AN APPROACH IN THE ASSESSMENT OF PACING HEMODYNAMICS - A COMPARISON OF VVI AND DDD

Previous methods for assessment of pacemaker hemodynamics have been li mited to a rigid hospital environment. An alternative is the ambulator y ventricular function monitor (C-VEST(R)) chat, with a single injecti on of technetium-99m, permits the continuous measurement of relative e jection fraction (EF) and cardiac output (CO) during the activities of daily living. A study of reproducibility and a comparison of dual cha mber (DDD) and fixed rate ventricular (VVI) pacing are presented. Repr oducibility was assessed in six patients (4 males; mean age 58, range 27-78 years) with a mean EF of 48.5% (range 34%-62%) and DDD pacemaker s, implanted for conduction abnormalities. In addition, 11 patients (7 males; mean age 55.5, range 34-75 years) with a mean EF of 48.5% (ran ge 34%-65%), chronic complete heart block, and DDD pacemakers were use d for the comparative study. After an initial multigated scan, the mon itor was positioned over the left ventricle and kept in place with the plastic C-VEST The patients undergoing the reproducibility study perf ormed three shuttle walking tests with 20 minutes of rest in between. The patients in the comparative study were randomized to either VVI or DDD mode and performed one shuttle walking test in each pacing mode. The results confirmed that the C-VEST produces reproducible results wi th no significant difference in peak CO between the three shuttle walk s. In addition, it confirmed previous hemodynamic studies showing that DDD pacing was superior to WI pacing bath at rest (P < 0.004) and at exercise (P < 0.002). These findings show the C-VEST to be an extremel y useful tool for the hemodynamic assessment of pacemaker patients.