VOR therapy is not associated with the induction of cardiac arrhythmias observed in clinical trials with three different pan-HDACIs, but these results suggest that more potent pan-HDAC inhibitory profiles may be more likely to cause adverse cardiac effects, including reduced myocardial electrical communication, that may predispose the heart to potentially fatal arrhythmias. Here, HDAC9 is linked to chronic obstructive pulmonary disease.