In vivo study of a new radioisotope-powered cardiac pacer

A new radioisotopic pulse generator has been developed. It is 6 cm. long, 4.7 cm. high, 1.92 cm. wide, and weighs 61 Gm. (2 oz.). It is the smallest pulse generator made and has a life expectancy of over 20 years. The circuit is a conventional ventricular-inhibited (V.V.I.) type. In vitro testing has passed all Atomic Energy Commission requirements. The present study is concerned with in vivo testing of the complete pacemaker system, by means of both myocardial and endocranial electrodes, in 20 dogs with and without induced heart block. Extensive testing for electromagnetic compatability was carried out on 1 animal with induced heart block and a special, fast-rate pulse generator. Based on studies to date, the Atomic Energy Commission has issued a license for limited clinical trial which has already begun at the collaborating institutions.