Safety and utility of CardioMEMS device for remote pulmonary artery monitoring in paediatric Fontan patients: a case series

Abstract

Background

Patients with single ventricle congenital heart disease who undergo total cavo-pulmonary anastomosis (Fontan surgery) suffer from elevated pulmonary artery pressure (PAP), which leads to multiple adverse sequelae. Traditionally, the Fontan pressures are assessed via invasive haemodynamic catheterization that exposes these medically fragile patients to the risks of vascular injury and anaesthesia. While the CardioMEM remote PAP monitor has been extensively used in adults with heart failure, the safety of this device has not been established in children.

Case summary

We report safety and utility of this device in eight paediatric Fontan patients. Our patients ranged from 9 to 18 years of age. There were no reported complications related to the implantation of the CardioMEMS device in our population.

Discussion

This is the first case series of safety of CardioMEMS device in paediatric Fontan Powered by Editorial Manager® and ProduXion Manager® from Aries Systems Corporation patients. Our experience indicates that the device may be safely utilized for the management of Fontan-related complications in this vulnerable population.

Learning points.

• CardioMEMS remote pulmonary artery pressure monitoring device has the potential to reduce invasive cardiac catheterization in paediatrc single ventricle heart disease patients.

• Our case series indicates that the device may be safely implanted in paediatric Fontan patients.

Introduction

Patients living with Fontan circulation require life-long surveillance for complications including Fontan-associated liver disease (FALD), protein-losing enteropathy (PLE), ventricular dysfunction, and plastic bronchitis.¹ Traditionally, the assessment of Fontan pressures [pulmonary artery pressure (PAP)] relies on cardiac catheterization (CC) and typically requires general anaesthesia (GA) for paediatric patients. In addition to exposing the patients to the risks of vascular injury, and GA, this haemodynamic data may not accurately reflect the Fontan pathway pressure during normal activity. Falsely low estimates of Fontan pressures can potentially impact risk categorization and delay the initiation of necessary treatment. Starting from September 2021, we initiated the process of implanting the remote PAP monitor (CardioMEMs) in select paediatric Fontan patients during their haemodynamic catheterization, to enable serial, non-invasive monitoring of PAP under normal physiological conditions.

Summary figure

Two paediatric Fontan patients underwent CardioMEMS implantation at our institute.

Methods

The study was approved by our institution’s Institutional Review Board (IRB). Patients with failing Fontan physiology were referred for haemodynamic catheterization. An appropriate distal, branch PA was identified by angiography, and the CardioMEMS device was implanted under fluoroscopic guidance (Figure 1). The device was calibrated with the mean PAP obtained in the cath lab. Caregivers were educated on obtaining device readings at home. Patients were placed on anticoagulation in addition to aspirin for 3 months.

Figure 1.

Angiographic image showing CardioMEM device placement in a Fontan patient.

As per the manufacturer’s specifications, the device would have an expected measurement error of 2 mmHg increase for every 300 m elevation.² Since we calibrated the device at our institute, which is ∼300 m elevation, we adjusted the measurements for patients returning to higher elevation.

Results

Eight paediatric Fontan patients underwent successful implantation of the CardioMEMs between September 2021 and April 2023 (Table 1). There were no procedural complications or subsequent episodes of device migration or thrombosis. We describe the details of two cases.

Table 1.

Characteristics of paediatric Fontan patients who underwent CardioMEM implantation

S no	Age (years)	Cardiac diagnosis	Time since Fontan surgery (years)	Type of Fontan	Indication for CardioMEMs	Follow-up (months)
1	9	HLHSa	7	Fenestrated ECF	FALD	13
2	11	HLHS	6	Fenestrated ECF	Exercise intolerance	11
3	13	HLHS	11	Fenestrated ECF	Advanced FALD Exercise intolerance	14
4	14	HLHS	11	Fenestrated ECF, s/p fenestration closure	Advanced FALD	7
5	15	HLHS	11	Fenestrated ECF	Advanced FALD Exercise intolerance	9
6	16	HLHS	14	Non-fenestrated lateral tunnel Fontan	Chronic PLE	20
7	16	HRHSb	13	Non-fenestrated ECF	Chronic PLE	5
8	18	HRHSb	15	Non-fenestrated lateral tunnel	Concern for advanced FALD	13

^aHypoplastic left heart syndrome.

^bHypoplastic right heart syndrome.

Case 1

This was a 12-year-old girl with functional single ventricle (FSV) (hypoplastic left heart variant) who underwent placement of an 18 mm fenestrated extra-cardiac Fontan conduit at 3 years of age (refer to Patient 3 on Table 1). She subsequently moved to a higher elevation (∼2100 m). At age 9, she was referred for a haemodynamic catheterization with concerns for pedal oedema. Her Fontan haemodynamics were satisfactory (mean PAP ∼ 12 mmHg, right ventricle end-diastolic pressure (EDP) ∼ 10 mmHg, pulmonary vascular resistance (PVR) = 1.8 U/m²) with no anatomic obstruction. With these reassuring data, she was managed conservatively.

She continued to experience worsening fatigue, dizziness, and bilateral leg oedema and was referred to our Fontan Clinic at age 12. Her echocardiogram showed normal single right ventricle function, with a patent fenestration (mean trans-pulmonary gradient ∼ 7 mmHg). Cardiopulmonary exercise testing (CPET) revealed a low functional capacity (VO₂ = 16.2 mL/kg/min; 43% predicted), with normal spirometry. Her blood chemistry revealed normal renal function, normal albumin, and normal liver enzymes, with elevated haematocrit (52%). A liver magnetic resonance elastogram (MRE) revealed moderate hepatic fibrosis. Our multi-disciplinary Fontan team suspected that her Fontan pressures were likely underestimated at the previous catheterization and referred her for CardioMEM implantation.

