Abstract 16516: CMR-ECG Imaging in Hypertrophic Cardiomyopathy Detects Electrophysiological Abnormalities Before Hypertrophy or ECG Changes

Abstract

INTRODUCTION: In hypertrophic cardiomyopathy (HCM), ventricular arrhythmia associates with severity of LVH and scar, and presence vs absence of a sarcomeric gene mutation (G+LVH+ vs G-LVH+). Also, ECG changes in subclinical HCM (G+LVH-) signal increased risk of phenotype progression. HYPOTHESES: ECG Imaging (ECGI) can detect: i) subtle electrophysiological (EP) abnormalities in subclinical HCM (pre-LVH). ii) EP abnormalities related to genetic status (G+ vs G-LVH+) and structural changes (late gadolinium enhancement [LGE], max. wall thickness [MWT]) in overt disease. METHODS: 200 participant multicenter study: 70 G+LVH-, 51 G+LVH+, 53 G-LVH+ and 26 healthy volunteers (HV) underwent 12-lead ECG (to detect abnormal Q-waves, repolarization changes, LVH criteria) and CMR-ECGI computing epicardial unipolar electrograms (UEGs) to derive: activation time (AT), activation-recovery intervals (ARIc), spatial gradients (activation: G AT , repolarisation: G RT ) and fractionation. RESULTS: Compared to HV, G+LVH- had prolongation of AT (40.3±7.3 vs 35.4±6.1 ms p=0.003) and steeper G RT (mean: 1.12±0.27 vs 1.00±0.23 ms/mm p=0.042, max: 11.7±2.8 vs 10.0±1.9 ms/mm p=0.005). AT was prolonged even in G+LVH- with a normal 12-lead ECG (p<0.004). Compared to G+LVH-, G+LVH+ had similar AT but a more prolonged ARIc (275±29 vs 245±26 ms p<0.001). Compared to G-LVH+, G+LVH+ had similar MWT and LGE, but more signal fractionation (0.02±0.02 vs 0.01±0.03% UEGs with ≥2 deflections p=0.002). In overt HCM (all LVH+), MWT associated with AT ( r s 0.25 p=0.011) while LGE burden associated with G AT ( r s=0.27 p=0.006) and fractionation ( r s=0.22 p=0.025). CONCLUSION: Cardiac activation prolongation and repolarization abnormalities occur in subclinical HCM (before hypertrophy). Activation is prolonged even in subclinical HCM with normal 12-lead ECG. In overt HCM, ECGI abnormalities track adverse structural changes and reveal greater fractionation in those with a sarcomeric mutation.