How Can severe Parkinson S Disease Be Treated?

I have wolfe parkinson white syndrome (paroxysmal atrial tachycardia due to aberrant av conduction - type 2). I have been taking inderal (various strengths, etc.) since 04/1973, Long ago my episodes of tachycardia were very infrequent and of short duration; currently i have 5-10 episodes a month and the long episodes have lasted up to 16 hours. I know my condition has deteriorated but i feel that the inderal medication has become ineffective. Is there a different medication that could help me subdue these frequent episodes of tachycardia? I am averse to cardiac ablation.