Abstract 10602: Impaired Autoregulation Of Cerebral Blood Flow In Patients With Low-normal Cardiac Output
Background: Autoregulatory mechanisms exist to maintain cerebral blood flow (CBF) homeostasis and cerebral function. However, it is unclear whether CBF autoregulation is maintained in patients with subtle cardiac dysfunction. The aim of this study was to investigate the correlation between cardiac index and CBF.
Methods and Results: Twenty-two patients who underwent pacemaker (PM) implantation for ≥1 year and had a spontaneous heart rate of <60 bpm at rest were enrolled. CBF and cardiac index (cardiac output/body surface area, CI) were evaluated twice at a PM rate of 60 bpm and at a PM rate of 70 bpm, before and after the PM rate was switched (13 patients increased and 9 decreased) with a 3-month interval. Whole CBF and CI were measured using single-photon emission computed tomography and transpulmonary thermodilution, respectively. Although CI changed in parallel with the PM rate in all patients, the CBF response was dependent on baseline CI. According to the tertile of baseline CI, in the patients with low to middle CI (≤3.0 L/min/m2), CBF increased significantly with an increase in CI, whereas in the patients with high CI (>3.0 L/min/m2), CBF showed no change. The percent increase in CBF with a CI increase of 1 L/min/m2 was: baseline CI <2.5 L/min/m2, 150.6%±34.0%; baseline 2.5 L/min/m2 ≤ CI ≤3.0 L/min/m2, 59.6%±20.3%; and baseline CI >3.0 L/min/m2, 1.8%±13.4%. The autoregulation curve for the association between CI and CBF is shown below. Blood pressure or plasma BNP did not change significantly after PM rate change.
Conclusions: These results suggest that CBF autoregulation is preserved in patients with high CI, whereas it is impaired in those with low normal or low CI after PM implantation.
- © 2012 by American Heart Association, Inc.