Faculty Bibliography

BACKGROUND:Although prior studies have described the anatomy of the mitral isthmus in patients undergoing left atrial (LA) ablation of atrial fibrillation (AF), none has examined the impact of isthmus anatomy on the likelihood of achieving conduction block. OBJECTIVE:The purpose of this study was to identify morphologic characteristics of the mitral isthmus that may influence the acute efficacy of linear ablation at the mitral isthmus. METHODS:Fifty-five patients (age 61 ± 10 years, 41 [75%] men, LA 46 ± 6 mm, ejection fraction 0.55 ± 0.11, AF duration 4 ± 3 years) underwent linear ablation at the mitral isthmus during an ablation procedure for persistent AF. Computed tomographic scan was performed before the procedure. The morphology of the mitral isthmus and its anatomic relationship to the adjacent vasculature were analyzed. RESULTS:Complete block along the mitral isthmus was achieved in 35 (64%) of 55 patients, 23 (66%) of whom required radiofrequency ablation in the coronary sinus (CS). Patients with incomplete block were more likely to have a pouch at the isthmus (40% vs 9%; P = .01), a greater isthmus depth (8.1 ± 4.2 mm vs 5.7 ± 3.4 mm; P = .04), and a higher prevalence of an interposed circumflex artery between the CS and the mitral isthmus (60% vs 20%; P = .003) compared to patients with isthmus block. An interposed circumflex artery was the only independent predictor of incomplete conduction block at the mitral isthmus (odds ratio 4.9, 95% confidence interval 1.3-18.2; P = .02). CONCLUSION/CONCLUSIONS:Preprocedural computed tomographic imaging identifies patients in whom linear ablation at the mitral isthmus is unlikely to be successful. Interposition of the circumflex artery between the mitral isthmus and the CS is associated with a lower probability of achieving complete mitral isthmus block.

BACKGROUND:Many available physical activity questionnaires (PAQs) are limited due to either focus on recreational activities or burdensome length. AIMS/OBJECTIVE:We sought to assess the reliability and validity of a new short PAQ that captures all activity types. METHODS:The 12-item multiple-choice PAQ-M included eight activity domains, providing a total Physical Activity Score (PAS-M) in kcal/kg/week. The new PAQ-M was administered with the previously validated Paffenbarger PAQ to 426 men, ages 50-79, undergoing colon-cancer screening. RESULTS:The PAQ-M had excellent test-retest reliability (intraclass correlation = 0.87). The PAS-M was moderately correlated with the Paffenbarger Physical Activity Score (PAS-P) (r = 0.31) and inversely correlated with BMI (r = -0.14) and waist circumference (r = -0.17). Adenoma prevalence was inversely associated with the PAS-M (3rd vs. 1st tertile adjusted odds ratio, 0.46; 95% confidence interval, 0.26-0.84) but not with the PAS-P. CONCLUSIONS:Our new short physical activity questionnaire has excellent test-retest reliability, and was correlated moderately with a widely used physical activity questionnaire and obesity measures. Furthermore, the new PAQ was a better predictor of adenoma prevalence in the expected direction than the Paffenbarger questionnaire in this largely sedentary population.

OBJECTIVE:The purpose of this study was to retrospectively determine CT-based normal reference values of left atrial volume, function, and diameter normalized by age, sex, and body surface area. MATERIALS AND METHODS/METHODS:The study group consisted of 74 subjects with normal findings at ECG-gated coronary CT angiography performed with retrospective gating. Analysis of left atrial volume (end-diastolic, end-systolic, and stroke volume) and function (ejection fraction) was performed with the Simpson method. Left atrial diameter was measured in the anteroposterior dimension. General linear model analysis was performed to model the data and assess statistical significance by age group after adjustment for sex and body surface area. RESULTS:The reference range for left atrial volume, function, and diameter was normalized (indexed) to age, sex, and body surface area in healthy subjects. A statistically significant difference was noted between left atrial volume and age without adjustment for sex and body surface area, but no statistically significant difference was found after adjustment for these variables. Sex and body surface area had a significant influence on left atrial volume, function, and diameter. CONCLUSION/CONCLUSIONS:Left atrial volume, function, and diameter normalized to age, sex, and body surface area can be reported from CTA datasets and may provide information important for patient care.

RATIONALE AND OBJECTIVES/OBJECTIVE:The aim of this study was to evaluate the effect of computer-aided diagnosis (CAD) on radiologists' estimates of the likelihood of malignancy of lung nodules on computed tomographic (CT) imaging. METHODS AND MATERIALS/METHODS:A total of 256 lung nodules (124 malignant, 132 benign) were retrospectively collected from the thoracic CT scans of 152 patients. An automated CAD system was developed to characterize and provide malignancy ratings for lung nodules on CT volumetric images. An observer study was conducted using receiver-operating characteristic analysis to evaluate the effect of CAD on radiologists' characterization of lung nodules. Six fellowship-trained thoracic radiologists served as readers. The readers rated the likelihood of malignancy on a scale of 0% to 100% and recommended appropriate action first without CAD and then with CAD. The observer ratings were analyzed using the Dorfman-Berbaum-Metz multireader, multicase method. RESULTS:The CAD system achieved a test area under the receiver-operating characteristic curve (A(z)) of 0.857 +/- 0.023 using the perimeter, two nodule radii measures, two texture features, and two gradient field features. All six radiologists obtained improved performance with CAD. The average A(z) of the radiologists improved significantly (P < .01) from 0.833 (range, 0.817-0.847) to 0.853 (range, 0.834-0.887). CONCLUSION/CONCLUSIONS:CAD has the potential to increase radiologists' accuracy in assessing the likelihood of malignancy of lung nodules on CT imaging.

RATIONALE AND OBJECTIVES/OBJECTIVE:To retrospectively investigate the effect of a computer-aided detection (CAD) system on radiologists' performance for detecting small pulmonary nodules in computed tomography (CT) examinations, with a panel of expert radiologists serving as the reference standard. MATERIALS AND METHODS/METHODS:Institutional review board approval was obtained. Our dataset contained 52 CT examinations collected by the Lung Image Database Consortium, and 33 from our institution. All CTs were read by multiple expert thoracic radiologists to identify the reference standard for detection. Six other thoracic radiologists read the CT examinations first without and then with CAD. Performance was evaluated using free-response receiver operating characteristics (FROC) and the jackknife FROC analysis methods (JAFROC) for nodules above different diameter thresholds. RESULTS:A total of 241 nodules, ranging in size from 3.0 to 18.6 mm (mean, 5.3 mm) were identified as the reference standard. At diameter thresholds of 3, 4, 5, and 6 mm, the CAD system had a sensitivity of 54%, 64%, 68%, and 76%, respectively, with an average of 5.6 false positives (FPs) per scan. Without CAD, the average figures of merit (FOMs) for the six radiologists, obtained from JAFROC analysis, were 0.661, 0.729, 0.793, and 0.838 for the same nodule diameter thresholds, respectively. With CAD, the corresponding average FOMs improved to 0.705, 0.763, 0.810, and 0.862, respectively. The improvement achieved statistical significance for nodules at the 3 and 4 mm thresholds (P = .002 and .020, respectively), and did not achieve significance at 5 and 6 mm (P = .18 and .13, respectively). At a nodule diameter threshold of 3 mm, the radiologists' average sensitivity and FP rate were 0.56 and 0.67, respectively, without CAD, and 0.67 and 0.78 with CAD. CONCLUSION/CONCLUSIONS:CAD improves thoracic radiologists' performance for detecting pulmonary nodules smaller than 5 mm on CT examinations, which are often overlooked by visual inspection alone.