Diagnosis of recent myocardial infarction with quantitative backscatter imaging: preliminary studies

Acute myocardial ischemia and chronic myocardial infarction may be recognized with ultrasound tissue characterization techniques because of myocardial acoustic changes caused by reduced perfusion and/or collagen deposition. Our purpose was to study the acoustic properties of recent myocardial infarction when the predominating pathologic finding was myocardial edema and leukocytic infiltration. We used a new quantitative backscatter imaging system to study 18 patients 9 +/- 5 days after myocardial infarction (eight patients with anteroseptal myocardial infarction and 10 with inferior myocardial infarction) and 20 normal subjects. The cyclic variation of relative integrated backscatter (end-diastolic minus end-systolic) was calculated from on-line measurements. Standard parasternal long- and short-axis and apical four- and two-chamber views were obtained. In the anteroseptal myocardial infarction group, the cyclic variation of relative integrated backscatter was lower in the septum (1.5 +/- 1.6 dB) than in the posteroinferior wall (3.2 +/- 1.2 dB); however, the sample size of only three patients (of eight patients imaged) in the latter group prevented statistical comparison. The cyclic variation of relative integrated backscatter in the infarcted septum was less than the measurement obtained in the septum of the control group (4.3 +/- 2.4 dB, p less than 0.05). In the inferior infarction group, the cyclic variation of integrated backscatter in the posteroinferior wall (1.8 +/- 1.7 dB) was not significantly different from the measurement obtained in the septum (3.7 +/- 3.6 dB); however, the cyclic variation in the posteroinferior wall was significantly less than that obtained in the control group posteroinferior wall (5.7 +/- 1.7 dB, p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)     

Cyclic variation of ultrasound backscatter in normal myocardium is view dependent: clinical studies with a real-time backscatter imaging system

Real-time ultrasound backscatter imaging is a new method of evaluating relative integrated backscatter in a clinically applicable manner. The potential clinical utility of real-time backscatter imaging of diseased tissue depends on recognition of normal variations in cyclic backscatter when measured from different echocardiographic image orientations. The view dependence of cyclic backscatter variation was studied in normal human volunteers. In twenty normal male subjects (mean age 28 +/- 5 years) cyclic variation in integrated backscatter (diastolic minus systolic backscatter) was assessed in multiple left ventricular regions with four standard two-dimensional echocardiographic views (parasternal long-axis and short-axis views, and apical two-chamber and four-chamber views). M-mode backscatter imaging was performed from the standard parasternal long-axis view. Cyclic variation in backscatter was present in the septum only when imaged from the parasternal long-axis view (2.7 +/- 3.1 [standard deviation] decibels [dB], p less than 0.01 for diastole versus systole). The posterior wall of the left ventricle demonstrated cyclic variation of integrated backscatter when imaged from both the parasternal long-axis (4.6 +/- 1.6 dB, p less than 0.01) and short-axis views (2.8 +/- 2.2 dB, p less than 0.01). Cyclic variation in integrated backscatter was not demonstrated in inferoseptal, septal, or lateral wall regions when imaged from the parasternal short-axis view. The apical views did not demonstrate cyclic variation in integrated backscatter in any of the segments studied.(ABSTRACT TRUNCATED AT 250 WORDS)     

Ultrasonic integrated backscatter two-dimensional imaging: evaluation of M-mode guided acquisition and immediate analysis in 55 consecutive patients

We have shown previously that cardiac cycle-dependent integrated backscatter characterizes the physical state of myocardium in patients with ischemic heart disease and cardiomyopathy. In the present study the clinical applicability of M-mode guided two-dimensional integrated backscatter imaging was defined in evaluation of 55 nonselected patients. The mean amplitude of cyclic variation of integrated backscatter in normal segments (long-axis view) was as follows: basal septum, 4.2 +/- 1.3 dB (mean +/- SD; n = 27), mid-septum, 4.5 +/- 1.0 dB (n = 26), basal posterior, 4.8 +/- 1.0 dB (n = 30), and mid-posterior, 4.8 +/- 1.2 decibels (n = 27). The respective mean delay values (R wave to nadir) were as follows: 0.89 +/- 0.09, 0.84 +/- 0.09, 0.86 +/- 0.09, and 0.85 +/- 0.12. At least one cardiac cycle could be analyzed fully in 62% of patients. Limitations included technically difficult two-dimensional echocardiography, inadequate M-line orientation, technically remediable errors, or poor quality integrated backscatter images. In abnormal segments (n = 13) cyclic variation was reduced and delay was prolonged (1.2 +/- 1.1 dB and 1.21 +/- 1.1, respectively). Intraobserver and interobserver variability for amplitude measurements were modest, with respective correlation coefficients of r = 0.93; r = 0.72. The findings demonstrate that M-mode--assisted integrated backscatter is a practical approach for characterization of regional myocardial properties promptly and at the bedside in a large portion of patients with cardiac disease.     

