Altered heart rate control in response to postural change in patients with Machado-Joseph disease (SCA3).

To assess heart rate (HR) regulation in Machado-Joseph disease (MJD), we evaluated HR variability at rest and the initial HR response to standing suddenly in 13 MJD patients and 26 normal control subjects. A head-up tilt (HUT) test involving the monitoring of blood pressure, HR, and cerebral oxy/deoxyhemoglobin concentration was also performed in each participant. There was no significant difference in HR variability at rest between the two groups, but the transient HR rise just after standing suddenly in the MJD group was significantly less than that in the control group (p < 0.01). The HUT test, where each participant was gradually tilted upward, induced a significantly greater HR increase in the MJD group compared with the controls (p < 0.01), while there were no significant differences in the blood pressure and cerebral oxygenation changes between the two groups. In our MJD study, the transient HR rise just after standing suddenly was diminished, and HR markedly increased during sustained orthostatic stress.