Optimal Timing of Surveillance Ultrasounds in Small Aortic Aneurysms

Small abdominal aortic aneurysms (AAA) surveillance intervals remain controversial and difficult to standardize. Current Society for Vascular Surgery guidelines lack quality evidence. The objective of this study is to examine patients followed in a high volume non-invasive vascular laboratory, determine if the current guidelines are fitting in clinical practice, and attempt to further identify risk factors for accelerated aneurysm growth.A retrospective analysis of patients who underwent at least two ultrasounds for AAA in the vascular laboratory during 2008 -2018 with baseline diameter less than 5.0 cm was conducted. Patient demographics were collected. Groups were then created for comparison using the size criteria according to SVS guidelines. In addition, we compared overall growth rates specifically evaluating rapid growth (rate of at least 1.0 cm/year and size change of at least 0.5 cm from previous imaging), expected growth (any growth below 1.0 cm/year and of at least 0.5 cm from baseline) and no growth.A total of 1581 patients (1232 male and 349 female) were identified with a total of 5945 ultrasound studies. The median age was 73 years and mean follow-up was 27.8 months. Baseline AAA size was 3.0 -3.9 cm in 986 patients and 4.0 -4.9 cm in 595 patients. The average maximum growth rate was 0.18 cm/year for AAAs 3.0 -3.9 cm and 0.36 cm/year for AAAs 4.0 -4.9 cm (P <0.001). Patients with AAA 4.0 -4.9 cm at baseline were more likely to be white, male, hypertensive and have chronic kidney disease (P <0.05). 1078 patients (68.2%) demonstrated no growth over the observed time period with 342 patients (21.6%) demonstrating expected growth and 161 (10.2%) rapid growth. Male gender and baseline AAA size of 4.0 -4.9 cm were more likely to demonstrate rapid growth (P = 0.002) and eventual repair (P <0.001). Metformin use was more common in the AAA group with no growth (P <0.05). Freedom from rapid growth and repair indication at 2 years was significantly lower in those patients with baseline aneurysms 3.0 -3.9 cm (P <0.001).The overall low rate of events in small AAAs supports continued surveillance every 3 years for AAAs 3.0-3.9 cm and yearly for male patients with AAAs 4.0 -4.9 cm as recommended by the SVS Guidelines. Female gender may have less rapid growth than previously reported but likely merit more rigorous surveillance particularly as the AAAs approach 5.0 cm. Metformin use continues to demonstrate it may abrogate aneurysmal growth. Lastly, there is a subset of patients that exhibit more rapid growth of their small AAAs, and further study will be required to classify these patients.