Surgery for type A aortic dissection in pregnant patients with Marfan syndrome

We read with interest the article by Sakaguchi et al. [1] on surgery for type A aortic dissection in pregnant patients with Marfan syndrome and the accompanying editorial by Dr. Jean Bachet. The authors have reported four cases over a 12-year period describing the methods of surgery, outcome for mother and foetus and some recommendations for these patients. We believe that the methods of cardiopulmonary bypass in pregnant patients undergoing cardiac surgery warrant more detailed attention in order to improve the outcome for both the mother and the foetus. Placental vasoconstriction and contraction cause foetal hypoxia and bradycardia. Placental vasoconstriction in turn is caused by hypothermia during bypass, rewarming phase and non-pulsatile flow. We have previously shown that the use of non-pulsatile perfusion contributes to foetal bradycardia and demise [2]. Pulsatile perfusion is thought to reduce uterine contractions by releasing endothelial-derived growth factor from the vascular endothelium. Champsaur et al. [3,4] have shown that pharmacological blockade of endothelial-derived growth factor after 30 min of pulsatile flow returns foetal haemodynamics to continuous flow conditions, suggesting that nitric oxide may be released by foetal endothelium during pulsatile bypass. Furthermore, experimental evidence suggests that placental vasoconstriction may be mediated by prostaglandins and that indomethacin and steroids administered during bypass prevent the increase in placental vascular resistance [5]. Full maternal and foetal monitoring improves outcome. Placental and foetal blood flows can be measured by means of transvaginal ultrasonography, where maternal uterine arteries, foetal umbilical artery, foetal aorta and cerebral arteries, and ductus venosus are identified with colour Doppler and frequency shift traces obtained with pulsed-wave Doppler. During foetal monitoring, heart rate deceleration may indicate hypoxia and distress although another cause of foetal bradycardia is foetal anaesthesia. Drugs that are known to be safe and do not cross the placenta must be used. Vasoconstrictors should be avoided because of their effect on the uterine spiral arteries. Glyceryl trinitrate infusions may reduce the risk of uterine contractions. In pregnancy, cardiopulmonary bypass is best conducted with mild hypothermia, pulsatile perfusion and high flow rates.