Automation of analysis of cardiovascular autonomic function from chronic measurements of arterial pressure in conscious rats

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Abstract
At present, there is no single software package that provides a comprehensive power spectral analysis of pulse interval (PI) and arterial blood pressure (BP), spontaneous cardiac baroreceptor reflex gain (sBRG) and respiratory rate. Furthermore, scientific validation of the software that is currently commercially available and employed has not been published. We introduce ‘Hey‐Presto’ software, which fully evaluates cardiovascular autonomic function from the BP signal obtained from rats. The program performs power spectral analysis of HR and BP variability, respiratory rate and, based on a time‐series method, spontaneous cardiac baroreceptor (sBRG). We have validated Hey‐Presto with conventional pharmacological agents to block cardiac vagal and cardiac sympathetic transmission in conscious rats fitted with a radio‐telemetery BP transducer. Following administration of atropine (1 mg kg−1, i.v.), high‐frequency (HF) power of the PI decreased (P < 0.01) and was associated with the expected increase in HR. Subsequent cardiac sympathetic blockade (atenolol, 1 mg kg−1, i.v.) reduced the low frequency (LF) to HF ratio (LF:HF) of the PI (P < 0.01), which was consistent with the observed reduction in HR. We also found that alterations in sBRG after blockade of cardiac autonomic transmission were highly comparable to values computed manually using vasoactive drugs administered intravenously. The software also detected circadian rhythms in sBRG, HF component of the PI, LF:HF of the PI and LF component of the BP as well as BP and HR during continuous 24 h recording. By demonstrating its application to humans, we found appropriate changes in the power of PI and the LF power of the BP during postural changes. These results demonstrate that Hey‐Presto allows a fully automated, reliable, fast and comprehensive evaluation of cardiovascular autonomic function based on chronic measurements of BP in rats. Moreover, we have confirmed its versatility by demonstrating its application to man.

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