RAPGEF3 and cardiac arrhythmia: The cardioprotective effect of the cAMP analogue 8-Br applied by the start of regional ischaemia or reperfusion may seem surprising, since it has been found that stimulation of β-adrenergic receptors (βARs) promotes cardiac arrhythmias through increased levels of cAMP, activation of PKA and Epac [32,33].