It's a relatively common side effect of depakote, to have some bronchial side effects, probably something like a mild asthma. It's not on the list of side effects that require immediate medical care. Only you can judge how prominent this symptom is, but it's not considered serious (most of the time). It would probably be a good idea to notify your doctor that you're having this side effect, though.

This may seem to come from left field, but there's a good chance that a commonly available vitamin, niacinamide (that's the AMIDE form of vitamin B3) might eliminate this symptom. It tends to reduce smooth muscle contraction, which could underly this feeling of chest pain that you're having. Can't hurt, might help. You can take up to 500 mg, four times a day. Make sure you get niacinamide, not niacin. They are not the same thing.

Also, magnesium supplementation may reduce this symptom. Both magnesium and niacinamide can make you sleepy (an occasional outcome), so be aware of that.

Lar