Response by Feola et al to Letter Regarding Article, “Localized Optogenetic Targeting of Rotors in Atrial Cardiomyocyte Monolayers”

We thank Houston et al for their interest in our study. In their letter, they raise the question whether the rotors and accompanied spiral waves observed in our study represent microreentrant circuits anchored to lines of conduction block/slowing (ie, anatomical reentry), instead of reentrant activity around an unexcited, yet excitable core region (ie, functional reentry). Their comment is based on a movie published on their website, showing high-resolution mapping, in an HL-1 culture, of reentrant activity that seems anchored to microregions of conduction abnormalities. Although appraisal of these data is difficult without a detailed description of methods and results, we still would like to …