WS03.04Impaired oxygen pulse during exercise following lung transplant in cystic fibrosis: a case series

Introduction

Bilateral single sequential lung transplantation (BSSLT) technique has supplanted the en-bloc method, as the preferred mode of lung transplantation (LTx) in cystic fibrosis (CF). However, despite adoption of BSSLT, all forms of LTx carry inherent risk of mediastinal nerve damage, which can result in cardiac dysfunction. This dysfunction may be detected non-invasively via cardiopulmonary exercise testing (CPET), whereby all people with CF are recommended to undergo regular testing as part of routine disease monitoring. This case series characterises prevalence of cardiac dysfunction – represented by the oxygen pulse (O₂P)– in a cohort of post-LTx patients with CF (pwCF)

Methods

Retrospective analysis of routine CPET – Cycle ergometry performed to volitional exhaustion – by six post-LTx pwCF under the care of a regional CF service.

Results

Data from six post-LTx pwCF was available for review (5 male; mean age = 41 years [range 34 – 49 years]; mean FEV₁ = 80% [range = 59-110%]). All patients had undergone LTx via BSSLT, with mean duration post-surgery being 8.3 years (range 6.0 – 11.8 years). Two patients – with longest time post-LTx (10.9, and 11.8 years) – exhibited diminished, and non-linear O₂P, failing to augment ≥10 mL^.beat^-1, the recognised threshold for impaired function. The remaining four pwCF all increased O₂P sufficiently ≥10 mL^.beat^-1 during exercise. Both pwCF with diminished O₂P reached peak heart rate values ≥90%_predicted, inferring inadequate stroke volume during exercise.

Discussion

This cohort of post-LTx pwCF, one-third displayed impaired O₂P and non-linear heart rate response to incremental exercise, suggesting a degree of autonomic dysfunction that may reflect mediastinal nerve damage seen in en-bloc LTx, and cardiac transplantation. Given increasing recognition of cardiac disease risk in CF, clinical teams must be aware of subclinical cardiac dysfunction, particularly in those post-LTx, which may be detected via routine CPET.