Differentiation of normal and ischemic right ventricular myocardium with quantitative two-dimensional integrated backscatter imaging.

We have previously shown that ultrasonic tissue characterization with two-dimensional (2D) guided M-Mode acquisition of integrated backscatter (IB) identifies ischemic and infarcted myocardium. However, there is no information regarding the applicability of IB in assessment of right ventricular (RV) myocardial acoustic properties. Thus, we performed IB imaging of the RV in a group of 45 consecutive patients and were successful in 16, all of whom had normal RV wall motion. This group was compared to 8 additional patients studied acutely with clinical criteria of RV infarction. Real-time IB from RV was obtained from parasternal long axis or subcostal views. Diastolic-to-systolic cyclic variation of IB in normals was 4.8 +/- 0.9 dB (+/- SD). No significant difference was observed between parasternal and subcostal views (5.2 +/- 0.8 and 4.5 +/- 0.9 dB). Mean value of delay (R wave to nadir of backscatter normalized to the electrocardiographic Q-T interval) was 0.85 +/- 0.07. Patients with RV infarction had significantly lower values averaging 3.2 +/- 0.8 dB (p less than 0.001 vs. normals); cyclic variation of IB was present in all despite severe hypokinesis in 4/8. Mean value of normalized delay was 0.80 +/- 0.04 and was not different from normals. Thus, tissue characterization provides quantitative information regarding RV myocardial structure and function. Preservation of IB cyclic variation in patients with RV infarction suggests residual RV myocardial viability.     

Dependence of "apparent" magnitude on the time delay of cyclic variation of myocardial backscatter.

The goal of this study was to determine if the "apparent" magnitude of the cyclic variation, defined as the difference between the values of integrated backscatter at end-diastole and end-systole, was dependent on the corresponding time delay. We measured the cyclic variation in four myocardial segments of the parasternal short-axis view in 23 healthy subjects. The "apparent" magnitude, actual magnitude, and time delay were compared for each segment. Measured time delays were: 2.22+/-0.71 (lateral wall); 1.65+/-0.66 (inferior septum); and approximately 1.0 for the anterior septum and posterior wall. Segments exhibiting large time delays (> 1.0) resulted in a reversal in sign of the "apparent" magnitude of cyclic variation in one instance, and underestimated the true magnitude in both cases. Thus, estimates of the "apparent" magnitude of the cyclic variation are dependent on the associated time delay, whereas a properly defined magnitude is not.     

Detection of remote myocardial infarction with quantitative real-time ultrasonic characterization

We have previously shown that the intrinsic properties of myocardium can be characterized quantitatively by the assessment of ultrasonic integrated backscatter. In this study we utilized a novel, real-time, two-dimensional system capable of quantitative integrated backscatter imaging to determine whether zones of remote myocardial infarction in dogs could be delineated definitively by ultrasonic tissue characterization. Detection of such zones in patients is needed as a basis for management decisions related to thrombolysis, angioplasty, and coronary surgery. Integrated backscatter was measured through the closed chest from 25 myocardial sites. Zones of infarction exhibited time-averaged integrated backscatter values approximately 10 dB (9.5 +/- 0.5 dB, standard error of the mean) greater than those in normal regions (p less than 0.001). In addition, the physiologic cardiac cycle--dependent variation of integrated backscatter was blunted significantly in zones of infarction [0.8 dB +/- 0.3 vs. 3.8 +/- 0.6 (p less than 0.01) for normal regions]. Ultrasonic results matched the histopathologic features assessed directly. Thus quantitative ultrasonic tissue characterization can differentiate infarcted tissue from normal myocardium and offers promise for quantitative detection of histopathology in vivo.     

Role of ultrasonic tissue characterization to distinguish reversible from irreversible myocardial injury.

