Commentary based on Bhat DP, Graziano JN, Garn BJ, Franklin WJ. Safety and utility of CardioMEMS device for remote pulmonary artery monitoring in paediatric Fontan patients: a case series. Eur Heart J Case Rep 2023;7:[ePub ahead of print].¹; Marshall WH, Rajpal S, Mah ML, et al. Early experience and lessons learned using implanted hemodynamic monitoring in patients with Fontan circulation. J Am Heart Assoc 2023;12:[ePub ahead of print].²

Study Question

What are the safety, utility, and prognostic implications of invasive implanted hemodynamic monitoring (IHM) using the CardioMEMS™ HF System (Abbott Laboratories, Abbott Park, Illinois) in patients with Fontan circulation (FC)?

Methods

The results of two single-center case series describing the use of IHM in patients with FC have recently been published (Table 1). The first is the only published report to date describing the use of IHM in pediatric patients with FC.¹ The second is the largest case series to date on the use of IHM in adult patients with FC; this series evaluated the impact of IHM on heart failure (HF) hospitalizations and the correlation of IHM pressures with long-term mortality rates and follow-up Model of End-Stage Liver Disease Excluding International Normalized Ratio (MELD-XI) scores.²

Table 1: Results of Two Single-Center Case Series Describing the Use of Invasive IHM in Patients With FC

Results

The eight-patient pediatric cohort included six patients with hypoplastic left heart syndrome and two with hypoplastic right heart syndrome.¹ The investigators reported no complications related to IHM implantation and described how IHM pressures could be measured serially, including measurement at different altitudes, and how IHM pressures led to changes in medical therapy, including pulmonary vasodilator therapy and diuretic agents, without performing cardiac catheterizations. All patients were anticoagulated with rivaroxaban for 3 months after IHM placement, with no thrombotic events reported.

The adult cohort data showed IHM placement in 17 patients, including 9 patients with systemic right ventricles and 8 with systemic left ventricles.² All patients were in New York Heart Association (NYHA) functional class II or III and had either previous HF hospitalization or worsening symptomatic HF. Compared with the year before IHM placement, there was no difference in HF hospitalizations in median follow-up of 35 months: 13 hospitalizations in 10 patients (median 1 [interquartile range (IQR) 0-1 hospitalizations per year]) versus 54 hospitalizations in 10 patients (median 0.6 [IQR 0-2.3] hospitalizations per year) (p = 0.268). However, there were limitations to this analysis, including only 46% of HF hospitalizations having an associated IHM reading and two patients accounting for 52% of the HF hospitalizations in the cohort.

The median IHM pressure within 30 days of placement had better correlation with the last MELD-XI score than did catheterization pressures on unadjusted analysis (IHM pressures: R² = 0.588, p < 0.001; catheterization pressures: R² = 0.14, p = 0.139). The long-term mortality rate in the cohort was 53% and, on unadjusted analysis, IHM pressures ≥18 mm Hg were associated with increased mortality (p_{log rank} = 0.041), which was not seen with the most recent catheterization pressures (p_{log rank} = 0.764).

Finally, in the adult cohort, there were no device-related procedural complications. All patients were anticoagulated with warfarin or apixaban for 6 months, after which five were transitioned to antiplatelet agents. One patient with a single-lung Fontan experienced a pulmonary embolism (PE) near the IHM device site 54 months after placement, which was considered possibly device related. In this patient, anticoagulation was held because of uterine bleeding leading to a hysterectomy 1 week earlier. The PE was treated with catheter-directed thrombolytics and resumption of anticoagulation.

Conclusions

These two-case series described a total of 25 patients with FC who underwent successful IHM implantation with no device-related procedural complications. Although there were no statistically significant reductions in HF hospitalizations, the results of both studies described utility in serial measurement of pulmonary artery pressures (PAPs) in patients with FC without repeated cardiac catheterizations, including the potential for prognostication based on IHM pressures (Figure 1).

Figure 1: Summary of Invasive IHM Use in Patients With FC and Diagrammatic Representation of IHM Placed in the LPA

Perspective

Most patients who are born with single-ventricle congenital heart disease and are palliated with FC now survive to adulthood.³ Unfortunately, HF remains the leading cause of death in this patient population,⁴ and is complex with multiple phenotypes. Furthermore, application of standard HF therapy in this population with unique hemodynamics, including a nonpulsatile pulmonary circulation, has not been effective to change this trajectory.⁵ Therefore, as this patient population continues to survive beyond childhood, new strategies for evaluation, treatment, and prognostication will be needed.

