Keywords
aorta - thoracoabdominal aorta - pregnancy
Introduction
Middle aortic syndrome consists of segmental narrowing of the aorta typically involving
the lower thoracic and upper abdominal aorta with or without renal artery involvement.
This results in arterial hypertension and symptoms of chronic lack of blood flow.
It is usually secondary to either a congenital developmental anomaly of the aorta
or to one of many acquired conditions such as Takayasu's arteritis, fibromuscular
dysplasia, neurofibromatosis, or mucopolysaccharidosis.[1] It is a very rare condition, comprising 0.5 to 2.0% of aortic coarctations.[2] If left untreated, it leads to life-threatening complications secondary to severe
hypertension, with significant mortality at a young age. Treatment usually entails
aortoaortic bypass of the diseased segment through a thoracoabdominal approach, with
excellent prognosis in the majority of patients. We present the case of a young female
with symptomatic middle aortic syndrome with the intention of getting pregnant in
the near future.
Case Presentation
A 30-year-old female with middle aortic syndrome, diagnosed at the age of 15, presented
to us with hypertension and significant buttock numbness after a brief period of sitting
down. Past cardiac history was also remarkable for a bicuspid aortic valve and mild
mitral regurgitation. She was medically managed with an angiotensin-converting enzyme
inhibitor and β-blockers for hypertension and was a nonsmoker who expressed strong
wishes to become pregnant. Her obstetrician was concerned that her condition would
not support her pregnancy owing to lack of blood flow to the pelvis during pregnancy.
The patient had two prior spontaneous miscarriages. Physical examination was remarkable
for hypertension, with systolic blood pressure ranging from 160 to 180 mm Hg. Strong
palpable pulses were noted in her upper extremities, with weaker palpable pulses in
her lower extremities.
Preoperative work-up included a magnetic resonance (MR) angiogram which revealed a
normal appearing thoracic aorta that tapers from 2.0 cm down to 8 mm in size. There
was no evidence of stenosis at the origin of the renal arteries or in the mesenteric
vessels ([Fig. 1]). A dynamic cardiac MR revealed a maximal gradient of 37 mm Hg at the level of the
diaphragm.
Fig. 1 Magnetic resonance angiogram imaging of the patient's aorta preoperatively.
The patient underwent a tunneled descending thoracic aorto-left common iliac artery
bypass, avoiding the need for a traditional large thoracoabdominal incision. The thoracic
aorta was accessed via a 10-cm left thoracotomy incision and the left common iliac
via an 8-cm left paramedian incision. A retroperitoneal tunnel was then created, and
an opening in the diaphragm was made to enter the thoracic cavity. The bypass was
performed using a 22 cm × 9 mm Dacron graft between the descending thoracic aorta
and the proximal left common iliac artery tunneled through the neo-diaphragmatic hiatus.
She did very well in recovery and was discharged from the hospital on postoperative
day 5 without any complications.
At her 3-week follow-up visit, the patient reported complete resolution of her buttock
pain and was able to discontinue her antihypertensive medication. The patient subsequently
became pregnant and delivered a full-term baby. At 1.5 years' follow-up, the patient
continues to do well.
Discussion
Middle aortic syndrome is an extremely rare cause of arterial hypertension, resulting
from an acquired or congenital condition causing segmental narrowing of the descending
aorta. If left untreated, the majority of patients usually die because of progressive
severe hypertension before the age of 35 to 40. The term “middle aortic syndrome”
was first coined by Sen et al[3] who described in 1962 four cases of narrowing of the aorta at unusual sites in the
subisthmal aorta. Taketani et al[4] described their experience of surgical treatment of atypical aortic coarctation
complicating Takayasu's arteritis in 33 cases over 44 years. The aortic coarctation
was proximal to the origin of the renal arteries in 29 patients with hypertension.
In the vast majority of cases, treatment was surgical with an aortoaortic bypass using
a 10- to 16-mm prosthetic graft via a left thoracoabdominal incision.
Ours is an unusual case where an aorto-left common iliac bypass was performed to treat
symptoms, increase survival, and prevent potential maternal and fetal morbidity during
pregnancy via a minimally invasive approach through a tunnel through the diaphragm.
To our knowledge, this has not been previously reported.
Pregnancy is associated with several significant physiologic changes in the cardiovascular
system, including systemic vasodilation that occurs as early as 5 weeks of gestation.
There is also up to 45% increase in cardiac output, and an increase in total blood
volume by approximately 45% that is proportionally more than red blood cell mass,
resulting in physiologic anemia.[5] These changes are necessary to adapt for the increased metabolic demands of both
the mother and the fetus. Cardiovascular disease in pregnancy is the leading cause
of maternal mortality in North America.[6] Some call pregnancy a “nature's stress test” since it can unmask underlying cardiovascular
pathology. It has been well documented that pregnant patients with Takayasu's arteritis,
an idiopathic, nonspecific aortoarteritis that can potentially cause segmental aortic
narrowing, have worse fetal outcome with significantly higher perinatal mortality
compared with unaffected patients.[7]
[8]
Our patient had managed her aortic coarctation nonsurgically as long as possible.
The standard repair involves a traditional thoracoabdominal incision. Endovascular
interventions involving balloon angioplasty and/or stenting may also be an option,
but they are limited to isolated aortic stenoses without visceral involvement, and
the long-term durability is unknown.[9]
[10] In a recent retrospective study, surgical bypass was compared with endovascular
treatment for patients with supra-aortic arterial occlusive disease in Takayasu's
arteritis.[11] In that series, surgical bypass demonstrated better patency rates compared to endovascular
treatment. In addition, symptom recurrence was more common with an endovascular approach.[11]
Our goal was to decrease expected mortality, ensure adequate uteroplacental circulation,
and prevent fetal demise. The underlying condition that our patient had, which included
an average 8-mm abdominal aortic diameter, coupled with her strong desire to have
a successful first child, made the situation highly risky.
