Co-Author(s):
Iain Sim, MBBS
Daniel O’Hare, BMBS
John Whitaker, MB BCh MA
Rahul Mukherjee, MBBS
Caroline Roney, PhD
Orod Razeghi, PhD
Steven Niederer, PhD
Alam Harith, MD
Eric Rosenthal, MD
Matthew Jones, MD
Matthew Wright, MBBS
Alessandra Frigiola, MD
Vivienne Ezzat, MD
Mark O’Neill, MB BCh BAO
Steven Williams, BSc MBChB
King’s College London
4th Floor North Wing, St Thomas’ Hospital Westminster Bridge Road London SE1 7EH
Introduction | Objectives: Uncorrected atrial septal defects (ASD) are associated with AF but the bi-atrial arrhythmia substrate is ill-defined in this cohort. We aimed to characterise the extent of electrical and structural remodelling in ASD patients, hypothesising that remodelling and ectopic foci would predominate in the RA and may be related to age and shunt fraction.
Methods: Bi-atrial invasive assessment of voltage, effective refractory periods (ERP) and conduction velocity (CV) and restitution properties was performed during percutaneous ASD closure. Late gadolinium enhancement cardiac MRI (CMR) was performed prior to ASD closure to quantify bi-atrial fibrosis. Ectopic triggers for AF were assessed with isoprenaline provocation and on Holter monitoring. Comparison was made to non-congenital heart disease AF patients.
Results:Electrical Assessment In 21 ASD and 21 control patients proportion of RA low voltage (< 0.5mV) and scar (< 0.05mV) was greater in ASD than control patients (P=0.02 and P=0.039). Low voltage and scar areas were greater in the RA than the LA in ASD patients (P=0.002 and P=0.010). In both atria steeper ERP (RA; P=0.005, LA; P=0.016) and CV restitution (RA; P=< 0.001, LA; P=0.007) was seen in ASD than control patients.CMR Assessment In 36 ASD and 36 control patients bi-atrial fibrosis burden on CMR was significantly greater in ASD than control patients (P< 0.001). RA fibrosis burden was greater in ASD patients with vs without atrial arrhythmias (P=0.034).Arrhyhmia Triggers During isoprenaline infusion and on non-invasive Holter assessment no differences in atrial ectopy origin was seen in ASD vs control patients.Remodelling and Exposure to Shunt No relationship was seen between the degree of structural or electrical remodelling and patient age or shunt fraction in ASD patients.
Conclusions: Electrical and structural remodelling is present to a greater degree in ASD vs AF control patients and predominates in the RA. RA fibrosis is associated with atrial arrhythmia suggesting a role for CMR in non-invasive risk assessment in these patients. Differences in ERP and CV restitution between ASD and control patient offer mechanistic insight into atrial arrhythmia. Further work is needed to fully define the arrhythmia substrate and guide therapy in this cohort.