In reply to David Hillebrandt: that seems a bit high handed David. The OP already has a PPM and is asking some general questions about pacemakers and outdoor activities/fitness and also looking to hear other patient experiences. There's nothing wrong with that and plenty of potential to get useful information and experiences on a forum without anyone playing diagnostics or getting specific to his case. Obviously he needs to talk through his own case with his cardiologist but there's plenty of useful general stuff that can be garnered from friendly individuals "down the pub" in the meantime. I greatly admire the mountain medicine diploma system you have set up but I'm not sure a diploma bearing GP or A&E doc reading from advice about PPMs and altitude/mountaineering has that much to offer with regards to the OP's questions on general fitness training - whereas for pacing cardiologists and pacemaker technicians this is daily bread and butter.
OP: you need to chat to your cardiologist and pacemaker technician about what your expectations are exercise wise so he knows what is normal for you. If people have AV block and no other heart problem then by and large a pacemaker will get them back to full activity - I've put PMs in 2 fell runners in the last year and both are back out on the hills. You need to find out if they feel there is any reason for you not to train hard and ask if the pacemaker settings are appropriate for this. Like most electronic goods the pacemakers come with factory settings and endless menus of parameters that can be reprogrammed. Default settings often require changing in very active people, sometimes taking quite a while to optimise. A lot of people feel washed out and take a good while to get back to normal after the whole thing of being ill/diagnosed/implanted. If you're still getting unpleasant symptoms keep asking about them. Some palpitations need treatment but many are a benign annoyance to live with - worth finding out if this latter has been established as the diagnosis.
You mention pros and cons of the treatment - clearly I don't know what went on with you but in most cases where PMs are implanted for heart block there isn't really a plan B on offer, the pacemaker is the only safe and effective treatment available - again ask your cardiologist.
Hope that's of some help, good luck with your training - PM me if you want
cheers, Paul