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Optimal ventricular pacing rate in fetal lambs with complete atrioventricular block
Ayustawati1, Hirohiko Shiraishi, Yutaka Kikuchi
1Department of Obstetrics and Gynecology, Jichi Medical School, Tochigi, Japan.
Objective:
This study was undertaken to determine the optimum ventricular pacing rate at which the optimal cardiac function can be attained in fetal lambs with complete atrioventricular block.
Study Design:
Complete atrioventricular block was created by cryosurgery in 12 fetal lambs, and the ventricle was paced randomly at rates of 60, 90, 120, 150, 180, 210, 240, and 270 beats/min. The aortic pressure, central venous pressure, and right ventricular cardiac output were measured before cryosurgery and during ventricular pacing.
Results:
Complete atrioventricular block was created in 9 of 12 fetal lambs. Systolic aortic pressure significantly decreased at pacing rates of 60, 90 and 240 beats/min (P <.01), and central venous pressure was increased significantly at a pacing rate of 60 beats/min (P <.01) compared with the control. Right ventricular cardiac output significantly decreased at pacing rates of 60, 90, 120, 180, 210, 240, and 270 beats/min (P <.01), although no significant difference was found at the pacing rate of 150 beats/min compared with control.
Conclusion:
Ventricular pacing at a rate of 150 beats/min gave the highest aortic pressure, the lowest central venous pressure, and the highest right ventricular cardiac output in fetal lambs with complete atrioventricular block.