Arterial elastance and its impact on intrinsic right ventricular function in palliated hypoplastic left heart syndrome

https://doi.org/10.1016/j.ijcard.2013.08.052Get rights and content

Abstract

Background

Systemic right ventricular (RV) function is a major determinant of long-term outcome in patients with palliated hypoplastic left heart syndrome (HLHS). Abnormal elastic properties of the reconstructed aorta may negatively impact on ventricular function. We therefore aimed to assess arterial elastance and its relationship to systemic RV function in these patients.

Methods

Fifty-six HLHS patients (median age 5.4 years; range 2.9–14.2 years) were studied at a median of 2.6 years (range 0.8–12.7 years) after completion of the Fontan circulation with the pressure–volume conductance system.

Results

Arterial elastance (Ea) was abnormally high and correlated inversely with RV ejection fraction (r =  0.42, P = 0.001). However, end systolic elastance (Ees) – a load independent measure of intrinsic systolic ventricular function – and more so end diastolic stiffness (Eed) were positively correlated with Ea (Ees vs. Ea: r = 0.44, P = 0.001: Eed vs. Ea: r = 0.62, P < 0.0001).

Patients who were treated for significant aortic arch obstruction after surgical palliation showed higher Ea and Eed even four years after successful treatment compared to the remainder of the group (Ea: 3.4 ± 1.2 vs. 2.8 ± 1.0 mm Hg/ml, P = 0.04 and Eed: 0.67 ± 0.44 vs. 0.45 ± 0.3 mm Hg/ml, P = 0.04).

Conclusions

Arterial elastance is abnormally high in palliated HLHS patients and negatively impacts on ejection fraction but not on intrinsic systolic RV function early after completion of the Fontan circulation. Increased arterial elastance, however, is associated with increased RV diastolic stiffness with potential adverse effects on long-term outcome. Furthermore, arterial elastance and diastolic stiffness are particularly high in patients who needed treatment for aortic arch obstruction.

Introduction

The right ventricle (RV) is not built to permanently withstand systemic afterload and fails prematurely when working as the systemic ventricle [1]. Arterial vascular load is the major determinant of ventricular afterload and reflects the properties of the vascular bed mainly the distensibility of the great arteries and peripheral vascular resistance. Arterial vascular load can be measured in a simplified way as arterial elastance (Ea), the steady-state ratio of end systolic pressure and stroke volume obtained from the pressure–volume loop [2]. Ea has been shown to be a useful marker to assess the impact of arterial vascular load on the human ventricle [3].

Extensive reconstructive surgery to the aortic arch using patch material is part of the first step of surgical palliation of hypoplastic left heart syndrome (HLHS) and data from non-invasive imaging studies suggest increased stiffness with decreased distensibility of the neo-aorta [4], [5]. We therefore thought to assess Ea in palliated HLHS patients and to relate this marker of ventricular afterload to ventricular function, especially to intrinsic, load independent function of the systemic RV. Furthermore, because aortic arch obstruction can complicate surgical palliation of HLHS and has been shown to acutely affect RV function we paid particular attention to this patient group [6].

Section snippets

Patients

72 consecutive patients with HLHS after the fenestrated lateral tunnel Fontan procedure were recruited to be studied with the pressure–volume conductance system between January 2005 and March 2011. Conductance data should be obtained during a routine cardiac catheterisation procedure. In 16 patients conductance data could not be analysed due to either poor signal quality or failure to correctly place the catheter in the RV. Therefore, functional data are available in 56 patients.

All except 3

Patient characteristics

Patient characteristics, surgical data and data on the functional result of aortic arch reconstruction are summarised in Table 1. Patients were studied at a median of 2.6 years after Fontan completion. There was no significant stenosis at the site of the reconstructed aortic arch at the time of the conductance catheter study.

Conductance derived data on ventriculo-arterial coupling

Data on RV function at baseline measurement and during dobutamine infusion are given in Table 2.

Cardiac index increased with dobutamine infusion as heart rate increased,

Discussion

The present study demonstrates that arterial elastance (Ea) is abnormally high in children with HLHS who underwent the Norwood operation and is associated with an increase in diastolic stiffness. Furthermore, it shows that Ea and diastolic stiffness are particularly elevated in patients who needed treatment of aortic arch obstruction albeit that treatment has been successful.

Conclusion

Arterial elastance, the major determinant of ventricular afterload, is abnormally high in palliated HLHS patients and negatively impacts on ejection fraction but not on load independent systolic myocardial function. Diastolic stiffness, however, is increased when aortic elastance is high.

The effects of abnormal arterial elastance on intrinsic systolic function and diastolic stiffness were more pronounced in patients who underwent successful treatment for aortic coarctation. Thus, prevention,

Funding

This work and the Department of Paediatric Cardiology, Kiel, were supported by the Fördergemeinschaft Deutsche Kinderherzzentren e.V.

Acknowledgement

The expert technical assistance of T. Hansen and A. Wegmann is gratefully acknowledged.

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