Greatbatch worked on the critical problems standing in the way of permanent cardiac pacing: battery life, proper insulation, and rising stimulation thresholds requiring higher and higher current to control the heart over time. (In the pro cess, Greatbatch invented the first long-lasting lithium battery, still in use today.) By the late summer of 1959, Greatbatch had used up his personal savings of $2,000 to handcraft fifty implantable pacemakers.
