Influence of symptomatic status on the prevalence of obstructive coronary artery disease in patients with zero calcium score
ABSTRACT CAC has been used to predict obstructive CAD on invasive coronary angiography. However, it is unknown how the prevalence of obstructive CAD in patients with zero CAC is influenced by the presence or absence of chest pain.
210 consecutive patients referred for CAC and CorCTA were included in this analysis. Chest pain was defined based on the Diamond-Forrester classification.
134 patients (64%) were symptomatic and 76 (36%) were asymptomatic. Seventy patients had negative (33%); 140 had positive CAC (67%). In the symptomatic group with zero CAC, 8.2% (4/49) had an obstructive, non-calcified plaque; of these, 3 were <45 years. Sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of CAC in the symptomatic population for detection of obstructive CAD were 0.86 (0.66-0.95), 0.42 (0.33-0.52), 0.28 (0.19-0.39) and 0.92 (0.8-0.97), respectively (p=0.007). No asymptomatic subject with zero CAC had obstructive CAD. Sensitivity, specificity, PPV and NPV of CAC in the asymptomatic population for detection of obstructive CAD were 1.00 (0.66-1.00), 0.32 (0.21-0.45), 0.18 (0.10-0.31) and 1.00 (0.80-1.00), respectively (p=0.05). Optimal cut-points to predict obstructive CAD and AUC were significantly different in symptomatic versus asymptomatic subjects (91 and 0.78 vs. 296 and 0.89, respectively) (p=0.005). CAC performed much better in symptomatic patients >45 years compared to younger patients to exclude obstructive CAD (AUC: 0.83 vs. 0.5, p<0.001; NPV=0.98).
CAC is better in asymptomatic compared to symptomatic subjects, especially in patients <age 45, to exclude obstructive CAD. Symptoms and age should be considered when interpreting CAC.
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ABSTRACT: The convergence of statistical (random) search for the minimization of an arbitrary function Q(w) is treated. It is shown that random search can be regarded as a gradient algorithm in the q-domain. Using this gradient to define the minimum of the function, the convergence is discussed at length-including convergence WP1, convergence in the mean and ¿-optimality. The proof of convergence is based upon the theorems of convergence of random processes of Braverman and Rozonoer. The relationship between random search and order statistics is explained. Finally, emphasis is put on the applicability of the theorems for the design of hierarchical search systems and statistical search with a mixture.
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ABSTRACT: In order to maintain a high quality output voltage, conventional UPS systems use complex filters with large passive components. To overcome this drawback, real-time feedback control schemes have been investigated. However, these techniques require a high inverter switching frequency to dynamically adapt to changing load conditions and reduce harmonics of the output voltage, thereby rendering the system inadequate for high power applications. This paper presents real-time digital signal processor (DSP) control of a UPS system feeding nonlinear loads to provide sinusoidal inverter output voltage. The control scheme is composed of an RMS voltage regulator, the load current harmonics regulator for the cancellation of output voltage harmonics and the output voltage harmonics regulator for system stability. The controller employs a Texas Instruments TMS320C40GFL50 DSPTelecommunications Energy Conference, 1997. INTELEC 97., 19th International; 11/1997
Conference Paper: Analysis of the impact of distributed generation on automatic reclosingPower Systems Conference & Exposition; 01/2004