Tissue characterization reflects structural and functional integrity of tissues. Inasmuch as reversible ischemia causes no structural damage and irreversible ischemia results in persistent structural myocardial damage, we postulated that ultrasonic tissue characterization can distinguish the two types of injuries. Anesthetized open chest dogs underwent 15 minutes (group 1, n = 5) and 90 minutes (group 2, n = 8) of acute total occlusion of the left anterior descending coronary artery, followed by 3 hours of reperfusion. Myocardial ischemia-infarction was confirmed with segment shortening, electronmicroscopic examination, and triphenyl tetrazolium chloride staining. Integrated backscatter Rayleigh 5 (IBR5), a measure of ultrasonic backscatter, and Fourier coefficient of amplitude modulation (FAM), an index of cardiac cycle dependent variation in backscatter, were measured at baseline, during ischemia, and after reperfusion. Group 1 (reversible ischemia) showed an increase in IBR5 from -48 +/- 1.2 dB at control to -45 +/- 1.0 dB (p less than 0.01) during ischemia, which returned to baseline after reperfusion (-47 +/- 1.3 dB). FAM was blunted during ischemia (6.2 +/- 1.0 dB during control versus 1.2 +/- 1.0 dB during ischemia, p less than 0.01) and recovered completely during reperfusion. Segment shortening was abolished during ischemia (18% +/- 3% during control versus -12% +/- 5% during ischemia, p less than 0.01) and recovered partially during reperfusion (4% +/- 5%). The group 2 animals with irreversible myocardial injury showed an increase in IBR5, from -49 +/- 1.2 dB during control to -44 +/- 1.0 dB during ischemia (p less than 0.01) and paradoxical bulging of the ischemic region (17% +/- 3% to -7% +/- 3%, p less than 0.01) during ischemia.(ABSTRACT TRUNCATED AT 250 WORDS)     

Cardiac cycle-dependent variation of integrated backscatter is not distorted by abnormal myocardial wall motion in human subjects with paradoxical septal motion

To define the dependence of cardiac cycle-dependent variation of integrated backscatter on regional myocardial wall motion, 8 children mean age 10.6 +/- 1.3 y with congenital cardiac lesions associated with paradoxical septal motion were studied (study group). Six healthy children mean age 9.0 +/- 0.3 y with no history of cardiac disease served as controls (control group). Subjects in the study group had paradoxical septal motion but normal septal wall thickening detected by conventional two-dimensional and M-mode echocardiography. The control group had normal septal motion evident by conventional echocardiographic criteria. The percentage of systolic septal thickening was 46 +/- 4.5% and 42 +/- 5.9% in the study and control groups (p = NS). Cyclic variation was measured in parasternal long-axis views from several septal sites in each subject. Mean values of the magnitude of cyclic variation from independent septal sites were averaged to yield a regional average value for each subject. The average regional magnitude of cyclic variation was 8.3 +/- 1.0 dB and 5.7 +/- 0.4 dB in the study and control groups (p = NS). The results indicate that the measurement of cyclic variation of integrated backscatter is not distorted by altered regional wall motion, and that it reflects intrinsic contractile function.     

Alterations in ultrasonic backscatter during intra-aortic balloon counterpulsation support in patients with acute myocardial infarction

Alterations of ultrasonic backscatter parameters have been evident in humans with myocardial infarction or ischemia. The backscatter variability could be restored in ischemic or stunned myocardium after reperfusion. The aims of this study were to determinate changes in regional myocardial ultrasonic backscatter during intra-aortic balloon counterpulsation (IABP) support in patients with acute myocardial infarction (AMI), and to evaluate whether backscatter imaging could be a functional guide of IABP support. A total of 9 patients with AMI were investigated during IABP support with a two-dimensional (2-D) ultrasonic backscatter imaging approach for parasternal short-axis view. Coronary angiography was performed in 6 of the 9 patients. A total of 21 vessel territories were studied in different modes of IABP support: 1:1, 1:2 and standby. Restoration of cyclic variation of backscatter after IABP support was demonstrated in 10 vessel territories. Failure of restoration of cyclic variation of backscatter after IABP support was noted in 6 vessel territories with severe coronary lesions (total or nearly total occlusion) or scar tissue. No changes of the ultrasonic backscatter were found in nonischemic vessel territories with patent coronary arteries or TIMI III coronary flow. In addition, the wall motion score did not change significantly with different IABP support. These results suggest that IABP could restore the cyclic variation of backscatter in ischemic myocardium. Myocardial anisotropy may play an influential role in the alterations of ultrasonic backscatter. We propose that ultrasonic backscatter could be a noninvasively functional guide of IABP use in patients with AMI.     

