Characterization of the electrophysiological substrate in patients with Barlow's disease

Background Myxomatous mitral valve prolapse (MVP) and mitral-annular disjunction (Barlow disease) are at-risk for ventricular arrhythmias (VA). Fibrosis involving the papillary muscles and/or the infero-basal left ventricular (LV) wall was reported at autopsy in sudden cardiac death (SCD) patients with MVP. Objectives We investigated the electrophysiological substrate subtending VA in MVP patients with Barlow disease phenotype. Methods Twenty-three patients with VA were enrolled, including five with syncope and four with a history of SCD. Unipolar (Uni < 8.3 mV) and bipolar (Bi < 1.5 mV) low-voltage areas were analyzed with electro-anatomical mapping (EAM), and VA inducibility was evaluated with programmed ventricular stimulation (PES). Electrophysiological parameters were correlated with VA patterns, electrocardiogram (ECG) inferior negative T wave (nTW), and late gadolinium enhancement (LGE) assessed by cardiac magnetic resonance. Results Premature ventricular complex (PVC) burden was 12 061.9 +/- 12 994.6/24 h with a papillary-muscle type (PM-PVC) in 18 patients (68%). Twelve-lead ECG showed nTW in 12 patients (43.5%). A large Uni less than 8.3 mV area (62.4 +/- 45.5 cm(2)) was detected in the basal infero-lateral LV region in 12 (73%) patients, and in the papillary muscles (2.2 +/- 2.9 cm(2)) in 5 (30%) of 15 patients undergoing EAM. A concomitant Bi less than 1.5 mV area (5.0 +/- 1.0 cm(2)) was identified in two patients. A history of SCD, and the presence of nTW, and LGE were associated with a greater Uni less than 8.3 mV extension: (32.8 +/- 3.1 cm(2) vs. 9.2 +/- 8.7 cm(2)), nTW (20.1 +/- 11.0 vs. 4.1 +/- 3.8 cm(2)), and LGE (19.2 +/- 11.7 cm(2) vs. 1.0 +/- 2.0 cm(2), p = .013), respectively. All patients with PM-PVC had a Uni less than 8.3 mV area. Sustained VA (ventricular tachycardia 2 and VF 2) were induced by PES only in four patients (one with resuscitated SCD). Conclusions Low unipolar low voltage areas can be identified with EAM in the basal inferolateral LV region and in the papillary muscles as a potential electrophysiological substrate for VA and SCD in patients with MVP and Barlow disease phenotype.