PACs, PVCs and Right Bundle Branch Block

I have very frequent PACs and occasional PVCs. I had a RF ablation for AV nodal reentry tachychardia two years ago. It was successful at the time, but the SVT has returned. I've chosen not to have a second ablation because of the increased risk of AV block. I am now taking Toprol, which seems to offer limited help for my symptoms but does not seem to decrease the frequency of the PACs/PVCs. In addition, I don't feel very well on the Toprol. I'm lightheaded and nauseated a lot of the time. I also have RBBB. Can RBBB contribute to my symptoms? I am very symptomatic during exercise when the pauses caused by the PACs seem especially long. Can RBBB contribute to or be the cause of the long pauses? Thank you for your time. Your answers to the many questions concerning PACs and PVCs have been very helpful to me in the past.

[CCF-M.D.-CRC]

Dear Erin,
Right bundle branch block (RBBB) is due to a delay in the conduction system within the heart.  It is generally benign and does not cause symptoms or pauses in the heart rate.  Premature atrial contractions (PACs) cause pauses by "resetting" the sinus node.  Usually these are brief but they may be more noticeable during exercise when the heart rate is higher.  Glad we've been able to help with your questions.