Leveraging Cardiovascular Magnetic Resonance Imaging for Precise Arrhythmia Risk Prediction in Tetralogy of Fallot Patients (RF_SA_489)

Tetralogy of Fallot (ToF) is a cyanotic congenital heart defect characterized by a ventricular septal defect, an overriding aorta, and right ventricular outflow tract obstruction. Cardiovascular magnetic resonance (CMR) imaging is commonly used to monitor disease progression in patients with ToF. Recent studies suggest that the right atrial coupling index (RACI), derived from right atrial (RA) and right ventricular (RV) volumes measured via CMR, may be useful in predicting life threatening arrhythmias [1]. In this study, we aim to assess the predictive value of RV volumes and function, as well as RACI, in accurately predicting the risk of arrhythmias in ToF patients at our center.

Methods:

A retrospective single-center study involving 38 patients was conducted to analyze risk factors predicting post-ToF repair arrhythmias, including RV volumes, function, and RACI (Table 1). RA and RV volumes were obtained from Circle CVI42 (Circle Cardiovascular Imaging) and used to calculate RACI as the minimum RA volume divided by the RV end-diastolic volume. A validated Importance-Factor (IF) scoring system was used to determine arrhythmia risk as previously described [1]. The IF score >2 defines patients at high risk for life threatening arrhythmias. Receiver operator characteristic (ROC) analysis was used to evaluate the ability of the imaging parameters to differentiate patients with IF score >2.

Results:

24 males and 14 females were analyzed in this analysis. The median age of ToF repair was 0.56 years (Table 1). As shown in Table 2, there was no significant correlation between RACI, and RV ejection fraction (EF), RV end-diastolic volume index (EDVi), and RV end-systolic volume index (ESVi). A weak correlation was observed between RV EF and RV ESVi. ROC analysis indicates that RACI is not a significant standalone predictor of IF score >2. RV EF was observed to be a significant predictor of IF score >2 in a model of its own (Figure 1). Combining RVEF, RV EDVi and RACI together in one model improved the differentiation of patients with IF score >2 (AUC=0.79).

Conclusion:

RV function measured from CMR imaging demonstrates the significant utility of CMR as a non-invasive imaging modality for predicting arrhythmias in ToF patients. In our analysis, RV EF emerged as an independent predictor of arrhythmias. RV EDVi demonstrated a trend toward being an independent predictor of arrhythmias. However, RACI was not a significant predictor of arrhythmias. A combined model incorporating all three variables (RV EF, RV EDVi, and RACI) yielded an improved predictive performance. In ToF patients, pulmonary stenosis often increases the load on the RV, eventually leading to dysfunction. This dysfunction, quantifiable through RV EF, likely explains its utility as a predictor of arrhythmias. Nevertheless, a small sample size constrained our analysis, and future studies aim to replicate this investigation across multiple institutions.

Figure 1. The receiver operating characteristic (ROC) curve was generated for predictors of Importance-Factor (IF) score>2. Right ventricular (RV) ejection fraction (EF) emerged as an independent predictor of arrhythmias (AUC = 0.74). RV end-diastolic volume index (EDVi) demonstrated a trend toward being an independent predictor of arrhythmias (AUC = 0.68). However, the right atrial coupling index (RACI) was not a significant predictor of arrhythmias (AUC = 0.52). A combined model incorporating all three variables (RV EF, RV EDVi, and RACI) yielded an improved predictive performance, with an AUC of 0.79. RACI = Right atrial coupling index. A p<0.05 considered statistically significant.