Effect of Neuronal NE on heart rate

Effect of beta blockers without ISA on heart rate

Beta blockers without ISA will decrease resting heart rate. However, in stress they will antagonize the increase in heart rate. This is the beneficial effect. The decrease in resting heart rate could be deleterious.
Effect of ISA on beta blockade

Beta blockers with ISA will not decrease resting heart rate. However, in stress, as neuronally release NE tends to increase heart rate, the beta blockers will antagonize this increase.