Strain detects substrate: Pioneering non-invasive visualization of atrial electropathology

BACKGROUND: Non-invasive assessment of arrhythmogenic substrates underlying persistent atrial fibrillation (AF) could potentially provide patient-tailored ablation therapy. Speckle Tracking Echocardiography (STE) is an imaging modality, which can be used to assess atrial biomechanical function. As biomechanical dysfunction is driven by electrical dysfunction, STE may serve as a diagnostic tool to detect AF-related arrhythmogenic substrates. PURPOSE: To investigate which non-invasive STE-derived measurements correlate best with invasively determined electrophysiological properties as a first step towards developing a novel, non-invasive diagnostic tool. METHODS: Intraoperative epicardial mapping during sinus rhythm was performed in adult patients (n = 19, mean age: 63 ± 13 years) undergoing cardiac surgery. Potential voltages, potential morphology, conduction velocity (CV), conduction block (CB: ≥12 ms) and uninterrupted lines of conduction delay (CD: ≥7 ms) and CB (CDCB) were quantified. Atrial end-diastolic reservoir and contractile strain values were used to calculate area under the curve, and the slopes of both the reservoir and contractile phases. RESULTS: Steeper LA reservoir strain slopes were associated with more CDCB, greater CV variation and lower overall CV around the pulmonary veins (ρ = 0.55, p < 0.001; ρ = 0.64, p = 0.004; ρ = -0.55, p = 0.019). A larger right atrial volume indexed correlated with more CDCB, fractionated potentials and reduced CV on Bachmann's Bundle (ρ = 0.64, p = 0.008; ρ = 0.52, p = 0.037; ρ = -0.61, p = 0.011). Right atrial end-systolic time strongly correlated with CB, low-voltage area's and fractionated potentials on Bachmann's Bundle (ρ = 0.68, p < 0.001; ρ = -0.63, p = 0.009; ρ = 0.53, p = 0.020). CONCLUSION: STE timing and slope parameters correlated most strongly with atrial electrophysiological properties, supporting their potential as non-invasive markers for arrhythmogenic substrates and patient-tailored ablation therapy.