Diltiazem versus nitroglycerin for myocardial protection following coronary artery bypass grafting as assessed by dobutamine stress echocardiography

BACKGROUND: Perioperative infusion of the calcium channel antagonist diltiazem reduces the occurrence and extent of postoperative myocardial ischemia. However, recent reports also mention nitroglycerin as the drug of choice to prevent conduit spasm after coronary bypass grafting. The diagnosis of myocardial ischemia in the perioperative setting is still problematic. Dobutamine stress echocardiography (DSE) is an established technique that combines inotropic stimulation with real-time myocardial imaging and delineates normal and abnormal regional contraction patterns. We assessed the perioperative anti-ischemic effects of diltiazem and nitroglycerin during hemodynamic stress using DSE. METHODS: 50 adult patients were included in a prospective randomized study. Diltiazem or nitroglycerin was used from the onset of extracorporeal circulation until 24 h postoperatively. Dobutamine stress echocardiography was performed in a stepwise fashion 2 to 3 h after elective coronary artery bypass grafting. RESULTS: In 42 of 49 patients, dobutamine stress echocardiography either reached a level of 40 micrograms/kg/min dobutamine or achieved the target heart rate. One patient improved in terms of segmental wall motion abnormalities and three patients developed new abnormalities without corresponding electrocardiographic changes. Analysis of ischemia-sensitive parameters showed lower creatine kinase MB (p = 0.032) and troponin I levels (p = 0.1) in the diltiazem group 24 h postoperatively. Heart rate was significantly lower in the diltiazem group (p = 0.0003). CONCLUSIONS: Under conditions of hemodynamic stress, DSE revealed no significant difference between diltiazem and nitroglycerin with regard to renewed ischemia.     

Dobutamine stress echocardiography early after myocardial infarction treated with thrombolysis

The aim of the study was to assess the ability of dobutamine stress echocardiography to detect myocardial viability and ischemia in patients with acute myocardial infarction treated with thrombolysis and to correlate the acute response to dobutamine with late spontaneous functional recovery at follow-up. Forty-two consecutive patients with myocardial infarction treated with thrombolysis underwent low- (5 and 10 mcg/kg/min) and high-dose (20 to 40 mcg/kg/min) dobutamine stress echocardiography at a mean of 7 ± 3 days of the acute phase. A follow-up 2D-echocardiogram was performed in all patients to evaluate the spontaneous recovery of function in the infarct area. On the basis of the response to the test, 3 groups of patients were identified: group 1 included 7 patients showing an improvement in left ventricular asynergy score index at low doses (from 1.5±0.3 to 1.3±0.2, p<0.05) with no deterioration at high doses, indicative of myocardial viability without ischemia; group 2 (23 patients) showed a significant improvement in the asynergy index at low doses (from 1.58±0.3 to 1.32±0.32, p<0.05) followed by a deterioration at high doses (1.68±0.4, p<0.05 vs low-dose), suggestive of residual myocardial ischemia in the infarct zone; group 3 included 12 patients who showed no significant changes in the baseline asynergy score index (1.67±0.2) either at low or at high doses. The acute response to dobutamine stress echocardiography accurately predicted the spontaneous recovery of function in the infarct area at follow-up: both group 1 and group 2 patients showed a significant reduction in the asynergy score index (group 1: 1.16±0.3 vs 1.5±0.2, p<0.001; group 2: 1.43±0.3 vs 1.58±0.3, p<0.05), while group 3 had no recovery in the asynergy index (1.67±0.2 vs 1.67±0.2). Thus, in patients with acute myocardial infarction treated with thrombolysis dobutamine stress echocardiography can detect myocardial viability in 71% and ischemia in the infarct zone in 55% of patients; moreover, the response to the test during the acute phase is correlated with the degree of the late spontaneous recovery of function in the infarct area.     

