Tiny pacemakers for tiny babies

Subxiphoid Insertion of a Pediatric Implantable Pulse Generator in a Neonate With Congenital Complete Heart Block

Permanent pacemaker placement is often indicated in newborns with congenital complete heart block (CCHB). The disproportionate size between commercially available devices and the neonate can lead to delayed intervention and high postoperative complication rates. Recently, Medtronic developed a Pediatric Implantable Pulse Generator (IPG); a very small single chamber pacemaker requiring a bipolar lead. This case report describes a minimally invasive approach for the implantation of this Pediatric IPG shortly after birth in a 2.32 kg neonate with CCHB.

Multicenter Results of a Novel Pediatric Pacemaker in Neonates and Infants

BACKGROUND

To address the unmet need for a smaller pacemaker for babies, a specially modified implantable pulse generator was developed containing a Medtronic Micra subassembly in a polymer header connecting to a bipolar epicardial lead. The aim of this study was to report midterm follow-up data and outcomes of patients who underwent implantation of this device.

METHODS

Deidentified data were collected from 12 of 15 sites in the United States implanting the pediatric implantable pulse generator between March 2022 and February 2024. All 29 patients at these 12 sites within this timeframe were included in the analysis.

RESULTS

The median age at implant was 15 days (range, 0 days to 3 years, including 1 outlier). The median weight was 2.3 kg (range, 1.3-11.4 kg). Gestational age was 28.5 weeks to term, with 23 (79%) patients born prematurely. Of those with anatomic information, 25% had congenital heart disease. The average duration of implant was 325 days (73-808 days). The most recent lead impedance mean was 612 ohms (450-840 ohms), ventricular capture threshold mean was 1 V @ 0.4 ms (range, 0.38-2.75 V), and R-wave sensing mean was 12.5 mV (3.6-20 mV). There were 7 generator explants (24%), removed at 6.5 to 31 months of age.

CONCLUSIONS

The pediatric implantable pulse generator can be safely implanted in neonates and infants. This multicenter report demonstrates that the devices remain stable, with effective pacing, normal electrical parameters, and battery longevity aligned with projections. This novel pediatric pacemaker provides a viable alternative to standard-size generators and addresses a vital unmet need for these small patients.

Cardiovascular imaging in children with cardiac implantable electronic devices

The number of children with cardiac implantable electronic devices (CIEDs) is increasing at a time of rapid growth in cardiac magnetic resonance (MR) and cardiac computed tomography (CT) utilization. The presence of CIEDs poses challenges with respect to imaging safety and quality. A thoughtful approach to cardiovascular imaging in patients with CIEDs begins with an awareness of the clinical indications to determine the most appropriate imaging modality. Understanding device characteristics allows one to ensure that the proper safety measures are taken before and during cardiac MR and cardiac CT examinations. Despite the propensity of CIEDs to cause image artifact, several techniques are available to counteract these artifacts and preserve imaging quality.

Epicardial pacing outcomes in infants with heart block: Lead and device complications from a multicenter experience

BACKGROUND

Infants with complete heart block (CHB) require epicardial pacemaker (PM) insertion. Prior studies described epicardial pacing outcomes in infants and children, although they were limited by small or heterogeneous populations.

OBJECTIVE

This study aimed to explore patient- and procedure-level associations with device complications in infants with CHB who received a permanent PM.

METHODS

This was a multicenter, retrospective cohort study including infants receiving an epicardial PM between 2000 and 2021 for CHB. The primary outcome was time to device-related adverse event: lead failure requiring revision; pocket infection; exit block requiring increased pacing output; or lead-related coronary artery compression. Time-to-event analysis was performed by the Kaplan-Meier method with a multivariable Cox proportional hazards model.

RESULTS

There were 174 infants who received an epicardial PM (282 bipolar, 39 unipolar leads) for CHB. Median age and weight at PM were 93.5 days and 4.5 kg, respectively. Pacing indication was postoperative CHB in 63% and congenital CHB in 37%. The median follow-up was 2.1 years. The primary outcome occurred in 26 infants at a median time to event of 0.6 year. Age ≤90 days at PM implantation was the most significant risk factor for a device-related adverse event (hazard ratio, 7.02; P < .001), primarily driven by pocket infections. Lead failure occurred in 3% of leads with a 5- and 10-year freedom from failure of 93% and 83%, respectively.

CONCLUSION

Device complications affect 15% of infants receiving a permanent PM for heart block. Age ≤90 days at PM implantation is especially associated with infectious complications. Epicardial lead durability appears similar to previously reported pediatric experiences.