IHM is appealing given the evidence for HF hospitalization reduction in patients with acquired HF.⁶ The study results summarized here are the first to report on IHM use in patients with FC since the original case report in 2016 and case series in 2019,⁷ which included six patients. Although both studies summarized here report cases in which IHM was useful in titration of medical therapy and reducing HF hospitalization rates, the findings of the adult series showed no statistically significant reduction in HF hospitalization rates overall. This finding is likely related to the study population with relatively advanced FC failure, the heterogeneity in HF in patients with FC, and the unique trajectory of HF, with hospitalizations for volume overload typically not seen until later in the disease process.

Fontan pressures are prognostic, with higher pressures by catheterization associated with worse long-term outcomes.^8,9 IHM pressures are PAPs; however, in patients with FC, PAPs are equal to the pressures in the superior and inferior vena cavae and Fontan conduit in the absence of any obstruction (Figure 1). Although the results of both series report that IHM may provide more physiologic measures of Fontan pressures/PAPs that are not confounded by sedation and fasting status from catheterization, caution should be taken in interpretation of the association of IHM pressure and mortality rates and MELD-XI scores in the adult series. Again, the cohort had advanced FC failure and given the small sample size, the analysis was not adjusted for confounding variables. Thus, until further data are available, it is premature to extrapolate these findings to all patients with FC.

Regarding complications, the only potential device-related complication occurred in a patient with a PE, which may have been provoked by recent surgery. However, given the high risk, if thrombotic events occur in patients with single-lung FC, avoiding IHM use may be warranted in this subset of patients. Furthermore, the heterogeneity of anticoagulation strategies warrants further study to determine the optimal medical therapy after IHM to avoid thrombotic complications.

In summary, even though further studies are needed to add to the safety and efficacy of IHM in patients with FC, the promise of serial assessment of Fontan pressures/PAPs and potential for prognostic information make this technology attractive in a patient population with a high prevalence of HF.

References

1. Bhat DP, Graziano JN, Garn BJ, Franklin WJ. Safety and utility of CardioMEMS device for remote pulmonary artery monitoring in paediatric Fontan patients: a case series. Eur Heart J Case Rep 2023;7:[ePub ahead of print].
2. Marshall WH, Rajpal S, Mah ML, et al. Early experience and lessons learned using implanted hemodynamic monitoring in patients with Fontan circulation. J Am Heart Assoc 2023;12:[ePub ahead of print].
3. Plappert L, Edwards S, Senatore A, De Martini A. The epidemiology of persons living with Fontan in 2020 and projections for 2030: development of an epidemiology model providing multinational estimates. Adv Ther 2022;39:1004-15.
4. Poh C, Hornung T, Celermajer DS, et al. Modes of late mortality in patients with a Fontan circulation. Heart 2020;106:1427-31.
5. Rychik J, Atz AM, Celermajer DS, et al.; American Heart Association Council on Cardiovascular Disease in the Young and Council on Cardiovascular and Stroke Nursing. Evaluation and management of the child and adult with Fontan circulation: a scientific statement from the American Heart Association. Circulation 2019;140:e234-e284.
6. Lindenfeld J, Zile MR, Desai AS, et al. Haemodynamic-guided management of heart failure (GUIDE-HF): a randomised controlled trial. Lancet 2021;398:991-1001.
7. Bradley EA, Jassal A, Moore-Clingenpeel M, Abraham WT, Berman D, Daniels CJ. Ambulatory Fontan pressure monitoring: results from the implantable hemodynamic monitor Fontan feasibility cohort (IHM-FFC). Int J Cardiol 2019;284:22-7.
8. Miranda WR, Borlaug BA, Hagler DJ, Connolly HM, Egbe AC. Haemodynamic profiles in adult Fontan patients: associated haemodynamics and prognosis. Eur J Heart Fail 2019;21:803-9.
9. Inai K, Inuzuka R, Ono H, et al. Predictors of long-term mortality among perioperative survivors of Fontan operation. Eur Heart J 2022;43:2373-84.