Many predators produce dormant offspring to escape harsh environmental conditions, but the evolutionary stability of this adaptation has not been fully explored. Like seed banks in plants, dormancy provides a stable competitive advantage when seasonal variations occur, because the persistence of dormant forms under harsh conditions compensates for the increased cost of producing dormant offspring. However, dormancy also exists in environments with minimal abiotic variation—an observation not accounted for by existing theory. Here it is demonstrated that dormancy can out‐compete perennial activity under conditions of extensive prey density fluctuation caused by overpredation. It is shown that at a critical level of prey density fluctuations, dormancy becomes an evolutionarily stable strategy. This is interpreted as a manifestation of Parrondo's paradox: although neither the active nor dormant forms of a dormancy‐capable predator can individually out‐compete a perennially active predator, alternating between these two losing strategies can paradoxically result in a winning strategy. Parrondo's paradox may thus explain the widespread success of quiescent behavioral strategies such as dormancy, suggesting that dormancy emerges as a natural evolutionary response to the self‐destructive tendencies of overpredation and related biological phenomena.

Background Incomplete anchoring of the Watchman left atrial appendage closure (LAAO) device can result in substantial device migration or device embolization requiring percutaneous or surgical retrieval. Purpose To report rates and characteristics of in-hospital and post-discharge Watchman device migration and embolization events in the United States. Methods We performed a retrospective analysis of Watchman procedures (January 2016 through March 2021) reported to the National Cardiovascular Data Registry LAAO Registry. We excluded patients with prior LAAO interventions, no device released, and missing device information. In-hospital events were assessed among all patients and post-discharge events were assessed among patients with 45-day follow-up. Results Of 120,278 Watchman procedures, device migration or embolization occurred in 0.07% of patients (n=84) during the index hospitalization and surgery was performed in 39 patients. The in-hospital mortality rate was 14% among patients with device migration or embolization and 20.5% among patients who underwent surgery. In-hospital migration or embolization was more common: at hospitals with a lower median annual procedure volume (24 vs. 41 procedures, p<0.0001), with first-generation Watchman versus next-generation Watchman FLX devices (0.08% vs. 0.04%, p=0.0048), with larger LAA ostia (median 23 mm vs. 21 mm, p=0.004), and with a smaller difference between device and LAA ostial size (median difference 4 mm vs. 5 mm, p=0.04). There were no differences by age, sex, hospital type, hospital size, or teaching versus non-teaching status. Of 98,147 patients with 45-day follow-up, device migration or embolization after discharge occurred in 0.06% (n=54) patients and cardiac surgery was performed in 7.4% (n=4) of cases. The 45-day mortality rate was 3.7% (n=2) among patients with post-discharge device migration or embolization. Post-discharge migration or embolization was more common among men (79.7% of events but 58.9% of all procedures, p=0.0019), taller patients (177.9 cm vs. 172 cm, p=0.0005), and those with greater body mass (99.9 kg vs. 85.5 kg, p=0.0055); in contrast to in-hospital events, there were no differences in hospital volume, device characteristics, or LAA characteristics. Conclusions Watchman device migration or embolization is rare but associated with high mortality (Figure 1) and frequently requires surgical retrieval. A substantial proportion of all device migration or embolization cases occur after discharge and different patient and procedure characteristics are associated with in-hospital versus post-discharge cases. Given the morbidity and mortality associated with device migration or embolization, risk mitigation strategies and on-site cardiac surgical back-up are of paramount importance. Funding Acknowledgement Type of funding sources: Public grant(s) – National budget only. Main funding source(s): National Institutes of Health

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