Peace, A (2021) Carotid Artery Reactivity: A potential novel, non-invasive test of endothelial function to predict post-cardiac surgery outcomes, cardiovascular events and survival. Doctoral thesis, Liverpool John Moores University.

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Abstract

In healthy individuals, coronary arteries dilate in response to sympathetic nervous system (SNS) stimulation, whereas in patients with increased cardiovascular disease (CVD) risk this produces a truncated dilation. Conversely, in patients with significant disease, these arteries constrict. Previous research has demonstrated a correlation between carotid and coronary artery function. In addition, a non-invasive measure of carotid artery response (CAR%) has been shown to predict adverse events in patients with peripheral arterial disease. In this thesis, these findings were extended to investigate the effect of blood pressure (BP) increase caused by the Cold Pressor Test (CPT) as a driver of CAR%. CAR% was then also investigated as a means to predict risk in patients with central arterial disease undergoing Coronary Artery Bypass Graft (CABG) surgery. Methods. The (CPT), a sympathetic nervous system stimulus (SNS) using cold water, was used to investigate carotid artery response to an SNS stimulus in two studies. The first investigated CPT alongside continuous blood pressure measurement. The second examined CAR% in patients with CVD undergoing CABG, with a 30-day follow-up period. Results. Study one: The timing of peak CAR% was significantly later than peak MAP. There was no significant difference in CAR% when participants are separated by MAP response. There was no significant difference in MAP in “dilation” vs “constriction” groups. Study two: There was a weak inverse correlation between CAR% and EuroSCORE II. Neither EuroSCORE II nor CAR% alone predicted risk. There may be a trend towards a marginal improvement in predictive capacity when CAR% is combined with EuroSCORE II. Although this did not predict risk. Discussion. Study one: This study provided evidence that CAR% is not significantly driven by increase in MAP throughout the CPT. In addition, it further supports the validity of CAR% as a surrogate of endothelial function. Study two: Alone, neither EuroSCORE II nor CAR% were predictors of risk. Combined, the two measures demonstrated marginal increased predictive capacity. This study suggests that CAR% may improve the predictive capacity of established prediction tools. This cannot be tested conclusively due to the low number of adverse events. Future Work: This thesis highlighted future areas for research including regulation of CAR%, areas for further technological and practical development and areas of potential clinical integration, namely in the identification and monitoring of endothelial function alongside interventions to improve function and reduce perioperative risk.

Item Type:	Thesis (Doctoral)
Uncontrolled Keywords:	Cardiovascular Science
Subjects:	R Medicine > R Medicine (General) R Medicine > RS Pharmacy and materia medica R Medicine > RT Nursing
Divisions:	Nursing & Allied Health
Date Deposited:	14 Jun 2021 09:02
Last Modified:	30 Aug 2022 15:55
Supervisors:	Lotto, R, Thijssen, D and Jones, I
URI:	https://researchonline.ljmu.ac.uk/id/eprint/15115

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