BACKGROUND: Anti-tachycardia pacing (ATP), which may avoid unnecessary ICD shocks, does not always terminate ventricular arrhythmias (VAs). Mean entropy calculated using cardiac magnetic resonance texture analysis (CMR-TA) has been shown to predict appropriate ICD therapy. We examined whether scar heterogeneity, quantified by mean entropy, is associated with ATP failure and explore potential mechanisms using computer modelling. METHODS: A sub-analysis of 114 patients undergoing CMR-TA where the primary endpoint was delivery of appropriate ICD therapy (ATP or shock therapy) was performed. Patients receiving appropriate ICD therapy (n = 33) were dichotomized into 'successful ATP' versus 'shock therapy' groups. In silico computer modelling was used to explore underlying mechanisms. RESULTS: A total of 16/33 (48.5%) patients had successful ATP to terminate VA and 17/33 (51.5%) required shock therapy. Mean entropy was significantly higher in the shock versus successful ATP group (6.1±0.5 vs. 5.5±0.7, p = 0.037). Analysis of patients receiving ATP (n = 22) showed significantly higher mean entropy in the 6/22 patients that failed ATP (followed by rescue ICD shock) compared to 16/22 that had successful ATP (6.3±0.7 vs. 5.5±0.7, p = 0.048). Computer modelling suggested inability of the paced wavefront in ATP to successfully propagate from the electrode site through patchy fibrosis as a possible mechanism of failed ATP. CONCLUSIONS: Our findings suggest lower scar heterogeneity (mean entropy) is associated with successful ATP whereas higher scar heterogeneity is associated with more aggressive VAs unresponsive to ATP requiring shock therapy which may be due to inability of the paced wavefront to propagate through scar and terminate the VA circuit. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.
BACKGROUND: Anti-tachycardia pacing (ATP), which may avoid unnecessary ICD shocks, does not always terminate ventricular arrhythmias (VAs). Mean entropy calculated using cardiac magnetic resonance texture analysis (CMR-TA) has been shown to predict appropriate ICD therapy. We examined whether scar heterogeneity, quantified by mean entropy, is associated with ATP failure and explore potential mechanisms using computer modelling. METHODS: A sub-analysis of 114 patients undergoing CMR-TA where the primary endpoint was delivery of appropriate ICD therapy (ATP or shock therapy) was performed. Patients receiving appropriate ICD therapy (n = 33) were dichotomized into 'successful ATP' versus 'shock therapy' groups. In silico computer modelling was used to explore underlying mechanisms. RESULTS: A total of 16/33 (48.5%) patients had successful ATP to terminate VA and 17/33 (51.5%) required shock therapy. Mean entropy was significantly higher in the shock versus successful ATP group (6.1±0.5 vs. 5.5±0.7, p = 0.037). Analysis of patients receiving ATP (n = 22) showed significantly higher mean entropy in the 6/22 patients that failed ATP (followed by rescue ICD shock) compared to 16/22 that had successful ATP (6.3±0.7 vs. 5.5±0.7, p = 0.048). Computer modelling suggested inability of the paced wavefront in ATP to successfully propagate from the electrode site through patchy fibrosis as a possible mechanism of failed ATP. CONCLUSIONS: Our findings suggest lower scar heterogeneity (mean entropy) is associated with successful ATP whereas higher scar heterogeneity is associated with more aggressive VAs unresponsive to ATP requiring shock therapy which may be due to inability of the paced wavefront to propagate through scar and terminate the VA circuit. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.