You will be shown an abstract from a biomedical research paper. Given this abstract, your task is to extract all unique entities of the following types: ["Outcome", "Participant", "Intervention"].

Please return the output as a JSON object of the format: {"Participant" : ["patients with COPD", ...], "Intervention" : ["Atenolol", ...], "Outcome" : ["blood pressure", ...]}. The keys should be entity types and values should be lists of extracted entities belonging to the corresponding type. If you cannot find entities belonging to a specific type, the value should be [].

Only output the JSON object and do not include any additional text.

Abstract:

β-Blockers in patients with intermittent claudication and arterial hypertension : results from the nebivolol or metoprolol in arterial occlusive disease trial . The use of β-receptor blockers in peripheral arterial disease is controversial for their impact on vasomotor tone . The β-blocker nebivolol possesses vasodilating , endothelium-dependent , NO-releasing properties that might be beneficial in peripheral arterial disease . The aim of the study was to evaluate the effects and tolerability of nebivolol in comparison with metoprolol in these patients . A total of 128 patients with intermittent claudication and essential hypertension were included and double-blind randomized to receive 5 mg of nebivolol ( N=65 ) or 95 mg of metoprolol ( N=63 ) once daily . End points were changes in ankle-brachial index , initial and absolute claudication distance , endothelial function assessed by flow-mediated dilatation of the brachial artery , blood pressure , and quality of life using the claudication scale questionnaire . End point analysis was possible in 109 patients ( 85.2 % ) . After the 48-week treatment period , ankle-brachial index and absolute claudication distance improved significantly in both patient groups ( P < 0.05 for both ) , with no difference across treatments . A significant increase of initial claudication distance was found in the nebivolol group . Adjusted mean change of initial claudication distance was 33.9 % after nebivolol ( P=0.003 ) and 16.6 % after metoprolol ( P=0.12 ) treatment . Quality of life was not influenced by either treatment , and there was no relevant change in flow-mediated dilatation in patients treated with nebivolol or metoprolol ( P=0.16 ) . Both drugs were equally effective in lowering blood pressure . In conclusion , β-blocker therapy was well tolerated in patients with intermittent claudication and arterial hypertension during a treatment period of ≈1 year . In the direct comparison , there was no significant difference between nebivolol and metoprolol .
{"Intervention": [], "Outcome": ["blood pressure", "effects and tolerability", "quality of life using the claudication scale questionnaire", "in ankle-brachial index , initial and absolute claudication distance , endothelial function assessed by flow-mediated dilatation of the brachial artery", "lowering blood pressure"], "Participant": []}