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.

Q: Context: Cardiac resynchronization therapy (CRT) by simultaneous biventricular pacing is now widely accepted as a new therapeutic option for patients with severe congestive heart failure (CHF). Recent studies have shown comparable hemodynamic benefits of left ventricular (LV) pacing alone. The clinical usefulness of CRT, however, might be compromised by potential exaggeration of arrhythmogenic substrates through a modification of ventricular repolarization.', 'We compared ECG parameters during sinus rhythm (SR), atrioventricular synchronous pacing at the right ventricular apex (RV(end)P), at LV epicardium (LV(epi)P), and at both sites (BiVP) in acute homodynamic studies of 14 CHF patients scheduled for CRT (QRS duration = 144 +/- 23 msec, LVEF = 27 +/- 10%). The maximum rate of increase in LV pressure (LVdp/dt(max)) was decreased significantly during RV(end)P, whereas it was increased similarly during LV(epi)P and BiVP compared with SR. QTc was increased during RV(end)P (by 10.2%) and LV(epi)P (by 26.1%). QTc dispersion (QTc(max)-QTc(min) in the six precordial leads) was also increased during LV(epi)P (by 66.5%). These parameters were unaffected during BiVP. JTc was unchanged, and the interval from the peak to the end of the T wave (Tc(peak-end)) was increased slightly (by 19.3%) during RV(end)P. Both JTc and Tc(peak-end) were increased dramatically during LV(epi)P (by 18.2% and 55.4%, respectively), but increased only modestly during BiVP (by 6.6% and 15.8%, respectively).
Answer: LV(epi)P causes much greater increase in spatial dispersion of ventricular repolarization than BiVP in CHF patients. BiVP may have a substantial advantage over LV(epi)P to minimize the proarrhythmic perturbation of ventricular repolarization in association with CRT.

A: Does biventricular pacing have an advantage over left ventricular epicardial pacing alone to minimize proarrhythmic perturbation of repolarization?
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Q: Context: This study was designed to evaluate the effects of a dorzolamide-timolol combination or dorzolamide on retinal ganglion cell (RGC) density and intraocular pressure (IOP) in glaucomatous eyes of adult rats.', 'Glaucoma was induced in the right eye of adult Wistar rats by episcleral venous occlusion. One experimental group was administered dorzolamide 2%-timolol 0.5% combination eye drops, while the other experimental group was administered dorzolamide 2% eye drops. Control groups had surgery without drug administration. Drug application was initiated either 2 weeks before surgery (Group A), from the day of surgery (Group B), 2 weeks after surgery (Group C), or 4 weeks after surgery (Group D). RGCs were labeled by intratectal Fluorogold injections and counted from flat-mount preparations, and IOP was measured using Tonopen.', 'Both dorzolamide-timolol combination and dorzolamide, when applied topically, significantly reduced IOP and improved RGC densities in experimental eyes when compared to control eyes. Earlier initiation, as well as longer duration of drug application, resulted in higher RGC densities.
Answer: Topical application of a dorzolamide-timolol combination or dorzolamide saved RGCs to a significant extent and reduced IOP in glaucomatous rat eyes.

A: Does dorzolamide and timolol save retinal ganglion cells in glaucomatous adult rats?
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Q: Context: Baseline carbohydrate antigen 19-9 (CA 19-9) is a useful prognostic marker in pancreatic ductal adenocarcinoma (PDA); however, data on the significance of a change in CA 19-9 following neoadjuvant therapy are lacking.', "All patients receiving neoadjuvant therapy for PDA from July 2010 to February 2013 were retrospectively reviewed. Resection rate, R0 resection rate, need for venous resection, and overall survival were correlated to CA 19-9 response. Fisher's exact test, Kaplan-Meier survival analysis, and multivariate analysis using Cox regression were used.", 'A total of 78 patients were studied (21 patients with resectable disease, 40 borderline resectable, and 17 with locally advanced disease). A variety of chemotherapies radiation were utilized during the study period. Overall, 56 patients (72 %) had a decrease in CA 19-9 of >50 % with neoadjuvant treatment. In borderline resectable patients, CA 19-9 response of >50 % predicted R0 resection (odds ratio 4.2; p = 0.05). In borderline resectable patients who had an increase in CA 19-9, none of five (0 %) underwent R0 resection compared with 80 % of the remaining cohort (p = 0.001). The complete pathologic response rate was 29 % in patients who had a CA 19-9 response of >90 % versus 0 % in the remaining patients (p < 0.001). A CA 19-9 response of >50 % resulted in improved overall survival (28.0 vs. 11.1 months; p < 0.0001) and was an independent predictor of survival (hazard ratio 0.26; 95 % CI 0.13-0.55; p < 0.0001).
Answer: CA 19-9 response to neoadjuvant therapy is associated with R0 resection rate, histopathologic response, and survival. Incorporation of this easily obtainable biomarker into future clinical trials may facilitate more rapid evaluation of novel regimens.

A:
Is serum CA 19-9 response to neoadjuvant therapy associated with outcome in pancreatic adenocarcinoma?
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