Side effects after stern implanted in descending artery in heart?

None. Suspect you mean left anterior descending artery and assume you had stent placed. There should be no significant side effects from the stent once over the minor pain of intrusion. Stents can develop clots in them. This will likely produce significant shortness of breath and chest pain. You are probably taking clopidogrel (plavix) to prevent this complication.
More information. Nothing is called descending artery in the heart , so is this a heart/coronary stent or stent in the descending thoracic aorta ? What kind of disease was the stent used to treat ?