Transient iatrogenic heart block following foetal intracardiac transfusion for severe twin anaemia-polycythaemia sequence

Introduction

Chronic foeto-foetal transfusion due to placental vascular anastomoses in monochorionic twin pregnancies may culminate in twin anaemia-polycythaemia sequence (TAPS). The ensuing communications result in transfusion of blood from the donor to the recipient twin gradually leading to a severely anaemic donor twin and a severely polycythaemic recipient co-twin [1]. TAPS can be diagnosed antenatally or postnatally. The absence of oligohydramnios and polyhydramnios on antenatal ultrasound is a prerequisite for the diagnosis of TAPS, as these signs are pathognomonic for the twin-oligopolyhydramnios sequence. Prenatal diagnosis of TAPS is based on Doppler ultrasound abnormalities showing decreased peak systolic velocity in the middle cerebral artery (MCA-PSV) in the recipient twin (suggestive of foetal polycythaemia) and increased MCA-PSV in the donor twin (suggestive of foetal anaemia) [2].

Laser coagulation of the small anastomoses is the only treatment of TAPS but this may be technically challenging, especially at advanced gestation. Intrauterine transfusion of the donor twin with partial exchange transfusion of the recipient twin is an alternative option with a view to prolonging the pregnancy, as this may temporarily alleviate the severity of the condition of both twins [3]. The technique for intravascular foetal blood transfusion has been described in the treatment of severe alloimmunisation in rhesus disease [4]. The umbilical vessels are commonly preferred to access the foetal circulation [5], but the intracardiac route is used when access to the umbilical vessels is not feasible due to placental or foetal position. The intracardiac route has been associated with foetal complications such as haemopericardium, asystole and severe foetal bradycardia [6]. We now novelly report a foetus/infant who suffered heart block as a consequence of the procedure and discuss the management of heart block presenting in the perinatal period.

Presentation of the case

The mother had a spontaneously conceived monochorionic, diamniotic twin pregnancy. Ultrasound scan at 29 weeks of gestation was suggestive of TAPS. The following management options were discussed with the parents: (a) expectant management with risk of foetal demise of one or both twins; (b) iatrogenic preterm delivery with significant prematurity-related morbidity; (c) endoscopic laser ablation of the placental anastomoses with substantial failure rate due to advanced gestation and (d) intrauterine blood transfusion of the anaemic (donor) twin with partial exchange transfusion of the polycythaemic (recipient) co-twin. Following counselling, the parents opted for the latter option. In view of placental and foetal position, the intracardiac route to transfuse the donor was deemed the most appropriate.

Normal sinus rhythm prior to the procedure was demonstrated for both twins. Access to the donor foetal heart was obtained via ultrasound-guided insertion of a spinal needle into the right ventricle. Foetal haemoglobin prior to the transfusion was 3.8 g/dL. Following intracardiac removal of 40 mL of foetal blood and intracardiac transfusion of 70 mL of O Rh negative donor blood, foetal haemoglobin of the donor twin increased to 9.5 g/dL. The procedure, however, was complicated by haemopericardium and foetal bradycardia and the twins were delivered via emergency caesarean section.

The donor female twin infant was born with a heart rate of <60 bpm and no respiratory effort. Endotracheal intubation was undertaken at 2 min of age. A blood transfusion at 20 mL/kg and normal saline at 10 mL/kg were administered. On admission to the neonatal unit, the heart rate was 70–80 bpm and haemoglobin was 13.8 g/dL. A chest radiograph taken at 2 h of age revealed a left-sided pneumothorax and pneumopericardium (Figure 1) which were evacuated with no effect on the heart rate. Echocardiography at 5 h of age revealed a structurally normal heart; 12 lead electrocardiography revealed complete heart block with ventricular rate of 70–78 bpm (Figure 2). Ventricular heart rate fluctuated between 60 and 80 bpm until 34 h of age, when atrioventricular (AV) conduction spontaneously recovered at a rate of 120–140 bpm. The chest drains were removed on day 4 after birth and the infant was successfully extubated on day 5 after birth. She was discharged well to the local hospital on day 19. No evidence of intracranial pathology was demonstrated on serial cranial ultrasound examinations.

Figure 1:

Chest radiograph taken at 2 h of age depicting left-sided tension pneumothorax and pneumopericardium.

Figure 2:

Electrocardiograph at 5 h of age: complete heart block with ventricular rate of 70–78 bpm.

The recipient twin sibling underwent a dilutional exchange transfusion on admission and was subsequently discharged to the local hospital on day 19.

Discussion

This report highlights a novel association of heart block and foetal intracardiac blood transfusion. Percutaneous entry to the foetal heart represents an alternative route by which the foetal circulation can be accessed if the umbilical vein is not accessible [7]. Comparative observational data suggest that the intracardiac route carries high procedure-associated risk and 33% mortality [6]. Of note, the currently accepted complication rate of 6.8% of intracardiac intrauterine transfusion is derived from 25 cases in which the procedure was used due to rhesus isoimmunisation in severely compromised foetuses [6].

In this case report the normal foetal heart rate before the procedure, the duration and resolution of the heart block and return to AV conduction suggest that the conduction system might have been injured during the cardiocentesis. Traumatic iatrogenic heart block is transient and self-resolving with supportive treatment. Traumatic AV block occurs in 2% of all cardiac operations and is associated with 7% mortality within the first 30 post-operative days owing to haemodynamic instability [8]. Recovery of AV conduction occurs in 55%–100% of cases; 95% of the patients who regain AV conduction do so by post-operative day 9 [8]. Cases that fail to regain AV conduction require permanent pacemaker implantation.

Traumatic heart block differs to congenital heart block (CHB) secondary to autoimmune disease and structural heart disease in that it follows a course that is more benign and of shorter duration. CHB is a rare disorder, defined as the conduction system disease of any form diagnosed within the first 28 days of life [9]. It is often related to maternal autoimmune disease and congenital heart disease. The anticipated clinical course of CHB secondary to maternal systemic lupus erythematosus is long and persistent, as the conduction system suffers essentially irreversible damage. Furthermore, CHB secondary to structural congenital heart disease is prolonged with the majority of cases needing permanent pacemaking. The major prognostic determinants of CHB are the presence of underlying structural heart disease or congestive heart failure and the ventricular rate. General therapeutic targets for the newborn include supportive treatment for low-output congestive heart failure as well as pacemakers for infants with significant bradycardia. Conservative management consists of administration of isoprenaline and accepting a ventricular rate exceeding 55 bpm as haemodynamically sufficient [7].