Scar architecture affects the electrophysiological characteristics of induced ventricular arrhythmias in hypertrophic cardiomyopathy

Background and aims: Late gadolinium enhancement cardiac magnetic resonance (LGE-CMR) detects myocardial scarring, a risk factor for ventricular arrhythmias (VA) in hypertrophic cardiomyopathy (HCM). LGE-CMR distinguishes core, borderzone (BZ) fibrosis, and BZ channels, crucial components of reentry circuits. We studied how scar architecture affects inducibility and electrophysiological traits of VA in HCM. Methods: We correlated scar composition with programmed ventricular stimulation (PVS)-inducible VA features using LGE intensity maps. Results: Thirty consecutive patients were enrolled. Thirteen (43%) were non-inducible, 6 (20%) had inducible non-sustained, and 11 (37%) had inducible sustained mono-(MMVT) or polymorphic VT/VF (PVT/VF). Of 17 induced VA, 13 (76%) were MMVT that either ended spontaneously, persisted as sustained monomorphic, or degenerated into PVT/VF.Twenty-seven patients (90%) had LGE. Of these, 17 (57%) had non-sustained or sustained inducible VA. Scar mass significantly increased (p = 0.002) from non-inducible to inducible non-sustained and sustained VA patients in both the BZ and core components.BZ channels were found in 23%, 67%, and 91% of non-inducible, inducible non-sustained, and inducible sustained VA patients (p = 0.003). All 13 patients induced with MMVT or monomorphic-initiated PVT/VF had LGE. The origin of 10/13 of these VTs matched scar location, with 8/10 of these LGE regions showing BZ channels. During follow-up (20 months, IQR:7-37) one patient with BZ channels and inducible PVT had an ICD shock for VF. Conclusions: Scar architecture determines inducibility and electrophysiological traits of VA in HCM. Larger studies should explore the role of complex LGE patterns in refining risk assessment in HCM patients.