If you go to the search at the top of the page and put in VT or Vtach, ventricular tachycardia you'll find a ton of info and doctors answers - look in the expert section where the Medhelp Doctors answer questions.
You can live well and function fine with 30,000 & even 50,000 pvc's - it's all a state of mine and letting them control your life or not. I had 50,000 pvc's for quite awhile and didn't know I had THAT many, heck I didn't even know it was pvc's until the dr put a name to what I felt. A few years ago, I was told by a doctor my heart was fine and I was "deconditioned" even though I was walking/running 4-5 times a week.
I sit on the pvc fence myself :P trying to reassure others that you probably won't have dangerous arrythmia's but at the same time know mine were brushed under the rug by a doctor. I had a ton even then - bigeminy & trigeminy patterns (couplets, triplets etc), but I have other things going on and that made my problem worse - in a structurally normal heart there is no problem with pvc's or even vt - so an echo would clear any question of that up for you.
PVC's in frequent continuous episodes can become a form of ventricular tachycardia (VT) and can become dangerous (V-Fib). Typically, if 3 or more PVCs occur in a row it is indicative of ventricular tachycardia, but NOT ALL VT's are dangerous.
I was told by my EP that only 1% of pvc's are considered dangerous, although I've read 1%-5%. Dr's typically treat between 6,000 - 8,000 pvc's with meds and anything above 15% - 20% of a total 24 HR they treat with surgery.
At higher continuous amounts, it can damage the heart and lead to cardiomyopathy. Although, follow up research has shown this can happen at much lower thresholds of >4000 pvc's - http://emedicine.medscape.com/article/761148-followup
I've suffered from frequent pvc's and vtach for awhile and it's something I still question - what triggers v-tach to become something dangerous? Dr's use a scale to categorize which ones they think will be dangerous; but it's debatable [the article expands on this method].
"LV function and where your PVC's originate is more important then your where you fit on the scale" - it's in the medscape article, I think page 3.
You can have many different arrythmia's originating from different areas, but for them to be dangerous they have to have the morphology that stands out (your cardio or EP will know). I have malignant polymorphic VT - and my pvc's were originating from one place - the RVOT; so I'm not sure on the multifocal part being more serious - I'm sure someone else will know.
Hopefully that answers some of your questions and I've explained correctly the way my doctors and research I've read.
Here's an example of one of the dr's posts: a thread about VT and an answer from one of the CC dr's
http://www.medhelp.org/posts/Heart-Disease/Idiopathic-Ventricular-Tachycardia-Ablation/show/1327314
"If your heart function is normal, there really isn't any danger from having the VT runs. The only thing worth assessing is the number of PVC's in a 24 hour period. If it's greater than 15% of all the heart beats than there is a small risk of developing a PVC induced cardiomyopathy."
"We typically don't ablate PVC's unless they are symptomatic or if they are very numerous (great than 15%). The VT isn't ablated unless it's sustained or very symptomatic with episodes of passing out or nearly passing out. Sometimes it's difficult to induce the Vt in the lab but becasue the PVCs typically look like the VT we sometimes go after them"
"This is very unlikley to progress to VF or SCD. If the PVC's/NSVT is really bothering you then you should have it done to relieve your symptoms, not to prevent SCD or VF"