Atrial Cardiopathy in the Absence of Atrial Fibrillation Increases Risk of Ischemic Stroke, Incident Atrial Fibrillation, and Mortality and Improves Stroke Risk Prediction.

Background Atrial fibrillation (AF) is a major, often undetected, cardiac cause of stroke. Markers of atrial cardiopathy, including left atrial enlargement (LAE) or excessive atrial ectopy (EAE) increase the risk of AF and have shown associations with stroke. We sought to determine whether these markers improve stroke risk prediction beyond traditional vascular risk factors (eg CHA2DS2-VASc score). Methods and Results Retrospective longitudinal cohort of 32 454 consecutive community-dwelling adults aged ≥65 years referred for outpatient echocardiogram or Holter in Ontario, Canada (2010-2017). Moderate-severe LAE was defined as men >47 mm and women >43 mm, and EAE was defined as >30 APBs per hour. Cause-specific competing risks Cox proportional hazards used to estimate risk of ischemic stroke (primary), incident AF, and death (secondary). C-statistics, incremental discrimination improvement and net reclassification were used to compare CHA2DS2-VASc with LAE and EAE to CHA2DS2-VASc alone. Each 10 mm increase in left atrial diameter increased 2- and 5-year adjusted cause-specific stroke hazard almost 2-fold (LAE: 2-year hazard ratio (HR), 1.72; P=0.007; 5-year HR, 1.87; P<0.0001), while EAE showed no significant associations with stroke (2-year HR, 1.00; P=0.99; 5-year HR, 1.08, P=0.70), adjusting for incident AF. Stroke risk estimation improved significantly at 2 (C-statistics=0.68-0.75, P=0.008) and 5 years (C-statistics=0.70-0.76, P=0.003) with LAE and EAE. Conclusions LAE was independently associated with an increased risk of ischemic stroke in the absence of AF and both LAE and EAE improved stroke risk prediction. These findings have implications for stroke risk stratification, AF screening, and stroke prevention before the onset of AF.

Characterization of 3-Dimensional PET Systems for Accurate Quantification of Myocardial Blood Flow.

Three-dimensional (3D) mode imaging is the current standard for PET/CT systems. Dynamic imaging for quantification of myocardial blood flow with short-lived tracers, such as 82Rb-chloride, requires accuracy to be maintained over a wide range of isotope activities and scanner counting rates. We proposed new performance standard measurements to characterize the dynamic range of PET systems for accurate quantitative imaging. METHODS: 82Rb or 13N-ammonia (1,100-3,000 MBq) was injected into the heart wall insert of an anthropomorphic torso phantom. A decaying isotope scan was obtained over 5 half-lives on 9 different 3D PET/CT systems and 1 3D/2-dimensional PET-only system. Dynamic images (28 × 15 s) were reconstructed using iterative algorithms with all corrections enabled. Dynamic range was defined as the maximum activity in the myocardial wall with less than 10% bias, from which corresponding dead-time, counting rates, and/or injected activity limits were established for each scanner. Scatter correction residual bias was estimated as the maximum cavity blood-to-myocardium activity ratio. Image quality was assessed via the coefficient of variation measuring nonuniformity of the left ventricular myocardium activity distribution. RESULTS: Maximum recommended injected activity/body weight, peak dead-time correction factor, counting rates, and residual scatter bias for accurate cardiac myocardial blood flow imaging were 3-14 MBq/kg, 1.5-4.0, 22-64 Mcps singles and 4-14 Mcps prompt coincidence counting rates, and 2%-10% on the investigated scanners. Nonuniformity of the myocardial activity distribution varied from 3% to 16%. CONCLUSION: Accurate dynamic imaging is possible on the 10 3D PET systems if the maximum injected MBq/kg values are respected to limit peak dead-time losses during the bolus first-pass transit.

Competency in Quality: Defining the Scope and Nature of Quality Competencies for Radiation Oncology Residency Programs.

