Background-Ischemic preconditioning provides strong cardioprotection from ischemia, but its molecular mechanisms remain unknown. Convincing evidence confirms a central role of hypoxia-inducible factor (HIF)-1 in mammalian oxygen homeostasis. Thus, we pursued HIF-1 as a central component of cardioprotection by ischemic preconditioning. Methods and Results-Murine studies of in situ preconditioning revealed a robust activation of cardiac HIF-1␣. Moreover, in vivo small interfering RNA repression of cardiac HIF-1␣ resulted in abolished cardioprotection by ischemic preconditioning. In contrast, pretreatment with the HIF activator dimethyloxalylglycine was associated with cardioprotection similar to that of ischemic preconditioning itself. Finally, selective small interfering RNA repression of prolylhydroxylase 2 resulted in significant activation of HIF-1␣ and attenuated myocardial infarct sizes (0.44Ϯ0.09-fold). As an end point of HIF-dependent cardioprotection, we defined the role of A2B adenosine receptor (A2BAR)

Using a duty-cycled, phased RF ablation system is safe and effective to isolate PVs. No Eso alteration was documented after ablation when LET was not monitored. This suggests that the LET probe may contribute to the thermal effect. Whether the documented increments in LET are due to direct tissue heating or possible interaction between the LET probe requires further investigation.

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