Exercise Transcutaneous Oxygen Pressure (Extcpo2) Measurement is a Reliable Method of Evaluation of Internal Iliac Artery flow Compromise

Abstract

Clinical differentiation of buttock claudication from pseudo-claudication (neuromuscular etiology) is often challenging and cannot be diagnosed non-invasively using standard ankle-brachial index (ABI) with exercise. The aim of this study was to evaluate the reliability of exercise transcutaneous oximetry (ExTcPO2) to accurately detect significant internal iliac artery (IIA) inflow stenosis. Methods: Data from a prospectively maintained registry of consecutive patients undergoing ExTcPO2 for evaluation of buttock and hip exertional discomfort as well as arterial imaging within 12 months were retrospectively analyzed. ExTcPO2 was performed on a treadmill (10% slope; 2 mph speed); measured at buttocks, upper back and calf (rest, with exercise) to document the baseline normal, degree of change with exercise and recovery patterns. A Delta from Resting Oxygen Pressure (DROP) (buttock- back TcPO2 mmHg) ≥15 mm Hg was considered significant. A blinded physician performed aorto-iliac arterial stenosis quantification and receiver operating characteristic (ROC) curve analysis was used to determine sensitivity and specificity to diagnose severe inflow reduction (≥70%) based upon a diagnostic DROP ≥15 mm Hg. Results: One hundred and eleven patients (M:F::79:32, mean age 70, range 18-90 years) with available concomitant imaging (CTA 90, DUS 21) were included in the study. Indications for testing were suspected vascular (82), or neuromuscular (29) symptoms. ExTcPO2 study confirmed the clinical suspicion of the state of IAA inflow in 81% (91/111) of patients. DROP ≥15 mm Hg had a sensitivity, specificity, PPV, NPV of 56, 80, 70, and 68% respectively for prediction of severe IIA inflow reduction (p value <0.001; OR 1.116, 95% CI 1.057-1.157; C- statistic 0.76, SE=0.03). Aorto-iliac arterial reconstruction to treat severe IIA flow compromise was performed in 16 patients. Revascularization was Direct Antegrade in 12 patients (IIA PTA /stenting – 4, aorto-ilac stenting /endarterectomy – 9), Direct Retrograde (aorto-biiliac bypass) in 1 and Indirect via increased collateral flow (profundoplasty) in 3. Post-operatively symptom relief was noted in 15/16 patients and objectively demonstrated on ExTcPo2 in 6/7 (Figure 2). One patient did not improve clinically, or on EXTcPO2 following Indirect revascularization. Conclusion: Exercise transcutaneous oximetry can reliably diagnose significant IIA inflow stenosis. It is simple, non-invasive and can serve as a valuable screening tool to differentiate buttock claudication from other neuromuscular causes of low back, buttock and hip discomfort as well as post-operatively to confirm adequacy of aorto-iliac revascularization in conjunction with standard, noninvasive vascular evaluation with ABI.