Discussion

Mid-aortic syndrome is a rare atypical aortic coarctation, which is characterised by progressive segmental or diffuse narrowing of the distal thoracic aorta and/or abdominal aorta, often involving bilateral the renal and other visceral arteries.^{Reference Rumman, Nickel and Matsuda-Abedini9} In very few cases, middle aortic syndrome is located in the distal part of the thoracic aorta. In the abdominal aorta, the suprarenal region is the most frequently affected site, followed by stenosis extending from suprarenal to infrarenal regions, whereas an exclusively infrarenal involvement is the least common occurrence. Renal artery stenosis presents in two third of cases, with about 60% of these instances being bilateral.^{Reference Pytlos, Michalczewska, Majcher, Furmanek and Skrzypczyk4,Reference Rumman, Nickel and Matsuda-Abedini9}

Although the pathogenesis of middle aortic syndrome remains unknown, it has been considered to arise from a failure of paired fusion of the embryonic dorsal aortas around the first month of fetal development.^{Reference Cohen and Birnbaum10} Middle aortic syndrome could also originate from an acquired anomaly because of inflammatory diseases, genetic disorder, or non-inflammatory causes, like fibromuscular dysplasia, and so on. Most cases of middle aortic syndrome are idiopathic and lack a definite underlying diagnosis.^{Reference Sen, Kinare, Engineer and Parulkar11–Reference Quek, Tan and F.14} In our patient, inflammatory markers and routine laboratory evaluation were within normal limits, and there were no clinical findings suggestive of systemic inflammatory disease or syndromic features associated with neurofibromatosis type 1, Williams syndrome, or Alagille syndrome.^{Reference Lazea, Al-Khzouz and Sufana15} Plasma renin activity and aldosterone levels were normal. Formal genetic testing was not performed due to the absence of phenotypic features suggestive of a specific genetic syndrome and local resource limitations. As a result, in our case, the pathology was regarded to be congenital hypoplasia. Documented ultrasound findings of middle aortic syndrome include segmental narrowing and tortuosity of the aorta, turbulent flow, focal increased peak systolic velocities (> 200 cm/s) in the narrowed region, poststenotic turbulence, and a renal aortic ratio > 3.5. However, the visualisation of the full anatomic course of the renal artery is not possible in more than 40% of the cases. Indirect signs of renal artery stenosis include “tardus-parvus” waveform patterns, increased acceleration time > 0.07 s, and acceleration index > 3 m/s³. CT angiography remains the gold standard imaging modality for diagnosing middle aortic syndrome. It can easily assess the location and length of the narrowed segment and evaluate the visceral artery abnormalities and collateral circulation. Initial management of middle aortic syndrome often involves pharmacological antihypertensive agents. Endovascular management includes renal and/or aortic angioplasty and renal artery stenting. Percutaneous transluminal renal angioplasty is an effective endovascular treatment for complete recovery, or for temporary relief of hypertension prior to surgical repair. Aortic angioplasty for middle aortic syndrome is less common than surgical intervention due to the high rates of reintervention and the risk of thrombosis, rupture or pseudoaneurysm. Surgery becomes the main treatment option for middle aortic syndrome complicated with visceral artery stenosis. An aorto-aortic bypass from the distal thoracic aorta to the infrarenal aorta, with revascularisation of all narrowed branches, is a preferred surgical approach for treating middle aortic syndrome.

Long-term outcomes in patients with middle aortic syndrome depend on the severity of vascular involvement, the presence of renovascular hypertension, and the timing of intervention. Untreated middle aortic syndrome is associated with an unfavourable prognosis due to persistent severe hypertension and progressive en-organ damage, including heart failure, renal insufficiency, cerebrovascular events, and premature cardiovascular disease1. Surgical and endovascular interventions may significantly improve blood pressure control and lower the risk of long-term complications; however, restenosis, graft stenosis, persistent hypertension, and the need for reintervention have been reported during follow-up. Complications of early reconstructive surgery must be weighed against the end-organ damage as a result of refractory hypertension. Looking for the appropriate balance between noninvasive treatment and surgical therapy remains an ongoing challenge.^{Reference Rumman, Nickel and Matsuda-Abedini9} Therefore, lifelong surveillance with clinical evaluation and periodic vascular imaging is essential. A multidisciplinary approach involving cardiologists, vascular surgeons, nephrologists, and radiologists is recommended to optimise long-term management and outcomes in these patients.^{Reference Bayazit, Yalcinkaya and Cakar16}

In conclusion, our case highlights that mid-aortic syndrome, although rare (0.5%– 2% of all coarctations), constitutes an important cause of arterial hypertension, especially in young patients. Thus, mid- aortic syndrome should be considered in the differential diagnosis of secondary hypertension. Aggressive medical management with antihypertensive regimens is crucial in addition to definitive endovascular or surgical treatment. Given the lack of prospective studies, future research into causation, diagnosis, and management is warranted.