Arrhythmogenic Mitral Valve Prolapse and Cardiac MRI : Is it electrical instability or arrhytmogenic substrate that matters or both? The Sphinx riddle that matters for life (RF_TH_149)

Mitral valve prolapse (MVP) can increase the risk of ventricular arrhythmias (VAs) and sudden cardiac death (1). However, the mechanisms driving electrical instability in MVP patients are not fully understood. A hypothesis suggests that myocardial fibrosis, induced by mechanical stretch of prolapsing leaflets, could create a substrate for reentrant VAs. This study aimed to evaluate the presence of ventricular tachycardia (VT) corridors using late gadolinium enhancement-cardiac magnetic resonance (LGE-CMR) imaging to explore this hypothesis.

Methods:

We studied 22 patients (mean age 44±13 years, 12 males) with an arrhythmogenic MVP phenotype, characterized by frequent Ventricular Extrasystoles (VES) ( >4000 events/24h) or non-sustained VT (NSVT) episodes documented by ECG, without significant mitral regurgitation. CMR was used to assess left ventricular volumes, ejection fraction, leaflet tethering, and mitral annular disjunction (MAD). LGE-CMR imaging was used to identify myocardial fibrosis and potential VT corridors.

High-resolution 3D whole heart LGE-CMR data were acquired 15 minutes post-gadolinium injection (isotropic resolutions of 1.5mm³ and 1.3mm³). Images were processed with ADAS-VT (Calgo Medical, Barcelona, Spain) software to generate a 3D heart model with 10 layers and Pixel Signal Intensity maps from the LGE data projected to each of the shells and  enabled automated detection of VT corridors (Figure 1).

Results:

Among the 22 patients, 7 (31.8%) had documented NSVT, while the remaining 15 exhibited frequent VES ( >4000/24h). The origin of VES was from the posteromedial papillary muscle (PM) in 12 patients, with others originating from the inferolateral wall (n=6) or LVOT (n=4). All patients had sub-epicardial/mid-wall fibrosis in the basal inferior/inferolateral walls and/or adjacent to the posteromedial PM. Specific cMRI findings included: LVEF 65±4.9%, LVEDVi 89.7±14.5 ml/m², MAD 7±2 mm, core LGE 1.3±0.8%, and (core+borderzone) LGE 11±8.6%. Significant tethering of the sub-mitral apparatus, with hypokinesia of the posteromedial PM and hyperkinesia of the basal inferolateral wall, was present in all patients.

VT corridors were identified in 4 of 7 patients with NSVT, located in the basal inferolateral wall near the PM, but were not observed in patients with isolated VES. A significant correlation (p< 0.03) was found between significant tethering and VES; other CMR characteristics did not achieve statistical significance.

Conclusion:

The absence of VT corridors in most MVP patients with notable arrhythmogenicity suggests that fibrosis alone may not fully explain VA development. Significant tethering and altered cardiac geometry due to MAD could contribute to early afterdepolarizations and triggered activity, presenting an alternative mechanism for VA in MVP patients.

VT corridors obtained by ADAS software using high resolution 3D LGE data projected on color-coded PSI maps