Central blood pressure and variability evaluation (cave-on): investigating peripheral and central blood pressure and blood pressure variability and their effects on the size and growth of abdominal aortic aneurysms
File(s)
Author(s)
Charles, Edmund
Type
Thesis
Abstract
Abdominal Aortic Aneurysms (AAA) progressively dilate with increasing risk of rupture. Hypertension is linked with an increased risk of rupture; while the evidence regarding its association with growth is conflicting, both blood pressure (BP) and BP variability (BPV) are closely linked with cardiovascular health. Pilot work showed a significant association between increased central diastolic BPV and faster AAA growth. We aimed to investigate the relationship between peripheral and central BP, BPV and AAA growth.
A systematic review was conducted to review the evidence for central BP, aortic stiffness and thoracic and abdominal aortic aneurysm growth. This found heterogeneity and inconsistency in reporting but central BP appeared to have the most consistent relationship with growth.
We recruited 137 patients with an AAA under surveillance to have their peripheral and central BP and AAA measured every four months for up to two years. We separately added patients from the AARDVARK trial who had central BP measured to analyse data for 345 patients. Our primary outcome was AAA growth, secondary outcome was time to reaching threshold for surgery or referral for repair and exploratory analyses investigated other causes of AAA growth.
We found peripheral and central BP and BPV were not related to AAA growth, nor did they affect the time it took to reach threshold for repair. Smoking was associated with faster growth and ischaemic heart disease (IHD), metformin and diuretics were associated with slower growth, independently of smoking and AAA size.
We provide robust evidence that there is no direct association between BP, BPV and AAA growth. Reduced growth in the presence of IHD may be attributable to better prescription of cardiovascular medications; metformin may also be effective. This strengthens the argument for the role best medical therapy may have in limiting AAA growth and supports further evaluation of its effectiveness.
A systematic review was conducted to review the evidence for central BP, aortic stiffness and thoracic and abdominal aortic aneurysm growth. This found heterogeneity and inconsistency in reporting but central BP appeared to have the most consistent relationship with growth.
We recruited 137 patients with an AAA under surveillance to have their peripheral and central BP and AAA measured every four months for up to two years. We separately added patients from the AARDVARK trial who had central BP measured to analyse data for 345 patients. Our primary outcome was AAA growth, secondary outcome was time to reaching threshold for surgery or referral for repair and exploratory analyses investigated other causes of AAA growth.
We found peripheral and central BP and BPV were not related to AAA growth, nor did they affect the time it took to reach threshold for repair. Smoking was associated with faster growth and ischaemic heart disease (IHD), metformin and diuretics were associated with slower growth, independently of smoking and AAA size.
We provide robust evidence that there is no direct association between BP, BPV and AAA growth. Reduced growth in the presence of IHD may be attributable to better prescription of cardiovascular medications; metformin may also be effective. This strengthens the argument for the role best medical therapy may have in limiting AAA growth and supports further evaluation of its effectiveness.
Version
Open Access
Date Issued
2025-02-01
Date Awarded
01/05/2025
License URL
Advisor
Poulter, Neil
Bicknell, Colin
Sponsor
Coronary Flow Trust
Publisher Department
Department of Medicine
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)