Again, I'm not really here...
There's emerging research from a number of groups that Lewy bodies eventually develop outside the brain, and there's a particular interest in Japan in cardiac conduction abnormalities in DLB.
If someone is taking a beta-blocker for high blood pressure, 41 might not be unexpectedly low. It would depend on activity level, time since the dose, etc. The bigger question is the rhythm quality across the entire Holter. If there's missed beats or "asystole pauses", it's probably not the beta blockade causing the problems. There's probably some conduction issue causing the problem, and there's a theoretical basis for it being part of the DLB. The *downside* is, cardiologists aren't neurologists, so you really want someone who is a specialist in conduction disorders - a cardiac electrophysiologist, or EP.
Not all electrophysiologists are members, but a good way to find a fellowship-trained EP is the locator at
http://www.hrsonline.org/PatientInfo/sp ... ocator.cfm
Consider this: if he's bradying down to the 30s/40s, he's probably having dizziness as a result. If he falls, he will likely be injured by the fall. If it happens in a bathroom upon arising from the toilet, for example, he could hit his head and have a horrific debilitating-but-not-fatal brain bleed. Consider carefully your ability to care for someone who is markedly worse than he is right now, possibly with substantial physical impairment.
This makes the idea of what will probably be one visit with a regular cardiologist, one visit with an electrophysiologist, one brief procedure under a local and a short-stay unit visit and nurse followups at two weeks, a month, two months, five months and roughly a year look substantially more appealing.
Fixing rhythm problems can really improve quality of life; when you're low, you feel worn out, short of breath, dizzy, "sick" and puny. Pacing could well provide enough of a support to maximize physical activity as long as possible.