Coronary CT radiation dose reduction strategies at an Australian Tertiary Care Center - improvements in radiation exposure through an evidence-based approach.

INTRODUCTION: Coronary CT Angiography (CCTA) is a rapidly increasing technique for coronary imaging; however, it exposes patients to ionising radiation. We examined the impact of dose reduction techniques using ECG-triggering, kVp/mAs reduction and high-pitch modes on radiation exposure in a large Australian tertiary CCTA service. METHODS: Data on acquisition modes and dose exposure were prospectively collected on all CCTA scans from November 2009 to March 2014 at an Australian tertiary care centre. A dose reduction algorithm was developed using published techniques and implemented with education of medical staff, radiographers and referrers. Associations of CCTA acquisition to radiation over time were analysed with multivariate regression. Specificity in positive CCTA was assessed by correlation with invasive coronary angiography. RESULTS: 3333 CCTAs were analysed. Mean radiation dose decreased from 8.4 mSv to 5.3, 4.4, 3.7, 2.9 and 2.8 mSv (P < 0.001) per year. Patient characteristics were unchanged. Dose reduction strategies using ECG-triggering, kVp/mAs reduction accounted for 91% of the decrease. High-pitch scanning reduced dose by an additional 9%. Lower dose was independently related to lower kVp, heart rate, tube current modulation, BMI, prospective triggering and high-pitch mode (P < 0.01). CCTA specificity remained unchanged despite dose reduction. CONCLUSION: Implementation of evidence-based CCTA dose reduction algorithm and staff education programme resulted in a 67% reduction in radiation exposure, while maintaining diagnostic specificity. This approach is widely applicable to clinical practice for the performance of CCTA.

Embolic stroke of undetermined source correlates to atrial fibrosis without atrial fibrillation.

OBJECTIVE: To examine the hypothesis that atrial fibrosis and associated atrial cardiopathy may be in the causal pathway of cardioembolic stroke independently of atrial fibrillation (AF) by comparing atrial fibrosis burden between patients with embolic stroke of undetermined source (ESUS), patients with AF, and healthy controls. METHODS: We used late-gadolinium-enhancement MRI to compare atrial fibrosis in 10 patients with ESUS against 10 controls (no stroke, no AF) and 10 patients with AF. Fibrosis was compared between groups, controlling for stroke risk factors. RESULTS: Mean age was 51 ± 15 years, and 43% of participants were female. Patients with ESUS had more atrial fibrosis than controls (16.8 ± 5.7% vs 10.6 ± 5.7%, p = 0.019) and similar fibrosis compared to patients with AF (17.8 ± 4.8%, p = 0.65). Odds ratios of ESUS per quartile of fibrosis were 3.22 (95% CI [CI] 1.11-9.32, p = 0.031, unadjusted) and 3.17 (95% CI 1.05-9.52, p = 0.041, CHA2DVASc score adjusted). Patients with >12% fibrosis had a higher percentage of ESUS (77.8% vs 27.3%, p = 0.02), and patients with >20% fibrosis had the highest proportion of ESUS (4 of 5). CONCLUSIONS: Patients with ESUS exhibit similar atrial fibrosis compared to patients with AF and more fibrosis than healthy controls. Fibrosis is associated with ESUS after controlling for stroke risk factors, supporting the hypothesis that fibrosis is in the causal pathway of cardioembolic stroke independently of AF. Prospective studies are needed to assess the role of anticoagulation in primary and secondary stroke prevention in patients with high atrial fibrosis.

Cleaning and Sterilization of Used Cardiac Implantable Electronic Devices With Process Validation: The Next Hurdle in Device Recycling.

OBJECTIVES: This study sought to develop a validated, reproducible sterilization protocol, which could be used in the reprocessing of cardiac implantable electronic devices (CIEDs). BACKGROUND: Access to cardiac CIED therapy in high-income and in low- and middle-income countries varies greatly. CIED reuse may reduce this disparity. METHODS: A cleaning and sterilization protocol was developed that includes washing CIEDs in an enzymatic detergent, screw cap and set screw replacement, brushing, inspection, and sterilization in ethylene oxide. Validation testing was performed to assure compliance with accepted standards. RESULTS: With cleaning, the total mean bioburden for each of 3 batches of 10 randomly chosen devices was reduced from 754 to 10.1 colony-forming units. After sterilization with ethylene oxide, with 3 half-cycle and 3 full-cycle processes, none of the 90 biological indicator testers exhibited growth after 7 days. Through cleaning and sterilization, protein and hemoglobin concentrations were reduced from 99.2 to 1.42 µg/cm2 and from 21.4 to 1.03 µg/cm2, respectively. Mean total organic carbon residual was 1.44 parts per million (range 0.36 to 2.9 parts per million). Endotoxin concentration was not detectable at the threshold of <0.03 endotoxin units/ml or <3.0 endotoxin units/device. Cytotoxicity and intracutaneous reactivity tests met the standards set by the Association for Advancement of Medical Instrumentation and the International Organization for Standardization. CONCLUSIONS: CIEDs can be cleaned and sterilized according to a standardized protocol achieving a 12-log reduction of inoculated product, resulting in sterility assurance level of 10-6.