Background and Goal of Study: Previous studies have demonstrated varying association between peak oxygen concentration (V02 peak) and anaerobic threshold (AT) determined by cardiopulmonary exercise testing (CPX), and postoperative mortality in abdominal aortic aneurysm repair (AAA). This study assesses the association between the results of preoperative CPX and long term outcome in AAA repair.
Materials and Methods: Patients from our institution undergoing AAA repair between 01/01/2007 and 31/12/2008 who underwent pre-operative CPX were included. V02peak and AT in ml/kg/min were recorded. Intervention type, and mortality data were obtained from case-notes. Patients were followed up until July 2010. Cox proportional hazard analysis was used to examine the association between functional capacity and long-term outcome.
Results and Discussion: 137 patients(118 male) were studied., 71 underwent open repair (OR) and 66 received endovascular aneurysm repair (EVAR). The median(range) age of the study population was 75.7(56.5 - 91.7) years. For OR age was 75.7(56.5 - 87.2) years, for EVAR age was (SD) 77.3(59.3 - 91.7) years. The age difference between the two groups was significant, p=0.002. Median(range) patient follow-up was 657(1-1318) days. During follow up, there were 30 deaths (21.9%), 12 post OR and 18 post EVAR (p=0.142).
The mean(SD) AT was 11.7(2.7) in OR patients and 10.2(2.8) EVAR patients (p=0.003). Mean(SD) VO2peak was 16.1(4.4) in OR patients and 14.2(4.1) in EVAR patients (p= 0.011). The hazard ratio (HR) for death during follow-up increased with decreasing AT and VO2peak. In OR patients the HR for death during follow-up per ml/kg/min decrease in AT was 1.01(0.75-1.35). The HR per ml/kg/min decrease in VO2peak was 0.97(0.84-1.12). For EVAR patients the HR for AT was 1.84(1.16-2.92); and 1.23(0.97-1.57) for VO2peak.
Conclusion: These data show a significant difference in AT between the OR and EVAR sub-groups and identifies the independent predictive value of CPX in longterm outcome and mortality post EVAR. Given the significant long term attrition of EVAR patients shown in this study there is a strong case for the early use of functional testing as part of the preoperative assessment of AAA patients. The results of such testing may serve as a key tool to help direct a multidisciplinary intervention decision making process.