Impairment of the autonomic functions in varying frequency and extent is found in Idiopathic Parkinson´s Disease (IPD) and multiple system atrophy (MSA) [1,2]. Symptomatic orthostatic hypotension is common and reflects the inability of the autonomic system to mediate a sufficient cardiovascular reaction [3]. Moreover it has been speculated whether cerebral autoregulation mechanisms are also affected and unables these patients to compensate for drops in systemic blood pressure [4,5].
Aim of our study is the assessment of cerebral autoregulation dynamics and autonomic nervous activity in IPD and MSA during orthostatic stress. Autoregulation testing involves introduction of variations in arterial blood pressure (ABP) by tilting and simultaneous measurements of cerebral blood flow velocity (CBFV) responses using transcranial Doppler (TCD). Aaslid [6] and Newell [7] demonstrated that relative changes in cerebral blood flow velocity reflect changes in CBF.
This paper presents our methodological approach and gives some preliminary results.
In two groups of patients (IPD, MSA) and age-matched controls tilt-table testing was performed.
After 15 minutes of supine resting in a quiet environment the patients were brought into a 70 ° head-up positon with a tilt-table for 15 minutes and were returned to rest for further 15 mins. ECG, a Finapress®- device to measure noninvasively blood pressure and a respiratory expansion belt were attached to the patients. The blood flow velocities in both middle cerebral arteries were recorded using a inflexibled probe holder with EME-Pioneer® transcranial Doppler equipment.
The data were AD-converted and continuously sampled on a PC with specially customized software (spike2®). Offline R-peaks in the ECG were recognized, a histogram of their consecutive distance produced and converted into the beat-to-beat heart rate. Blood pressure and Doppler signals were decomposed into their beat-to beat systolic, mean and diastolic values.
Fast Fourier Analysis of each variability signal of heart rate, blood pressure and CBFV were performed to determine sympathetic and parasympathetic mediated modulations in their spectral power (i.e. HF-peak, HF to LF-power ratio). Cross correlations of the different variability signals were calculated to assess occurence and magnitude of similarities and differences in periodical rhythmical changes.