Diagnosis and Management of Fetal Arrhythmias in the Current Era

Diagnosis and management of fetal arrhythmias have changed over the past 40-50 years since propranolol was first used to treat fetal tachycardia in 1975 and when first attempts were made at in utero pacing for complete heart block in 1986. Ongoing clinical trials, including the FAST therapy trial for fetal tachycardia and the STOP-BLOQ trial for anti-Ro-mediated fetal heart block, are working to improve diagnosis and management of fetal arrhythmias for both mother and fetus. We are also learning more about how "silent arrhythmias", like long QT syndrome and other inherited channelopathies, may be identified by recognizing "subtle" abnormalities in fetal heart rate, and while echocardiography yet remains the primary tool for diagnosing fetal arrhythmias, research efforts continue to advance the clinical envelope for fetal electrocardiography and fetal magnetocardiography. Pharmacologic management of fetal arrhythmias remains one of the most successful achievements of fetal intervention. Patience, vigilance, and multidisciplinary collaboration are key to successful diagnosis and treatment.

New Guidelines of Pediatric Cardiac Implantable Electronic Devices: What Is Changing in Clinical Practice?

Guidelines are important tools to guide the diagnosis and treatment of patients to improve the decision-making process of health professionals. They are periodically updated according to new evidence. Four new Guidelines in 2021, 2022 and 2023 referred to pediatric pacing and defibrillation. There are some relevant changes in permanent pacing. In patients with atrioventricular block, the heart rate limit in which pacemaker implantation is recommended was decreased to reduce too-early device implantation. However, it was underlined that the heart rate criterion is not absolute, as signs or symptoms of hemodynamically not tolerated bradycardia may even occur at higher rates. In sinus node dysfunction, symptomatic bradycardia is the most relevant recommendation for pacing. Physiological pacing is increasingly used and recommended when the amount of ventricular pacing is presumed to be high. New recommendations suggest that loop recorders may guide the management of inherited arrhythmia syndromes and may be useful for severe but not frequent palpitations. Regarding defibrillator implantation, the main changes are in primary prevention recommendations. In hypertrophic cardiomyopathy, pediatric risk calculators have been included in the Guidelines. In dilated cardiomyopathy, due to the rarity of sudden cardiac death in pediatric age, low ejection fraction criteria were demoted to class II. In long QT syndrome, new criteria included severely prolonged QTc with different limits according to genotype, and some specific mutations. In arrhythmogenic cardiomyopathy, hemodynamically tolerated ventricular tachycardia and arrhythmic syncope were downgraded to class II recommendation. In conclusion, these new Guidelines aim to assess all aspects of cardiac implantable electronic devices and improve treatment strategies.

Emerging Technologies for the Smallest Patients

Pediatric and congenital heart disease patients may require cardiac implantable electronic device implantation, inclusive of pacemaker, ICD, and implantable cardiac monitor, for a variety of etiologies. While leads, generators, and monitors have decreased in size over the years, they remain less ideal for the smallest patients. The potential for a miniature pacemaker, fetal micropacemaker, improving leadless technology, and rechargeable devices creates hope that the development of pediatric-focused devices will increase. Further, alternative approaches that avoid the need for a transvenous or surgical approach may add more options to the toolbox for the pediatric and congenital electrophysiologist.

Leadless epicardial pacing at the left ventricular apex: an animal study

AIMS

State-of-the-art pacemaker implantation technique in infants and small children consists of pace/sense electrodes attached to the epicardium and a pulse generator in the abdominal wall with a significant rate of dysfunction during growth, mostly attributable to lead failure. In order to overcome lead-related problems, feasibility of epicardial implantation of a leadless pacemaker at the left ventricular apex in a growing animal model was studied.

METHODS AND RESULTS

Ten lambs (median body weight 26.8 kg) underwent epicardial implantation of a Micra transcatheter pacing system (TPS) pacemaker (Medtronic Inc., Minneapolis, USA). Using a subxyphoid access, the Micra was introduced through a short, thick-walled tube to increase tissue contact and to prevent tilting from the epicardial surface. The Micra's proprietary delivery system was firmly pressed against the heart, while the Micra was pushed forward out of the sheath allowing the tines to stick into the left ventricular apical epimyocardium. Pacemakers were programmed to VVI 30/min mode. Pacemaker function and integrity was followed for 4 months after implantation. After implantation, median intrinsic R-wave amplitude was 5 mV [interquartile range (IQR) 2.8-7.5], and median pacing impedance was 2235 Ω (IQR 1725-2500), while the median pacing threshold was 2.13 V (IQR 1.25-2.9) at 0.24 ms. During follow-up, 6/10 animals had a significant increase in pacing threshold with loss of capture at maximum output at 0.24 ms in 2/10 animals. After 4 months, median R-wave amplitude had dropped to 2.25 mV (IQR 1.2-3.6), median pacing impedance had decreased to 595 Ω (IQR 575-645), and median pacing threshold had increased to 3.3 V (IQR 1.8-4.5) at 0.24 ms. Explantation of one device revealed deep penetration of the Micra device into the myocardium.

CONCLUSION

Short-term results after epicardial implantation of the Micra TPS at the left ventricular apex in lambs were satisfying. During mid-term follow-up, however, pacing thresholds increased, resulting in loss of capture in 2/10 animals. Penetration of one device into the myocardium was of concern. The concept of epicardial leadless pacing seems very attractive, and the current shape of the Micra TPS makes the device unsuitable for epicardial placement in growing organisms.