Fig. 2.
Triggered activity (TA) and subthreshold SCR events in wedge preparations under control (CNTL) and isoproterenol (Iso) conditions. A: representative ECG, action potentials (see Vm trace), and Ca2+ transients recorded during the induction of a triggered beat (TA) by rapid pacing (S1) in a HF preparation during Iso administration. Below the 3 separate traces for ECG, transmembrane potential (Vm), and Ca2+ are superimposed traces for Vm and Ca2+ on an expanded time scale during the triggered beat. The occurrence of TA was significantly greater in HF-Iso conditions compared with HF-CNTL conditions. B: representative ECG, action potentials, and Ca2+ transients recorded during the induction of a subthreshold SCR and delayed afterdepolarization (DAD) in a HF preparation. Below the 3 separate traces for ECG, Vm, and Ca2+ are superimposed traces for Vm and Ca2+ on an expanded time scale during the SCR/DAD. Summary data show that SCR activity was significantly greater in HF compared with N. The numbers in parentheses are the number of preparations demonstrating the event by the total number of preparations.