Given a passage, 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.

Q: To compare the safety and success of a retrograde approach using a microcatheter vs. a sheath in the treatment of superficial femoral artery (SFA) chronic total occlusions (CTOs).', 'From April 2007 to December 2012, 188 consecutive patients underwent EVT for 229 de novo SFA CTOs using the retrograde approach in 68 patients (35 men; mean age 72 years). This cohort was divided into cases performed with a 4-F or 6-F sheath (n=28, 36 limbs) and those with a 2.1-F microcatheter (n=35, 49 limbs). The primary outcomes were mean time to hemostasis and number of intra- and postoperative puncture site complications, as well as the success of popliteal artery puncture, lesion crossing, and reperfusion.', 'There were no significant differences between two groups in baseline characteristics. PA puncture was successful in all limbs, and the success in crossing the lesion with the wire was not significantly different (91.9% in the sheath group vs. 89.8% in the microcatheter group). Mean time to hemostasis was 8.98.8 minutes in the microcatheter group vs. 47.713 minutes in the sheath group (p<0.0001). There was a significant difference in intraoperative and postoperative complications (22.2% in the sheath group vs. 2.0% in the microcatheter group, p=0.002).

A: Is a sheathless retrograde approach via the popliteal artery useful and safe for treating chronic total occlusions in the superficial femoral artery?
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Q: Beta blockers and calcium antagonists are widely used in the management of angina pectoris in the belief that the combination is more efficacious than either drug alone.', 'This double blind randomised crossover placebo controlled study compares the effects of nicardipine, atenolol and their combination in 30 patients with chronic stable angina. Each treatment period lasted 6 weeks with dose titration after 3 weeks. Symptom limited treadmill exercise testing and radionuclide ventriculography at rest was carried out at the end of each treatment period.', 'Total exercise duration and time to 1-mm ST-segment depression was significantly prolonged by nicardipine and atenolol when compared to placebo, the combination offered no additional benefit. Time to onset of angina was significantly prolonged by nicardipine and the combination but not by atenolol. Indices of left ventricular function were not significantly affected by any treatment other than an increase in left ventricular end diastolic volume on atenolol and the combination.

A: Is atenolol or nicardipine alone as efficacious in stable angina as their combination : a double blind randomised trial?
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Q: A small subset (10-15%) of gastrointestinal stromal tumours (GISTs) lack mutations in KIT and PDGFRA (wild-type GIST). Recently, a novel BRAF exon 15 mutation (V600E) was detected in imatinib-naive wild-type high-risk intestinal GISTs (4%). However, the frequency and distribution of BRAF mutations within the spectrum of GISTs, and whether they might represent secondary events acquired during tumour progression, remain unknown.', '69 GISTs (39 KIT mutants, 2 PDGFRA mutants and 28 wild-type) were analysed for mutations in BRAF exon 15 and KRAS exon 2. To assess the stage at which these mutations might occur in GIST, a considerable number of incidental gastric (n = 23) and intestinal (n = 2) tumours were included.', 'BRAF mutations (V600E) were detected in 2 of 28 wild-type GISTs (7%), but in none of the 41 KIT/PDGFRA mutants. No KRAS mutation was detected. The two BRAF-mutated GISTs measured 4 mm in diameter and originated in the gastric body and the jejunum in two men (mean age, 76 years). Both tumours were mitotically inactive KIT-positive spindle-cell GISTs that were indistinguishable histologically from their more common KIT-mutated counterparts.

A:
Are v600E BRAF mutations alternative early molecular events in a subset of KIT/PDGFRA wild-type gastrointestinal stromal tumours?
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