Given a passage with a context and an answer, construct a question on the basis of the information present in the passage. Construct the question in such a way that (i) it is unambiguous, (ii) it is answerable from the passage, (iii) its answer is unique (iv) it answer uses text phrases from the passage. Avoid creating questions that (i) can't be answered correctly without actually understanding the passage and (ii) uses the same words or phrases given in the passage.

[EX Q]: Context: The aim of this study was to investigate the relationship between intraoperative vasopressin infusion and postoperative cardiac enzymes.', 'A prospective, double-blind, randomized, controlled study.', 'A single tertiary cardiac center.', 'One hundred consecutive patients undergoing cardiac surgery with or without cardiopulmonary bypass.', 'The study was approved by the Institutional Review Board, and patients provided informed consent to participate. Patients were randomized by computer into 2 equal groups: Vasopressin or control. The blinded study included vasopressin administered at a dose of 1.8 U/h or 1.8 mL/h of normal saline, along with catecholamines. The drug was administered continually during surgery while patients needed catecholamines. The intervention was discontinued upon admission to the intensive care unit when information regarding the true character of the drug was reported to the doctor in charge of patients in the intensive care unit by one of the investigators. Primary outcomes were CK-MB and troponin T levels measured at 0, 6, and 12 hours postoperatively.', 'Of the 100 patients, 8 were excluded; the remaining 92 were randomized to either the vasopressin (n = 47) or control (n = 45) group. There were no significant differences in demographic data between the groups. Postoperatively at 0, 6, and 12 hours, there were no differences in CK-MB (U/l) (37.5 ± 57.9 v 32.0 ± 21.5, 29.4 ± 41.1 v 24.4 ± 23.1, and 21.4 ± 21.3 v. 21.8 ± 32.4, respectively) and troponin T (752.4 ± 638.2 v 762.7 ± 557.1, 753.8 ± 507.3 v 777.6 ± 515.0, and 774.6 ± 572.6 v 698.7 ± 540.2, respectively) values.
Answer: Vasopressin infusion has been used to treat catecholamine-unresponsive shock. In this study, intraoperative vasopressin was used safely as a possible first-line drug for treating hypotension; however, it did not increase the levels of cardiac enzymes after cardiac surgery.
[EX A]: Does vasopressin raise cardiac enzymes following cardiac surgery : a randomized double-blind clinical trial?

[EX Q]: Context: Impaired endothelial function, as assessed by brachial artery flow-mediated dilation (FMD), is an established risk factor for cardiovascular events. FMD is impaired in heart failure (HF) patients, but less is known about hyperemic brachial artery flow. We investigated the relationship between FMD and hyperemic flow with adverse clinical outcomes in HF patients.', 'Brachial artery FMD and hyperemic flow were assessed in 156 patients (70.5 % Male; 45.5% Caucasian; mean age (± SD) = 56.2 (±12.4) years) with HF and reduced left ventricular ejection fraction (LVEF). Cox proportional hazard models were used to assess the potential explanatory association of FMD and hyperemic flow with the composite outcome of death or cardiovascular hospitalization over a median 5-year follow-up period.', 'Both FMD and hyperemic flow were negatively correlated with age, but unrelated to sex, race, body mass index, LVEF or N-terminal pro-B-Type natriuretic peptide (NT-ProBNP). Reduced hyperemic flow, but not FMD, was associated with an increased risk of death or cardiac hospitalization after controlling for traditional risk factors.
Answer: The association of reduced hyperemic flow with increased risk of adverse clinical outcomes suggests that micro-vascular function may be an important prognostic marker in patients with HF.
[EX A]: Is reactive hyperemia associated with adverse clinical outcomes in heart failure?

[EX Q]: Context: MRI of tissues with rapid transverse relaxation can be performed efficiently using the zero echo time (ZTE) technique. At high bandwidths leading to large relative initial radiofrequency (RF) dead times, the method becomes increasingly sensitive to artifacts related to signal stemming from outside the field of view, particularly from the RF coils. Therefore, in this work, a birdcage coil was designed that is virtually free of 1H signal.', 'A transmit-receive birdcage RF coil for MRI of joints at 7T was designed by rigorously avoiding materials containing 1H nuclei, by using purely mechanical connections without glue, and by spoiling of unwanted signal by application of ferromagnetic materials. The coil was tested for residual 1H signal using ZTE phantom and in vivo joint imaging.', 'In standard ZTE imaging, no 1H signal was detected above noise level. Only at extreme averaging, residual signal was observed close to conductors associated with 1H-containing molecules at adjacent glass surfaces. Phantom images with dead times up to 3.8 Nyquist dwells were obtained with only negligible background artifacts. Furthermore, high-quality ZTE images of human joints were acquired.
Answer: A virtually 1H-free birdcage coil is presented, thus enabling in vivo ZTE MRI practically free of background signal, even at high bandwidths. Magn Reson Med, 2016. © 2016 International Society for Magnetic Resonance in Medicine.
[EX A]:
Do a virtually 1H-free birdcage coil for zero echo time MRI without background signal?