Her repeat haemodynamic data again showed low Fontan pressures (mean PAP ∼ 13 mmHg, RVEDP = 9 mmHg, normal cardiac index ∼ 3.3L/min/m²); however, her liver biopsy revealed severe FALD with cirrhosis. As she returned to higher elevation (2100 m), her CardioMEMS recordings were significantly higher (PAP ∼ 18–20 mmHg). She was started on pulmonary vasodilator therapy and oxygen. Subsequent monitoring showed reduction in Fontan pressure to ∼12 mmHg, with improvement in symptoms.

CardioMEMS device was also utilized to assess Fontan pressures with exercise. The device showed a mean PAP of ∼11 mmHg at rest, which increased to ∼25 mmHg with exercise, and returned to ∼12–13 mmHg during recovery. There was mild improvement in her functional capacity (VO₂ = 18.6 mL/kg/min)

At the time of writing this manuscript, her liver function has remained stable, with no episodes of PLE, improvement in haematocrit to 45% (down from 52%).

Case 2

This is a 16-year-old male born with FSV (severe Ebstein’s anomaly) who underwent placement of a non-fenestrated extra-cardiac Fontan procedure at age 3 (refer to Patient 7 on Table 1).

About 12 years after his Fontan surgery, he presented with large ascites and bilateral pedal oedema and was diagnosed with PLE. His Fontan haemodynamics at presentation showed mean PAP ∼ 13 mmHg; and left ventricle EDP ∼ 7 mmHg. Over the next 1 year, he had recurrent PLE episodes despite medical therapy and was referred to our Fontan Clinic. His echocardiogram showed mildly decreased single left ventricle function. Cardiopulmonary exercise testing showed a low functional capacity (VO₂ = 21 mL/kg/min, 44% of predicted). Liver elastography was suggestive of advanced fibrosis or cirrhosis (liver elasticity ∼ 2.3 m/s).

We suspected that his previous haemodynamic data had falsely low mean PAP and referred him for CardioMEMS placement. His repeat haemodynamic data again showed low Fontan pressures (mean PAP ∼ 10 mmHg, LVEDP = 7 mmHg, PVR = 1.9 units × m²) with unobstructed Glenn and Fontan pathways. A fenestration was created. CardioMEM device was implanted.

He was responding to inpatient management until Day 3, when his CardioMEMS recordings showed an increase in mean PAP to about 18–20 mmHg. Repeat imaging showed spontaneous closure of the fenestration. With further optimization of medical therapy, his PLE improved, with a decrease in Fontan pressure of ∼13–14 mmHg. A few weeks after discharge, the team noted an increase in his Fontan pressure (∼18–19 mmHg) via remote monitoring, and he was subsequently diagnosed and treated for PLE recurrence. Currently, he is being evaluated by the heart transplant team.

Discussion

Our case series of eight paediatric Fontan patients shows that the CardioMEM device can be safely implanted in this medically fragile population. Our two cases also confirmed our suspicion that Fontan pressures assessed during a routine catheterization may be underestimated, especially if patients are intubated and heavily sedated. In patients with signs of Fontan-related complications, CardioMEM appears to provide a useful adjunct for closer monitoring and optimizing therapy.

CardioMEMS has shown benefit in managing adults with heart failure.³ There is limited experience with SRV patients. Bradley et al. described their experience with six adult Fontan patients.⁴ We have shown that the device is safe even in paediatric FSV patients. The device implantation was technically simple and feasible. No device-related complications or caregiver concerns have been reported during our regular follow-up. To the authors’ knowledge, this is the first case series of CardioMEM device in paediatric Fontan patients.

Fontan pressures may be adversely affected at higher elevation.^5,6 Our first patient lived at a high elevation but had her haemodynamic catheterization performed at a much lower elevation. Her haemodynamic data showed low Fontan pressure that could not explain her symptoms or progressive liver fibrosis. CardioMEMS readings on the other hand showed much higher Fontan pressures when she was at home. This case illustrates that CC performed at lower elevation may potentially underestimate the true Fontan pressures. CardioMEMS thus can be a useful tool in managing these children.

Failure of Fontan circulation predisposes these patients with various long-term sequelae such as liver fibrosis and PLE.^7,8 Our second case reveals that remote monitoring allowed us to detect recurrence of PLE before the patient noted symptoms, highlighting another potential use of the device. Our case report also shows the utility of CardioMEMS in assessing exercise-related changes to Fontan circulation.

Short term aspirin is the standard recommended post-device regimen, however, we elected to keep our patients on anticoagulant (rivaroxaban) for at least 3 months, as Fontan circulation is presumed to be at a higher risk for thrombosis. Data remain limited on the ideal anticoagulation regimen for these patients.

Limitations

To the best of authors’ knowledge, this is the largest reported series on the safety of the CardioMEMS device in paediatric Fontan patients. However, we acknowledge that the sample size is still limited to generalize the results. Further longitudinal studies are needed to establish long-term safety of this device.

Conclusions

CardioMEMs can be safely implanted in paediatric patients with failing Fontan physiology and can be a useful adjunct for ambulatory monitoring, thus reducing the need for invasive diagnostic cardiac catheterization.

Lead author biography

Deepti P. Bhat is a board-certified paediatric cardiologist in Arizona, USA, who serves as the director of the multi-disciplinary Paediatric Fontan Clinic and the director of echocardiography at Phoenix Children's Hospital. She is dedicated to enhancing the management and quality of life for paediatric patients with complex congenital heart disease and has a keen interest in improving health outcomes for underserved populations across the globe.

Data availability

The authors would like to confirm that the data underlying this article will be shared on reasonable request to the corresponding author. We also confirm that the data cannot be shared publicly to protect the privacy of the study subjects including minors who participated in the study.