Hi, thank you for answering my question in advance. I am a 35 year old active female, diagnosed with SVT after I went through the standard tests. I had an EP study in July, then another for a 2nd opinion at Johns Hopkins two weeks ago. During the 2nd study, they were not able to produce my symptoms, but found that I had a very low heart rate during that point in the study and was noted a "heart block" was found. When I spoke to their office after the study, the nurse stated that they were concerned the condition was worsening. I am now on Toprol XL 150mg once a day (still having the rapid heartbeat)and am scheduled to go back to the EP at Hopkins in January. They stated there was a good possibility that I may need an ablation to the AV node with a possible pacemaker. I was wondering, is a pacemaker always needed with this procedure, and what node is the heart block usually in - the sinus node or AV node? Thank you!