In this task, you are given a passage which has a question and the context. You have to generate an answer to the question based on the information present in the context.

Q: Context: Impaired neurodevelopmental outcome represents a major morbidity for survivors of infant heart surgery for congenital heart defects. Previous studies in these neonates have reported preoperative microcephaly, periventricular leukomalacia, and other findings. The hypothesis of this study is that preoperative cerebral blood flow is substantially diminished and might relate to preoperative neurologic conditions.', 'Preoperative brain magnetic resonance imaging was performed. Cerebral blood flow measurements in infants with congenital heart defects were obtained by using a novel noninvasive magnetic resonance imaging technique, pulsed arterial spin-label perfusion magnetic resonance imaging. Cerebral blood flow was measured before the operation under standard ventilation and repeated after increased carbon dioxide.', 'A total of 25 term infants were studied. The average age at the time of the operation was 4.4 +/- 4.6 days. Congenital heart defects varied widely. Microcephaly occurred in 24% (6/25). Baseline cerebral blood flow was 19.7 +/- 9.2 mL . 100 g -1 . min -1 (8.0-42.2 mL . 100 g -1 . min -1 ). Five patients had cerebral blood flow measurements of less than 10 mL . 100 g -1 . min -1 . Mean hypercarbic cerebral blood flow increased to 40.1 +/- 20.3 mL . 100 g -1 . min -1 (11.4-94.0 mL . 100 g -1 . min -1 , P < .001). Pairwise analyses found that low hemoglobin levels were associated with higher baseline cerebral blood flow values ( P = .04). Periventricular leukomalacia occurred in 28% (7/25) and was associated with decreased baseline cerebral blood flow values ( P = .05) and a smaller change in cerebral blood flow with hypercarbia ( P = .003).\Question: Is preoperative cerebral blood flow diminished in neonates with severe congenital heart defects?

A: Structural brain abnormalities are common in these neonates before surgical intervention. Preoperative cerebral blood flow for this cohort was low and drastically reduced in some patients. Low cerebral blood flow values were associated with periventricular leukomalacia. Carbon dioxide reactivity was preserved but might be compromised by some aspects of the cardiac anatomy. The full spectrum of cerebral blood flow measurements with this technique in congenital heart defects and their long-term significance require continued investigation.
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Q: Context: T-wave alternans (TWA) is an indicator of vulnerability to ventricular arrhythmias and is useful for predicting sudden cardiac death (SCD) in patients with various structural heart diseases. We evaluated whether high levels of time-domain TWA on ambulatory ECG (AECG) are associated with a history of ventricular fibrillation (VF) in Brugada syndrome (BrS) patients.', 'We examined the associations among VF history, family history of SCD, spontaneous type 1 electrocardiogram (ECG), late potentials, VF induction by programmed electrical stimulation, and TWA in 45 BrS patients (44 males; mean age, 45 ± 15 years). TWA analyzed from 24-h AECG recordings using the modified moving average method was positive in 13 of 43 patients (30%). Patients with a history of VF had a significantly higher incidence of a positive TWA test (82% vs. 13%; P < 0.001) and spontaneous type 1 ECG (92% vs. 38%; P = 0.007) than those without VF history. Multivariate analysis indicated that positive TWA (OR 7.217; 95% CI 2.503-35.504; P = 0.002) and spontaneous type 1 ECG (OR 5.530; 95% CI 1.651-34.337; P = 0.020) were closely associated with VF history. Spontaneous type 1 ECG had high sensitivity (92%) but low specificity (63%). Positive TWA was a reliable marker with high sensitivity and specificity (82% and 88%, respectively).\Question: Is time-domain T-wave alternans strongly associated with a history of ventricular fibrillation in patients with Brugada syndrome?

A: Elevated time-domain TWA on AECG confirms arrhythmia risk in symptomatic BrS patients without the need for provocative stimuli.
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Q: Context: To study the value of the cervical length (CL) measurement at 11-14 weeks in predicting second trimester miscarriage occurring at 16-24 weeks.', 'Prospective study in routine obstetric population using transvaginal ultrasound examination to measure the length of the endocervical canal at 11-14 weeks.', 'The study group consisted of 2836 singleton pregnancies. Eleven (0.0038%) women miscarried between 16 and 24 weeks whereas 2825 delivered after 34 weeks. CL was significantly shorter (Mann-Whitney U test, p\u2009=\u20090.001), in women that had a second trimester miscarriage in comparison to those who delivered after 34 weeks (median CL 28\u2009mm versus 32\u2009mm, respectively). First trimester CL was predictive of a late miscarriage (OR\u2009=\u20090.7093304, R(2\u2009)=\u20090.1211, AUC\u2009=\u20090.7838, p\u2009<\u20090.001). The detection rate was 63.64% for 20% screen positive rate.\Question: Is first trimester cervical length associated with mid-trimester loss?

A:
First trimester endocervix is significantly shorter in women destined to miscarry between 16 and 24 weeks. In low risk singleton pregnancies, first trimester CL can be useful in predicting second trimester miscarriage.
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