LQTS Type 3

My daughter age 15 has been diagnosed with LQTS, her cardiologist is thinking that is going to be type 3, since her holter monitor showed significant numbers while she was sleeping (480-495). She has also suffered a seizure while sleeping, and her EEG shows abnormal, so now we are going to do a 24 hr. EEG to see what her brain is doing. We are going in for genetic testing, and I am wanting to know if Type 3 is fairly common or not. Her dr. put her on Inderal 80mg od. and would like to get her up to about 120mg od. If you have any info. to share I would really appreciate it. Thanks!