Is it possible that a known tachycardia won't be able to be induced and mapped during an ep study?

Yes: It is uncommon, but occasionally abnormal rhythms cannot be reproduced during an electrophysiologic study. Sedation is typically used for these procedures and may be a complicating factor. If an abnormal rhythm or electrical connection cannot be demonstrated, there is nothing to map.

Yes: While uncommon, it does happen. The right circumstances have to come together for some arrhythmias to occur. The ep study attempts to create those circumstances. Sometimes sedation or other medicines may interfere with the ability to induce an arrhythmia. I find that another trip to the ep lab on a different day is usually worth it.

Yes: Sometimes a clinical arrhythmia is not induced in the EP lab. This is frustrating to the physician as well. Light sedation or high doses of intravenous cardiostimulant medications can minimize this risk.