The heterogeneity of regional specific ventilation is unchanged following heavy exercise in athletes.

Heavy exercise increases ventilation-perfusion mismatch and decreases pulmonary gas exchange efficiency. Previous work using magnetic resonance imaging (MRI) arterial spin labeling in athletes has shown that, after 45 min of heavy exercise, the spatial heterogeneity of pulmonary blood flow was increased in recovery. We hypothesized that the heterogeneity of regional specific ventilation (SV, the local tidal volume over functional residual capacity ratio) would also be increased following sustained exercise, consistent with the previously documented changes in blood flow heterogeneity. Trained subjects (n = 6, maximal O2 consumption = 61 ± 7 ml·kg(-1)·min(-1)) cycled 45 min at their individually determined ventilatory threshold. Oxygen-enhanced MRI was used to quantify SV in a sagittal slice of the right lung in supine posture pre- (preexercise) and 15- and 60-min postexercise. Arterial spin labeling was used to measure pulmonary blood flow in the same slice bracketing the SV measures. Heterogeneity of SV and blood flow were quantified by relative dispersion (RD = SD/mean). The alveolar-arterial oxygen difference was increased during exercise, 23.3 ± 5.3 Torr, compared with rest, 6.3 ± 3.7 Torr, indicating a gas exchange impairment during exercise. No significant change in RD of SV was seen after exercise: preexercise 0.78 ± 0.15, 15 min postexercise 0.81 ± 0.13, 60 min postexercise 0.78 ± 0.08 (P = 0.5). The RD of blood flow increased significantly postexercise: preexercise 1.00 ± 0.12, 15 min postexercise 1.15 ± 0.10, 45 min postexercise 1.10 ± 0.10, 60 min postexercise 1.19 ± 0.11, 90 min postexercise 1.11 ± 0.12 (P < 0.005). The lack of a significant change in RD of SV postexercise, despite an increase in the RD of blood flow, suggests that airways may be less susceptible to the effects of exercise than blood vessels.

MR enterography correlates highly with colonoscopy and histology for both distal ileal and colonic Crohn's disease in 310 patients.

BACKGROUND AND AIMS: To evaluate the efficacy of MR enterography (MRE) in patients with known or suspected Crohn's disease without the use of anti-peristaltic pharmacologic agents compared to colonoscopy and histology. METHODS: A retrospective review of 850 consecutive patients who underwent routine MRE to evaluate known or suspected Crohn's disease was performed. Of these, 310 patients also underwent colonoscopy with biopsy(s) within 90 days. The results of the MRE were compared to the colonoscopy and pathology reports to determine the presence or absence of disease in evaluable bowel segments. Individual imaging parameters (including wall thickening, enhancement, T2 signal, mesenteric vascular prominence and adenopathy) were also separately analyzed to determine their independent predictive value. RESULTS: In 310 patients, the overall sensitivity and specificity of MRE (using endoscopy as a gold standard) were 85% and 80% respectively (kappa=0.65). The sensitivity of MRE for detection of pathologically severe disease was 87% in the terminal ileum (TI) and 88% in the colon. In the subset of 162 patients who underwent colonoscopy within 30 days of MRE, the overall sensitivity remained 85% but the specificity increased to 85% (kappa=0.69). Wall thickening and abnormal enhancement were sensitive indicators of Crohn's disease (75% and 78%), while abnormal T2 signal, mesenteric vascular prominence and adenopathy were specific (86%, 91% and 93%). CONCLUSION: MRE compares favorably to colonoscopy for evaluation of known or suspected Crohn's disease noninvasively and without the exposure to ionizing radiation associated with CT enterography (CTE).

Electrocardiographic identification of drug-induced QT prolongation: assessment by different recording and measurement methods.

BACKGROUND: Careful assessment of QT interval prolongation is required before novel drugs are approved by regulatory authorities. The choice of the most appropriate method of electrocardiogram (ECG) acquisition and QT/RR interval measurement in clinical trials requires better understanding of the differences among currently available approaches. This study compared standard and Holter-derived 12-lead ECGs for utility in detecting sotalol-induced QT/QTc and RR changes. Manual methods (digitizing pad and digital on-screen calipers) were compared for precision of QT and RR interval measurement. METHODS AND RESULTS: Sixteen hundred pairs of serial 12-lead digital ECGs were recorded simultaneously by standard resting ECG device and by continuous 12-lead digital Holter over 3 days in 39 healthy male and female volunteers. No therapy was given on the 1st day followed by 160 mg and 320 mg of sotalol on the 2nd and 3rd day, respectively. Holter-derived and standard ECGs produced nearly identical sotalol-induced QT/QTc and RR changes from baseline, as did the manual digipad and on-screen caliper measurements. The variability of on-screen QT measurement in this study was greater than that of digipad. CONCLUSIONS: Digital 12-lead Holter and standard 12-lead ECG recorders, as well as the manual digitizing pad and digital on-screen calipers, are of equal utility for the assessment of drug-induced change from baseline in QT and RR interval, although the variability of the on-screen method in this study was greater than of the digipad.