Background: Electrical storm (ES) characterized by frequent arrhythmic episodes resulting in ICD shocks is associated with poor prognosis and can be treated with catheter ablation (CA). Patients who present for CA while in ES have a poor post-ablation prognosis, but it is unknown if this is also true for patients who have prior ES.
Objective: We sought to characterize myocardial substrate and outcomes for patients with a history of ES undergoing CA.
Methods: The 125 patients with structural heart disease who underwent CA for VT between March 2014 and November 2016 at Vanderbilt Medical Center were included. ES was defined as ≥ 3 distinct episodes of VT or VF in 24 hours. Mapping was performed both in sinus rhythm and VT when feasible with the procedural endpoints of targeting critical isthmi, eliminating areas of local abnormal ventricular activation, and VT non-inducibility. Analysis was performed using Student’s t-test of unpaired values with unequal variance and the multivariate cox proportional hazards model.
Results: Of 125 patients who underwent EP studies during this timeframe, six (5%) patients with prior VT ablations and 41 (33%) patients with incomplete myocardial substrate characterization during their EP study were excluded. Fifty seven (72%) patients had a history of ES compared to 22 (28%) without ES. The mean follow-up interval was 314 days. Patients with a history of ES were found to have an average of 2.1 inducible sustained monomorphic ventricular tachycardias (SMVTs) compared to 1.4 in those without prior ES (p=0.02). There were similar areas of bipolar scar (89.78 cm2 vs 74.0 cm2; p=0.32), late activation as defined by isochronal late activation mapping (22.1 cm2 vs 22.2 cm2; p=0.99), and catheter ablation (24.8 cm2 vs 21.8 cm2; p=0.43) between patients with and without prior ES. The two groups of patients had similar outcomes with respect to VT recurrence (HR 1.71, CI 0.7-4.1, p=0.234), recurrent shock (HR 0.93, CI 0.23-3.9, p=0.925), and a combined endpoint of death, transplant, or VAD (HR 1.6, CI 0.12-20, p=0.733).
Conclusion: Patients with a history of ES have more complex myocardial substrate for VT as evidenced by more inducible SMVTs. Despite this finding, they have similar post-ablation outcomes during long-term follow-up.