Search

Computed tomographic coronary artery calcium scanning enables cardiovascular risk stratification; however, exposing patients to high radiation levels is an ongoing concern. New-generation computed tomographic systems use lower radiation doses than older systems do. To quantify comparative doses of radiation exposure, we prospectively acquired images from 220 patients with use of a 64-slice GE LightSpeed VCT scanner (control group, n=110) and a 256-slice GE Revolution scanner (study group, n=110). The groups were matched for age, sex, and body mass index; statistical analysis included t tests and linear regression. The mean dose-length product was 21% lower in the study group than in the control group (60.2 ± 27 vs 75.9 ± 22.6 mGy·cm; P <0.001) and also in each body mass index subgroup. Similarly, the mean effective radiation dose was 21% lower in the study group (0.84 ± 0.38 vs 1.06 ± 0.32 mSv) and lower in each weight subgroup. After adjustment for sex, women in the study group had a lower dose-length product (50.4 ± 23.4 vs 64.7 ± 27.6 mGy·cm) than men did and received a lower effective dose (0.7 ± 0.32 vs 0.9 ± 0.38 mSv) (P=0.009). As body mass index and waist circumference increased, so did doses for both scanners. Our study group was exposed to radiation doses lower than the previously determined standard of 1 mSv, even after adjustment for body mass index and waist circumference. In 256-slice scanning for coronary artery calcium, radiation doses are now similar to those in lung cancer screening and mammography. [ABSTRACT FROM AUTHOR]

Coronary computed tomographic angiography (CCTA) with prospective electrocardiographic gating reduces radiation exposure, but its prognostic power for predicting cardiovascular risk in patients with suspected CAD has not been fully validated. To determine whether prospective gating performs as well as retrospective gating in this population, we compared these scan modes in patients undergoing 64-slice CCTA. From January 2009 through September 2011, 1,407 patients underwent CCTA; of these, 915 (mean age, 57.8 ± 13.5 yr; 54% male) had suspected coronary artery disease at the time of CCTA and were included in the study. Prospective gating was used in 195 (21%) and retrospective gating in 720 (79%). The mean follow-up duration was 2.4 ± 0.9 years. Overall, 390 patients (42.6%) had normal results on CCTA, 382 (41.7%) had nonobstructive coronary artery disease, and 143 (15.6%) had obstructive disease. Major adverse cardiac events occurred in 32 patients (3.5%): 11 cardiac deaths, 15 late revascularizations, and 6 nonfatal myocardial infarctions. Total event occurrences were similar in both groups (retrospective, 3.8%; prospective, 2.6%; P=0.42), as were the occurrences of each type of event. On adjusted multivariate analysis, nonobstructive (P=0.015) and obstructive (P <0.001) coronary artery disease were independently associated with major adverse cardiac events. Scan mode was not a predictor of outcome. The mean effective radiation dose was 4 ± 2 mSv for prospective compared with 12 ± 4 mSv for retrospective gating (P <0.01). The prognostic value of CCTA with prospective electrocardiographic gating compares favorably with that of retrospective gating, and it involves significantly less radiation exposure. [ABSTRACT FROM AUTHOR]

Implanted cardioverter-defibrillators can prevent sudden cardiac death in at-risk patients. In comparison with conventional transvenous systems, entirely subcutaneous implantable cardioverter-defibrillators have produced similar reductions in the rate of sudden cardiac death but with fewer sequelae. An infrequently reported drawback of subcutaneous devices, however, is the potential for generating attenuation artifact during nuclear myocardial perfusion imaging. We had concerns about potential attenuation artifact in a 65-year-old man with coronary artery disease but found that having positioned the pulse generator in the midaxillary zone avoided problems. [ABSTRACT FROM AUTHOR]