大剂量多巴酚丁胺负荷试验结合二维应变成像技术早期诊断冠心病的价值

目的 探讨大剂量多巴酚丁胺负荷试验结合二维应变成像技术早期诊断冠心病的价值.方法 对临床可疑的冠心病患者28例进行大剂量多巴酚丁胺负荷试验,分别在静息状态及各级负荷状态下观察室壁运动情况,测定左室各心肌节段心内膜下心肌的纵向收缩期峰值应变,比较大剂量多巴酚丁胺负荷试验目测法及大剂量多巴酚丁胺负荷试验结合二维应变成像技术诊断缺血心肌的敏感性和特异性;计算正常组、冠心病组缺血节段和非缺血节段的纵向收缩期峰值应变平均值并进行组内及组间比较,利用ROC曲线下面积评价纵向收缩期峰值应变预测缺血心肌的敏感性和特异性.结果 冠心病组多巴酚丁胺剂量为40μg·kg-1·min-1时目测法检出室壁运动异常6例(共20个节段),通过计算纵向收缩期峰值应变检出缺血心肌15例(共148节段);冠心病组大多数缺血节段纵向收缩期峰值应变较正常组及非缺血节段相同负荷状态明显减低(P＜0.05);大剂量多巴酚丁胺负荷试验目测法和大剂量多巴酚丁胺负荷试验结合二维应变成像技术诊断缺血心肌的敏感性分别为35.3%和88.2%(P＜0.01),特异性分别为100%和100%(P＞0.05)、准确性分别为60.7%和92.8%(P＜0.01).多巴酚丁胺剂量为40μg·kg-1·min-1时以纵向收缩期峰值应变绝对值≤14.9%为截断值,预测缺血心肌节段的敏感性和特异性分别为83.3%和91.7%.结论 大剂量多巴酚丁胺负荷试验结合二维应变成像技术可以提高检出缺血心肌的敏感性,定量评价心肌收缩功能的微小改变,发现隐匿性心肌缺血,为临床诊断早期冠心病患者提供了无创性新方法 .

Abstract：

Objective To investigate the value of high-dose dobutamine stress echocardiography combined with two-dimensional strain imaging in early diagnosis of coronary artery disease. Methods Highdose dobutamine stress echocardiography was performed to 28 patients with suspected coronary artery disease. All wall movements were observed during resting condition and at all stress levels,respectively;the peak systolic longitudinal strain in each endomyocardial segment of left ventricular was measured; the sensitivity and specificity between visual method and two-dimensional strain imaging in diagnosing myocardial ischemia with high-dose dobutamine stress echocardiography were compared. The average peak systolic longitudinal strain was calculated against control group, coronary artery disease group during ischemia segments and non-ischemia segments, and a comparison was made inside each group as well as against the other groups. The area under receiver operating characteristic curve of the peak systolic longitudinal strain was used to predict the sensitivity and the specificity of myocardial ischemia. Results With dobutamine dose of 40 μg·kg-1 · min-1 ,wall motion abnormalities were diagnosed in 6 patients (20 segments) through visual method, myocardial ischemia was found in 15 patients (148 segments) through computing the peak systolic longitudinal strain. Inside the coronary artery disease group during ischemic　segments,the majority of peak systolic longitudinal strain was significantly reduced ( P＜0.05) compared to the non-ischemic segments and the control group. In diagnosing myocardial ischemia in high-dose dobutamine stress echocardiography, the sensitivity of visual method and two-dimensional strain imaging were 35.3％ and 88.2％(P＜0.01), specificity 100％ and 100％(P＞0.05), and accuracy 60.7％ and 92.8％ (P＜0.01). The cutoff value of the peak systolic longitudinal strain was less than or equal to 14.9％, its sensitivity and specificity in predicting myocardial ischemia were 83.3％ and 91.7％,respectively. Conclusions High-dose dobutamine stress echocardiography combined with two-dimensional strain imaging can increase the sensitivity of detecting myocardial ischemia and detect concealed myocardial ischemia. High-dose dobutamine stress echocardiography combined with two-dimensional strain imaging can be used in early diagnosis of coronary artery disease.     

