CASE REPORT

Acute aortic dissection during pregnancy

Walkiria Samuel Avila; Ricardo Dias; Renato Takeshi Yamada; Adriano Armelin

Heart Institute and University of São Paulo Medical School - FMUSP - São Paulo, SP - Brazil

Mailing Address

ABSTRACT

Acute aortic dissection is one of the most dreaded clinical conditions during pregnancy. Difficulties in establishing a diagnosis and limitations regarding invasive studies increase mortality rates associated with the disease. The limited experience reported in the literature does not allow the determination of guidelines for clinical and/or surgical management of aortic dissection in pregnancy. The authors present a case of acute aortic dissection in a woman in her 33^rd week of gestation and discuss the diagnostic approach considering the peculiarities of the disease's manifestation.

Key words: Aortic dissection, pregnancy, cardiac surgery.

Acute aortic dissection is a rare but severe event during pregnancy and one of the most dreaded clinical conditions during this period. Difficulties in establishing a diagnosis and assessing of symptoms, that can be mistaken for those of a normal pregnancy, as well as limitations regarding invasive studies, due to potential risk to the conceptus, result in treatment delay and further increase mortality rates associated with the disease.

The heterogeneous presentation of cases and limited experiencereported in the literature do not yet allow the determination ofguidelines for clinical and surgical management of aorticdissection in pregnancy. However, treatment must always offerchances of survival for both the mother and fetus, taking intoaccount the mother's clinical status, gestational age, and theopportunity for surgical intervention, if indicated.

The authors present a case of acute aortic dissection in awoman in her 33^rd week of gestation and discuss thediagnostic approach considering the peculiarities of thedisease's manifestation.

Case Report

A 35-year-old physician, nullipara, primigravida, asymptomatic, in her 33^rd week of gestation and with no personal history of heart disease or hypertension experienced severe retrosternal pain unrelated to exertion and accompanied by a drop in blood pressure (80/40mmHg), followed by gradual and spontaneous improvement. The patient was seen in the emergency room and treated with antispasmodic medication. Over the following 48 hours she presented respiratory discomfort, malaise, and lower extremity edema. At that time, the patient was advised to have an echocardiogram, which showed a DeBakey type-I aortic dissection, mild aortic regurgitation and significant left ventricular diastolic dysfunction (Fig. 1), and was immediately referred to the Heart Institute.

The patient reported that routine prenatal tests performedduring the first weeks of pregnancy were normal. In the29^th week, she presented brief palpitation, whichprompted conventional electrocardiogram and transthoracicechocardiogram, both of which showed no abnormality. In the32^nd week, a urinalysis revealed leukocyturia(71,000/mL).

At admission, the patient was conscious, dyspneic ++/++++,acyanotic, afebrile, and pale ++/++++. Her blood pressure (BP)was 130/60 mmHg and her heart rate (HR) was 90 beats per minute(bpm); peripheral pulses were palpable and symmetrical, and pulsepressure was high. Pulmonary auscultation revealed normalvesicular breath sounds bilaterally, with no adventitious sounds.Cardiac examination showed regular rate and rhythm, withoutmurmurs. She had lower extremity edema ++/++++, but there was nohepatomegaly. Her abdomen showed a pregnant uterus 30 weeks insize.

Computed tomography at admission showed increased diameters of the left heart cavities and confirmed the diagnosis of type-I aortic dissection, involving the brachiocephalic trunk and the ascending and descending aorta (Fig. 2). Obstetric and transabdominal ultrasonographic examinations demonstrated a single viable fetus showing vitality, gestational age of 33 weeks, and estimated weight of 2,300g.

Based on the progressive risk of aortic rupture and takingfetal viability into account, the medical team indicatedimmediate corrective surgery for the aortic dissection andtermination of pregnancy with cesarean section prior tothoracotomy.

The patient participated in and agreed with the decision. She was conscious when she entered the operating room, with stable vital signs, as shown by invasive monitoring. During anesthetic induction for cesarean section, a sudden hypotension occurred, followed by asystolic cardiac arrest. Under external cardiac massage, the baby was immediately delivered by a cesarean section through median laparotomy. As the mother's heart rate was not restored, an exploratory sternotomy was performed, revealing significant hemopericardium. After pericardial drainage, the heart rate was restored and the patient stabilized hemodynamically. Cardiopulmonary bypass was established by antegrade perfusion through the brachiocephalic trunk and venous drainage by a single cannula advanced to the right atrium; myocardial protection was carried out with cold blood cardioplegic solution and hypothermia at 20°C. Aortic dissection repair was carried out by inserting a Dacron tube into the ascending aorta (fig. 3) and right subclavian artery, after it was detached from the brachiocephalic trunk during arterial line placement.

Pathological studies showed partial delamination of the aortaat the media layer and hemorrhage within the adventitia, withmoderate accumulation of mucoid substance in de media andintima.

