will exercise help or make hyperthropy worse

I have recently had my 2 lead pacemaker upgraded to a 3 wire biventrticular pacemaker. The good news is my ejection fraction was .35 with the old pacemaker, now it is in the normal range .55- .70. The bad news is I do not feel any better. I still suffer from fatigue and brain fog,also poor balance. I believe that he remaini  roblem is, my heart is not filling properly  This would cause the ejection fraction to look good, while I am in fact not feeling well, because I not getting enough blood to my muscles, nor to my brain. I believe that during the 2years that I had the right side only pacemaker, myheart was beating out of synchrony, this caused it to have to work harder, this caused the muscles to thicken, this means they cannot relax diastolic, and fill, so I end up not getting enough blood. I need to make these left ventricle walls less thick, so it will fill.  MY question is: will exercise make them thicker? What can I do to make them less thick?