Assessing ASD arrhythmogenic substrate using atrial strain echocardiography: a prognostic tool?

Background Patients with atrial septal defects (ASD) experience chronic right atrial volume overload, leading to structural remodeling of the atria, which in turn affect atrial electrical and mechanical properties. Prior studies demonstrated that low atrial strain values assessed by speckle tracking echocardiography, were particularly present in patients with chronic volume overload and atrial tachyarrhythmias. The exact relationship between atrial strain parameters are related to electrical properties of the atria, is, however, unknown. Purpose To assess associations between atrial strain parameters and epicardial electrical properties in ASD patients measured at a high resolution scale. Methods Intraoperative high-density epicardial mapping (192 unipolar electrograms) during sinus rhythm was performed in adult patients undergoing surgical ASD closure (N=39). The unipolar potential voltages and fractionation, conduction delay (CD: ≥7ms) and conduction block (CB: ≥12ms) were measured. Preoperative transthoracic echocardiograms were used to derive end-diastolic reservoir, conduit, and contractile strain values for both atria. Based on these strain curves, cycle durations, area under the curve, and the slopes of both the reservoir and contractile phases were calculated. Results were compared to a reference group with minimal changes in electrical properties (N=19). Results Mean age was 47±12 years, with indexed left atrium (LA) and right atrium (RA) volumes of 37.0±13.7ml and 59.0±23.8ml, respectively. Higher RA reservoir strain correlated with more single potentials, as well as less CD and CB (ρ=0.50, p<0.01; ρ=-0.49, p<0.01; and ρ=-0.47, p<0.01 respectively). Similar correlations were found for RA reservoir slope and conduit strain. A steeper slope preceding the LA reservoir strain was correlated with fewer fractionated potentials and less CD and CDCB lines (ρ=-0.43, p=0.01; ρ=-0.46, p=0.01; and ρ=-0.40, p=0.02 respectively), whereas larger LA size correlated with more complex fractionated potentials around the pulmonary veins (ρ=0.47, p<0.01). ASD patients showed significantly flatter LA contractile slopes, RA reservoir slopes, and longer strain cycles for both LA and RA compared to patients with limited arrhythmogenic substrate (p<0.01). Conclusion In ASD patients, lower atrial strain values and flatter slopes showed a moderate but significant correlation with various electrical parameters indicative of a potential arrhythmogenic substrate. These results indicate atrial strain echocardiography as a non-invasive diagnostic tool to identify patients at risk.