After surgery, the patient was maintained on assistedventilation for 48 hours and received routine postoperative drugsand the usual doses of oxytocic agent. She remainedhemodynamically stable, presenting no bleeding, with normaluterine contractility and lochia flow. During the first sevenpostoperative days she developed lower-extremity edema,significant arterial hypertension (mean BP 180/120 mmHg), andsinus tachycardia (mean HR 110 bpm), which were graduallycontrolled with atenolol 200 mg/day, captopril 150 mg/day,amlodipine 20mg/day, and furosemide 80mg/day.Low-molecular-weight heparin was also administered inprophylactic doses for six weeks. In the days that followed, drugdosages were adjusted to maintain BP around 100/60 mmHg and HR atapproximately 70 bpm. The patient was discharged on the15^th postoperative day. Atenolol and amlodipinedosages were maintained; captopril dosage was reduced (75mg/day).Due to the lack of aseptic and antiseptic techniques foremergency laparoscopy and thoracotomy, antibiotic prophylaxis wasinstituted with vancomycin 500 mg/day and ceftriaxone 1g/day for21 consecutive days.

The baby boy was born the 33^rd gestational weekunder general anesthesia and during maternal cardiacresuscitation maneuvers. He presented bradycardia, cyanosis, andpallor, with Apgar score 1 at one minute, 5 at five minutes, and7 at ten minutes.

The infant was placed on mechanical ventilation with 100%oxygen in an anesthetic bag during the first minute, and hisheart rate, skin color, and spontaneous breathing rapidlyimproved; however, he was hypotonic and had no reflexirritability. He progressed to respiratory failure, requiringintermittent mechanical ventilation and endotracheal surfactantadministration for two hours, which improved ventilationparameters. The baby was extubated while still in his first dayof life and was kept on oxygen nasal catheter with continuouspositive airway pressure (CPAP).

On his second day of life, the baby was diagnosed with rightpneumothorax and reduced oxygen saturation. He was then intubatedagain and maintained on mechanical ventilation and vasoactiveagents. After two chest drainages and high-frequency ventilation,both his clinical condition and ventilation parameters improved,which allowed him to be extubated on his 9^th day oflife, although he was still kept in the incubator with oxygencatheter. As his respiratory condition enhanced, theadministration of oxygen and vasoactive drugs was progressivelyreduced. Chest tubes were removed on the 12^th day,when enteral feeding was initiated through orogastric tube.

Due to his difficulties to coordinate sucking and swallowing,non-nutritive stimulation was required, with gradual transitionto oral feeding. Despite normal total blood count and negativeblood culture, the neonate was kept on antibiotics for 10 days,because the radiographic examination showed an area of opacity atthe right lung base, C-reactive protein levels were high for hisage (6.8), and there was a history of maternal urinary infectionat the time of delivery. Neurological examination wasunremarkable, as were the Doppler echocardiogram and brainultrasound; brain tomography showed mild attenuation of whitematter in both cerebral hemispheres. Responsive to suckingstimuli and being fed all milk volume orally, the baby wasdischarged at 34 days of life in good condition.

Discussion

Aortic dissection in young women is an uncommon disease,sometimes of unknown etiology, potentially catastrophic andvariable in extension, beginning with a rupture of the aorticintima.

In young patients, the most common clinical conditionspredisposing to aortic dissection are collagen diseases (Marfan,Ehlers-Danlos) or those that primarily affect the vessel, such asaortic coarctation and bicuspid aortic valve¹.However, in healthy women, a strong correlation between aorticdissection and pregnancy has been reported, based on the highincidence of this event during pregnancy^2,3. Indeed,in the Schnitker and Bayer review 24 out of 49 aortic dissectionsin women younger than 40 were associated with pregnancy, and 20of them occurred before labor⁴. The cause of thisassociation (pregnancy/aortic dissection) in women consideredhealthy at admission is still unclear.

At first, it was suggested that physiological increments inblood volume and cardiac output might be potential causes for theevent. However, this hypothesis does not explain the lowerincidence of dissection during labor⁵, when mostcirculatory impact occurs – as compared to other phases of thepregnancy-puerperal cycle – due to major hemodynamicoscillation.

It has also been argued that vascular structural changesobserved during pregnancy – and which are similar to cysticmedial necrosis and responsible for increased aortic diameter andcompliance (more marked at pregnancy term) – may play asignificant role in dissection⁵. Mucoid degenerationof the media and intima layers described in the pathologicalexamination of the aorta of the case under discussion, coincideswith literature reports on dissections that occur during thethird trimester of pregnancy. In this framework, a recent geneticstudy is worth noting. The study demonstrated variable expressionof matrix metalloproteinase genes of the aorta that greatlyinfluence physiological vascular remodeling duringpregnancy⁶.

The exact influence of hormones on vascular connective tissueremains unknown. Animal studies, however, have demonstrated thatestrogens inhibit collagen and elastin deposition in the aorta,whereas progesterone accelerates – although minimally – thedeposition of noncollagenous proteins in the vesselwalls⁷.

