It doesn't sound like garden variety palpitations to me. The combo of the faint, the heart rate of 39 bpm, and the spells of some kind of odd heartbeat would personally cause me to drag hubby to a cardiologist for a workup. He needs a basic EKG, and since these spells come on unpredictably, you should maybe discuss wearing a Holter monitor for a longer period to see if it might catch what's going on.
not sure what's going on with your husband, but there's many of us who have thousands of pvc's daily for quite a while...I've had different arrhythmia's VT runs etc with fainting episodes, since age 9 and was told they were ok until I was age 42 when they became very numerous (50,000 pvc's daily)
fainting can be due relatively minor things such as low bp, low blood sugar or it can be a sign of autonomic nervous system problems, cardiac related - only a dr can tell with proper testing
here's a great link: http:// www. cccgroup. info/ neurosyn. asp (take out the spaces)
Energy drinks contain caffeine and can cause palpitations...here is a link of interest.
They are not healthy!
http://www.npr.org/templates/story/story.php?storyId=94973371