Heart rate and heart rate variability changes in the intracarotid sodium amobarbital test

Purpose: Changes in heart rate and heart rate variability have been found in prior studies performed during the intracarotid sodium amobarbital (ISA) test. However, these results. are not entirely consistent with current models of differential cerebral involvement in the modulation of the heart. This study was designed to re-investigate this topic with a larger N than has heretofore been used. Methods:. The electrocardiogram was recorded during left and right ISAs in 73 subjects. Raw heart rate and heart rate variability were calculated. Results: Raw heart rate increased during inactivation of either hemisphere, but more so for the right hemisphere. Heart rate variability changes consistent with decreasing parasympathetic tone also were found to occur during either ISA, but to a significant degree, only during right ISA. Conclusions: The right hemisphere appears to have a greater role in cerebral regulation of cardiac function, perhaps by virtue of the modification of parasympathetic effects.