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Baroreflex Sensitivity impairment

The baroreflex is a vital homeostatic mechanism that maintains blood pressure at a steady level, playing a key role in the short-term control of blood pressure.

Baroreceptors are located in major arteries and veins, and in the heart. Through their feedback mechanism, they enable the autonomic nervous system to swiftly adjust the heart rate and arterial resistance, using a rapid negative feedback loop. It minimizes fluctuations in blood pressure, keeping it close to its operational level, thus ensuring optimal delivery of oxygen to the organs.

The baroreflex sensitivity (BRS) reflects the speed with which the reflex corrects the blood pressure. It is measured routinely in various pathologies. Indeed, a high BRS means that heart rate is quickly affected by a change of pressure, and that the reflex is working well, while a reduction in BRS is a poor prognosis factor, particularly in cardiovascular diseases. It is also included in additional studies of the S7A directive on pharmacological safety studies.

Two analysis techniques are mainly used to measure the BRS: The Spectral analysis and the Sequence analysis. emka TECHNOLOGIES uses the Sequence analysis, based on the measurement of blood pressure and heart rate values for each cardiac cycle.

Related Hardware

Post-processing software

Implantable telemetry

In order to perform a sequence analysis that provides the BRS index, the Electrocardiogram (ECG) and the blood pressure (BP) must be measured. Implantable telemetry allows for continuous and stress-free measurement of these parameters in rodents and large animals.

ecgAUTO BRS module looks for ramps of several consecutive beats where Blood Pressure (usually the systolic BP) and Beat to Beat (usually RR) Intervals both increase or both decrease. The slope of the relation between BP and RR is the index of BRS.

In addition to the BRS index, the software also provides other useful information, displayed in result tables and customizable graphics, such as:

  • The correlation coefficient for each sequence
  • The blood pressure operating range
  • The set point, corresponding to the median value of all SBP/RR values, and reflecting the pressure/heart rate value that the reflex attempts to recover after a disturbance.
  • The pressure ramps sign, in order to know if BRS is increasing or decreasing.

Several steps, corresponding to experimental phases, can be defined in the protocol and are reported in the BRS module. They can be selected to be displayed on the graph on request.

ecgAUTO software is highly configurable, allowing to define:

  • X and Y axis parameters: usually, X axis is for systolic blood pressure, and Y is for RR. However, heart rate can be derived from the blood pressure signal and Y axis can be used for the pulse interval.
  • Minimum consecutive beat number: minimum number of consecutive beats that exhibit a simultaneous increase (or decrease) of BP and RR to constitute a valid series
  • Latency beat number: the variation of heart rate to a change in pressure is not immediate. This setting allows you to test different hypothesis about the delay in reaction of heart rate.
  • Minimal correlation: Once a sequence of successive beats has been found long enough and where beat to beat variation meet the minimum value requirement, a linear fit is produced. Only those sequences for which the quality of fit is higher than this minimum correlation will remain valid and be reported.

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