The second group of children with aortic isthmus stenosis remain asymptomatic for a longer period. These children become conspicuous due to hypertension in the upper half of the body and hypotension in the lower half. Typical times for first diagnosis in these children are pediatric check-ups and pre-school medical examinations. At the physical examination, the inguinal pulse may be only weakly palpable, if at all, in comparison with the pulse in the radial artery, depending on the severity of the stenosis. Symptoms include headache, epistaxis and intermittent claudication.
Untreated adults: Untreated adults usually become symptomatic due to their untreated hypertension. Typical symptoms with late diagnosis are headache, epistaxis, intermittent claudication, heart failure and acute aortic dissection. The annual mortality rate in untreated patients with aortic isthmus stenosis is age-dependent and shows a peak frequency in the first year of life. According to data from the first half of the twentieth century, the mean life expectancy for individuals with untreated aortic isthmus stenosis is 34 (Abbott 1928; Campbell and Baylis 1956). Reasons for the high mortality rate include frequent accompanying anomalies with severe cardiac insufficiency (Table 2.1-10). Another extremely important factor is the risk of rupture or dissection of the aorta, which must be regarded as high in the presence of a simultaneous bicuspid aortic valve and due to systemic weakness in the wall of the aorta, particularly in patients with untreated or inadequately controlled hypertension.
Table 2.1–10 Causes of death in patients with untreated aortic isthmus stenosis (Campbell 1979).
| Cause of death | % | Average age(years) | Decade of life |
| Decompensated cardiac failure | 26 | 39 | 3rd–5th |
| Rupture or dissection of the aorta | 21 | 25 | 2nd–3rd |
| Bacterial endocarditis | 18 | 29 | 1st–5th |
| Intracranial bleeding | 12 | 29 | 2nd–3rd |
| Aortic isthmus stenosis not the cause of death | 24 | 47 | 4th–6th |
2.1.10.4 Diagnosis
Clinical examination
Blood pressure and pulse: A classic sign of aortic isthmus stenosis both in adults and children is a difference in systolic pressure between the upper and lower extremities. In contrast to the systolic pressure, diastolic blood pressure often shows no differences between the upper and lower extremities (Brickner et al. 2000). Blood pressure is usually the same in the right and left arm, corresponding to a location of the aortic isthmus stenosis distal to the original of the left subclavian artery. When the subclavian artery arises distal to the isthmus stenosis, blood pressure in the left arm may be lower than in the right. Very rarely, when both subclavian arteries arise distal to the isthmus stenosis, it is possible for similarly reduced blood pressures to be present in all four extremities. The current guidelines for diagnostic clarification of hypertension therefore recommend that pulse and blood pressure should be examined and compared in the upper and lower extremities (Warnes et al. 2008). Auscultation: In addition to cardiac murmurs in associated malformations, a typical finding in aortic isthmus stenosis is a short midsystolic murmur that can also be heard for longer than the second heart sound and is best heard in a left paravertebral position. In addition, continuous flow murmurs may be heard over collateral vessels.
Electrocardiography: In children with aortic isthmus stenosis, there are often signs of right ventricular hypertrophy, while signs of left ventricular hypertrophy are typical in adults.
Exercise tests: Ergometric exercise with electrocardiographic or echocardiographic monitoring may be useful, particularly for recognizing exercise hypertension or diagnosing a raised transisthmic gradient (Warnes et al. 2008). However, these examinations are not recommended as a general routine for follow-up in patients with aortic isthmus stenosis.
Imaging
The entire diagnostic work-up for an aortic isthmus stenosis can be carried out noninvasively. For diagnosis and follow-up in patients with aortic isthmus stenosis, the classic chest x-ray has been abandoned for echocardiography and other tomographic methods. Even though a chest x-ray is still a frequently used screening procedure, particularly for acute diagnosis, it cannot provide important information about the presence of aortic pathology (von Kodolitsch et al. 2004; Hiratzka et al. 2010). Although changes in the ascending aorta often cannot be recognized in the mediastinal shadow, larger aneurysms in the descending thoracic aorta are often surprisingly well demonstrated (Hiratzka et al. 2010). On a sagittal noncontrast image, an isthmus stenosis may be demarcated as a notch-like dent in the aorta at the junction of the aortic arch and descending aorta, known as the “3 sign” of aortic isthmus stenosis. When one is assessing aortic isthmus stenosis radiographically, it should be borne in mind that the characteristic defects from the third to eighth ribs (notching on the underside of the ribs) usually appear only after the age of 8. These defects arise as a result of dilated intercostal arteries (known as Dock’s sign; Fig. 2.1-28). In general, a chest x-ray only has very limited diagnostic reliability, with a sensitivity of < 20% for detecting re-stenoses after correction of an aortic isthmus stenosis (Therrien et al. 2000).
Fig. 2.1–28a, b Posteroanterior (a) and lateral (b) radiographs in a 37-year-old patient with aortic isthmus stenosis. Rib defects can be seen as typical radiographic signs of aortic isthmus stenosis, as well as a notch in the descending aorta. Left ventricular hypertrophy is present as a secondary sign. A localized luminal constriction in the aorta can be seen in the area of the aortic isthmus on the lateral image.
Echocardiography: The aortic valve, ascending aorta and aortic arch with the origins of the supra-aortic branches can usually be well assessed with transthoracic echocardiography. It is important to carry out the examination from a suprasternal direction, which allows Doppler echocardiographic assessment of the gradient across the aortic isthmus stenosis (Warnes et al. 2008). Both Doppler echocardiography and invasive measurement of pressure gradients may underestimate the severity of an isthmus stenosis when there is good collateral flow (Warnes et al. 2008). Echocardiography has a sensitivity of 87% and a specificity of 78% for diagnosing recurrent stenoses of the aortic isthmus, while