Ultrasonic myocardial tissue characterization in the operating room: initial results using transesophageal echocardiography.

Ultrasonic tissue characterization provides quantitative assessment of myocardial function and viability. We have previously reported that normal myocardium is characterized by a diastolic-to-systolic cyclic variation of integrated backscatter (IB), whereas ischemic myocardium exhibits blunting of this pattern. To define the applicability of this measurement to characterize the left ventricular myocardium in the operating room, we studied 26 consecutive patients undergoing open heart surgery (12 coronary artery bypass graft, 13 valvular, 1 other) with 5 MHz transesophageal echocardiography. Images of the left ventricle were obtained in the short-axis plane (papillary muscle level) before cardiopulmonary bypass. M-mode acquisition of myocardial IB was attempted from the anterior and inferior segments in each patient. The cyclic variation of IB was measured in at least two consecutive cycles in addition to a qualitative assessment of wall motion. Quantitative measurement of IB was possible in 39/52 (75%) myocardial segments. Cyclic variation of IB averaged 5.7 +/- 1.4 dB (SD) in segments with normal wall motion (n = 25); no difference was noted in the cyclic variation of IB among anterior or inferior walls. Hypokinetic segments demonstrated significant reduction of the cyclic variation (3.8 +/- 1.8 dB; p less than 0.001). Difficulty with obtaining myocardial IB was related to near-field artifact or lateral displacement of the left ventricular wall during systole. Transesophageal echocardiography holds promise for the evaluation of myocardial function and its preservation during cardiac surgery.     

心脏超声组织定征研究:急性缺血与再灌注过程中心肌组织回声强度变化及其与心肌收缩力的关系

目的：观察心肌组织在急性缺血与再灌注过程中回声强度的变化及其与心肌收缩力的关系。方法：用自制ＤＦＹ－Ⅰ型超声图像定量分析诊断仪对６只犬正常、缺血及再灌注过程中超声心动图局部心肌组织回声强度（ｄＢ值）及其心动周期变化幅度（ＣＶｄＢ）进行了动态定量分析,并同时测定室壁厚度和收缩期增厚率的变化。结果：冠脉阻断后２０分钟,缺血区ｄＢ值增高（Ｐ＜０．０１）,ＣＶｄＢ值降低（Ｐ＜０．０１）。再灌注后１０分钟,ｄＢ值即恢复正常（Ｐ＝ＮＳ）,ＣＶｄＢ值的恢复过程则相对缓慢,并与室壁收缩期增厚率的恢复同步且密切相关（ｒ＝０．８１,Ｐ＜０．０１）。结论：急性缺血时,心肌组织ｄＢ值增高,ＣＶｄＢ值降低;ＣＶｄＢ值与心肌组织收缩力的改变密切相关;通过定量分析超声心动图心肌组织回声强度变化,不但能区别正常与缺血心肌,同时可评估心肌组织的收缩功能。与国外学者所测背向散射积分一致。     

Ultrasonic myocardial integrated backscatter and myocardial wall thickness in animal experiments

The purpose of this study was to distinguish between normal and ischemic myocardium using ultrasonic integrated backscatter (IB) measurements and to relate IB with myocardial wall thickness. IB was measured in 9 open-chested Yorkshire pigs (24-30 kg) before, after 30 minutes of partial occlusion of the proximal left anterior descending coronary artery (LADCA), and after 60 minutes of subsequent reperfusion. The ultrasound transducer (4 MHz) was sutured onto the epicardial surface perfused by the LADCA. IB measurements were made with a repetition rate of 50 times per heart rate simultaneously with a left ventricular pressure signal. Myocardial wall thickness was measured off-line. The measurements of integrated backscatter, left ventricular pressure and wall thickness were based on mean values of ten subsequent cardiac cycles. End-systolic IB measurements were 5.3 dB higher during occlusion as compared to the reference measurements (7.1 +/- 3.2 dB versus 1.8 +/- 2.6 dB; p = 0.002). No statistically significant differences were found in end-systolic IB measurements. End-systolic wall thickness was 5 mm smaller during occlusion as compared to the reference measurements (7.2 +/- 1.4 mm versus 12.2 +/- 1.2 mm; p less than 0.001). Simple linear regression analysis showed a statistically significant inverse relationship between IB measurements and wall thickness in 21 out of the 23 sequences in which wall thickness could be measured. End-systolic IB measurements are favourable to distinguish acute ischemic myocardium from normal myocardium. There is a distinct inverse relationship between IB and myocardial wall thickness.     

