A study of 1774 patients who had experienced an acute myocardial infarction showed that sexual activity was a likely contributor in fewer than 1% of cases. In fact, regular physical exertion, such as that associated with sexual activity, was associated with a decreased risk of cardiac events in patients!Now that's helpful!
Recall that defibrillators are designed to detect rapid, potentially life-threatening arrhythmias. Most of the time, sexual activity does not lead to heart rates at a level that ICD's would consider elevated during intercourse. (This, of course is patient-specific). While your doctor can tell you the rate cut-off at which your ICD might possibly fire, watching your heart rate rise with a monitor during those moments might be a bit of a, shall we say, turn-off..
My rule of thumb: if you have a defibrillator (ICD) and can walk up two flights of stairs without getting a shock, you'll probably be okay having sex. (Be sure to check with your doctor, these are just my ballpark recommendations. Also, this rule of thumb may not apply to those involved in extramarital affairs. As we've heard, heart rates accelerate much more when a naughty, clandestine element is involved). But please be careful: if one flight of stairs makes you too exhausted or short of breath, you'd better check with your doctor first.
Now, what about the partner? What happens if the defibrillator fires and you're at the peak of passion?
First, you might give out a "yelp." That's because the shock often causes the diaphragm and vocal cords to contract. It happens very suddenly, and your partner might not mind this part, but the kids down the hall... well, that's another thing.
Second, ICD shocks won't hurt you partner. On the contrary, it might be... well, let's put it this way... interesting!
Third, if repetetive shocks occur as a result of your activities, well, sorry my friend, you've had enough and probably should head to the ER. Realize this is an infrequent event, but any time there are back-to-back shocks it means one of several things: (1) you're having a lot of rhythm problems, (2) your device might need to be reprogrammed to avoid shocks at this level of exertion, or (3) (least likely) you might have a faulty lead that needs repair.
Common sense should dictate each person's individual approach, but for the most part, ICD's needn't hold you back!
Reference: Lauren D. Vazquez, PhD; Samuel F. Sears, PhD; Julie B. Shea, MS, RNCS, FHRS; Paul M. Vazquez, DO. "Sexual Health for Patients With an Implantable Cardioverter Defibrillator." Circulation. 2010;122: e465-e467.