Complete heart block, also known as third degree atrioventricular (AV) or simply third degree heart block is a disorder of the cardiac conduction system with complete absence of AV conduction. Aetiologically, CHB can be divided into two groups: congenital complete heart block and acquired complete heart block (ACHB) . Congenital CHB in pregnancy is associated with connective tissue disease but this was not present in our patient. Most cases reported in the literature suggest that uncomplicated brady-arrhythmia during pregnancy in the absence of significant underlying heart disease, results in a favourable outcome for both mother and baby. In addition, uncomplicated brady-arrhythmias including asymptomatic CHB has not been reported to cause any maternal death . However, our patient also had additional risk factors mainly massive bleeding secondary to placenta accreta and potential disseminated intravascular coagulation. Thus, our patient is unique in that when faced with massive bleeding, she potentially would not be able to mount an adequate heart rate response due to the CHB. In light of that, a temporary pacemaker was inserted to cope with this likely possibility.
In the 1950s, Epstein and Altman suggested that without pacemaker insertion, pregnancy in women with complete heart block was associated with high maternal and fetal mortality . However, subsequent case series reported experiences without the insertion of pacemaker in uncomplicated pregnancies and deliveries . These deliveries however were not at risk of obstetric haemorrhage. While our patient did not at any juncture use the temporary pacemaker, we felt that the insertion was fully justified to cover for the eventuality of a life-threatening situation.
The team took measures to reduce the risk of haemorrhage by ensuring that she had no coagulation abnormality despite the intra-uterine death. Bilateral uterine artery embolization was performed in this patient before the fetus was delivered as it was already confirmed dead. This procedure does not compromise long term uterine integrity . Traditional methods of controlling obstetric haemorrhage are by bilateral uterine artery or hypogastric artery ligation. These traditional methods produce low success rates in bleeding reduction due to the presence of extensive collateral circulation in the pelvis and has been estimated to be as low as 42% . This is in comparison to embolization which has a success rate of more than 90% . In addition, if a caesarean hysterectomy is needed, embolization can slow the rate of blood loss hence improving the surgical field. Caesarean hysterectomy in the presence of severe haemorrhage is an extremely challenging procedure which carries a high risk of iatrogenic damage to other pelvic structures especially ureters and bladder . Slowing the rate of blood loss improves the surgical field, making the procedure technically easier thus reducing the risk of surgical complications . In the presence of a significant blood loss in our patient, the team felt it was safer to proceed with hysterectomy to reduce the risk of post partum bleeding.
In patients at risk of major haemorrhage, choosing the best form of anaesthesia can be challenging. The advantage of regional anaesthesia is that it omits the use of volatile agents, which may contribute to uterine atony. Regional anaesthesia has also been shown to reduce transfusion requirements [12–14]. We chose general anaesthesia over regional anaesthesia as our patient had a definite risk of major obstetric haemorrhage complicated with CHB. With general anaesthesia, we had a better haemodynamic control and could focus on keeping up with the blood loss correction. Furthermore, the risk of conversion from regional to general anaesthesia at the time of torrential haemorrhage may add to further cardiovascular instability.
Etomidate was chosen over thiopentone as our induction agent as the former has been shown to be superior in maintaining cardiovascular stability. With the pacemaker in place we felt confident about using fentanyl, etomidate and suxamethonium, the combination of which can potentially cause bradycardia . Our patient did not suffer this complication during the induction process.