Hauser, Mary F.

Abstract A quality control (QC) program for bone mineral measurements at the proximal femur by dual-energy x-ray absorptiometry (DXA) was designed for the osteoporosis component of the Third National Health and Nutrition Examination Survey (NHANES III). Major elements of the QC program are (1) a QC center for review of all scans, (2) setup procedures for and continuous monitoring of daily QC procedures, (3) reference standards for cross-calibration, (4) longitudinal studies for assessment of instrument stability, (5) monitoring of technologist performance, and (6) training. This report describes the results of the QC program of the first half of this 6 year study, which began in 1988. Measurements were performed on 7376 subjects in three mobile examination centers, which traveled to a new location about every 3 months, a total of 44 locations. A small percentage (3.5%) of all scans were rejected, mostly because of patient motion during scanning, but 33% of the remaining scans required reanalysis at the QC center to refine the location of the regions of interest. Precision in spine and hip phantoms was below 1% at all ROIs. In 535 subjects with duplicate scans, age 20–91 of both sexes, examined in a blinded review, precision for BMD at the femur neck ROI was 3.2% (CV) and 5.1% for Ward's triangle BMD. The central review improved scan quality, increased the number of usable scans, and reduced significantly the range of the mean percentage difference in the duplicate scans. Minor alterations in machine function were observed and corrected. QC results on phantoms were similar to those obtained with stationary instruments in dedicated laboratories. Retrospective analysis of the regression slopes from QC records did not show a need for correction of the data base, indicating that the instruments were stable during the course of the study.

Background— Although segmental or circumferential ablation is effective in eliminating pulmonary vein (PV)–mediated atrial fibrillation (AF), this procedure may be complicated by the occurrence of PV stenosis. Methods and Results— To establish the clinical presentation, diagnostic manifestations, and interventional management of PV stenosis, 23 patients with stenosis of 34 veins complicating ablation of AF were evaluated. Each patient became symptomatic 103±100 days after undergoing ablation. In 8 veins, the ablation producing the PV stenosis was a repeated procedure for continued AF. Nineteen patients presented with dyspnea on exertion, 7 with dyspnea at rest, 9 with cough, and 6 with chest pain. On multirow spiral computed tomography examination, the narrowest lumen of the affected PVs measured 3±2 mm compared with 13±3 mm at baseline ( P ≤0.001). The relative perfusion of affected lung segments on isotope scans was reduced to 4±3% of total perfusion compared with 22±10% in unaffected segments. At percutaneous intervention, these veins showed 80±13% stenosis, with a mean gradient of 12±5 mm Hg. This was significantly reduced to a residual stenosis of 9±8% ( P ≤0.001) and a residual gradient of 3±4 mm Hg ( P ≤0.001). Twenty veins were treated with balloon dilatation alone, whereas 14 veins were stented with standard 10-mm-diameter bare-metal stents. Although the symptomatic response was nearly immediate and impressive, 14 patients developed in-stent or in-segment restenosis, requiring repeated interventions in 13. Conclusions— Percutaneous intervention produces rapid and dramatic symptom relief in patients with highly symptomatic PV stenosis after radiofrequency ablation for AF. Nevertheless, alternative treatment methods will be required to decrease recurrent in-stent or in-segment restenosis.