School of Medicine and Health Sciences Poster Presentations

Title

Long Term Changes in Flow-Mediated Dilation Among Postoperative Abdominal Aortic Aneurysm Patients

Document Type

Poster

Abstract Category

Cardiology/Cardiovascular Research

Keywords

Vascular surgery, AAA, Clinical Research

Publication Date

Spring 5-1-2019

Abstract

Ruptured abdominal aortic aneurysms (AAA) cause around 175,000 deaths globally per year. Several studies have explored flow-mediated dilation (FMD) of arteries as a biomarker for endothelial dysfunction, a component of aneurysm pathophysiology. A previous study from this group (OxAAA) found that decreased FMD of the right brachial artery was correlated with AAA progression; after AAA surgical repair, FMD among participants improved. The purpose of this study was to evaluate the long-term changes in endothelial function of a subset of previous participants and to determine if improvements persisted. The study utilized the OxAAA database of participants who received any form of AAA repair at The John Radcliffe Hospital in Oxford, UK since 2013. Participants who underwent preoperative and postoperative FMD evaluation were included in the study (N=43). Participants were recalled to the hospital for blood sample collection and FMD measurement using high-frequency ultrasound. Brachial arterial diameter was measured at baseline, during 4 minutes of occlusion, and immediately after release of occlusion. The data were analyzed using the validated “Brachial Analyzer,” to determine FMD. The Wilcoxon Sign Rank Test was used to compare patients’ FMD values pre-surgically to 1-4 year follow up, while ANOVA was used to analyze changes in pre-surgical, post-surgical, 1 year, and 2-4 year follow up FMD values. Demographic information and FMD protocol have previously been published; the subgroup was 97% male and 100% white, consistent with UK AAA epidemiology. The average number of days from surgery to follow up was 996.7. Analysis showed a statistically significant increase in FMD among all 43 patients between 1-4 years after AAA repair (p=0.0061), as well as a statistically significant increase in FMD at each point of follow-up after surgery (p=0.0079) for the 13 participants for whom all data points were available. This study demonstrates improved FMD years after AAA repair among patients, and supports the hypothesis that AAAs are systemic diseases. The exact mechanism is unknown at this time. Current vascular research indicates the aortic thrombus is a possible source of systemic inflammation; another UK study found that even sub-surgical AAAs increase the risk of MI or stroke among patients. FMD could therefore potentially be used as a cost-effective and non-invasive biomarker in determinations of surgical interventions. Though the study power is limited, the data provides initial evidence for long-term improvement in endothelial function after AAA surgery.

Open Access

1

Comments

Presented at Research Days 2019.

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Long Term Changes in Flow-Mediated Dilation Among Postoperative Abdominal Aortic Aneurysm Patients

Ruptured abdominal aortic aneurysms (AAA) cause around 175,000 deaths globally per year. Several studies have explored flow-mediated dilation (FMD) of arteries as a biomarker for endothelial dysfunction, a component of aneurysm pathophysiology. A previous study from this group (OxAAA) found that decreased FMD of the right brachial artery was correlated with AAA progression; after AAA surgical repair, FMD among participants improved. The purpose of this study was to evaluate the long-term changes in endothelial function of a subset of previous participants and to determine if improvements persisted. The study utilized the OxAAA database of participants who received any form of AAA repair at The John Radcliffe Hospital in Oxford, UK since 2013. Participants who underwent preoperative and postoperative FMD evaluation were included in the study (N=43). Participants were recalled to the hospital for blood sample collection and FMD measurement using high-frequency ultrasound. Brachial arterial diameter was measured at baseline, during 4 minutes of occlusion, and immediately after release of occlusion. The data were analyzed using the validated “Brachial Analyzer,” to determine FMD. The Wilcoxon Sign Rank Test was used to compare patients’ FMD values pre-surgically to 1-4 year follow up, while ANOVA was used to analyze changes in pre-surgical, post-surgical, 1 year, and 2-4 year follow up FMD values. Demographic information and FMD protocol have previously been published; the subgroup was 97% male and 100% white, consistent with UK AAA epidemiology. The average number of days from surgery to follow up was 996.7. Analysis showed a statistically significant increase in FMD among all 43 patients between 1-4 years after AAA repair (p=0.0061), as well as a statistically significant increase in FMD at each point of follow-up after surgery (p=0.0079) for the 13 participants for whom all data points were available. This study demonstrates improved FMD years after AAA repair among patients, and supports the hypothesis that AAAs are systemic diseases. The exact mechanism is unknown at this time. Current vascular research indicates the aortic thrombus is a possible source of systemic inflammation; another UK study found that even sub-surgical AAAs increase the risk of MI or stroke among patients. FMD could therefore potentially be used as a cost-effective and non-invasive biomarker in determinations of surgical interventions. Though the study power is limited, the data provides initial evidence for long-term improvement in endothelial function after AAA surgery.