I had a Medronic Dual Chamber P.M. install in March 2006 after collapsing with a full heart block. Since having the p.m. installed I have experienced episodes of feeling that I am going to blackout. These episode's last from a split second to 10 seconds. I have seen my cardiologist who has scanned my carotid arteries, heart, kidneys and I wore a heart monitor for ten days. In addition my p.m. has been checked several times and is functioning correctly. All test have shown that no abnormalities have been found. Has anybody experienced any similar symptoms.