Sensitive detection of myocardial viability in chronic coronary artery disease by ultrasonic integrated backscatter analysis.

BACKGROUND: Myocardial viability is not synonymous with contractile reserve and identifiable in a significant percentage of dysfunctional myocardial segments without contractile reserve. The usefulness of ultrasonic tissue characterization by the phase-corrected magnitude of cyclic variation of integrated backscatter (MVIB) in chronic coronary artery disease is not fully validated. Thus, whether MVIB predominantly reflects the contractile reserve or myocardial viability of chronically dysfunctional myocardium was determined. METHODS: The MVIB of severely dysfunctional interventricular septum or posterior wall was measured in 34 consecutive patients with previous myocardial infarction. Dobutamine stress echocardiography and fluorine-18 fluorodeoxyglucose positron emission tomography were used as the standards of contractile reserve and myocardial viability, respectively. RESULTS: Among 44 dysfunctional segments, only 15 were judged as having contractile reserve and 29 were judged as not by dobutamine stress echocardiography, whereas 26 segments showed myocardial viability using fluorine-18 fluorodeoxyglucose positron emission tomography and 18 did not. MVIB was greater in segments with than in those without contractile reserve (4.7 +/- 2.2 vs -1.4 +/- 4.9 dB, P < .0001), but there was considerable overlap between the groups. On the other hand, MVIB of segments with and without myocardial viability (4.1 +/- 2.6 vs -4.3 +/- 3.3 dB, P < .0001) was distinctly different and predicted myocardial viability with a sensitivity of 92% and a specificity of 94%. CONCLUSIONS: For patients with chronic coronary artery disease, MVIB better reflects myocardial viability than it does contractile reserve. Ultrasonic tissue characterization, in concordance with fluorine-18 fluorodeoxyglucose positron emission tomography, is a sensitive method for detecting myocardial viability.     

Potential relationships among myocardial stiffness, the measured level of myocardial backscatter ("image brightness"), and the magnitude of the systematic variation of backscatter (cyclic variation) over the heart cycle.

BACKGROUND: In a number of recently published studies comparing measurements from patients with those from control subjects, a decreased magnitude of the systematic variation of backscattered energy over the heart cycle (cyclic variation) is accompanied by an increased level of overall myocardial backscatter (calibrated myocardial image brightness) when measured at a specific phase of the heart cycle (eg, end systole or end diastole). The goal of this study was to investigate whether this observation is consistent with predictions based on a model of the mechanisms of cyclic variation incorporating changes in relative intracellular and extracellular acoustic impedance over the heart cycle. METHODS: A previously described 3-component Maxwell-type model of muscle mechanics representing cardiac cell mechanical behavior was utilized to predict the systematic variation in the relative acoustic impedance differences between intracellular and extracellular elastic properties over the heart cycle and hence the observed magnitude of cyclic variation and overall myocardial scattering level. Predictions were obtained for a series of specific values of relative intracellular and extracellular acoustic impedance. RESULTS: Results indicate that the predicted magnitude of cyclic variation can be directly related to the overall myocardial backscatter level. For example, specific changes in the acoustic impedance (stiffness properties) of the extracellular matrix without any change in the intracellular acoustic impedance result in predicted values of -43.5 dB, -38.5 dB, and -33.5 dB for end-diastolic myocardial backscatter levels with corresponding values of 5.0 dB, 2.5 dB, and 1.3 dB for the predicted magnitude of cyclic variation, respectively. CONCLUSION: This study suggests that observed decreases in the magnitude of cyclic variation with concomitant increases in the measured overall myocardial backscatter level are consistent with predictions from a model based on the relative acoustic impedance differences between intracellular and extracellular elastic properties over the heart cycle. These results suggest that ultrasonic backscatter measurements may provide a noninvasive approach for assessing some relationships among myocardial stiffness, degree of fibrosis, and contractile performance.     

Myocardial tissue characterization in heart failure by real-time integrated backscatter.

