Accuratezza diagnostica e implicazioni prognostiche della fibrosi ventricolare destra evidenziata tramite risonanza magnetica cardiaca in pazienti adulti con tetralogia di Fallot corretta

Background: Repaired Tetralogy of Fallot (RToF) patients show structural and functional right ventricular (RV) changes which can act as substrates for malignant ventricular arrhythmias. Left ventricular late gadolinium enhancement (LGE) detected by cardiac magnetic resonance (CMR), has been demonstrated to be a predictor of such arrhythmias in a variety of cardiac diseases. However, the sensitivity and prognostic value of RV-LGE is less well established and its role for risk stratification of RToF patients is still unproven. The aims of our study were: 1) to compare the accuracy of RV scar detection in RToF between CMR and histological findings on whole heart specimens; 2)to validate the use of three-dimensional CMR (3D-CMR) for RV scar detection/quantification in RTOF using invasive electroanatomic mapping as gold standard; 3) to assess whether the extent and/or location of RV LGE significantly correlates with ventricular tachycardia (VT) inducibility during electrophysiological study (EPS) and with outcomes at follow-up. Methods: 1)Searching the CMR database of Padua University Hospital, collecting scans from January 2004 to present, patients with RTOF aged >18 years at the time of scan were selected; all available RV LGE images were then analysed and cross-matched within the Anatomical Collection of Congenital Heart Diseases (CHD) (Cardiovascular Pathology of the University of Padua) in order to perform macroscopical and histopatological analysis on those hearts which underwent CMR in vivo. 2) 3) Among adults with congenital heart disease followed up at Royal Brompton Hospital (London, UK), the study prospectively enrolled, since 2009, consecutive patients with RToF who underwent both 3D-CMR evaluation with LGE and electrophysiological study with RV voltage mapping (CARTO® system) and programmed ventricular stimulation. The presence and amount of RV LGE were assessed with a dedicated software and correlated with the results of the EPS and the occurrence of major events (cardiac death, ventricular fibrillation - VF, sustained ventricular tachycardia - SVT- and appropriated ICD intervention) during follow up. Results: 1) Among the 16 adult patients with rTOF scanned, 15 patients (11 males, 57.5%; median age 35.7 years, 22.7-41.9) with RV LGE suitable for analysis were identified. Semiquantitative 2D LGE analysis showed a median RV LGE of 27.22 (12.2-40.8) g, with a percentage of 22.5 (10.1-29.9) % of the RV myocardium. Cross-matching with the Cardiovascular Pathology Registry lead to the identification of a single patient, and clear correlation was seen of areas of RV fibrosis demonstrated in vivo by CMR and the whole heart. 2) and 3) Among the 63 patients initially enrolled, 55(35 males, 63.6%; median age 38.3 years, 29.6-50.9) both underwent full EPS and had 3D LGE CMR suitable for analysis. 3D CMR imaging revealed the presence of RV LGE in all patients, with a median extent of 23.8 (15-32.2) cm3. Concordance between regional distribution of RV LGE and low-voltage area at endocardial voltage mapping was high (88%, κ= 0.73, p<0.001), and the extent of RV LGE significantly correlated with VF/SVT inducibility (p=0.005). During a mean follow up of 5,8±2,8 years, 11 patients out of 55 (20%) experienced major cardiac events (VT/VF and/or cardiac death). 9 out of 11 patients (81.8%) with events at follow up had a RVLGE ≥30 cm3, compared to 11/44 (25%) without events (p=0.001). There was no association between morfofunctional parameters such as RV volumes and function or RV LGE localization and major events during follow-up. Conclusions: Evaluation of RV-LGE by 3D CMR appears to be an accurate non-invasive technique for assessment of RV scars compared to current invasive gold-standard (electroanatomic voltage mapping) and for non-invasive arrhythmic risk stratification in RToF. Further follow-up studies on larger populations are required to validate the prognostic role of RV-LGE in this setting.