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: ["Disease", "Chemical"].

Please return the output as a JSON object of the format: {"Chemical" : ["Naloxone", ...], "Disease" : ["Hypotensive", ...]}. 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:

Low-molecular-weight heparin for the treatment of patients with mechanical heart valves. BACKGROUND: The interruption of oral anticoagulant (OAC) administration is sometimes indicated in patients with mechanical heart valves, mainly before noncardiac surgery, non-surgical interventions, and pregnancy. Unfractionated heparin (UH) is currently the substitute for selected patients. Low-molecular-weight heparin (LMWH) offers theoretical advantages over UH, but is not currently considered in clinical guidelines as an alternative to UH in patients with prosthetic valves. HYPOTHESIS: The aim of the present study was to review the data accumulated so far on the use of LMWH in this patient population and to discuss its applicability in common practice. METHODS: For this paper, the current medical literature on LMWH in patients with mechanical heart valves was extensively reviewed. RESULTS: There were eight series and six case reports. None of the studies was randomized, and only one was prospective. Data to establish the thromboembolic risk were incomplete. After excluding case reports, the following groups were constructed: (a) short-term administration, after valve insertion (n = 212); (b) short-term, perioperative (noncardiac)/periprocedural (n = 114); (c) long-term, due to intolerance to OAC (n = 16); (d) long-term, in pregnancy (n = 10). The incidence rate of thromboembolism was 0.9% for all the studies and 0.5, 0, 20, and 0% in groups a, b, c, and d, respectively; for hemorrhage, the overall rate was 3.4% (3.8, 2.6, 10, and 0% for the respective groups). CONCLUSIONS: In patients with mechanical heart valves, short-term LMWH therapy compares favorably with UH. Data on mid- and long-term LMWH administration in these patients are sparse. Further randomized studies are needed to confirm the safety and precise indications for the use of LMWH in patients with mechanical heart valves.
{"Chemical": ["Low-molecular-weight heparin", "Unfractionated heparin", "UH", "LMWH"], "Disease": ["thromboembolism", "thromboembolic", "hemorrhage"]}