I used to wear the heart monitor when I re-started running but have stopped: frankly the heart rate doesn't move very much outside a 50-140 range, even when I try (damn beta-blockers).
I saw the cardiologist several times in the first year, but now they don't want to see me but once a year. My ICD sends data to the Hearth Hospital remotely every three months. Last time I was actually there (Sept) they said that the ICD had monitored two instances of elevated (180+) heart rate but I hadn't felt faint or even noticed them. No news good news, it seems.
Seems this thread has been dormant for a while, but I wanted to throw my experience in for good measure. Up until Nov 2010 I was ran 25-40 mpw and trained for duathlons and the like (terrible swimmer) - then out of the blue one evening at age 34 I had a cardiac arrest and was saved by the quick and determined action of a friend at a dinner party. Long story and coma short, I was diagnosed with ARVC, received an ICD and emerged very glad to be alive but wondering what kind of running, cycling and swimming I could do. As everyone else here says, there's not very much definitive advice. As an American, I would have been told back home to give everything up, but my consultants at the Heart Hospital here in London are more vaguely open to moderate exercise. I'm not sure what that means, given I used to do a lot of hill training, intervals, fartleks, etc. Like a lot of others I'm on beta-blockers which slows things down, but I've taken the view that life - while longer than it might have been - is still pretty short, and I don't want to die of clogged arteries or insanity on the sofa. I run most days 30-30 minutes - with 10 minutes of warm-up and 10 min cool-down, and some form of very short interval, exercise (lunges, strides e.g.) in between. I try to get in a longer (50-60 min) run every weekend, but do that along 10-and-1 lines (10 min run, 1 min walk). In fact I will often walk a minute here and there during most runs for a bit of recovery.
The first few months of running after the cardiac arrest were pretty miserable - sluggish, heavy. But a year and a half on, things have settled down and running is a pleasure again - if a much slower one. There hasn't been any further deterioration in my right ventricle (if anything a slight improvement from the shocked state after the cardiac arrest and multiple defibrillations), and I've been fortunate enough not to have experienced any ICD shocks yet. I realise this is still early days, and this is anecdotal/particular to my heart, but for what it's worth, it seems possible to regain some semblance of normality.
Now I'm just waiting for those stem cell treatments to come online so that we can all regenerate healthy heart tissue!