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By far the commonest cause of hypertension in pregnancy is pre-eclampsia, but other causes must not be forgotten.
On the second day after a normal delivery a woman aged 16 was referred because of uncontrolled hypertension. 2 years previously she had been found hypertensive when taking the combined oral contraceptive pill. Six months after stopping the pill she had been treated for missed abortion, at which time her blood pressure was 160/95 mmHg. There was no family history of hypertension or congenital heart disease. In the last trimester of her second pregnancy, blood pressure was again noted to be high. She had intermittent headaches; there was no peripheral oedema or proteinuria. On examination postpartum, blood pressure was 210/122 mmHg in the right arm and 200/110 mmHg in the left arm. The femoral pulses were weak, with radiofemoral delay, and the lower-limb blood pressure was 122/88 mmHg. An ejection systolic murmur was audible all over the precordium, radiating to the interscapular region. Physical examination was otherwise unremarkable. The electrocardiogram showed sinus rhythm with left axis deviation and biphasic T wave changes but no strain pattern. The chest X-ray was normal, as were laboratory data including serum cortisol and urinary catecholamines. Transthoracic echocardiography showed concentric left ventricular hypertrophy with good systolic function. Colour doppler from the suprasternal view revealed turbulence in the upper thoracic aorta consistent with coarctation. The peak systolic gradient was just over 100 mmHg and there was a diastolic tail on spectral doppler in keeping with a diastolic gradient across the stenosis. To control the hypertension, oral labetalol was added to the bendrofluazide she was already taking.
On left heart catheterization under general anaesthesia the ascending aortic pressure was 135/62 mmHg and the descending aortic pressure 84/63 mmHg, giving a peak transcoarctation gradient of 50 mmHg. An arch aortogram (Figure 1) showed a discrete segment coarctation of the descending aorta distal to the left subclavian artery with large collateral arteries. A 58 mm uncovered peripheral stent (Jostent, Jomed, Rangendingen, Germany) mounted on a Merck balloon, 15 mm diameter and 45 mm length (Merck Ltd, Alton, UK) was placed across the coarctation, intravenous adenosine being used to induce transient cardiac standstill during deployment. The gradient was completely abolished and the angiogram showed a satisfactory result (Figure 2). The procedure time was 47 min and the fluoroscopy time was 8.2 min. Clopidogrel was prescribed, 75 mg daily for six months. Eighteen months post-procedure she is taking labetalol 200 mg twice daily—one-third of the dose she required before stenting. Blood pressure in the right arm is 145/85 mmHg and the femoral pulse volume is normal on both sides. The latest echocardiogram shows regression of left ventricular hypertrophy, a patent stent with no aneurysm formation and no doppler evidence of recoarctation.
Coarctation of the aorta accounts for around 5% of congenital heart defects. It is the main non-renal cause of systemic hypertension in children and infants. Although 80% of cases are diagnosed in infancy or childhood, the disorder may present or first be recognized in adult life. Although corrective treatment has greatly improved the outlook, hypertension may persist and follow-up should be indefinite11. Clarkson showed 20% of adult patients still hypertensive 5 years after coarctectomy; thereafter prevalence of hypertension increases2.
Women with coarctation may have uneventful pregnancies, but the maternal mortality rate is 3-8% and morbidity too can be considerable3. In our patient the risk of fetal and maternal morbidity and mortality was high in view of the severe pregnancy-induced hypertension in the third trimester and the tight coarctation. Maternal risks include rupture of the aorta, intracerebral bleeding, hypertensive heart failure and infective endocarditis. Fetal mortality in patients with uncorrected coarctation is said to be 11-13%4. Repeated miscarriages are common, probably related to placental ischaemia5.
Despite these risks to mother and fetus invasive treatment during pregnancy is only indicated if there is severe uncontrolled hypertension or complications have developed, such as heart failure, cerebral ischaemia or suspicion of dissection.
For treatment, the options are percutaneous balloon angioplasty or coarctectomy. Balloon angioplasty was first used in children6. In a subsequent series, 23 of 27 adults had a substantial drop in antihypertensive drug requirements7. With good patient selection angioplasty is inexpensive and safe, though long-term follow-up is essential. The advent of stents allows more controlled dilatation with less risk of recurrence or aneurysm formation. Surgery is technically more demanding in adults than in children because of large collaterals, hypertension and sometimes a calcified aorta. In women who have had successful surgery or angioplasty the outcome of further pregnancies is good, if the residual gradient is less than 20 mmHg; their incidence of pre-eclampsia is similar to that in the general population8.
The possibility of coarctation of the aorta should be considered in any young patient with hypertension. By careful examination of the femoral pulses, clinicians can detect the condition early and prevent its very serious complications.