T-Wave Peak-to-End Changes Quantified by Time-Warping Predicts Ventricular Fibrillation in a Porcine Myocardial Infarction Model

Background: The $\mathrm{T}_{pe}$-interval time-warping-based morphology variation index, derived from a spatially transformed PCA lead, $d^{\text{PCA}}_{w,{\scriptscriptstyle \mathrm{T}_{pe}}}$, has previously demonstrated utility in tracking repolarization changes induced by a 5-minute ischemia model in humans. The value of $d^{\text{PCA}}_{w,{\scriptscriptstyle \mathrm{T}_{pe}}}$ as a predictor of ventricular fibrillation (VF) episodes is assessed in a 40-minutes porcine infarction model. Preocclusion and occlusion ECG recordings from 10 pigs who suffered a late VF episode and 16 who did not were analyzed. The $d^{\text{PCA}}_{w,{\scriptscriptstyle \mathrm{T}_{pe}}}$ series was measured by comparing $\mathrm{T}_{pe}$ morphologies at different stages of the occlusion relative to a baseline. During baseline, $d^{\text{PCA}}_{w,{\scriptscriptstyle \mathrm{T}_{pe}}}$ remained stationary with an intra-recording median [IQR] value of 1.60 [1.33] ms. During occlusion, $d^{\text{PCA}}_{w,{\scriptscriptstyle \mathrm{T}_{pe}}}$ followed a well-marked gradual increasing trend, reaching a median of 14.58 [17.72] ms. $d^{\text{PCA}}_{w,{\scriptscriptstyle \mathrm{T}_{pe}}}$ averages were significantly higher in the VF group than in the Non-VF group at five time intervals taken every 5 minutes after occlusion onset with median values of 12.5, 18.8, 26.8, 24.0, and 31.0, vs 6.3, 7.6, 8.0, 7.8, and 7.8, and also at three consecutive 5-minute intervals prior to VF 18.6, 25.0 and 28.8 vs 8.5, 7.2 and 6.0 ms, respectively. The $\mathrm{T}_{pe}^{\text{PCA}}$ interval was also significantly higher in the VF group at all analyzed time periods, but with a lower significance level. Pigs with maximum $d^{\text{PCA}}_{w,{\scriptscriptstyle \mathrm{T}_{pe}}}$ ≥ 20.0 ms and $\mathrm{T}_{pe}^{\text{PCA}}$ ≥ 85.4 ms in the early 5-10 minutes interval after occlusion, had significantly higher risk for VF occurring with 90.0%/75.0% and 80.0%/69.0% sensitivity/ specificity, respectively. In conclusion, $d^{\text{PCA}}_{w,{\scriptscriptstyle \mathrm{T}_{pe}}}$ is a stronger VF predictor than $\mathrm{T}_{pe}^{\text{PCA}}$ during ischemia in a porcine model.