Generally, IV atropine in the recommended dosages (2010 guidelines dose is 0.5mg IV, repeatable every 3-5 minutes up to 3mg total) improves heart rate and alleviates symptoms associated with bradycardia. It is important to note, however, that atropine will generally be ineffective in 2nd degree type 2 (Mobitz 2) or third degree heart block, or in heart transplant patients. These patients are better treated with b-adrenergic drugs (low dose dopamine or epinephrine) or trans-cutaneous pacing.
Be aware that small doses of atropine (smaller than 0.5mg IV) can have a paradoxical effect, causing a further drop in heart rate.
Atropine has been removed from the pulseless arrests algorithms, as it was not found to be beneficial in these cases.