Pregnancy and aortic dissections

This editorial refers to ‘Pregnancy-associated arterial dissections: a nationwide cohort study’†, by S.E. Beyer et al., on page 4234. It is established that cardiovascular disease is a common cause of morbidity and mortality in maternal health in the developed world.1 Data from a US observational study (2011–2013) have previously shown a pregnancy-related mortality rate of 1.7 in 100 000 live births.1 A less common cause of morbidity and mortality in pregnancy is vascular arterial dissection, with the most commonly published cohorts having been in association with spontaneous coronary artery dissection.2 The consensus has been that aortic bed dissections are generally linked to pregnant women with underlying connective tissue disease, and the outcomes are usually known to be fatal.3 However, other cardiovascular risk factors have not been well explored. Thus far, there is a handful of case series and reports on aortic dissections in pregnancy and postpartum, with most publications having been linked to patients with underlying connective tissue disease such as Marfans and Ehrlers Danlos syndrome.3–5 A meta-analysis of aortic dissection in pregnancy by De Martino et al. demonstrated that, though this was rare, the mortality could be fatal, in particular in association with underlying connective tissue disease.4,6 However, other risk factors such as hypertension have been attributed to dissection in medium and small aortic beds.7,8 The aetiology of aortic dissections in pregnancy is thought to be due to hormonal changes that alter the aortic architecture in order to allow for remodelling and pregnancy-induced haemodynamic changes including increased stroke volume. The overall effect is weakening of the aortic wall which is particularly noted in the late gestation period, mainly caused by fragmentation of reticulum fibres and reduction in the mucopolysaccharide level, altering the aortic extracellular matrix.9,10 This process allows for aortic dilatation required for the increased volumes the aorta has to manage during the late stages of pregnancy. In the case of underlying connective tissue disease, there is an increased risk of progressive dilatation or dissection of the aorta in these women. The presence of hypertension increases the risk further.6,11 A previous comparative study by Kemal et al. in 2016, a case series of aortic dissection in the 6 months before delivery until 3 months after delivery, showed an aortic dissection incidence of 5.5 per million compared with 1.4 per million during an equivalent period a year later,12 demonstrating that pregnancy itself is a risk factor for aortic dissections. However, other smaller published case series have illustrated the coronary arterial bed as a site vulnerable to spontaneous dissection in the last trimester of pregnancy and postpartum.13 In this regards, Beyer et al. provide a unique and important new piece of information in this issue of the European Heart Journal, presenting a nationwide cohort study on aortic dissections and pregnancy.14 The study collected data from a large population-based database of admissions (2010–2014) across 27 states of the USA. Data codes and hospitalization and provider cost codes were used to identify 18 151 897 pregnant patients. Using cost codes referred to as the Healthcare Cost and Utilization Project (HCUP), data were collected on 993 inpatients diagnosed with pregnancy and dissections. The data from this study illustrated the risk factors associated with pregnancy and aortic dissection. They also provided an insight into the distributions of aortic dissection in different stages of pregnancy and outcomes. The study has confirmed that the incidence of aortic dissections in pregnancy is 5.5 per 100 000 hospitalized pregnant or postpartum women. Though the incidence postpartum for aortic dissection is found to be higher, it is also associated with more fatal outcomes. The most common aortic dissection is of the coronary tree followed by aortic and intracranial arteries. However, there were differences in dissection pre- and postpartum. Aortic, coronary, and vertebral dissection were more frequent in the antepartum and delivery phase, whereas coronary, intracranial, and aortic dissections were mostly observed in the postpartum phase. The clinical characteristics and pregnancy-specific risk factors for aortic dissections in addition to traditional cardiovascular factors included older age, multiple gestations, gestational diabetes, and hypertension, as well as pre-eclampsia and eclampsia. In addition, gestational diabetes was more prominent in postpartum dissections. The in-hospital mortality was 3.7%. Though this is lower than what has been reported previously,1,15,16 this study may indicate that with improved diagnostics tools over the last decade and overall reduced maternal mortality with improved maternal health, the overall mortality from aortic dissection in pregnancy is lower than previously observed. The strength of this nationwide population study is defining the incidence of aortic dissections in pregnancy and the postpartum phase. In addition, the study adds value to previous publications which have mainly focused on arterial dissections in association with connective tissue disease.4,12 This study highlights pregnancy-specific risk factors as well as cardiovascular risk factors that increase the risk of aortic dissection in peripartum and postpartum stages. It also demonstrates the variation of the dissections within the arterial bed at different stages of pregnancy and postpartum that may be driven by physiological and hormonal changes.17,18 The outcomes from this study are comparable with spontaneous coronary artery dissection and pregnancy studies that have shown an increase in coronary dissections predominantly in the postpartum phase, though the risk factor characteristics may differ. However, there are limitations to this study as the data points were collected using billing and diagnostic codes from insurance and health providers. Inaccuracy in administrive data from billing by the providers would make the data susceptible to misclassification. The coding did not distinguish between type A and B dissections; however, prior algorithm modelling was utilized to assume that most are type B dissections. In addition, this registry data only incorporated data from hospital admissions, and was deficient in data on out-of-hospital dissections or deaths which is a caveat and would not have been represented by this study. Given that these are registry data, the data are only available for confirmed cases who have had the imaging diagnosis of an arterial dissection. It may be that pregnant women are less likely to be investigated with an imaging modality that consumes radiation and there may be more missed cases of dissections in the antepartum period that are not accounted for in this study. Overall, this is an excellent study of a US registry on aortic dissection in pregnancy, eliciting pregnancy and non-pregnancy risk factors that predispose to arterial dissections in all stages of pregnancy as well as postpartum. It also includes data on the secondary outcomes including investigations and management in relation to various dissections and mortality. It is well written and illustrated with figures and very detailed supplementary data. This study emphasizes to physicians to consider all types of arterial dissection that can occur at multiple stages of pregnancy. In addition, it provides insight and knowledge that women with pregnancy-related and cardiovascular risk factors are at higher risk of potential aortic dissections. These risk factor profiles should be incorporated in pregnancy risk assessment and consideration for aggressive risk factor management where possible to reduce risk of aortic dissections. Conflict of interest: none declared. The opinions expressed in this article are not necessarily those of the Editors of the European Heart Journal or of the European Society of Cardiology.