INTRODUCTION: Quality and safety in radiation treatment have garnered increasing attention in recent years. With the introduction of the CanMEDS 2015 Physician Competency Framework, incorporation of patient safety and quality improvement will be required across all seven established physician roles for radiation oncology residents. An appreciation for the competency areas relevant to radiation oncologists (ROs) in the quality and safety domain is thus needed to inform training in this area. METHODS: Semistructured interprofessional focus groups were held with ROs, medical physicists, and radiation therapists to ascertain the scope of quality principles required of newly certified ROs, to identify current teaching best practices, and to define required competencies in this area. Audio recordings were transcribed verbatim and data analyzed iteratively and coded using a constant comparison method. RESULTS: Three focus groups were held with 20 participants overall, and an average duration of 68 minutes (range 47-81 minutes). Participants found it difficult to define quality but noted that for residents it might encompass competencies in peer review, incident and change management, and quality culture. Although addressed in various ways in current residency programs, it was thought that explicit acknowledgment of relevant "nonmedical expert" quality competencies would ensure adequate attention in residency. CONCLUSIONS: Quality and safety are important concepts in radiation oncology, warranting attention in residency training to develop the knowledge, skills, and behaviour necessary in practice.

Clinical interpretation standards and quality assurance for the multicenter PET/CT trial rubidium-ARMI.

UNLABELLED: Rubidium-ARMI ((82)Rb as an Alternative Radiopharmaceutical for Myocardial Imaging) is a multicenter trial to evaluate the accuracy, outcomes, and cost-effectiveness of low-dose (82)Rb perfusion imaging using 3-dimensional (3D) PET/CT technology. Standardized imaging protocols are essential to ensure consistent interpretation. METHODS: Cardiac phantom qualifying scans were obtained at 7 recruiting centers. Low-dose (10 MBq/kg) rest and pharmacologic stress (82)Rb PET scans were obtained in 25 patients at each site. Summed stress scores, summed rest scores, and summed difference scores (SSS, SRS, and SDS [respectively] = SSS-SRS) were evaluated using 17-segment visual interpretation with a discretized color map. All scans were coread at the core lab (University of Ottawa Heart Institute) to assess agreement of scoring, clinical diagnosis, and image quality. Scoring differences greater than 3 underwent a third review to improve consensus. Scoring agreement was evaluated with intraclass correlation coefficient (ICC-r), concordance of clinical interpretation, and image quality using κ coefficient and percentage agreement. Patient (99m)Tc and (201)Tl SPECT scans (n = 25) from 2 centers were analyzed similarly for comparison to (82)Rb. RESULTS: Qualifying scores of SSS = 2, SDS = 2, were achieved uniformly at all imaging sites on 9 different 3D PET/CT scanners. Patient scores showed good agreement between core and recruiting sites: ICC-r = 0.92, 0.77 for SSS, SDS. Eighty-five and eighty-seven percent of SSS and SDS scores, respectively, had site-core differences of 3 or less. After consensus review, scoring agreement improved to ICC-r = 0.97, 0.96 for SSS, SDS (P < 0.05). The agreement of normal versus abnormal (SSS ≥ 4) and nonischemic versus ischemic (SDS ≥ 2) studies was excellent: ICC-r = 0.90 and 0.88. Overall interpretation showed excellent agreement, with a κ = 0.94. Image quality was perceived differently by the site versus core reviewers (90% vs. 76% good or better; P < 0.05). By comparison, scoring agreement of the SPECT scans was ICC-r = 0.82, 0.72 for SSS, SDS. Seventy-six and eighty-eight percent of SSS and SDS scores, respectively, had site-core differences of 3 or less. Consensus review again improved scoring agreement to ICC-r = 0.97, 0.90 for SSS, SDS (P < 0.05). CONCLUSION: (82)Rb myocardial perfusion imaging protocols were implemented with highly repeatable interpretation in centers using 3D PET/CT technology, through an effective standardization and quality assurance program. Site scoring of (82)Rb PET myocardial perfusion imaging scans was found to be in good agreement with core lab standards, suggesting that the data from these centers may be combined for analysis of the rubidium-ARMI endpoints.