Implantation of a Modified Micra Pediatric Implantable Pulse Generator for Epicardial Pacing

This is part of an ongoing series following the recovery of a patient who was previously seen for correction of pentalogy of Cantrell. This segment of the series occurred prior to discharge from the CVICU and two months postoperation, aimed at maintaining proper sinus rhythm. As of now, the patient has been fully discharged to her home and is recovering well. View the surgical correction of pentalogy of Cantrell here.  

This is a case presentation of a 23-month-old female infant who was diagnosed prenatally with pentalogy of Cantrell, including ectopia cordis, TET-type double outlet right ventricle, inlet and subaortic ventricular septal defect, a secundum atrial septal defect, an unroofed coronary sinus, and a persistent left superior vena cava. 

One month prior to this operation, the patient had undergone surgical repair of her ectopia cordis, TET-type double outlet right ventricle, closure of all septal defects, and creation of an intra-atrial baffle between the left superior vena cava and right atrium. 

While in the cardiovascular ICU, she developed an unspecified atrioventricular heart block. Due to the patient’s small size, epicardial lead placement was required. However, due to diaphragmatic and abdominal wall reconstruction, traditional placement options were limited, if not impossible. For this reason, the cardiothoracic surgical team obtained access for a modified Micra Pediatric Implantable Pulse Generator with a header block to allow connection of an IS-1 epicardial lead via the Emergency Use Pathway. Placement of the bipolar leads into the fifth intercostal space through a left anterior thoracotomy was determined by nongated chest CT imaging. 

After timeout, the patient was prepped for surgery in the usual fashion. Due to the patient’s diagnosis of ectopia cordis and previous abdominal repair, an incision was made in the fifth intercoastal space. Dense adhesions were noted between the pericardial space and the chest wall. A small area of the diaphragmatic surface was dissected, and bipolar leads were sutured into the myocardium. The right ventricle was clearly visualized, surrounded by dense adhesions. Attention was then drawn to the creation of the pacemaker pocket. The pacemaker pocket was created underneath the pectoralis muscle. The modified generator was then attached to the pacemaker leads, looped, and secured within the pacemaker pocket with 2-0 silk sutures into the intercostal muscles. Due to the dense adhesions within the pleural cavity, 2-0 Vicryl sutures were inserted directly through the ribs to close the thoracotomy. Complete closure of the chest cavity was finished in the normal fashion. The patient remained in the cardiovascular intensive care unit following pacemaker placement and the previous correction of pentalogy of Cantrell. The longevity of the modified Micra Pediatric Implantable Pulse Generator varies depending on pacing rates, impedance, and pacing outputs, with predicted longevity ranging from less than one year to nine years. 

Discussion 

Pacemaker placement in neonates is especially challenging due to their small size, concurrent structural defects, and the proportionally larger size of traditional pacemaker options, resulting in high rates of complications and mortality (1-3). Emergency use of the Micra Pediatric Implantable Pulse Generator with a modified header block for epicardial pacing has shown to be beneficial for small patients (2). Due to the patient’s small size and previous repair for pentalogy of Cantrell, ectopia cordis, and the baffling of the persistent left superior vena cava to the right atrium, modification of the Micra Pediatric Implantable Pulse Generator provided an alternative option for the treatment of atrioventricular heart block. While long-term follow-up is needed to assess long-term cardiac function and safety, the small Micra pacemaker adapted with epicardial leads provides an advantage in permanent pacing compared to other pacemaker options available (2)

References

1. Costa, R., et al., Minimally Invasive Epicardial Pacemaker Implantation in Neonates with Congenital Heart Block. Arquivos Brasileiros de Cardiologia, 2017.
2. Karim, F., et al., Epicardial Implantation of a Micra™ Pacemaker in a Premature Neonate with Congenital Complete Heart Block. The Journal of Innovations in Cardiac Rhythm Management, 2024/01. 15(1).
3. Shepard, C.W., et al., Surgical Placement of Permanent Epicardial Pacing Systems in Very Low-Birth Weight Premature Neonates. World Journal for Pediatric and Congenital Heart Surgery, 2012. 3(4): p. 454-458.

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