however, the potential role of CAC among individuals who have no risk factors (RFs) is less established. We sought to examine the relationship between the presence and burden of traditional RFs and CAC for the prediction of all-cause mortality. Methods and Results-The study cohort consisted of 44 052 consecutive asymptomatic individuals free of known coronary heart disease referred for computed tomography for the assessment of CAC. The following RFs were considered: (1) current cigarette smoking, (2) dyslipidemia, (3) diabetes mellitus, (4) hypertension, and (5) family history of coronary heart disease. Patients were followed for a mean of 5.6±2.6 years for the primary end point of all-cause mortality. Among individuals who had no RF, Cox proportional model adjusted for age and sex identified that increasing CAC scores were associated with 3.00-to 13.38-fold higher mortality risk. The lowest survival rate was observed in those with no CAC and no RF, whereas those with CAC≥400 and ≥3 RFs had the highest all-cause fatality rate. Notably, individuals with no RF and CAC≥400 had a substantially higher mortality rate compared with individuals with ≥3 RFs in the absence of CAC (16.89 versus 2.72 per 1000 person-years). Conclusions-By highlighting that individuals without RFs but elevated CAC have a substantially higher event rates than those who have multiple RFs but no CAC, these findings challenge the exclusive use of traditional risk assessment algorithms for guiding the intensity of primary prevention therapies. (Circ Cardiovasc Imaging. 2012; 5:467-473).

Objectives To further study the interplay between smoking status, Coronary Artery Calcium (CAC) and all-cause mortality. Background Prior studies have not directly compared the relative prognostic impact of CAC in smokers versus non-smokers. In particular, while zero CAC is a known favorable prognostic-marker, whether smokers without CAC have as good a prognosis as non-smokers without CAC is unknown. Given computed tomography (CT) screening for lung cancer appears effective in smokers, the relative prognostic implications of visualizing any CAC versus no CAC on such screening also deserve study. Methods Our study cohort consisted of 44,042 asymptomatic individuals referred for non-contrast cardiac CT (age 54±11 years, 54% males). Subjects were followed for a mean of 5.6 years. The primary endpoint was all-cause mortality. Results Approximately 14% (n=6020) of subjects were active smokers at enrollment. There were 901 deaths (2.05%) overall, with increased mortality in smokers vs. non-smokers (4.3% vs. 1.7%, p<0.0001). Smoking remained a risk factor for mortality across increasing strata of CAC scores (1-100, 101-400, and >400). In multivariable analysis within these strata, we found mortality hazard ratios (HRs) of 3.8 (95% CI, 2.8-5.2), 3.5 (2.6-4.9), and 2.7 (2.1-3.5), respectively, in smokers compared to nonsmokers. At each stratum of elevated CAC score, mortality in smokers was consistently higher than mortality in non-smokers from the CAC stratum above. However, among the 19,898 individuals with CAC=0, the mortality HR for smokers without CAC was 3.6 (95% CI, 2.3-5.7), compared to non-smokers without CAC. Conclusion Smoking is a risk factor for death across the entire spectrum of subclinical coronary atherosclerosis. Smokers with any coronary calcification are at significantly increased future mortality risk than smokers without CAC. However, the absence of CAC may not be as useful a “negative risk factor” in active smokers; as this group has mortality rates similar to non-smokers with mild to moderate atherosclerosis.

Objectives: Recent research describes failed needle decompression in the anterior position. It has been hypothesized that a lateral approach may be more successful. The aim of this study was to identify the optimal site for needle decompression.Methods: A retrospective study was conducted of emergency department (ED) patients who underwent computed tomography (CT) of the chest as part of their evaluation for blunt trauma. A convenience sample of 159 patients was formed by reviewing consecutive scans of eligible patients. Six measurements from the skin surface to the pleural surface were made for each patient: anterior second intercostal space, lateral fourth intercostal space, and lateral fifth intercostal space on the left and right sides.Results: The distance from skin to pleura at the anterior second intercostal space averaged 46.3 mm on the right and 45.2 mm on the left. The distance at the midaxillary line in the fourth intercostal space was 63.7 mm on the right and 62

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OBJECTIVE The purpose of this study was to compare radiation dose and image quality of 320- and 64-MDCT angiography using prospective gating. MATERIALS AND METHODS One hundred seventy-four patients underwent 320-MDCT, and 95 patients underwent 64-MDCT. The scan parameters for 320-MDCT were 120 kVp, 400 mA, and gantry rotation of 350 milliseconds; the parameters for 64-MDCT were 120 kVp, 600 mA, and gantry rotation of 350 milliseconds. Effective dose (ED) was calculated from the dose-length product and a conversion factor (k = 0.014 mSv / mGy × cm). Two observers independently assessed image quality using a 3-point scale, where 3 denotes excellent quality and 1 denotes nondiagnostic quality, using a 16-segment model. Discrepancies were settled by consensus. RESULTS The ED was significantly lower in patients undergoing 320-MDCT angiography, with a median ED of 4.4 mSv (interquartile range [IQR], 3.4–6.2 mSv), compared with 64-MDCT angiography, with a median ED of 6.2 mSv (IQR, 5.5–6.9 mSv) (p = 0.0001). In patients with a heart rate of 65 beats/min or less (92%), the median radiation dose using 320-MDCT was 4.1 mSv (IQR, 3.2–6.1 mSv), and that for 64-MDCT angiography was 6.2 mSv (IQR, 5.8–6.9 mSv) (p = 0.0001). In patients with heart rate greater than 65 beats/min (8%), the median dose was higher with 320-MDCT (8.7 mSv; IQR, 5.9–14.3 mSv) than with 64-MDCT (5.8 mSv; IQR, 5.3–6.7 mSv) (p = 0.02). Segmental image quality was significantly better for 320-MDCT (excellent or good quality, 96.66%; nondiagnostic quality, 0.1%) than for 64-MDCT angiography (excellent or good quality, 86%; nondiagnostic quality, 3.33%) (all p < 0.0001). CONCLUSION Image quality was good for both 320- and 64-MDCT angiography. Overall radiation dose was significantly lower in 320-MDCT angiography when the heart rate was 65 beats/min or less. Every effort should be made to control heart rate to minimize radiation dose.

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