I've seen pacemakers made for children. I would think if a pacer and leads can fit into a child, they could certainly find a fit for you. Is there some other information we're missing?
What has your doctor advised. A heart pumping only 20% of capacity with each heartbeat will not be operated on unless it is a life threatening event. About 6 years ago, I had an EF below 29%, and there was not a surgical option. The risk is very high, and the success rate is not very good as the heart almost never returns to normal functioning.
It seems a pacemaker lead can be inserted into a vein...there must be an application...what does your doctor say?