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Background: Idiopathic ventricular fibrillation (IVF) can be associated with undetected distinct conditions such as microstructural cardiomyopathic alterations (MiCM) or Purkinje (Purk) activities with structurally normal hearts., Objectives: This study sought to evaluate the characteristics of recurrent VF recorded on implantable defibrillator electrograms, associated with these substrates., Methods: This was a multicenter collaboration study. At 32 centers, we selected patients with an initial diagnosis of IVF and recurrent arrhythmia at follow-up without antiarrhythmic drugs, in whom mapping demonstrated Purk or MiCM substrate. We analyzed variables related to previous ectopy, sinus rate preceding VF, trigger, and initial VF cycle lengths. Logistic regression with cross validation was used to evaluate the performance of criteria to discriminate Purk or MiCM substrates., Results: Among 95 patients (35 women, age 35 ± 11 years) meeting the inclusion criteria, IVF was associated with MiCM in 41 and Purk in 54 patients. A total of 117 arrhythmia recurrences including 91% VF were recorded on defibrillator. Three variables were mostly discriminant. Sinus tachycardia (≤570 ms) was more frequent in MiCM (35.9% vs 13.4%, P = 0.014) whereas short-coupled (<350 ms) triggers were most frequent in Purk-related VF (95.5% vs 23.1%, P = 0.001), which also had shorter VFCLs (182 ± 15 ms vs 215 ± 24 ms, P < 0.001).The multivariable combination provided the highest prediction (accuracy = 0.93 ± 0.05, range 0.833-1.000), discriminating 81% of IVF substrates with a high probability (>80%). Ectopy were inconsistently present before VF., Conclusions: Characteristics of arrhythmia recurrences on implantable cardioverter- defibrillator provide phenotypic markers of the distinct and hidden substrates underlying IVF. These findings have significant clinical and genetic implications., Competing Interests: Funding Support and Author Disclosures Dr Haissaguerre has received grant support from Biosense Webster. Dr Marijon has received grant support and consulting fees from Medtronic, Boston Scientific, Abbott, Microport, Biotronik, and Zoll. Pr Gandjbakhch has received lecture fees from Biotronik; and consulting fees from Medtronic, Microport, and Abbott. Dr Tilz is a consultant for Boston Scientific, Biotronik, Biosense Webster, and Abbott Medical; has received speaker honoraria from Boston Scientific, Biotronik, Biosense Webster, Abbott Medical, and Lifetech; and has received research grants from Abbott, Biosense Webster, and Lifetech. Dr Roten has received research grants from Medtronic, the Swiss National Foundation, the Swiss Heart Foundation, the Immanuel and Ilse Straub Foundation, and the Sitem Insel Support Fund, all for work outside the submitted study; and has received speaker/consulting honoraria from Abbott and Medtronic. Dr Reichlin has receivedresearch grants from the Swiss National Science Foundation, the Swiss Heart Foundation, the Sitem Insel support funds, Biotronik, Boston-Scientific, and Medtronic, all for work outside the submitted study; and has received speaker/consulting honoraria or travel support from Abbott/SJM, Biosense-Webster, Biotronik, Boston-Scientific, and Medtronic, all for work outside the submitted study. Support for his institution’s fellowship program from Abbott/SJM, Biosense-Webster, Biotronik, Boston-Scientific, and Medtronic for work outside the submitted study. Dr Sacher has receivedspeaking honorarium from Abbott, Boston Scientific, and Biosense Webster; and equity from InHeart. Dr Nogami has received lecture fees from Abbott; and endowments from Medtronic. Dr Massoullié has received lecture fees from Boston Scientific, Biosense Webster, and Abbot. All other authors have reported that they have no relationships relevant to the contents of this paper to disclose., (Copyright © 2024 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.)

Potential climate tipping points pose a growing risk for societies, and policy is calling for improved anticipation of them. Satellite remote sensing can play a unique role in identifying and anticipating tipping phenomena across scales. Where satellite records are too short for temporal early warning of tipping points, complementary spatial indicators can leverage the exceptional spatial-temporal coverage of remotely sensed data to detect changing resilience of vulnerable systems. Combining Earth observation with Earth system models can improve process-based understanding of tipping points, their interactions, and potential tipping cascades. Such fine-resolution sensing can support climate tipping point risk management across scales., (© 2024. The Author(s).)