| Backgrounds and Objective: Ischemia leads to abnormal myocardial metabolism and abnormal myocardial contractility in coronary heart disease(CHD). Normal ventricular myocardial contractility depends on sufficient blood perfusion. Myocardial contrast echocardiography(MCE) is a newly developed technique to quantify myocardial blood perfusion, displaying the replenishment process of microbubbles into myocardium after microbubbles being destroyed by a high energy pulse. The replenishment of contrast can be characterized by a time-intensity curve, which can be fitted to a monoexponential function: y=A×(1-eβt)+C. The plateau value(A) of the replenishment curve reflects the myocardial blood volume, and the slope(β) reflects the reappearance rate of microbubbles. The product of A×β therefore represents myocardial blood flow. Thus MCE could analyze quantitatively the microvascular blood perfusion in regions of interest in myocardium with specialist software.Coronary artery has powerful compensation capacity, so mild to moderate stenosed coronary vessel will supply adequate blood to maintain normal function at rest, so echocardiography may display no abnormality in LV wall motion and perfusion. Stress will induce an increase of myocardial consumption of oxygen, but in stenosed artery the blood supply could not increase accordingly, leading to ischemia in the victim territory, therefore abnormal wall motion and perfusion will be found in echocardiography. Dobutamine stress echocardiography(DSE) is one of the favorite stress methods, and is often applied to two dimensional echocardiography(2DE) and MCE, to evaluate the myocardial motion or blood perfusion in both stress and rest condition and further to evaluate the reserves, thus increases the technique’s sensitivity and accuracy, and has potential to anticipate prognosis.The aim of this study, according to the results of coronary angiocardiography(CAG), to assess the characteristics of myocardium perfusion at rest and stress in different degree of coronary artery stenosis by using MCE and DSE.Methods: The MCE was performed in 19 randomized CHD patients, under a different dose of dobutamine stress with continuously infused Sono Vue, acquired images of AP4, AP2, AP3 and SAX. Images were copied to Phillips QLAB 9.1 postprocess workstation. ROI software were used to analyze contrast images with 16 myocardium segments, and yielded the plateau value A(A reflects the myocardial blood volume), the slope β(β reflects the myocardial velocity) of the replenishment curve. Calculate the product of A×β(A×β represents myocardial blood flow). The myocardial perfusion reserve was determined as the ratio of the data of stress to that of the baseline, including A reserve, β reserve, A×β reserve. The myocardial segments were classified into 4 groups according to the stenosed coronary artery diagnosed by CAG. Group A(<50%); Group B(50%~69%); Group C(70%~89%); Group D(≥90%). Perfusion images of the segments were analyzed to obtain the refilling curves. Parameters of A, β and A×β at baseline and perk-dose stress state were compared among groups.Results: All patients successfully underwent the MCE and DSE examination and had no significant side effect.Compared among groups at baseline: no significant difference were found in perfusion parameters among group A, B and C at baseline( A, β and A×β, P>0.05). The all perfusion parameters were significantly lower in the group D than in other groups at baseline(A, β and A×β, P<0.001).Compared among groups after DSE: Compared with baseline, perfusion parameters of A, β and A×β of group A, B and C increased obviously(P<0.001). Perfusion parameters of group D did not changes significantly after dobutamine stress(P>0.05). All perfusion variables of the group A and B were higher significantly in the group C and D at dobutamine stress(P<0.001). All perfusion variables of the group C is higher compared with group D at dobutamine stress( P<0.001).Perfusion reserve variables compared among groups: The A reserve(2.02±0.20 d B) were higher in the group C than in other groups, the A reserve were significantly lower in the group D than the group A(1.11±0.09 d B)(P<0.001). β reserve and A×β reserve of group C and D(1.47±0.46 S-1 and 1.36±0.32 S-1; 2.13±0.51 d B/s and 1.56±0.28 d B/s) decreased significantly, compared with group A and B(2.68±1.21 S-1 and 2.14±0.89 S-1; 3.44±1.47 d B/s and 3.21±0.89 d B/s)(P<0.001). A reserve, β reserve and A×β reserve decreased obviously in group D, compared with other groups(P<0.001).Changes of improvements and improved rate were consistent. The improvement of β and A×β were significantly lower in group B, C and D than group A(P<0.001). The improvement of all variables(A, β and A×β) were significantly lower in group D than other groups after DSE.ROC curve analysis: β(0.43 S-1) and A×β(2.17 d B/s) at peak-dose DSE had best diagnostic value of coronary stenosis(≥70%), with sensitivity and specificity of β(76.9% and 85.5%) and A×β(87.1% and 81.0%), positive predicating value and negative predicting value of(84.14% and 78.73%) and of A×β(82.09% and 86.26%).Conclusion: Myocardial microcirculation perfusion could be analyzed qualitatively and quantitatively by MCE. MCE combined with DSE can be used as a sensitive method to indentify and stratify CAD, and to asses myocardial perfusion reserve. Myocardial perfusion parameters A×β and β had a good predicting value for diagnosis of coronary stenosis(≥70%). |
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