AFRICA Cardiovascular Journal of Africa • SAHS Biennial Congress 2024 12 Submission ID: 1630 Introduction In various cardiovascular diseases the reduction of heart rate (HR) with β-blockers or other HR reducing agents is mandatory. However, decreases in HR are associated with increases in central aortic pulse pressure (PPc), which is concerning as increased central pressure pulsatility produces organ damage. However, whether the inverse relationship between HR and PPc is modified by either peripheral arterial blood pressure (BP) or aortic stiffness is unclear. Our aim was to determine, in an intervention study, the impact of arterial BP and aortic stiffness on the relationship between HR and PPc. Methods Patients with artificial cardiac pacemakers (n=16) were recruited from Life Flora Hospital in Roodepoort, Johannesburg between 2023 and 2024. Participants were paced in 10 bpm intervals in a range of 50-90 bpm. At each interval, central aortic BP was recorded using a SphygmoCor device and echocardiography was performed to assess aortic outflow tract diameter and flow velocity. Aortic characteristic impedance (aortic stiffness, Zc) was calculated from central aortic pressure and aortic flow using a standard formula. An average of 3 sets of measurements per participant (range of 2-4) was obtained, resulting in a total sample size of 48. To assess the impact of arterial BP, the study group was divided into those with systolic/diastolic BP below (n=20, low BP) versus above (n=28, high BP) 130/85mm Hg. To assess the impact of Zc, the study group was divided according to the median value of Zc (110dynes.s/cm5) (n=20 below [low Zc] and n=28 above [high Zc]). Multiple linear regression models adjusting for age, sex, body mass index and either peripheral arterial PP or mean arterial pressure (MAP) were used to determine the relationship between PPc and HR and the effects of peripheral arterial BP and aortic Zc on this relationship. Results Central aortic PP was inversely related to HR (r=-0.287, p<0.05), whereas peripheral arterial PP was not (r=-0.058, p=0.70). The PPc – HR relationship was independent of confounders including peripheral PP (partial r=-0.474, p<0.005) and MAP (partial r=-0.409, p<0.01). In patients with high BP, there was a strong PPc – HR relationship (partial r=-0.729, p<0.0005); whereas in patients with low BP, the relationship was weaker (partial r=-0.508, p=0.05). In patients with high Zc there was a strong PPc – HR relationship (partial r=-0.672, p<0.0005); whereas in patients with low Zc, the relationship was not significant (partial r=-0.293, p=0.27). Conclusion In an intervention study, we show that central aortic PP is inversely related to HR and that this relationship is modified by both peripheral arterial BP and aortic stiffness. These data suggest that in patients requiring HR reducing pharmacological agents, peripheral BP should be maintained at below 130/85 mm Hg in order to prevent organ damage associated with increased pulsatile loads. Furthermore, in conjunction with HR reducing agents, the use of pharmacological agents that reduce aortic stiffness, such as aldosterone receptor antagonists, is advisable. Name: Presenting Author Information Article Category Abstract Title University of Witwatersrand 2105607@students.wits.ac.za English Abstract Students - Currently enrolled postgraduate students Effects of Arterial Blood Pressure and Aortic Stiffness on the Inverse Relationship between Central Pulse Pressure and Heart Rate Author Affiliation: Email: Zak Coetzee Science Theme Basic Authors Name & Surname Title Expertise Affiliation Email Country Zak Coetzee Mr, Student University of Witwatersrand 2105607@students.wits.ac.za South Africa Vernice Peterson Dr. Cardiovascular Physiology University of Witwatersrand Vernice.Peterson@wits.ac.za South Africa Danelle Els Miss. Cardiovascular Physiology University of Witwatersrand nellyels14@gmail.com South Africa Ferande Peters Prof. Cardiologist University of Witwatersrand ferande.peters@gmail.com South Africa Angela Woodiwiss Prof. Cardiovascular Physiology University of Witwatersrand angela.woodiwiss@wits.ac.za South Africa ORAL PRESENTATION
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