Restitution Threshold Index Identifies Atrial Fibrillation-mediated cardiomyopathy in Patients With Late Gadolinium Enhancement on Cardiac MRI

Abstract

Introduction Objectives: Left Ventricular Late gadolinium enhancement (LGE) on cardiac MRI has been associated with impaired recovery after Atrial Fibrillation (AF) ablation in patients with reduced LV Ejection Fraction (LVEF), and LGE+ patients still have AF-mediated cardiomyopathy (AMC), with a poor negative predictive value.1 The Restitution Threshold Index (RTI) quantifies the short R-R interval burden during AF, associated with AMC.2 The Study Objective was to determine whether RTI can stratify recovery after AF ablation in patients with reduced LVEF, in patients with LGE. Method(s): Consecutive patients with persistent AF and LVEF = 5% defining LGE+ status) on baseline MRI was calculated by two independent operators and qualitatively reviewed. RTI was derived from a 10-min Holter ECG during AF at rest as the percentage of RR intervals 22% burden associated with AMC. Cardiac recovery at 6 months in sinus rhythm was defined as improvement in >= 2 of: LVEF on echo, peak VO2 on CPET, and NT-proBNP, using parameter-specific thresholds.3-5 Results: 53 patients were enrolled (age:59 +/- 12 years; 8 (15.1%) female, LVEF 34 +/- 9%) from January 2022 to September 2023. Responders had a significantly lower LGE burden than non-responders (2.7% (1.7, 7.3) vs 19.5% (16.4, 27.5) p = 0.005). LGE burden correlated inversely with DELTALVEF (r = -0.39, p = 0.009). 17/53 (34%) were LGE + . 76.5% had mid-myocardial and 35.3% had subendocardial LGE distribution. LGE status predicted response with a PPV of 1.0 but a low NPV of 0.25. RTI > 22% identified all responders despite ventricular fibrosis. In LGE-positive patients, Sequential stratification based on RTI had a PPV of 0.91 and an NPV of 0.60 in this subgroup. Conclusion(s): Conclusion(s): Both LGE on MRI and RTI can identify patients with AMC. Sequential measurement can help select LGE+ patients with reversible myocardial dysfunction who experience multi-parametric recovery after AF ablation.