A Novel Mathematical Model for Correcting the Physiologic Variance of Two-Dimensional Echocardiographic Measurements in Healthy Chinese Adults.

BACKGROUND: To facilitate differentiation between normal and abnormal values, it is necessary to correct echocardiographic measurements for physiologic variance induced by age, gender, and body size variables. METHODS: A total of 34 two-dimensional echocardiographic parameters were measured in 1,224 healthy Chinese adults with body mass index < 25.0 kg/m2. An optimized multivariate allometric model and scaling equations were first developed in 858 subjects (group A), and their reliability was then verified in the remaining 366 subjects (group B). The traditional single-variable isometric model in which parameters are linearly corrected by a single body size variable (height, weight, body mass index, or body surface area) was used for comparison. The success of correction was defined as the absence of significant correlations (r > 0.20, P < .05) between the corrected values and age or any body size variables, while maintaining high correlations (r > 0.80) between the corrected and uncorrected values. RESULTS: Before correction, all 34 parameters correlated significantly with one or more of the physiologic variables of age and body size and differed significantly between men and women on 29 parameters (85.3%) in both groups. The success rate of correction with the single-variable isometric model was only 11.0% (15 of 136 corrections due to four variable corrections used for each parameter), while use of the optimized multivariate allometric model successfully corrected all 34 parameters (100%) for physiologic variance induced by age and body size variables and eliminated the gender differences in 32 parameters (94.1%). A new set of reference values for corrected echocardiographic measurements independent of age, gender, and body size variables were established. CONCLUSIONS: The novel optimized multivariate allometric model developed in this study is superior to traditional the single-variable isometric model in the correction of echocardiographic parameters for physiologic effects of age, gender, and body size variables and thus should be encouraged in both scientific research and clinical practice.

Region of interest tracking in real-time myocardial contrast echocardiography.

The real-time myocardial contrast echocardiography (RT MCE) is a new echocardiography technology, which allows clinicians to noninvasively evaluate the perfusion of myocardial capillary of patients, using the quantitative analysis of RT MCE. But the accurate analysis requires tracking the position of region of interest (ROI) within the myocardial area, so as to compensate for the translation or rotation offsets, which are due to such uncontrollable factors as heart motion. We used diamond search method and Brox's coarse-to-fine warping optical flow technique for this ROI tracking problem. We validated our methods by comparing the quantitative analysis results of RT MCE using our methods with those using Lucas & Kanade's optical flow technique, which had been report to be accurate enough for this ROI tracking. We finally present some examples of animal experiment to show the effectiveness and the clinical application value of our ROI tracking methods.

Numerical methods and workstation for the quantitative analysis of real-time myocardial contrast echocardiography.

Using the quantitative analysis of real-time myocardial contrast echocardiography (RT MCE), clinicians can assess the myocardial perfusion of patients, noninvasively and accurately. We designed a workstation to assist clinicians to automatically implement the accurate analysis of RT MCE. The workstation can compute some hemodynamic parameters of myocardial microcirculation, e.g., myocardial blood flow, myocardial blood flow mean velocity, and myocardial blood volume. Our new methods involved in the quantitative analysis of RT MCE are summarized as follows. 1) A novel orthogonal array optimization (OAO) technique was proposed and used to estimate the unknown parameters of the nonlinear model to guarantee numerical stability. 2) Brox's coarse-to-fine warping optical flow technique was employed to automatically track the region of interest located inside the myocardial area to ensure the accuracy of the quantitative analysis. Finally, we illustrate some examples of clinical studies to indicate the effectiveness of the system and the reliability of the methods.

[Generation of a P19-alphaMHC-EGFP reporter line and cardiomyocyte differentiation].

OBJECTIVE: To generate a P19-alphaMHC-EGFP reporter line and induce cardiomyocyte differentiation of this reporter line. METHODS: The P19 cells were transfected with palphaMHC-EGFP, a P19-alphaMHC-EGFP reporter line was obtained after G418 selection and limited dilution of recombinant clones. The reporter line was induced to differentiate into cardiomyocytes which would beat and express green fluorescent protein. A comparison of cardiomyocyte differentiation rate and cTnI expression amount between the reporter line and the untransfected P19 cells was also performed. The ultrastructure was observed under transmission electron microscope. RESULTS: The ultrastructure characteristics indicated cardiomyocytes-like changes on induction day 10. The beating cardiomyocytes which express GFP appear in the seventh induction day. The cardiomyocyte differentiation rate and cTnI expression amount of P19-alphaMHC-EGFP reporter line were similar as those in untransfected P19 cells (P > 0.05). CONCLUSION: The P19-alphaMHC-EGFP reporter line is of great benefit for identifying and purifying cardiomyocytes from undifferentiated P19 cells without influencing the differentiation of P19 cells. This feature makes P19-alphaMHC-EGFP reporter line a promising cell source for clinical cardiomyocyte replacement therapy.

Quantification of transmural gradient of blood flow in myocardial ischemia with real-time myocardial contrast echocardiography and dipyridamole stress test.

Transmural redistribution of myocardial blood flow (MBF) is the earliest sign of myocardial ischemia. We aimed to evaluate the ability of real-time myocardial contrast echocardiography (MCE) combined with dipyridamole stress to quantify the transmural gradient of MBF during graded coronary stenosis. Real-time MCE was performed in 14 open-chest dogs at seven experimental stages: baseline; hyperemia induced by 6-min infusion of dipyridamole; 50%, 75% and 90% reduction of hyperemic flow after constriction in each stage for 10 min; reperfusion for 10 min; and subtotal occlusion of the left anterior descending coronary artery (LAD) for 90 min. We obtained MCE perfusion parameters from subendocardial (A-endo, beta-endo and A x beta-endo) and subepicardial (A-epi, beta-epi and A x beta-epi) layers of the ventricular septum and calculated their transmural gradients (A-EER, beta-EER and A x beta-EER) and systolic wall thickening (SWT). The sensitivity and specificity of each parameter for predicting 75% reduction of hyperemic flow, which was defined as mild myocardial ischemia, were derived by receiver operating characteristic (ROC) curve analysis. No transmural gradients were found at baseline; during maximal hyperemia and 50% reduction of hyperemic flow. beta-endo, A x beta-endo, beta-EER and A x beta-EER decreased significantly when the hyperemic flow was reduced by 75% or more. In contrast, SWT remained unchanged until the hyperemic flow was reduced by 90%. Among all parameters measured, beta-EER and A x beta-EER had the highest and SWT the lowest sensitivity and specificity in predicting mild myocardial ischemia. In conclusion, real-time MCE combined with dipyridamole stress allows for quantification of the transmural gradient of MBF. beta-EER and A x beta-EER are more sensitive than SWT and other MCE parameters in detecting mild myocardial ischemia.