BackgroundThis study sought to prospectively and directly compare three cardiovascular magnetic resonance (CMR) viability parameters: inotropic reserve (IR) during low-dose dobutamine (LDD) administration, late gadolinium enhancement transmurality (LGE) and thickness of the non-contrast-enhanced myocardial rim surrounding the scar (RIM). These parameters were examined to evaluate their value as predictors of segmental left ventricular (LV) functional recovery in patients with LV systolic dysfunction undergoing surgical or percutaneous revascularisation. The second goal of the study was to determine the optimal LDD-CMR- and LGE-CMR-based predictor of significant (≥ 5%) LVEF improvement 6 months after revascularisation.MethodsIn 46 patients with chronic coronary artery disease (CAD) (63 ± 10 years of age, LVEF 35 ± 8%), wall motion and the above mentioned CMR parameters were evaluated before revascularisation. Wall motion and LGE were repeatedly assessed 6 months after revascularisation. Logistic regression analysis models were created using 333 dysfunctional segments at rest.ResultsAn LGE threshold value of 50% (LGE50) and a RIM threshold value of 4 mm (RIM4) produced the best sensitivities and specificities for predicting segmental recovery. IR was superior to LGE50 for predicting segmental recovery. When the areas under the ROC curves is compared, the combined viability prediction model (LGE50 + IR) was significantly superior to IR alone in all analysed sets of segments, except the segments with an LGE from 26% to 75% (p = 0.08). The RIM4 model was not superior to the LGE50 model. A myocardial segment was considered viable if it had no LGE or had any LGE and produced IR during LDD stimulation. ROC analysis demonstrated that ≥ 50% of viable segments from all dysfunctional and revascularised segments in a patient predict significant improvement in LVEF with a 69% sensitivity and 70% specificity (AUC 0.7, p = 0.05). The cut-off of ≥ 3 viable segments was a less useful predictor of significant global LV recovery.ConclusionsLDD-CMR is superior to LGE-CMR as a predictor of segmental recovery. The advantage is greatest in the segments with an LGE from 26% to 75%. The RIM cut-off value of 4 mm had no superiority over the LGE cut-off value of 50% in predicting the segmental recovery. Patients with ≥ 50% of viable segments from all dysfunctional and revascularised had a tendency to improve LVEF by ≥ 5% after revascularisation.
Strongly consistent and asymptotically normal estimators of the Hurst parameter of solutions of stochastic differential equations are proposed. The estimators are based on discrete observations of the underlying processes.
IntroductionRecently long range dependence (LRD) became one of the most researched phenomena in statistics. It appears in various applied fields and inspires new models to account for it. Stochastic differential equations (SDEs) are widely used to model continuous time processes. Within this framework, LRD is frequently modeled with the help of SDEs driven by a fractional Brownian motion (fBm). It is well known that the latter Gaussian process is governed by a single parameter H ∈ (0, 1) (called the Hurst index) and that values of H in (1/2, 1) correspond to LRD models. In applications, the estimation of H is a fundamental problem. Its solution depends on the theoretical structure of a model under consideration. Therefore, particular models usually deserve separate analysis. In this paper, we concentrate on the estimation of H under the assumption that an observable continuous time process (Xt) t∈[0,T ] satisfies SDE Xt = ξ + t
Strongly consistent and asymptotically normal estimators of the Hurst index and volatility parameters of solutions of stochastic differential equations with polynomial drift are proposed. The estimators are based on discrete observations of the underlying processes.
BackgroundA number of myocardial Doppler-derived velocity, strain myocardial imaging parameters (DMI) and speckle tracking imaging (STI) have been proposed for the quantification of myocardial ischemia during stress echocardiography. The purpose of the study was to identify the best single ultrasound quantitative parameter for prediction of significant coronary stenosis and compare it with visual assessment during dobutamine stress echocardiography (DSE).MethodsProspective analysis included data of 151 patients (age 61.8 ± 9.2) who underwent dobutamine stress echocardiography for known (n = 35) or suspected coronary artery disease (CAD) (n = 36) or symptomatic chest pain (n = 80), excluding patients with previous myocardial infarction. Systolic, post-systolic and diastolic velocities, strain and strain rate parameters were obtained at rest and at peak dobutamine challenge. Derivative markers as E'/A' ratio, post-systolic index and changes from rest to stress were calculated (98 parameters overall, predominantly longitudinal). Coronary angiography was chosen as reference method considering at least one stenosis ≥70% per patient as significant CAD. The predictive value of quantitative parameters and wall motion score index (WMSI) was obtained using logistic regression and ROC analysis.ResultsThe value of single parameters discriminated as independent predictors of CAD appeared to be modest (area under the curve [AUC] ranged from 0.63 to 0.72 for 16 PW-DMI, 12 CC-DMI and 12 STI markers), comparing to AUC of WMSI 0.88. Sensitivity, specificity and accuracy of visual DSE evaluation was 82.4% (95%CI 77.4%; 85.2%), 92.6% (95%CI 83.4%; 97.5%) and 86.0% (95%CI 79.5%; 89.6%), respectively, Youden index 0.75. Sensitivity, specificity and accuracy of single predictors ranged from 40.0% to 93.3% (95% CI 22.7%; 99.2%), from 34.2% to 88.7% (95% CI 25.6%; 94.1%) and from 45.8% to 80.0% (95% CI 37.5%; 87.2%) respectively, Youden index ranged from 0.20 to 0.52.ConclusionsMultiple single quantitative parameters showed limited predictive ability to identify significant coronary artery stenosis. Visual assessment of DSE appears to be more accurate than single velocity and strain/strain rate markers in the diagnosis of CAD.
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