168 | Chapter 8 Study Outcomes The primary outcome of the study was first sustained VA after TFC-based ARVC diagnosis. In accordance with the published ARVC risk calculator, sustained VA was defined as sustained ventricular tachycardia lasting ≥30 s at ≥100 bpm, aborted cardiac arrest, or appropriate ICD therapy. Incident heart transplantation, cardiovascular mortality and all-cause mortality were also recorded during follow-up. Follow-up duration was defined as the time interval between baseline echocardiography and VA or censoring, which was defined as last clinical visit if lost to follow-up or 1st of January 2023. Statistical analysis Analyses were performed with RStudio (v. 2022.12.0, Boston, USA) and Stata (v. 16.0, Statacorp, Texas, USA). Continuous variables were expressed as mean with SD or median with interquartile range (IQR) and compared using independent sample t-test or Mann–Whitney U test. Categorical variables were presented as frequencies (%) and compared using the Fisher exact test. VA-free survival probability was estimated using the Kaplan–Meier method and Cox proportional hazard regression analysis. For Kaplan-Meier analysis of continuous variables, categorization was based on threshold regression analysis. All deformation imaging variables were subjected to linearity and proportional hazards assumption testing criteria. P-values were two-sided, and values <0.05 were considered significant. Model testing The overall discriminative performance of the ARVC risk calculator was measured using the optimism-corrected Harrell’s C-statistic. The 5-year risk of sustained VA for an individual patient as per the published model was calculated using the following equation4: 5 year VA risk = 1 − 0.84exp(PI) where the prognostic index (PI) was calculated according to the equation: PI = male sex * 0.49 – age * 0.022 + cardiac syncope * 0.66 + NSVT * 0.81 + ln(24-h PVC count) * 0.17 + TWI * 0.11 − RVEF * 0.025 Based on the 5-year risk of sustained VA, patients were stratified into low risk (<5%), intermediate risk (5 – 25%) and high risk (>25%) subgroups. Of note, the baseline hazard for 5-year prediction (0.84) has been corrected since the initial publication in 2019.23 To assess the predictive ability of deformation imaging for VA events, Cox proportional hazards models of VA events were fitted to deformation imaging results. The strongest deformation imaging parameters were identified by stepwise backward selection in a multivariable Cox proportional hazards model and tested for prognostic value independent of the ARVC risk calculator PI (incorporated as a fixed offset variable). Model discriminations were assessed using a nonparametric concordance-based C-statistic. The added value of deformation imaging to the ARVC risk calculator for predicting VA events was assessed by comparison of optimism-corrected C-statistics. The Akaike information criterion (AIC) was estimated for the risk models, for which a reduction of >2 was considered a significant improvement.
RkJQdWJsaXNoZXIy MTk4NDMw