Eduard J. Meijer

Background: A flow limitation in the iliac arteries (FLIA) in endurance athletes is notoriously difficult to diagnose with the currently available diagnostic tools. At present, a commonly used diagnostic measure is a decrease in ankle brachial index with flex hips (ABI_Flexed) following a maximal effort exercise test. Near-infrared spectroscopy (NIRS) is a non-invasive technique that measures skeletal muscle oxygenation as reflected by the balance of O₂ delivery from microvascular blood flow and O₂ uptake by metabolic activity. Therefore, NIRS potentially serves as a novel technique for diagnosing FLIA. The purpose of this study is to compare the diagnostic accuracy of NIRS-derived absolute, amplitude, and kinetic variables in legs during and after a maximal exercise test with ABI_Flexed. Methods: ABI_Flexed and NIRS were studied in 33 healthy subjects and 201 patients with FLIA diagnosed with echo-Doppler. Results: After maximal exercise, NIRS kinetic variables, such as the half value time and mean response time, resulted in a range of 0.921 to 0.939 AUC for the diagnosis of FLIA when combined with ABI_Flexed. Conversely, ABI_Flexed measurements alone conferred significantly worse test characteristics (AUC 0.717, p < 0.001). Conclusions: NIRS may serve as a diagnostic adjunct in patients with possible FLIA.

The ankle‐brachial index is an accurate tool for detecting claudication in atherosclerotic patients. However, this technique fails to identify subtle flow limitations of the iliac arteries (FLIA) in endurance athletes. Near‐infrared spectroscopy (NIRS) is a noninvasive technique that measures skeletal muscle tissue oxygenation status. The aim of the present study is to examine the absolute and relative test–retest reliability of NIRS and evaluate its potential as a diagnostic tool in FLIA. NIRS‐derived exercise variables were analyzed during exercise and recovery in FLIA 17 patients and 19 healthy controls. The relative reliability of absolute variables (such as the maximal value) were slight to yet predominantly substantial (intraclass correlation coefficient [ICC], ICC range: 0.06–0.76) with good to excellent absolute reliability (absolute limits of agreement [ALoA], ALoA range: 0.8 ± 10.2 to 0.7 ± 13.1; coefficient of variation [CV], CV range: 5%–11%). Absolute values encompassing signal amplitudes showed moderate to almost perfect relative reliability (ICC range: 0.51–0.89) and poor to good absolute reliability (ALoA range: −1.3 ± 7.0 to −2.5 ± 15.7; CV range: 15%–32%). Kinetic variables showed moderate to almost perfect relative reliability for most recovery kinetics variables (ICC range: 0.54–0.86) with fair to good absolute reliability (ALoA range: 0.4 ± 12.2 to 3.9 ± 37.9; CV range: 18%–27%). Particularly, kinetic variables showed significant differences between patients and healthy subjects. NIRS is found to be a reliable method for examining muscle tissue oxygenation variables. Given the significant differences in especially recovery kinetics between normal subjects and patients, NIRS may contribute to diagnosing FLIA in endurance athletes.

Endurance cyclists have a substantial risk to develop flow limitations in the iliac arteries during their career. These flow limitations are due to extreme hemodynamic stress which may result in functional arterial kinking and/or intravascular lesions. Early diagnosis may improve outcome and could prevent the necessity for surgical vascular repair. However, current diagnostic techniques have unsatisfactory sensitivity and cannot be applied during exercise. Near-infrared spectroscopy (NIRS) has shown great diagnostic potential in peripheral vascular disease and might bring a solution since it measures tissue oxygenation in real time during and after exercise. This report describes the first experiences of the application of NIRS in the vastus lateralis muscle during and after maximal graded cycling exercise in ten healthy participants and in three patients with flow limitations due to (1) subtle functional kinking, (2) an intravascular lesion, and (3) severe functional kinking. The results are put into perspective based on an empirically fitted model. Delayed recovery, showing clearly different types of patterns of tissue reoxygenation after exercise, was found in the affected athletes compared with the healthy participants. In the patients that had kinking of the arteries, tissue reoxygenation was clearly more delayed if NIRS was measured in provocative position with flexed hip. In this pilot experiment, clearly distinctive reoxygenation patterns are observed during recovery consistent with severity of flow limitation, indicating that NIRS is a promising diagnostic tool to detect and grade arterial flow limitations in athletes. Our findings may guide research and optimization of NIRS for future clinical application.