OBJECTIVE: Differentiation between normal and abnormal physical state of the myocardium, not possible with conventional echocardiography, so far could be done with integrated backscatter (IBS) as a research tool only. METHODS: This study investigates myocardial texture analysis with new commercially available real time IBS in 12 normal individuals and in 18 patients with severe left ventricular dysfunction due to coronary artery disease (CAD) in 8 and dilated cardiomyopathy (DCM) in 10 patients. Analysis of IBS amplitude and cyclic variation (dB) in the parasternal long and short axis view of the septum and the posterior wall were measured and corrected with IBS curve of the blood to get absolute values. RESULTS: Compared to normal individuals patients with left ventricular dysfunction had a reduced myocardial cyclic variation (P<0.0001), which correlated to regional systolic wall thickening (r=0.64, P=0.001) and global shortening fraction (r=0.62, P<0.01). Although systolic wall thickening in the posterior wall was lower in CAD patients (% thickening, 11.9+/-10 vs. 21.9+/-8, P=0.004), absolute cyclic variation was reduced in both, CAD and DCM patients in the same order of magnitude. However, the higher maximal IBS amplitude in the posterior wall observed in CAD when compared to DCM patients (13.2+/-4.4 vs. 9.2+/-2.4 dB; P=0.002) indicate fibrosis or scar. The dissociation between cyclic variation and systolic wall thickening could implicate hybernating myocardium. CONCLUSION: Real-time IBS has progressed from research to routine as a tool to obtain additional and valuable information to conventional echocardiography in daily practice.     

Cyclic Variation of Integrated Backscatter: Dependence of Time Delay on the Echocardiographic View Used and the Myocardial Segment Analyzed

To determine the influence of myocardial anisotropy in ultrasonic tissue characterization, we measured the time delay (and magnitude) of the cyclic variation of myocardial integrated backscatter from specific segments visualized in the 4 standard transthoracic echocardiographic views. The cyclic variation data in 10 myocardial regions were obtained from analyses of 2-dimensional integrated backscatter images from 23 healthy subjects. Resultant values (mean ± SD) for the time delay were as follows: parasternal long-axis view: 1.08 ± 0.17 (septum) and 1.00 ± 0.14 (posterior wall); parasternal short-axis view: 1.03 ± 0.16 (anterior septum), 1.03 ± 0.14 (posterior wall), 2.22 ± 0.71 (lateral wall), and 1.65 ± 0.66 (posterior septum); apical 4-chamber view: 1.08 ± 0.31 (septum) and 2.20 ± 0.79 (lateral wall); and apical 2-chamber view: 1.68 ± 0.62 (inferior wall) and 2.04 ± 0.72 (anterior wall). Hence, results of this study indicate that myocardial ultrasonic characterization that uses the cyclic variation is influenced by the echocardiographic view and the specific segment of the left ventricle. (J Am Soc Echocardiogr 2000;13:9-17.)     

超声背向散射积分和回声强度定量在急性心肌缺血与再灌注过程中的变化及其与心肌收缩力的关系

目的： 观察犬心肌组织背向散射积分 （ＩＢ） 及其心动周期变化幅度 （ＣＶＩＢ） 和回声强度 （ＥＩ） 及其心动周期变化幅度 （ＣＶＥＩ） 在急性心肌缺血与再灌注过程中的变化, 以及ＣＶＩＢ 和ＣＶＥＩ与局部心肌收缩力的关系。方法： 用ＨＰ－５５００ 型超声诊断仪和自制ＤＦＹ 型超声图像定量分析诊断仪, 测量了１０ 只犬冠状动脉左前降支阻断前、后及再灌注不同时间左室前壁心肌组织ＩＢ、ＥＩ值和ＣＶＩＢ、ＣＶＥＩ值, 并同时测量室壁厚度 （Ｗ Ｔ） 和收缩期增厚率（ＴＨ％ ） 的动态变化。结果： 冠脉阻断 ２０ 分钟后, 缺血心肌组织ＩＢ 和ＥＩ均增高 （Ｐ＜ ０．０１）, ＣＶＩＢ 和ＣＶＥＩ均降低 （Ｐ 均＜ ０．０１）。再灌注１０ 分钟, ＩＢ 和ＥＩ即恢复正常, 与Ｗ Ｔ 相关。ＣＶＩＢ 和ＣＶＥＩ的恢复相对缓慢, 至再灌注９０ 分钟后方恢复正常, ＣＶＩＢ 和ＣＶＥＩ的变化与ＴＨ％ 的变化密切相关 （ｒ１＝ ０．８７, ｒ２＝ ０．８２, Ｐ＜ ０．０１）。结论： 心肌组织背向散射积分和回声强度在急性缺血与再灌注过程中存在相同的变化规律;ＣＶＩＢ 和ＣＶＥＩ与局部心肌组织收缩功能密切相关; 通过分析ＣＶＩＢ 和ＣＶＥＩ的变化不但能区别正常和缺血心肌组织, 同     

Dipyridamole stress ultrasonic myocardial tissue characterization in patients with Kawasaki disease.

