Hi there --
This is an easy question to answer, yet difficult. You'll see. FIrst, the difference between a couplet and a run is one beat (or more). A couple is two in a row without a break or normal beat in between. A run is technically three or more. That was the easy part.
What's more difficult is to tell the perceived difference between a PAC and PVC. Depending upon the timing, they can feel the same and both can feel quite different depending on timing and area of origin. So generally we consider that they feel the same. Usually they do, at least for practical purposes. Further, a three or four beat run of either can feel the same and both are quite common in young, healthy people. Runs of more than three or four are most often (statistically) atrial beats. In the absence of any structural heart disease neither has much diagnostic nor prognostic significance.
Bloating, gas, GI upset, etc., as well as slowing down and nearing sleep (along with a lot of other innocent factors) can cause or predispose to both isolated and paired premature beats (usually ventricular) and runs. The list of benign causes is as long as your arm.
The act of rolling over onto one's side (usually the left, sometimes the right) can often bring the stomach into close enough contact with the heart to trigger and/or make these events much more noticeable. It generally means nothing, but it can feel creepy at the least.
I hope this helps answer your concerns. Please follow up with us here as needed.
John Kenyon, EMT, CCT
Non-invasive cardiology tech, Emergency and Critical Care technician, Critical Incident Stress Mgmt. specialist