Transvenous, transmediastinal, and transthoracic ventricular pacing: a comparison after complete two-year follow-up.

Two hundred and five patients who received a total of 247 electrode systems-129 transvenous, 68 transmediastinal and 50 transthoracic-are compared after complete uniform two-year followup. The transvenous patients had low hospital morbidity (19%) and short hospital stays (75% < 8 days) but a high incidence of electrode failure by 24 months (38%). The transmediastinal and transthoracic patients had more hospital complications (35% and 34%) and longer periods of hospitalization (57% and 70% > 8 days) but fewer instances of failure by 24 months (16% and 11%). Most transvenous electrode failures were secondary to dislodgement. Transmediastinal right epicardial electrodes had the unique problem of threshold elevation and failure between six and 12 months after implantation as well as a high incidence of sudden death in this same period. Although the high incidence of endocardial elec rode instability dictates the need for an alternative approach to permanent pacing, the failure of the transmediastinal approach to significantly alter postoperative morbidity (as compared with transthoracic electrodes) and the incidence of threshold elevation remote from right ventricular implantation suggest that limitation of thoracotomy (via the transmediastinal approach) should not take precedence over left ventricular implantation. Development of electrodes which would provide more permanent low resistance fixation to right ventricular endocardium or epicardium may be necessary before the transthoracic approach can be abandoned.