Well I've just been to St Caths Cardio Rehab fro my Exercise Tolerance Test prior to starting a second round of rehab following having my ICD fitted on 19th August.
For anyone who isn't familiar with an ETT, they wire you up to an ECG and a BP monitor then put you on a treadmill, slowly increasing the speed and incline until they reach a point where you heart is pumping at what they regard as 75% of your capacity.
At the end of it the nurse said "that was good, it took us nearly 13 minutes to get you up to the point where your heart was going at 75%, when we tested you when you initially came for the first test in March it only took 7 minutes, so you've definitely made good progress, the downside is that we're now going to have to devise a fiendishly hard program for you next week!"