Clinical implication
As is known to all, pregnancy is a risk factor for AD15. Previous studies have reported a higher incidence rate of TAAD in pregnancy than TBAD4, 12. However, recent data indicates an increasing trend in the occurrence of TBAD, especially in women with pregnancy3. Consistent with this, all five pregnant patients with AD admitted to our hospital were Stanford type B in the past two years. In our study, advanced in maternal age, preeclampsia and cesarean delivery may be contributing risk factors of TBAD, which is consistent with literature reports16, 17. It is recommended that patients with high risks for aortic dissection should receive transthoracic ultrasound every 4-6 weeks of pregnancy as part of routine prenatal examination18, and should be given more attention to the occurrence of AD.
Early identification and diagnosis of AD are crucial for treatment. However, the diagnosis of AD in pregnancy is challenging. The symptoms vary among patients, especially in those with TBAD, and are easily confused with physiological discomfort and other diseases during pregnancy19. Given the rarity of AD, it is easily misdiagnosed. CTA has high sensitivity and specificity in the detection of dissection20. However, patients may refuse to undergo CTA due to concerns about the impact of radiation on the fetus. In fact, fetal radiation doses delivered by CT examinations are generally below the consensus levels for negligible risk (< 50 mGy)21. In addition, although iodinated contrast agents typically traverse the placenta, the use of contrast agents in pregnancy is considered relatively safe22. Transthoracic echocardiography (TTE) is recommended as a preliminary screening method for pregnant women complicated with AD because of its high safety and technical popularity12, 23. However, only lesions near the aortic root can be detected by transthoracic echocardiography, and missed diagnosis may occur in the diagnosis of TBAD24. In our study, all five patients were diagnosed TBAD timely through CTA. Notably, not all the patients had no signs of TBAD in transthoracic echocardiography. Since cardiac Magnetic Resonance imaging (MRI) is time-consuming, we did not choose MRI before treatment. Based on our experience, CTA is the optimal examination for pregnant patients with suspected TBAD. It can not only quickly detect the existence of dissection, but also clarify the type and extent of the lesion. Moreover, CTA can show the iliac artery tortuosity and pathological changes, which is essential for selecting safest surgical approaches25.
Complicated TBAD with malperfusion or rupture is considered a medical emergency and requires surgery management26. In the endovascular era, new technologies are constantly emerging. TEVAR has been shown to have lower mortality and morbidity compared with open aortic repair in patients with TBAD 27, 28. Currently, there are limited reports on the application of TEVAR in pregnant patients with TBAD. The timing of TEVAR and cesarean section is also controversial. Considering the negative impact of cardiac surgery on fetus, a cesarean section was recommended before any surgical intervention with the mother19, 29. Shu et al., reported two cases of TBAD in late pregnancy, who were successfully treated through TEVAR11. They suggested that for the late third trimester of pregnancy (beyond 37 weeks gestational age), emergency intervention on the aorta should be before delivery if accompanied by the complication11. In our study, the first case experienced dissection rupture during cesarean section and died unexpectedly. On the contrary, the following four patients who underwent TEVAR before cesarean section survived following successful treatment. Thus, we think that for patients with complicated TBAD in the third trimester, there is a risk of dissection rupture during delivery. This may be because of the cessation of placental circulation and an increase in cardiac blood volume after fetal delivery. Given this, performing TEVAR first may be a wise choice. Even though, this treatment method is still challenging as TEVAR may become complex in patients with late pregnancy. Due to the compression of the uterus, the stent-graft delivery system is difficult to pass through the iliac artery. One patient in our study experienced rupture of right iliac artery because of above reason. Moreover, the amount of radiation was limited for the safety of the fetus. Thus, TEVAR during pregnancy requires experienced and skilled cardiac surgeons to ensure the safety and short duration of the surgery.
Due to the small numbers reported globally, there is a lack of recorded long-term outcomes for pregnant patients with TBAD who were treated by TEVAR. The outcomes are satisfying in our series. Despite complications, such as internal leakage, iliac artery rupture, and progression to TAAD, which occurred during the treatment process, patients successfully completed TEVAR and survived. Moreover, no major late complication was detected, and a recovery of cardiac function was observed at last follow-up. Another concern for applying TEVAR in pregnancy is the safety of the fetus. It was reported that the total radiation dose during endovascular therapy and one year after surgery is lower than 50 mGy30, which is within the safe range for the fetus. In addition, except for the death of one neonate with preoperative fetal distress died, three neonates survived TEVAR without any complications. It is undeniable that brief neonatal asphyxia has occurred and may worsen if the surgical time is extended. Besides trying to control the duration of surgery, other methods to ensure the safety of newborns should be explored.