Dipyridamole stress integrated backscatter (IBS) was used for evaluation of myocardial ischemia or damage in 31 children with coronary artery lesions caused by Kawasaki disease, in comparison with thallium-201 myocardial imaging. All patients underwent echocardiography at rest and after dipyridamole stress at the anterior interventricular septum, posterior wall (PW), and inferior wall (INF). At rest, no significant difference was seen in cyclic variation (CV) of IBS in the regions with normal or abnormal distribution on Tl-201 imaging. But in the regions showing abnormal distribution after stress, CV decreased significantly. A delayed study after stress showed the recovery of CV to the level at rest in all patients. Sensitivity of abnormal cyclic variation integrated backscatter was 75% in the PW and 91% in the INF, and specificity was 91% in the PW and 90% in the INF, compared with the results of thallium-201 imaging. Dipyridamole stress IBS can provide sensitive detection of myocardial ischemia or damage in Kawasaki disease.     

背向散射积分技术评价硝酸甘油对犬顿抑心肌收缩功能延迟保护

目的探讨背向散射积分技术定量评价硝酸甘油对犬顿抑心肌收缩功能的延迟保护.方法20只健康成年杂种犬随机分成缺血再灌注组(A组)和硝酸甘油组(B组),缺血及再灌注阶段检测室壁增厚率(WT)及心动周期变异幅度(CVIB),图像平均强度(AⅡ)的动态变化.实验结束后对心肌组织行病理检查.结果缺血时两组相应区域心肌CVIB和WT明显减低,曲线形态不规则.再灌注后有逐渐恢复趋势.CVIB的动态变化与WT相似,二者具有较好的相关性.再灌注120 min时B组收缩功能抑制分别较对照组减少了34%,30%.应用小剂量多巴酚丁胺后两组相应区域心肌运动增强.AⅡ,标化AⅡ在不同观测时间点之间的差异均无显著性意义.结论背向散射积分技术中的CVIB可用于检测顿抑心肌的收缩功能,多巴酚丁胺负荷试验结合背向散射积分技术可检测顿抑心肌的收缩功能储备,硝酸甘油对犬顿抑心肌收缩功能具有延迟保护作用.     

The relative contributions of myocardial wall thickness and ischemia to ultrasonic myocardial integrated backscatter during experimental ischemia

The purpose of this study was to assess the empirical relationship between myocardial integrated backscatter (IB) and myocardial wall thickness (WT) in normal myocardium. A second object was to estimate the additional contribution to acute ischemic integrated backscatter levels given this relationship. Myocardial IB measurements and simultaneous myocardial WT measurements were made in 16 open-chested pigs with intact coronary circulation (normal myocardium) and 10 min after the flow in the left anterior descending coronary artery had been reduced to 20% of its baseline value (ischemic myocardium). Measurements were made 50 times during one cardiac cycle and averaged over 10 cardiac cycles. IB and WT measurements were normalized with respect to the nonischemic end-diastolic values. The relationship between IB and WT in normal myocardium was estimated in every individual pig by simple linear regression. Estimates of IB during ischemia were calculated on the basis of this relationship and the ischemic WT measurements. Differences of the estimator and the actual measurement made during ischemia depict the actual contribution of the state of acute ischemia, without the influence of WT. The slope of the relationship between IB and WT during normal myocardial contraction ranged from -0.16 to 0.03 dB/% (mean = -0.036 dB/%, SD = 0.06 dB/%). The additional contribution of ischemia ranged from -3.84 to 5.56 dB (mean = 0.31 dB, SD = 2.72 dB). It was concluded that the average contribution of ischemia to IB measurements is insignificant if the IB dependency on WT is removed from the data and that the higher level of ischemic IB measurements can be explained by the decrease in wall thickness during ischemia and not by the ischemia itself.