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Comparative Study
. 2018 Dec;11(12):e006730.
doi: 10.1161/CIRCEP.118.006730.

Predictive Score for Identifying Survival and Recurrence Risk Profiles in Patients Undergoing Ventricular Tachycardia Ablation: The I-VT Score

Pasquale Vergara  1 , Wendy S Tzou  2 , Roderick Tung  3 , Chiara Brombin  4 , Alessandro Nonis  4 , Marmar Vaseghi  5 , David S Frankel  6 , Luigi Di Biase  7 , Usha Tedrow  8 , Nilesh Mathuria  9 , Shiro Nakahara  10 , Venkat Tholakanahalli  11 , T Jared Bunch  12 , J Peter Weiss  12 , Timm Dickfeld  13 , Dhanunjaya Lakireddy  14 , J David Burkhardt  15 , Pasquale Santangeli  6 , David Callans  6 , Andrea Natale, Francis Marchlinski, William G Stevenson  16 , Kalyanam Shivkumar  5 , William H Sauer  2 , Paolo Della Bella  1
Affiliations
Comparative Study

Predictive Score for Identifying Survival and Recurrence Risk Profiles in Patients Undergoing Ventricular Tachycardia Ablation: The I-VT Score

Pasquale Vergara et al. Circ Arrhythm Electrophysiol. 2018 Dec.

Abstract

Background: Several distinct risk factors for arrhythmia recurrence and mortality following ventricular tachycardia (VT) ablation have been described. The effect of concurrent risk factors has not been assessed so far; thus, it is not yet possible to estimate these risks for a patient with several comorbidities. The aim of the study was to identify specific risk groups for mortality and VT recurrence using the Survival Tree (ST) analysis method.

Methods: In 1251 patients 16 demographic, clinical and procedure-related variables were evaluated as potential prognostic factors using ST analysis using a recursive partitioning algorithm that searches for relationships among variables. Survival time and time to VT recurrence in groups derived from ST analysis were compared by a log-rank test. A random forest analysis was then run to extract a variable importance index and internally validate the ST models.

Results: Left ventricular ejection fraction, implantable cardioverter defibrillator/cardiac resynchronization device, previous ablation were, in hierarchical order, identified by ST analysis as best predictors of VT recurrence, while left ventricular ejection fraction, previous ablation, Electrical storm were identified as best predictors of mortality. Three groups with significantly different survival rates were identified. Among the high-risk group, 65.0% patients were survived and 52.1% patients were free from VT recurrence; within the medium- and low-risk groups, 84.0% and 97.2% patients survived, 72.4% and 88.4% were free from VT recurrence, respectively.

Conclusions: Our study is the first to derive and validate a decisional model that provides estimates of VT recurrence and mortality with an effective classification tree. Preprocedure risk stratification could help optimize periprocedural and postprocedural care.

Keywords: cardiomyopathies; catheter ablation; mortality; risk assessment; ventricular tachycardia.

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Figures

Figure 1.
Figure 1.
Schema of the decision tree, consisting of nodes and leaves. The root note of the tree (shown on top) comprises all the patients; it splits into daughter nodes; the splitting process continues recursively for each subsequent node. Subsequent splitting allows for the identification of subgroups with homogeneous risk profile. At the top of the tree HR is 1, since the baseline hazard of the entire cohort of the study is used as reference. Each intermediate node and final leaf (lower boxes) indicates a class with a homogeneous risk profile: low-risk patients (HR<0.7) are in green boxes, medium-risk (0.7≤HR≤1.4) in yellow boxes, high-risk (HR>1.4) in red boxes. HR: Hazard Ratio for the patients in the group (leaf). Pte: number of patients with the event in the group. Ptg: total number of patients in the group.
Figure 2.
Figure 2.
Survival Tree for 1-year VT recurrence and Kaplan-Meyer analysis in derived groups. A. Survival Tree (left panel): The figure follows the schema of the Survival Tree with decisional points, nodes and final classification leafs shown in Figure 1. LVEF appears as the first decision point: patients with LVEF<30% had a higher VT recurrence risk (HR 1.6), as compared to patients with LVEF ≥30% (HR: 0.7). Following split variables are Device, type of cardiomyopathy, Previous Abl. B (Right panel): Kaplan-Meier estimates with 95% confidence intervals of VT recurrence for patients with low (green line), medium (yellow line) and high-risk profile (red line).
Figure 3.
Figure 3.
Survival Tree for 1-year death after VT ablation and Kaplan-Meyer analysis in derived groups. A. Survival Tree (left panel): The figure follows the schema of the Survival Tree with decisional points, nodes and final classification leafs shown in Figure 1. LVEF appears as the first decision point: patients with LVEF<30% had a higher death risk (HR 2), as compared to patients with LVEF ≥30% (HR: 0.2). In patients with LVEF≥30% occurrence of a previous ablation (Previous Abl) was identified as further splitting variable. In patients with LVEF<30%, 4 subsequent splitting variable were identified by the procedure, thus allowing for a more precise risk stratification: ES, LVEF, Age, Device. B (Right panel): Kaplan-Meier estimates with 95% confidence intervals of 1-year death for patients with low (green line), medium (yellow line) and high profile (red line).
Figure 4.
Figure 4.
Survival Tree for re-estimation of the VT recurrence risk after the procedure and Kaplan-Meyer analysis in derived groups. A. Survival Tree (left panel): The figure follows the schema of the Survival Tree with decisional points, nodes and final classification leafs shown in Figure 1. LVEF remains as the most predictive variable also for post-operative risk estimation. In patients with LVEF<30%, the result of programmed stimulation after the procedure (PES), Age and occurrence of a previous ablation (Previous Abl) provided further risk stratification. No VT: absence of any VT inducible at programmed stimulation after the ablation; NC-VT: Non clinical ventricular tachycardia inducible after the ablation; C-VT: Clinical ventricular tachycardia inducible after the ablation; NT: not tested. B (Right panel): Kaplan-Meier estimates with 95% confidence intervals of VT recurrence for patients with low (green line), medium (yellow line) and high profile (red line).
Figure 5.
Figure 5.
Survival Tree for re-estimation of the mortality risk after the procedure and Kaplan-Meyer analysis in derived groups. A. Survival Tree. Left panel: The figure follows the schema of the Survival Tree with decisional points, nodes and final classification leafs shown in Figure 1. LVEF remains as the most predictive variable also for post-operative risk estimation. In patients with LVEF<30%, the result of programmed stimulation after the procedure (PES), Diabetes Mellitus (DM), ES (Electrical Storm), Age provided further risk stratification. In patients with LVEF≥30% occurrence of a previous ablation (Previous Abl) was identified as further splitting variable. No VT: absence of any VT inducible at programmed stimulation after the ablation; NC-VT: Non clinical ventricular tachycardia inducible after the ablation; C-VT: Clinical ventricular tachycardia inducible after the ablation; NT: not tested. B. Right panel: Kaplan-Meier estimates with 95% confidence intervals of VT recurrence for patients with low (green line), medium (yellow line) and high profile (red line).
Figure 6.
Figure 6.
Comparison of mortality prediction between the i-VT score and the PAAINESD score by ROC curves. In the panel A only pre-procedure variables were included in the i-VT score; in panel B, both pre and post procedure variables were included in the i-VT score
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