On the cover: Ca2+ signaling in individual myocytes of intact rat left ventricular epicardium during a pacing-induced ventricular tachycardia (VT). The top panel shows the ECG from a Langendorff-perfused rat heart during basal pacing at a cycle length of 500ms (first 4 responses), during rapid pacing at a cycle length of 130ms for 2.5 seconds, then during a run of induced VT (the last 21 beats following the stimulus train). The VT terminates spontaneously and is succeeded by 2 intrinsic beats of ventricular origin during the posttrain pause. The bottom panel shows transverse line-scan recordings using single photon laser scanning confocal microscopy to measure Ca2+ transients (fluo-4AM) in 15 myocytes in the LV subepicardium during this episode. Cellular Ca2+ signaling is highly complex during both rapid pacing and during VT, showing extremely heterogeneous activity between neighboring myocytes and even within individual cells. See related article, page E65.