.^{Reference Bush, Hoffman, Del Rosario, Eiriksson and Rome7} To get over these limitations, endovascular stents, including different types of balloon-expandable and self-expanding stents, were applied by and by in the management of middle aortic syndrome.^{Reference O’Laughlin, Perry, Lock and Mullins8}

The optimum stent to be used in middle aortic syndrome should be able to be delivered through small sheaths, be flexible, redilatable up to 15–18 mm maximum size, have little shortening, and have good radial strength, among other characteristics.^{Reference Quandt, Ramchandani and Bhole9} Due to their limited radial strength, self-expanding stents cannot be overdilated and hence do not meet the criteria.^{Reference Redington, Weil, Somerville and Br Heart10} Balloon-expandable stents are commonly used stents in paediatric cardiology. Coronary balloon-expandable stents are extremely flexible and may be inserted using 4F sheaths or 6F guide catheters, but they cannot be extended beyond 6 or 7 mm in diameter. These limitations have resulted in the creation of novel stent designs.

The Cook Formula stent family is a relatively new hybrid cell design that has been approved for use in biliary, renal, and peripheral vascular procedures. The major advantage of Cook stent is that while other Balloon-expandable stents length can vary by up to 53% during dilatation, Cook stent’s length changes minimally even as its diameter increases.^{Reference Quandt, Ramchandani and Bhole9} This provides the opportunity to perform stent redilatation over time, especially in children who have not completed their development.

In our patient, no intervention was performed on the narrowing at the proximal level of the right renal artery. We decided against it because of the significant risk of restenosis, which has been reported in approximately 20–26% of children^{Reference Srinivasan, Krishnamurthy and Fontalvo-Herazo11}, as well as other problems. Because the patient’s blood pressure can be regulated, a surgical treatment may be performed after the patient’s growth and development is complete.

In conclusion, middle aortic syndrome is utterly a severe form of aortic coarctation and leads intractable hypertension and end-organ failure. Because surgical approach has several limitations and risks of reoperation, transcatheter endovascular stent implantation should be kept in mind as a feasible alternative treatment. This could be anyway a good example of effective stenting implantation with a relatively new hybrid stent family that provides the opportunity to perform stent redilatation over time. Because of well-known high incidence of restenosis and reintervention after percutaneous intervention, follow-up is needed with this new type of stent.