In February, I had a severe EBV flare which made all my symptoms much worse. It especially bothered my heart. As a result, I ended up tapering off of Cytomel to see if the high heart rate would resolve. It did, but it threw me into low BP, low heart rate, but I still had shortness of breath and heart palpitations like mad (along with the full body constellation of symptoms). My doc ended up letting me try Mestonin for the autonomic issues, but I immediately washed out of the trial because it sent my pulse and pressure even lower. I finally went back on Cytomel and the pulse and pressure stabilized (low but acceptable). Next I decided to finally try Famvir, I've been on it ~4 weeks and am having some major discomfort with palps and shortness of breath. I am back to having high heart rate and a lot of discomfort. I have to split the Famvir into 250mg 4x per day to tolerate the heart effects. I decided to trial Mestonin again 4 or 5 days ago - and WOW has that helped! I am only taking a quarter tab 4x per day with my Famvir. The high pulse is GONE. The palps are GONE. The insomnia is much better - I had been staying awake at night with a racing heart and now it is quiet at night and I'm sleeping all night! There is a theater production that my husband loves to go to once a year (3 late nights, the only thing we ever go out to at night, LOL). I had planned to only go one night and expected to struggle, but tonight will be the 3rd night and I've actually enjoyed it! I wanted to post in case anyone else is struggling with the heart effects of going on Famvir in hopes that a combo with Mestonin may be helpful. It does, to me, point to the idea that Famvir or its effects somehow depress vagus function further, and cause some of the really bad side effects. As always with any positive 'improvement', I am knocking on wood that the effect lasts.