Background: The increasing age of coronary artery disease (CAD) patients and the occurrence of sarcopenia in the\r\nelderly population accompanied by ââ?¬Ë?fear of movingââ?¬â?¢ and hospitalization in these patients often results in a\r\nsubstantial loss of skeletal muscle mass and muscle strength. Cardiac rehabilitation can improve exercise tolerance\r\nand muscle strength in CAD patients but less data describe eventual morphological muscular changes possibly by\r\nmore difficult access to imaging techniques. Therefore the aim of this study is to assess and quantify the reliability\r\nand validity of an easy applicable method, the ultrasound (US) technique, to measure the diameter of rectus\r\nfemoris muscle in comparison to the muscle dimensions measured with CT scans.\r\nMethods: 45 older CAD patients without cardiac event during the last 9 months were included in this study. 25\r\npatients were tested twice with ultrasound with a two day interval to assess test-retest reliability and 20 patients\r\nwere tested twice (once with US and once with CT) on the same day to assess the validity of the US technique\r\ncompared to CT as the gold standard. Isometric and isokinetic muscle testing was performed to test potential\r\nzero-order correlations between muscle diameter, muscle volume and muscle force.\r\nResults: An intraclass correlation coefficient (ICC) of 0.97 ((95%CL: 0.92 - 0.99) was found for the test-retest\r\nreliability of US and the ICC computed between US and CT was 0.92 (95%CL: 0.81 - 0.97). The absolute difference\r\nbetween both techniques was 0.01 Ã?± 0.12 cm (p = 0.66) resulting in a typical percentage error of 4.4%. Significant\r\nzero-order correlations were found between local muscle volume and muscle diameter assessed with CT (r = 0.67,\r\np = 0.001) and assessed with US (r = 0.49, p < 0.05). Muscle strength parameters were also significantly correlated\r\nwith muscle diameter assessed with both techniques (range r = 0.45-r = 0.61, p < 0.05).\r\nConclusions: Ultrasound imaging can be used as a valid and reliable measurement tool to assess the rectus\r\nfemoris muscle diameter in older CAD patients
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