Unfortunately, you probably won't get any doctors responding in this portion of the forum, but you will, however, hear from people with decades of PVC/PAC and medication experience, along with some nurses versed in treatment from both the professional and patient side of the equation.
But here's an article you might find of interest:
http://www.medhelp.org/forums/cardio/archive/5212.html
The gist of it is, if you consider a PVC or PAC a "cardiac event", then possibly. But if you're wondering if taking the Zoloft is going to precipitate a life-threatening episode of arrhythmia, it appears the answer is no. But certainly, read the article for yourself. That one WAS answered by a doctor.
In the meantime, do what you can to relieve any stressors you have at the moment.