# Characterization of di‐gital, tri‐gital, and tetra‐gital temporal movement of systolic blood pressure on the arterial pulse waveform of rats at different vascular stiffness

## TL;DR

This study found that systolic blood pressure on rat arterial pulse waveforms shifts in discrete steps rather than gradually when vascular stiffness changes.

## Contribution

The study introduces 'n-gital' systolic BP fluctuations as a new parameter for analyzing arterial pulse waveforms in rats.

## Key findings

- Systolic blood pressure on rat arterial pulse waveforms oscillates between discrete temporal positions during changes in vascular stiffness.
- N-gital systolic BP fluctuations remain approximately constant despite large changes in systolic pressure and cardiovascular stiffness.
- The temporal position of diastolic BP shifts digitally between two positions ~8–12 ms apart during changes in systolic pressure.

## Abstract

An arterial stiffness is an indicator of many cardiovascular diseases. The temporal position of systolic blood pressure (BP) on aorta pulse waveform is assumed to gradually shift on the waveform in response to increasing/decreasing vascular stiffness. The animal model of rats and invasive methods that cannot be used in humans was applied to test the assumption on arterial pulse waveform (APW) of anesthetized rat. The aim of this study was to characterize the temporal movement of diastolic and systolic pressures on the APW of anesthetized rats during increasing/decreasing vascular stiffness.

The right jugular vein of anesthetized normotensive and spontaneously hypertensive rats was cannulated for intravascular administration of vascularly active compounds to alter systolic pressure and vascular stiffness. The left carotid artery was cannulated to detect APW, from which numerous APW parameters were evaluated.

During increases/decreases in systolic BP or stiffness, the temporal position of diastolic BP of individual heartbeats di‐gitally shifted on the APW between two temporal positions ~8–12 ms apart, and the temporal position of systolic BP on the APW did not gradually shift during increases/decreases in vascular stiffness, as expected, but oscillated between constant di‐gital, tri‐gital, or tetra‐gital temporal positions.

Introducing new APW parameters, n‐gital systolic BP fluctuations on rat APW were found. Fluctuations in n‐gital were approximately constant during large changes in systolic pressure despite significant changes in augmentation index and cardiovascular stiffness, which may challenge the assumption of a gradual temporal location of systolic pressure on rat APW under these conditions.

The example of the time dependent fluctuation of systolic pressure on rat arterial pulse waveform in ms. The four levels of the systolic pressure fluctuation show di‐gital, tri‐gital and tetra‐gital fluctuation. The red dots represent particular heartbeats.