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Hemodynamic stability during biventricular pacing after cardiopulmonary bypass.

OBJECTIVE
To assess the stability of cardiac output, mean arterial pressure, and systemic vascular resistance during biventricular pacing (BiVP) optimization.


DESIGN
Substudy analysis of data collected as part of a randomized controlled study examining the effects of optimized temporary BiVP after cardiopulmonary bypass (CPB).


SETTING
A single-center study at a university-affiliated tertiary care hospital.


PARTICIPANTS
Cardiac surgery patients at risk of left ventricular failure after CPB.


INTERVENTIONS
BiVP was optimized immediately after CPB. Atrioventricular delay (7 unique settings) was optimized first, followed by the left ventricular pacing site (3 unique settings) and then the interventricular delay (9 unique settings). Each setting was tested twice for 10 seconds each time. Vasoactive medication and fluid infusion rates were held constant.


MEASUREMENTS AND MAIN RESULTS
Aortic flow velocity and radial artery pressure were digitized, recorded, and averaged over single respiratory cycles. Least squares and linear regression/Wilcoxon analyses were applied to the first 7 patients studied. Subsequently, curvilinear analysis was applied to 15 patients. Changes in mean arterial pressure and systemic vascular resistance were statistically insignificant or too small to be meaningful by least squares analysis. During interventricular synchrony optimization, cardiac output and mean arterial pressure decreased (mean changes -5.7% and -2.5%, respectively; with standard errors 2.3% and 1.5%, respectively), whereas SVR increased (mean change 3.1% with standard error 3.4%). Only the change in cardiac output was statistically significant (p = 0.043). Curvilinear fits to data for 15 patients demonstrated progressive hemodynamic stability over the total testing period.


CONCLUSION
BiVP optimization may be done safely in patients after CPB. With continuous monitoring of mean arterial pressure and cardiac output, the procedure results in no harmful hemodynamic perturbation.