Two cases of pregnancy with coarctation of the aorta

An increasing number of women with previously repaired coarctation of the aorta are now becoming pregnant; uncorrected coarctation may also present for the first time in pregnancy with hypertension. There are vital issues pertaining to maternal risk and management.

CASE HISTORIES

Case 1

This patient was originally thought to have pulmonary stenosis at the age of 2 years. Subsequently lost to follow-up, she was noted to be hypertensive at the age of 17 years, when she reported breathlessness, exertional chest pain, syncope and cold feet. Blood pressure in the left arm was 150/100 mmHg, 150/110 mmHg in the right. Despite referral to the general cardiology outpatient clinic, she did not attend until she was 19; echocardiography at that time revealed a native coarctation with a doppler gradient of 3.8 m/s (33 mmHg), a tricuspid aortic valve without gradient, normal left ventricular dimensions/wall thickness and normal aortic root. Before the planned MRI had been performed, she arrived at the obstetric booking clinic. Her blood pressure at 12 weeks' gestation was 130/80 mmHg and there were no new features on echocardiography. She smoked ten cigarettes a day. Fetal echocardiography was subsequently unremarkable. During pregnancy her cardiologist felt that antihypertensive treatment was not indicated.

At 35 weeks' gestation she was admitted with a frontal headache and ankle oedema. Heart rate was 125/min and right arm blood pressure 176/98 mmHg; there was no visual disturbance and her reflexes were normal. A cardiotocograph showed good fetal reactivity. There was no evidence of pre-eclampsia and she was managed with home bed rest. A healthy boy (2.94 kg) was delivered by caesarean section (with antibiotic prophylaxis); despite good epidural analgesia her blood pressure at the time of delivery was 210/100 mmHg.

Subsequent ambulatory monitoring revealed that blood pressure was in the hypertensive range through the day; a Bruce protocol exercise test was terminated after 7 minutes because of fatigue, at which time the peak blood pressure was 180/95 mmHg and heart rate 110/min. She was effectively treated with Inderal LA (propranolol hydrochloride), chosen because of negligible excretion in breast milk. An MRI scan demonstrated a prominent ledge, with a luminal dimension of 9 mm×6 mm (normal 14-29 mm) (Figure 1). She has since been accepted for balloon dilatation, with stenting of her native coarctation.

Figure 1.

MRI scan of native coarctation. T1 weighted images fast spin echo series

Case 2

At the age of 8 days this patient had an end-to-end anastomosis of the aorta with resection of severe coarctation; the main pulmonary artery was banded, since she had a large ventricular septal defect. When this closed spontaneously at the age of 8, the pulmonary artery was debanded but pericardial patch enlargement of the main pulmonary artery was required. She was lost to cardiological follow-up. At the age of 28 her general practitioner referred her to the grown-up congenital heart (GUCH) clinic for prepregnancy assessment. By the time of review she was already 8 weeks pregnant. On clinical examination she had radiofemoral delay, an ejection systolic murmur in the pulmonary area with a fixed S2, right bundle branch block on electrocardiogram and an early diastolic murmur of aortic regurgitation. There were bruits over the left scapula. Blood pressure was 148/78 mmHg and subsequent ambulatory blood pressure monitoring revealed a borderline hypertensive pattern through the day. A Bruce protocol exercise test was terminated after 9.5 minutes because of tiredness; peak blood pressure was 180/95 mmHg. A 12-lead electrocardiogram met voltage criteria for left ventricular hypertrophy. The echocardiogram showed increased septal wall thickness but a normal free wall. There was a 15 mmHg gradient across the right pulmonary artery; the aortic valve was tricuspid with normal aortic root dimensions and mild aortic regurgitation secondary to a thickened leaflet, which created an eccentric jet. The gradient across the coarctation site was 3 m/s (36 mmHg), and dilated collaterals were seen arising from the aortic arch. The MRI demonstrated recoarctation and the lumen measured 10 mm×8 mm; there was a high velocity jet extending into the descending aorta. There was no significant stenosis of the right pulmonary artery nor was there aneurysmal dilatation at the site of the pulmonary artery pericardial patch.

