Clinical Outcome Prediction Model in Tetralogy of Fallot Without Pulmonary Valve Replacement Using Contraction Fraction From the SCOUT-TOF Registry.

BACKGROUND

Few large scale prediction models of clinical outcomes in repaired tetralogy of Fallot (rTOF) exist. Further, contraction fraction, a novel parameter indexing stroke volume by mass reflecting myocardial efficiency, has not been studied. The goals of this study were to develop and validate an rTOF prediction model of clinical outcome from a single center, the SCOUT-TOF (Single Center Outcomes Using Cardiac Magnetic Resonance in Tetralogy of Fallot) registry, using readily available cardiac magnetic resonance parameters and explore novel metrics.

METHODS AND RESULTS

We retrospectively reviewed cardiac magnetic resonance parameters of patients with rTOF undergoing cardiac magnetic resonance from 2005 to 2021. Composite outcome 1 (CO1) included death, transplantation, ventricular tachycardia, and pacemaker placement, and composite outcome 2 (CO2) added cardiovascular hospitalizations. An elastic net was used to identify significant variables to enter a best subsets logistic regression. A group of 761 patients with rTOF were studied with a median follow-up of 4.15 years; 31 and 44 CO1 and CO2 events occurred respectively. Right ventricular (RV) contraction fraction was the most significant predictor for CO1 (area under the curve, 0.72; odds ratio [OR], 0.54; =0.01) and CO2 (area under the curve, 0.69; OR, 0.60; =0.01). RV contraction fraction was lower for those met that CO1 and CO2 end points (median 1.84 [1.48-2.39] versus 2.34 [1.72-3.02] and 1.88 [1.51-2.53] versus 2.34 [1.72-3.02] cc×cm/g×m, <0.01 respectively). Additional significant predictors for CO1 were indexed RV mass/volume and left ventricular ejection fraction whereas for CO2, left ventricular global function index and left ventricular mass were additional predictors.

CONCLUSIONS

In rTOF, RV contraction fraction, a novel biomarker of ventricular efficiency, may be used to possibly improve risk stratification. In addition, not only RV but left ventricular measures of remodeling should be considered in the follow-up of these patients.