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.