The feasibility and accuracy of evaluating lipid management performance metrics using an electronic health record.

BACKGROUND: Over the past decade, electronic health records (EHRs) have emerged as a potential tool to assess quality of care; however, the feasibility and accuracy of EHRs to assess adherence to lipid management performance measures have not been evaluated. METHODS: We created a retrospective cohort of 3779 patients with coronary artery disease who were followed up in a cardiology clinic at an academic medical center using an EHR database. Of these 3779 patients, 300 randomly-selected charts were reviewed to identify reasons for failure to adhere to lipid management performance measures. RESULTS: Based on the EHR, a low-density lipoprotein cholesterol measurement was obtained in 73% of patients within the past 3 years; of which, 34% had low-density lipoprotein cholesterol levels ≥100 mg/dL and statin therapy had been prescribed in 88%. Manual chart review revealed that many of these apparent failures were actually false positives, due to inaccurate capture of indications and contraindications to lipid measurement and statin prescription, patient/provider treatment preferences, and external data sources. CONCLUSIONS: While it is possible to monitor adherence to lipid management performance measures using an EHR, the accuracy of this assessment is currently limited and may underestimate provider quality of care.

Does access modality matter? Evaluation of validity in reusing clinical care data.

Self-service database portals may improve access to institutional data resources for clinical research or quality improvement, but questions remain about the validity of this approach. We tested the accuracy of data extracted from a clinical data repository using a self-service portal by comparing three approaches to measuring medication use among patients with coronary disease: (1) automated extraction using a portal, (2) extraction by an experienced data architect, and (3) manual chart abstraction. Outcomes included medications and diagnoses (e.g., myocardial infarction, heart failure). Charts were manually reviewed for 200 patients. Using matched criteria, self-service query identified 7327 of 7358 patients identified by the data analyst. For patients in both cohorts, agreement rates ranged from 0.99 for demographic data to 0.94 for laboratory data. Based on chart review, the self-service portal and the analyst had similar sensitivities and specificities for comorbid diagnoses and statin use.

Critical scale of propagation influences dynamics of waves in a model of excitable medium.

BACKGROUND: Duration and speed of propagation of the pulse are essential factors for stability of excitation waves. We explore the propagation of excitation waves resulting from periodic stimulation of an excitable cable to determine the minimal stable pulse duration in a rate-dependent modification of a Chernyak-Starobin-Cohen reaction-diffusion model. RESULTS: Various pacing rate dependent features of wave propagation were studied computationally and analytically. We demonstrated that the complexity of responses to stimulation and evolution of these responses from stable propagation to propagation block and alternans was determined by the proximity between the minimal level of the recovery variable and the critical excitation threshold for a stable solitary pulse. CONCLUSION: These results suggest that critical propagation of excitation waves determines conditions for transition to unstable rhythms in a way similar to unstable cardiac rhythms. Established conditions were suitably accurate regardless of rate dependent features and the magnitude of the slopes of restitution curves.

Identifying coronary artery flow reduction and ischemia using quasistationary QT/RR-interval hysteresis measurements.

Because myocardial ischemia induces QT/RR hysteresis, a correlation was hypothesized to exist between the extent of myocardial flow reduction and the magnitude of QT/RR hysteresis. Graded reductions in regional myocardial perfusion in the distribution of the left anterior descending coronary artery in open-chest pigs were used to model 1-vessel coronary artery disease. At each reduced level of left anterior descending coronary artery flow, the heart was electrically paced at progressively higher and lower rates between an initial control and maximum heart rate values. Digitized surface and intramyocardial electrograms and aortic pressure were used to measure QT/RR hysteresis, QT-interval adaptation, ST- and TQ-segment depression, and cardiac contractility. Intraexperimental blood samples were analyzed to assess inflammatory response (interleukin 6), oxidative stress (protein carbonyls), and myocyte injury (creatine kinase). Higher values of QT/RR hysteresis correlated with the severity of ischemia as assessed by TQ-segment depression in intramyocardial electrograms (P = .002). Lower flow rates were strongly associated with higher values of QT/RR hysteresis and slower QT-interval adaptation (P or= .02). Significant increases in systemic measures of inflammation, oxidative stress, and cardiac myocyte injury and major decrease in cardiac contractility preceded the most severe stages of flow reduction (30% and 20% of normal flow). We determined QT/RR hysteresis index thresholds corresponding to these mechanical and immunochemical responses. QT/RR hysteresis is a strong indicator of reduced myocardial perfusion and may provide information for noninvasive assessment of mechanical and immunochemical changes associated with early stages of coronary artery disease.