Cardiovascular Journal of Africa • SAHS Biennial Congress 2024 19 AFRICA Submission ID: 1646 Introduction The pulsatile blood pressure (BP) components, systolic BP and pulse pressure (PP), have a greater impact on cardiovascular mortality and morbidity than the steady components, diastolic BP and mean arterial pressure (MAP). To prevent cardiovascular events, PP should be reduced. However, the causes of increased PP are currently unclear, as most previous studies have been association and not intervention studies. Conducting intervention studies in humans, is ethically and practically challenging. Furthermore, invasive measurements in animal studies are often terminal, making it difficult to obtain repeated measurements over time. Non-invasive methods, such as PulsePen have been developed to address this issue. The aim of this study was to determine the accuracy of PulsePen®, with a specific focus on systolic and diastolic blood pressure, as well as the first systolic inflection point. Methods In 58 rats arterial BP was measured invasively (fluid filled catheter coupled to a high-resolution pressure transducer and PowerLab software) and non-invasively (applanation tonometry and PulsePen® software). The rats were placed under anaesthesia induced with 5% - 8% isoflurane in oxygen and maintained with 2% isoflurane. First the fluid-filled catheter was inserted into one carotid artery and via the pressure transducer a clear arterial pressure trace, indicating the first (inflection point, Pi) and second systolic peak (SBP), was continuously recorded. Secondly, the PulsePen® tonometers were positioned one on the skin perpendicular to the other carotid artery and one on the femoral artery. Prior to each pressure recording, calibration of the PulsePen® was performed using invasive PowerLab pressure values. Once a series of overlapping pressure traces had been obtained, the recorded data was automatically saved and analysed by the PulsePenLab® software. A wide range of pressure values (approximately 10 per rat) was obtained by the means of acute administration of vasoconstrictor agents. The pressures (SBP, Pi and PP) obtained non-invasively (PulsePen®) were compared to those obtained invasively (PowerLab) using paired t-test, Person’s correlations and Bland-Altman plots. Results Systolic BP (r2=0.92, p<0.0001), PP (r2=0.78, p<0.0001), Pi (r2=0.83, p<0.0001), and diastolic BP (r2=0.95, p<0.0001), as measured by the two devices were well correlated. However, when comparing non-invasive to invasive measurements, systolic BP was 18.71±11.6 mm Hg lower (p<0.0001), PP was 17.98±8.93 mm Hg lower (p<0.0001), Pi was 4.54±13.37 mm Hg higher (p<0.0001), and diastolic BP was marginally higher 0.73±6.40 mm Hg (p=0.0045). The Bland-Altman plots revealed consistent underestimation of systolic BP and PP, and overestimation of Pi and diastolic BP over a wide range of BP values. Conclusion The non-invasive device overestimated Pi and underestimated systolic BP and PP. This could be due to a delay in the sampling rate of the PulsePen® given the high heart rate of the rats. Name: Presenting Author Information Article Category Abstract Title University of the Witwatersrand, Johannesburg South Africa 1034376@students.wits.ac.za English Abstract Students - Currently enrolled postgraduate students Exploring Central Haemodynamic Pressure Assessment in Spontaneously Hypertensive Rats: A Comparison of Non-Invasive versus Invasive Techniques. Author Affiliation: Email: Shayur Arijune, Angela J Woodiwiss, Nonhlanhla Mthembu, Hamza Bello, Glenda Norman, Suraj M Yusuf, Vernice R Peterson Science Theme Basic Author Name & Surname Title Expertise Affiliation Email Country Shayur Arijune Mr Physiology University of Witwatersrand 1034376@students.wits.ac.za South Africa ORAL PRESENTATION
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