Clinical History
A 21-year-old male patient with a one-year history of resistant arterial hypertension was referred by a general clinician for investigation of secondary hypertension. Negative family history and no risk factors. The physical examination revealed a blood pressure of 153/75 mmHg (left arm), without other abnormal signs and with a normal ECG.
Imaging Findings
To exclude renovascular hypertension the first examination requested was a renal ultrasound with Doppler evaluation of renal arteries. This revealed a small amplitude waveform with a prolonged systolic rise on spectral Doppler (parvus-tardus waveform) in both renal arteries (both proximal and distal) and its branches, with extension to the abdominal aorta, ruling out renal arterial stenosis and suggesting a more proximal stenosis in the aorta. There was a diffuse decrease in the renal arterial resistive index (RI) too. After that a CT angiography was performed and revealed a narrowing of the proximal descending thoracic aorta, distal to the left subclavian artery, associated with dilated internal mammary arteries and intercostal collateral arteries due to high grade stenosis as a result of aortic coarctation.
Discussion
Coarctation of the aorta is a congenital malformation that results in narrowing of the aortic lumen in the region of the ligamentum arteriosum just distal to the left subclavian artery [1, 2, 4, 5]. The stenotic segment frequently develops in a juxtaductal location but may show extension into the aortic arch and isthmus [4]. There is a male predominance. Coarctation may be associated with other cardiovascular malformations including bicuspid aortic valve, cerebral aneurysms and Turner syndrome [1, 4]. The symptoms depend on the severity of the condition, most people are asymptomatic or develop arterial hypertension. The characteristic sign is blood pressure differential between upper and lower limbs.
The imaging studies contribute to the diagnosis, namely chest radiograph, echocardiogram, CT and MRI angiography. On plain film the classic sign of coarctation is an abnormal mediastinal contour known as the “figure of 3 sign” produced by the combination of prestenotic dilatation of the aortic arch and left subclavian artery, effacement of the aortic knob, and poststenotic dilatation of the proximal descending aorta [1]. Other signs include inferior rib notching that occurs secondary to collateral circulation through the intercostal arteries [1, 3, 4]. Both CT and MRI angiography can accurately demonstrate the location and morphology of the aortic narrowing [1] and detect the presence of collateral circulation, which manifest as dilatation and tortuosity of the internal mammary arteries, thyrocervical and costocervical trunks, and intercostals arteries.
Treatment options are variable and usually consist of primary surgical repair or balloon angioplasty. Nontreated aortic coarctation has a poor prognosis.
Renal ultrasound with Doppler is very useful and frequently performed to identify the potential cause of secondary hypertension, especially renal artery stenosis. When bilateral tardus-parvus waveform is detected (as in this case), bilateral renal artery stenosis and aortic stenosis (including aortic coarctation) should be considered. To differentiate between aortic stenosis and bilateral renal artery stenosis, the wave patterns of the aorta should be checked – in our case it also revealed a parvus-tardus waveform ruling out bilateral renal artery stenosis, and suggesting a proximal aortic stenosis – that was confirmed on CT. Although diagnosis of aortic coarctation is mostly done by physical examination, there are some situations in which the outcome is normal. Our case serves as a representative example of the usefulness of Doppler ultrasound on evaluation of renovascular hypertension in young patients with high blood pressure and no suspicion of aortic coarctation.
Differential Diagnosis List
Aortic coarctation
Pseudo-coarctation of the aorta
Chronic large vessels arteritis
