[Measurement of the myocardial stimulation threshold in chronic and acute patients with pacemaker implanted (author's...

Eighty-two patients, with electrodes implanted for varying periods of time, have been divided into three groups: acute (at implantation); intermediate (3 to 36 months) and chronic (37 to 124 months). In these groups, respectively 28, 26 and 28 myocardial stimulation threshold measurements have been performed. Measurements have been performed with MEEMR (Myocardial Excitation Energy Meter), an instrument deviced and built by the Institute of Elaboration of Information, CNR and University of Pisa. Microjoule has been chosen as unit of measure. More commonly used units of measure, such as threshold current in milliamp, have been calculated from values in microjoules. Mean values was 0.6 muJ in the first group, 6.9 muJ in the second one and 8.3 in the third one. Student test has been performed on such measurements, divided into groups, with the following results: p less than 0.01 between 1st and 2nd group, non significant difference between 2nd and 3rd group, p less than 0.01 between 1st and 3rd group. Such results suggest a trend toward myocardial threshold stabilization over a long period of time, as had already been hypothized by others Authors. Further useful information may be drawn from these data if they are evaluated in relation to a life-time pacemaker, as is nowadays desirable in view of recent progress in circuit technology and energy sources.