Pulse Rate

In the past I have periodically had heart palpations very late at night time.  However, recently, I have been experiencing the opposite, consisting of feeling a weak heart rate, again I notice this late at night.  My pulse fluxuates and gets down as low as 48 at times.  I have also noticed being very fatigued during the day.  I recently had a blood test which listed LOW for following: triglycerides (22.2), VLDL (4.4), ALK PHOS (29.5), LDH (81.8), GGT (12.4) and RDW (9.2).  I also had a sonogram of my heart, which suspected mitro valve prolapse, however, inconclusive.  There was difficulty with the scan due to having breat implants.

[BRAZZY3]

I also have very low pulse rate at times and frequent palpitations, seem like palps come when I stand up or are doing normal things around the house.  I walk 40 minutes daily but do not notice palps or low pulse.  I've been told by Dr's that I have sinus bradycardia but I also wonder if it drops even lower at times because I get lightheaded & lil dizziness.  What have Dr's advised you?