Teaching Case

A 19-year-old female patient with no previous history of chronic diseases was referred to our hospital for suffering long-standing headache, dizziness and weakness. Raised arterial pressure (160/100mmHg) was found on physical examination, as well as elevated creatinine levels on blood tests. An abdominal ultrasound was performed under the suspicion of renovascular hypertension.

No parenchymal renal anomalies were found. However, a “parvus et tardus” waveform (prolonged systolic acceleration with small systolic amplitude) was detected in the Doppler study when examining both renal arteries and the abdominal aorta. The resistance index of these arteries was low (0.4-0.5) and the renal interlobar arteries had a similar Doppler pattern.

Renovascular hypertension was ruled out as a possible diagnosis and a magnetic resonance angiography (MRA) was performed under the suspicion of a proximal anatomical vascular defect. The MRA study proved an aortic coarctation with a stenotic defect distal to the left subclavian artery origin.

The stenotic segment diameter was 5 mm and numerous collateral vessels were associated, providing downstream blood flow through the left subclavian artery, internal mammaries and thoracic arteries.

After conducting an evaluation by conventional angiography, a transcatheter stent was planned, but the patient ultimately refused to complete the treatment.

Aortic coarctation (CoA) is defined as a narrowing of the thoracic aorta.  It is often a discrete stenosis, but can also involve long segments of the aorta, being typically located at the insertion of the ductus arteriosus just distal to the left subclavian artery.

It can occur in association with other congenital heart defects, such as bicuspid aortic valve (60%), aortic arch hypoplasia or other arch anomalies (18%), ventricular septal defect (13%), mitral valve abnormalities (8%), subaortic stenosis (6%), among others [1].

The cause of discrete aortic coarctation remains unclear, but is likely multifactorial. Prenatal environmental exposures have been associated with CoA and other left-sided lesions. However, a genetic basis for development of these lesions has also been described [2].

Most adult patients are asymptomatic. However, some may present with severe hypertension leading to headaches, epistaxis, heart failure, and/or aortic dissection. Patients who are normotensive at rest, should be tested for exercise-induce hypertension [3] through a cardiopulmonary exercise test with a treadmill ergometer using an incremental protocol (Naughton protocol or the modified Bruce protocol).

Symptoms might be mitigated in some patients by collateral vessels, which originate in segments proximal to the coarctation to provide arterial flow to hypoperfused tissues distal to the coarctation [4].

Vascular ultrasound in patients with suspected aortic coarctation demonstrate reduced aortic distensibility, which is associated with increased afterload and significant hypertension in the aorta and proximal branch vessels to the coarctation. This eventually leads to ventricular dysfunction, vessel aneurysm formation, and premature atherosclerosis.

Multidetector computed tomography (MDCT) angiography with multiplanar and three dimensional techniques is a non-invasive method for characterizing the location, degree and length of the narrowing, relationship to the left subclavian artery, presence of collateral circulation and associated cardiovascular abnormalities [5, 6].

Cardiac magnetic resonance imaging (CMR) provides futher analysis of velocity acceleration and estimation of shunt fraction (to assess associated intracardiac shunts) [7].  It can also be used to identify predictors of coarctation‘s severity, such as heart rate-corrected mean flow deceleration in the descending aorta as well as the smallest aortic cross-sectional area [8], measured by gadolinium-enhanced 3D MRA or Gadolinium free angiographic imaging consisting of a slab-selective inversion preparation for background suppression followed by segmented 3D steady-state free precession (SSFP) acquisition and fast 4D imaging of the aorta [9].

Transcatheter intervention might be crucial in some cases to asses the coarctation gradient, although this might be misleading in patients with longstanding native coarctation who have developed significant collateral flow over time, because they may have a lower measured gradient despite severe coarctation [10].

A measured peak-to-peak gradient greater than or equal to 20 mmHg by cardiac catheterization is an indication for intervention. Therefore, patients with extensive collaterals should undergo intervention even if the peak-to peak gradient is less than 20 mmHg. (10) Finally, patients with other heart defects tend to have worse outcomes, requiring more frequent reoperation when there is an associated aortic valve disease [11].