The hyperaemic response of the forearm is a widely used technique to assess the vascular reactivity. Little is known about the short-term reproducibility and the possible exhaustion of this response in normal or diseased states. As such, the current study was conducted to assess this phenomenon using a unique nuclear medicine- (NM-) based technique. 19 patients with coronary artery disease (CAD) undergoing NM exercise stress tests and 15 low risk (LR) participants completed 2 reactive hyperaemia tests, using a SPECT-based technique, separated by 15? min. Analyses revealed that CAD patients had lower hyperaemic responses than LR participants ( ), and that there was a significant group × time interaction ( ), such that LR participants showed a larger decrease in the reactivity ( to ) than the CAD patients ( to ). These results suggest that there is a variability, due to disease states, in the reproducibility of the hypaeremic reactivity. This needs to be taken into account in short-term repeated measure studies. 1. Introduction Endothelial dysfunction is thought to be a major factor in the development and progression of coronary artery disease (CAD) [1]. Over the past several years, measures of endothelial function have become widely used in medical research. One such technique that has gained popularity is the occlusion-induced ischemia of the forearm using a blood pressure cuff. Release of the ischemia induces a hyperaemic reactivity measurable in the brachial artery [1, 2]. This assessment technique has been shown to have reasonable [2–5], though not perfect [6, 7], long-term reproducibility (e.g., day-to-day or month-to-month). However, little is known about the short-term (15?min) reproducibility of hyperaemic reactivity, or if this reproducibility is different between patients with CAD and healthy controls. Given the desirability of being able to conduct multiple tests over a short period of time for use in clinical trials and the assessment of acute exposures (e.g., exercise, acute psychological stress, pharmacological) such information would be important to be known. We previously compared hyperaemic reactivity in CAD patients and low risk participants using a nuclear medicine based forearm hyperaemic reactivity technique (FHR) [3]. This measure has very good discriminant properties and good day-to-day reproducibility. However, its short-term reproducibility is unknown and, as such, the objectives of the current study were to test this reproducibility in a sample of CAD patients and low risk controls. 2. Materials and Methods 2.1. Participants A
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