Clinical manifestations of aortic dissection – classicallyexpressed through severe retrosternal and/or abdominal pain –were, in this case, underestimated and undifferentiated from thechest pain resulting from mechanical effects of the pregnantuterus and constipation, which are common in normal pregnancies.Regarding differential diagnosis, amniotic fluid embolism,premature placental detachment, uterine rupture, and spontaneouspneumothorax are to be considered as frequent causes of chestpain during pregnancy.

Despite posing limitations for the diagnosis of aorticdissection, the echocardiography proved to be useful in earlyinvestigation, since it is a non-invasive and easy-to-performexamination. Computed tomography, combining the advantage ofrapid evaluation and relatively low cost, confirmed the diagnosisand, especially, dissection classification – key to therapeuticapproach definition.

The localization of aortic dissection in the ascending aortaand extending into the descending aorta has characterized thepresent case being as DeBakey type I, which prompted immediatesurgical correction, since medical treatment for that kind ofdissection is associated with increasing mortality rates,reaching 80% in the first week after thediagnosis⁸.

In recent years, three relevant data for treating this severedisease successfully have been identified: the early referral ofthese patients for surgery, surgeon's greater experience, andpostoperative care. Nonetheless, corrective surgery for aorticdissection is still associated with severe cardiac complicationsand operative mortality rates between 9% and 36%⁹. Aswith the risk posed to the mother, heart surgery causes fetalmorbidity and mortality risks of approximately 30% and 9%,respectively - which may vary according to the type of procedure,time of cardiopulmonary bypass, hypothermia, nonpulsatile flow,and previous maternal clinical conditions¹⁰.

In the present case, the priority indication for pregnancytermination prior to the aortic dissection repair aimed atsparing the lives of both the mother and conceptus, since thelatter, already viable, would have better chance of survival thanif it had been maintained inside the uterus during this highlycomplex surgery. While considering such approach, the high riskof acute fetal distress was taken into account, as it wouldrequire emergency cesarean section during intra- or postoperativeperiod, thus seriously worsening the patient's prognosis.

Our approach was consistent with data described in theliterature, in which the best survival rates (mother's andfetus's) are based on gestational age. Therefore, if the eventoccurs up to 28 weeks of pregnancy, surgical aortic dissectionrepair should be carried out during intrauterine life; after 32weeks, when the fetus is viable, surgical repair should beperformed after the cesarean section. A more difficult decisionto be made is when aortic dissection occurs between 28 and 32weeks of gestation. During this period, delivery must be decidedbased on the conceptus' conditions, and caesarean section shouldbe indicated in case of fetal distress, or pregnancy may becontinued if the fetus can tolerate maternalsurgery¹¹.

Cardiac tamponade and subsequent cardiac arrest are strongwarnings for the risk and severity of delaying surgicalprocedure. In the present case, laparotomy prior to thoracotomysaved the conceptus and freed the surgeon to repair the aortawithout the additional concern with the intrauterine fetus. Thesuccessful outcome was undoubtedly due to the indication ofsurgical intervention in the aorta immediately after diagnosiswas confirmed.

The clinical conditions shown by the neonate presuppose acuteintrauterine distress. The satisfactory response to earlyresuscitation maneuvers allows us to presuppose that thisasphyxia did not last long; however, it was long enough tocompromise the central nervous system, although temporarily, asshown by the length of time taken for the tonus and reflexirritability recovery. Although ultrasound examination wasnormal, in prematures with significant perinatal asphyxiaintracranial hemorrhage^{12, 13} is expected tooccur.

At a gestational age of 33 weeks, surfactant production is notyet enough to keep appropriate fetal alveolar distension. Thesituation is aggravated by asphyxia, which favors higherinactivation and increased surfactant consumption. For thatreason, its use has been indicated to improve respiratoryconditions, thus favoring earlier weaning from mechanicalventilation¹³.

Pulmonary traumas resulting from pressure and volumevariations are more closely associated with the use of surfactantduring mechanical ventilation, while pneumothorax is less commonin patients under positive alveolar pressure. Despite that,complete lung re-expansion was obtained through bilateraldrainage, and no pulmonary sequelae were reported.

The suck and swallow deficit after gestational week 34 maysignal some degree of impairment of the central nervoussystem¹⁴. Nevertheless, the child responded well tosucking stimulus, and the neurological assessment was considerednormal for his age, resulting in good prognosis.

After hospital discharge, counseling on family planning ismandatory due to the high risks of a new pregnancy in patientswith aortic diseases. Vascular changes fail to normalize afterpregnancy, resulting in predisposition to new cardiovascularevents. Therefore, it is a consensus that aortic diseases are acontra-indication to pregnancy¹⁵, and tubal ligationfor sterilization is the most effective contraceptive method forsuch cases.

Acknowledgements

To Dr Leon Gustavo dos Reis Macedo, intern at the HeartInstitute, for the postoperative follow-up of the patient, and toDr. Maéve Barros Correia, hemodynamicist, for proofreadingthe text.

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Mailing Address:
Walkiria Samuel Avila
Rua Apiacás, 688/31
05017-020 – São Paulo, SP, Brazil
E-mail: walkiria@incor.usp.br

Received on 10/08/05
Accepted on 17/10/05