Arrythmias and synthroid

Hi:

I have had svt's and pvc's for the past 2 years and recently had to have the right lobe of my thyroid removed.  I am now told that I need to go on synthroid.  This makes me nervous because I'm told that synthroid can cause palpatations.  

1) Does this always happen or only if you take too much synthroid?
2) How soon after starting the synthroid will I have palpatations if I'm going to get them (how long does it take to build up levels in your blood)?
3) Is it possible to avoid the problem if I work up to the required dose very slowly and if so, do you have any idea, for example, how long I should take .025mg before I move up to .05mg?
4) Could an underactive thyroid cause pvc's or svt's?

I appreciate your help, this is making me very nervous.

[CCF CARDIO MD JMF]

In response to your questions:

1) Does this always happen or only if you take too much synthroid? Generally, if your thyroid tests are followed closely and you are on an appropriate replacement dose, then this not a concern.
     2) How soon after starting the synthroid will I have palpatations if I'm going to get them (how long does it take to
     build up levels in your blood)?
You should not expect to have palpitations.

     3) Is it possible to avoid the problem if I work up to the required dose very slowly and if so, do you have any
     idea, for example, how long I should take .025mg before I move up to .05mg?
Generally endocrinologist will start at smaller doses and follow your thyroid test to determine an appropriate does.
     4) Could an underactive thyroid cause pvc's or svt's?

Generally not.