Intracellular calcium dynamics and acetylcholine-induced triggered activity in the pulmonary veins of dogs with pacing-induced heart failure.

BACKGROUND

Heart failure increases autonomic nerve activities and changes intracellular calcium (Ca(i)) dynamics.

OBJECTIVE

The purpose of this study was to investigate the hypothesis that abnormal Ca(i) dynamics are responsible for triggered activity in the pulmonary veins (PVs) during acetylcholine infusion in a canine model of heart failure.

METHODS

Simultaneous optical mapping of Ca(i) and membrane potential was performed in isolated Langendorff-perfused PV-left atrial (LA) preparations from nine dogs with ventricular pacing-induced heart failure. Mapping was performed at baseline, during acetylcholine (1 micromol/L) infusion (N = 9), and during thapsigargin and ryanodine infusion (N = 6).

RESULTS

Acetylcholine abbreviated the action potential. In four tissues, long pauses were followed by elevated diastolic Ca(i), late phase 3 early afterdepolarizations, and atrial fibrillation (AF). The incidence of PV focal discharges during AF was increased by acetylcholine from 2.4 +/- 0.6 beats/s (N = 4) to 6.5 +/- 2.2 beats/s (N = 8; P = .003). PV focal discharge and PV-LA microreentry coexisted in 6 of 9 preparations. The spatial distribution of dominant frequency demonstrated a focal source pattern, with the highest dominant frequency areas colocalized with PV focal discharge sites in 35 (95%) of 37 cholinergic AF episodes (N = 8). Thapsigargin and ryanodine infusion eliminated focal discharges in 6 of 6 preparations and suppressed the inducibility of AF in 4 of 6 preparations. PVs with focal discharge have higher densities of parasympathetic nerves than do PVs without focal discharges (P = .01), and periodic acid-Schiff (PAS)-positive cells were present at the focal discharge sites.

CONCLUSION

Ca(i) dynamics are important in promoting triggered activity during acetylcholine infusion in PVs from pacing-induced heart failure. PV focal discharge sites have PAS-positive cells and high densities of parasympathetic nerves.