RESUMEN
Introduction: Current abdominal aortic aneurysm (AAA) assessment relies on analysis of AAA diameter and growth rate. However, evidence demonstrates that AAA pathology varies among patients and morphometric analysis alone is insufficient to precisely predict individual rupture risk. Biomechanical parameters, such as pressure-normalized AAA principal wall strain (ερ+¯/PP, %/mmHg), can provide useful information for AAA assessment. Therefore, this study utilized a previously validated ultrasound elastography (USE) technique to correlate ερ+¯/PP with the current AAA assessment methods of maximal diameter and growth rate. Methods: Our USE algorithm utilizes a finite element mesh, overlaid a 2D cross-sectional view of the user-defined AAA wall, at the location of maximum diameter, to track two-dimensional, frame-to-frame displacements over a full cardiac cycle, using a custom image registration algorithm to produce ερ+¯/PP. This metric was compared between patients with healthy aortas and AAAs (≥3â cm) and compared between small and large AAAs (≥5â cm). AAAs were then separated into terciles based on ερ+¯/PP values to further assess differences in our metric across maximal diameter and prospective growth rate. Non-parametric tests of hypotheses were used to assess statistical significance as appropriate. Results: USE analysis was conducted on 129 patients, 16 healthy aortas and 113 AAAs, of which 86 were classified as small AAAs and 27 as large. Non-aneurysmal aortas showed higher ερ+¯/PP compared to AAAs (0.044 ± 0.015 vs. 0.034 ± 0.017%/mmHg, p = 0.01) indicating AAA walls to be stiffer. Small and large AAAs showed no difference in ερ+¯/PP. When divided into terciles based on ερ+¯/PP cutoffs of 0.0251 and 0.038%/mmHg, there was no difference in AAA diameter. There was a statistically significant difference in prospective growth rate between the intermediate tercile and the outer two terciles (1.46 ± 2.48 vs. 3.59 ± 3.83 vs. 1.78 ± 1.64â mm/yr, p = 0.014). Discussion: There was no correlation between AAA diameter and ερ+¯/PP, indicating biomechanical markers of AAA pathology are likely independent of diameter. AAAs in the intermediate tercile of ερ+¯/PP values were found to have nearly double the growth rates than the highest or lowest tercile, indicating an intermediate range of ερ+¯/PP values for which patients are at risk for increased AAA expansion, likely necessitating more frequent imaging follow-up.
RESUMEN
OBJECTIVE: Few general surgery residencies offer rural rotations. We aim to evaluate the contribution of our institution's rural rotation to meeting the Accreditation Council for Graduate Medical Education (ACGME) minimum case requirements for graduation, and residents' perceptions of the educational value of this rotation. DESIGN: ACGME case log data were obtained from categorical general surgery residents who had completed at least 1 month-long rural surgery rotation and 1 month-long general surgery rotation at our academic medical center within the same clinical year. Cases were classified per ACGME defined categories. For each category, the number of cases per month per resident was calculated, and the means for each educational setting were compared using the paired t-test. Residents also completed a 10-question Likert scale survey regarding their perceptions of the rotation. SETTING: Residents rotated at Vidant Medical Center, a tertiary AMC1 affiliated with East Carolina University in Greenville, NC, and at Vidant Chowan, a critical access hospital within the Vidant Health hospital system located in Edenton, NC. PARTICIPANTS: Categorical general surgery residents eligible to rotate through the rural surgery rotation and the general surgery rotation at the AMC. RESULTS: Eleven total residents completed 23 months of rural surgery (mean 2.1 months per resident) and 39 months at the AMC (mean 3.5 months per resident). Significantly more endoscopic cases, hernia repairs, breast cases, and vascular cases were performed on the rural surgery rotation. More abdominal and alimentary tract cases in addition to endocrine, thoracic, and head/neck cases were performed at the AMC. Frequencies of biliary and soft tissue cases were not significantly different. Survey responses regarding the rural rotation were universally positive including more hands-on experience, increased satisfaction with patient care and continuity, and operative confidence and competence. CONCLUSIONS: At our institution, residents benefit from an enriching rural surgery rotation that provides case numbers different from the comparative AMC general surgery rotation.