The hypertension was initially treated with beta-blockers, methyldopa being added at 20 weeks' gestation. Blood pressure settled to 130/60 mmHg and ambulatory blood pressure was satisfactory. Fetal echocardiography gave normal results. At 30 weeks she was admitted with chest discomfort and dyspnoea on slight exertion. Bibasal crepitations were present and she was treated with bed rest, 20 mg frusemide daily, potassium supplements and low-molecular-weight heparin. Further echocardiography and MRI yielded no evidence of aortic dissection but her ventricular function was less dynamic; spiral CT angiography excluded pulmonary emboli. She had no further episodes of chest pain.

An elective caesarean section was performed at 38 weeks' gestation (with antibiotic prophylaxis) and a healthy boy was delivered. She has now been referred for consideration of balloon dilatation and stenting of her recoarctation.

COMMENT

Coarctation of the aorta accounts for 11% of cases seen in the GUCH clinic at our hospital. In most patients it has been diagnosed in early infancy; if coarctation is not relieved at this point, the incidence of hypertension is much higher. Late complications are persistent hypertension (30% at 10 years; 66% at 40 years), premature coronary artery disease (25%) and berry aneurysms (2-3%). Restenosis of the coarctation site occurs in up to 35% and aneurysm formation in 16%—dependent on the type of repair.¹ In view of these continuing hazards, lifelong follow-up is mandatory and any patient noted to have a history of coarctation must be sought out and referred for follow-up. Investigations would include MRI of the coarctation site to look for restenosis or aneurysm formation; ambulatory blood pressure measurement; and echocardiograms to allow the identification of bicuspid aortic valves (associated in up to 50% of all coarctations) as well as dilatation of the ascending aorta.

The two cases reported here highlight issues to be considered in women contemplating pregnancy. The first is the risk of aortic dissection, which is increased in the presence of a bicuspid aortic valve (reflecting concomitant ascending aortopathy) or Turner's syndrome (donated embryo pregnancy).² The second is restenosis, best assessed with echocardiography and MRI—which are safe in pregnancy.³ In both of these cases, despite moderate (RR)-coarctation, we felt that they would tolerate the pregnancy, with intervention after delivery (balloon dilatation and stenting being the preferred mode in these cases).⁴

Thirdly, hypertension must be controlled adequately with beta-blockers (plus methyldopa if necessary), and this should be initiated if the blood pressure is more than 130/80 mmHg before 20 weeks' gestation. Borderline values should be evaluated with ambulatory recording. Clearly it is important to strike a balance between good blood pressure control, vital for maternal wellbeing, and adequate fetal growth. Concern over fetal growth retardation should not delay the initiation of therapy; there does not appear to be a relation between fetal growth retardation and hypertension, duration of therapy or cause of hypertension. Calcium antagonists, thiazide diuretics and angiotensin converting enzyme inhibitors are all contraindicated.

Fourthly, early discussion between cardiologist, obstetrician and anaesthetist will allow planned management of pregnancy and delivery. This is one reason why, at our hospital, a multidisciplinary maternal medicine meeting has been introduced. We recommend elective caesarean section, to avoid the second stage and to reduce the need for Valsalva manoeuvres with their associated surges in blood pressure; the potential for rupture of berry aneurysms is pertinent.⁵ Antibiotics should be prescribed at the time of delivery; the only two cases of maternal death with coarctation and pregnancy in the mortality statistics 1997-99 were associated with endocarditis.⁶ Finally, genetic counselling should be offered since there is a 3% incidence of coarctation in the offspring and fetal echocardiography at 20 weeks' gestation may be helpful. Of the 17 women with coarctation in our GUCH clinic, 10 have had eighteen pregnancies (1 baby had congenital heart disease). Other district general hospitals are likely to have a similar population.