Key Words
Aortic dissection - Surgery - Pregnancy - Aortic aneurysm
Introduction
Type A aortic dissection is a rare and life-threatening complication of pregnancy
that most commonly occurs in the context of connective tissue disease (CTD)[1]. We present two cases of successful delivery and surgical repair of aortic dissection.
Case Presentation
Case One
A 32-year-old parturient presented at 32 weeks with anterior chest pain, radiating
to her back. Before this, she had been in good health with an uncomplicated pregnancy.
Echocardiography revealed a Type A aortic dissection with torrential aortic regurgitation.
Intravenous antihypertensive agents were administered, followed by urgent transfer
to our center. Under general anesthesia (GA), a Caesarean section was performed and
the healthy, preterm baby girl was admitted to the neonatal unit.
Subsequently, a midline sternotomy incision was made, confirming Type A aortic dissection
with the intimal tear across the sinotubular junction. Cardiopulmonary bypass was
established using the right axillary artery for arterial return and the right atrium
for venous drainage, and the aorta was clamped. Myocardial protection was by antegrade
and retrograde multidose cold-blood cardioplegia. The aorta was opened and the valve
excised. The coronary ostia were mobilized on aortic buttons. A bileaflet mechanical
ATS valved conduit (ATS Medical, Inc., Minneapolis, MN, USA) was sutured in place
and the ostia were reimplanted within the graft. The distal anastomosis was completed
with the clamp on, and air was evacuated from the heart. The heart took over the circulation
without support. The patient made an uneventful recovery and was discharged on day
5. Histology of the aorta showed only mild myxoid degeneration, with no evidence of
CTD, and related genetic tests were all negative. Her Beighton score (which quantifies
joint laxity) was 1/9.
Case Two
A 38-year-old woman presented in the 38th week of her twin pregnancy with severe breathlessness
and a 2-week history of anterior chest pain radiating to the neck and back with syncopal
episodes. There were clinical signs of hypoxia and frank pulmonary edema. The patient
had preeclampsia and was being treated with methyldopa. Echocardiography revealed
acute Type A aortic dissection involving the entire thoracic aorta with severe aortic
regurgitation. She was treated initially with glyceryl trinitrate and transferred
to our center.
Under GA, a Caesarean section was performed, delivering a baby boy and then a baby
girl, both healthy. A midline sternotomy incision was made, confirming Type A aortic
dissection. The intimal tear was in the noncoronary sinus. Cardiopulmonary bypass
was established using the right axillary artery for arterial return and the right
atrium for venous drainage, and the aorta was clamped. Myocardial protection was by
antegrade and retrograde multidose cold-blood cardioplegia. The ascending aorta was
resected, including the region of the root containing the tear. The valve was resuspended
and the aortic layers were reapproximated with Bioglue. A 30 mm graft was implanted
at the sinotubular junction. The distal anastomosis was completed with the clamp on,
and air was evacuated from the heart. The heart took over the circulation without
support. The patient made an uneventful recovery and was discharged on day 9.
Genetic testing for common CTD was all negative, but the geneticist believed features
suggestive of Ehlers-Danlos syndrome type IV were present. Furthermore, there was
a family history of aortic dissection and of death of unknown cause during childbirth.
Comment
The challenges of managing an acute aortic dissection in pregnancy begin at diagnosis,
where delay increases mortality, which rises by 1 to 3% every hour, with a 25% mortality
by 24 hours[2]. The classical presentation of anterior chest pain radiating to the back always
merits prompt investigation. The diagnosis of aortic dissection is more challenging
in preeclampsia, which presents with hypertension and epigastric pain, potentially
masking the presenting features of an acute aortic dissection. Indeed, attributing
epigastric pain and hypertension to preeclampsia alone may delay the diagnosis[3]. Distinguishing between these two conditions is further confounded by the fact that
dissection, like preeclampsia, is more likely in the third trimester, when the hyperdynamic
circulation and hormonal effects on the vasculature may predispose to dissection[4]. Echocardiography is a noninvasive, highly sensitive, and specific aid to diagnosis[5].
Anesthesia in these circumstances is challenging, requiring experienced input and
consideration of the well-being of both mother and baby. Regional anesthesia is generally
the method of choice for Caesarean section because GA carries a risk of aspiration,
failed intubation, and hypoxemia associated with physiological changes in pregnancy[4]. In the setting of acute Type A aortic dissection, however, the choice of anesthetic
type is altered. Regional anesthesia for Caesarean section has been used in the context
of acute dissection[6], but the need for full systemic heparinization increases the risk of epidural hematoma.
Blood pressure control, needed to reduce the risk of aortic rupture during delivery,
is easier in GA. A rapid sequence induction will minimize the risk of aspiration;
patients should be preoxygenated, and equipment for difficult airways must be available.
A high-dose opioid technique is often used to ensure hemodynamic stability and diminish
the hypertensive response to intubation, which could cause extension or rupture of
the dissection, but this is associated with respiratory depression, so that the neonate
may require intubation and ventilation after delivery. The mother should be placed
in a 15° left lateral tilt until delivery to avoid compression of inferior vena cava
and aorta by the gravid uterus. Strict blood pressure control is of paramount importance:
glyceryl trinitrate, labetalol, hydralazine, and nifedipine can be used in pregnancy
without any adverse fetal effects. Esmolol may be used, but propranolol can cause
fetal hypoglycemia and bradycardia. Sodium nitroprusside should be avoided, as accumulation
of cyanide ions can be fetotoxic.
Cardiac surgical outcomes are poorer in pregnant women, and neonatal survival is poor,
especially if dissection happens well before term[7]. Multiple pregnancy poses an even greater risk of dissection complication, due to
an elevated maternal cardiac output[8]. This is the first reported mother of twins in the United Kingdom, and one of very
few worldwide, to survive aortic dissection during pregnancy without fetal loss.
Genetic investigation is indicated in aortic dissection. A diagnosis of CTD has implications
for future pregnancies: 50% of aortic dissections in pregnancy occur in patients with
Marfan syndrome[1]. The CTD-caused changes in the aorta, combined with the hemodynamic and vascular
changes in pregnancy, elevate the risk of a dissection. Neither of our patients had
mutations associated with the most common CTDs, although one may have clinical features
of Ehlers-Danlos syndrome.
The detection and management of aortic dissection in pregnancy is challenging. The
successful outcomes in these cases highlight two important points. First, due to the
life-threatening nature of aortic dissection, thorough investigation of anterior chest
or epigastric pain is essential in pregnancy, even against a background of preeclampsia,
and ultrasound offers a quick, safe, and accurate means of diagnosis. Second, the
management of aortic dissection in pregnancy requires a multidisciplinary approach
in which the anesthetist, obstetrician, neonatologist, and cardiac surgeon must urgently
collaborate to ensure the protection of both mother and baby.