Can dobutamine echocardiography distinguish necrotic from ischemic myocardium,early after myocardial infarction?

The aim of this study was to evaluate the usefulness of dobutamine echocardiography (DE) in distinguishing necrotic from ischemic myocardium in infarct zones. We performed DE in 39 patients, 3 to 5 days after admission for a first, acute myocardial infarction, treated with thrombolysis. DE was considered positive if wall motion in the infarct zone worsened progressively during increasing dose of dobutamine or if wall motion in the infarct zone initially improved at low dose of dobutamine and deteriorated at higher dose. The results of DE were correlated to the evolution of wall motion in the infarct zone after 3 months and to the need for supplementary balloon dilatation. In 15 of the 39 patients, there was evidence of residual ischemia in the infarct zone. Twenty of the 39 patients had a positive dobutamine echocardiogram. Eleven of these 20 patients had evidence of residual ischemia in the infarct zone. They showed generalized changes of wall motion in the total infarct territory during DE. The other 9 patients demonstrated only localized changes of wall motion in isolated segments of the infarct zone during DE. None of these patients had evidence of residual ischemia. In conclusion: DE seems worthwhile in the detection of residual ischemia in the region of infarction. To reduce the number of false positive DE early after myocardial infarction, only extensive changes of wall motion in the total infarct territory should be accepted as indicative of residual ischemia in the infarct zone.     

Improved detection of inferobasal ischemia during dobutamine echocardiography with doppler tissue imaging.

OBJECTIVES: The purpose of this study was quantitative evaluation of the inferobasal segment during dobutamine stress echocardiography using Doppler tissue imaging (DTI). BACKGROUND: Overdiagnosis of myocardial ischemia during dobutamine echocardiography is a common problem. DTI may permit more accurate quantitative diagnosis of ischemia. METHODS: A total of 50 patients with normal contraction of the inferobasal segment at rest were referred for dobutamine stress echocardiography. All underwent coronary angiography. Systolic and diastolic myocardial velocities were measured from apical 2-chamber view at rest and at the peak of dobutamine infusion. RESULTS: Stenosis of the right coronary artery >or= 70% was detected in 11 patients. Conventional stress echocardiography was falsely positive in 10.3% and falsely negative in 27.3%. When DTI was combined with conventional stress echocardiography, sensitivity and specificity was 81.8% and 97.4%, respectively. CONCLUSION: DTI may enhance the diagnosis of inferior ischemia during dobutamine echocardiography and can be added to conventional imaging in the treatment of these patients.     

MR imaging of myocardial perfusion and viability

CMR is a rapidly developing new modality with applications in clinical cardiology for detection and assessment of myocardial ischemia and viability. CMR perfusion results for the detection of ischemia in comparison with stress echocardiography and scintigraphic techniques are reasonable, but all the studies reported to date have been conduced in selected patients. Larger studies in patient populations reflecting a broader spectrum of disease are necessary before perfusion CMR can be envisaged as a clinically reliable and robust diagnostic tool. Other CMR techniques provide a variety of novel methods of obtaining information on postischemic viability. Signs of viability that can be observed by CMR are the absence of late gadolinium-based contrast enhancement in a myocardial region involved in a recent infarct, any sign of wall thickening at rest (which is detectable with high accuracy by CMR), wall thickening after stimulation by low-dose dobutamine, and preserved wall thickness. Conversely, myocardial necrosis is characterized by signal enhancement of the infarct area after injection of Gd-DTPA, reduced wall thickness in chronic infarcts, and absence of a contractile reserve during dobutamine stimulation. Dobutamine CMR and late enhancement contrast-enhanced CMR predict contractile improvement after revascularization.     

Transesophageal dobutamine stress echocardiography with tissue Doppler imaging for detection and assessment of coronary artery disease.

BACKGROUND: Transesophageal dobutamine stress echocardiography (T-DSE) has been shown to be a sensitive and specific technique for the detection of myocardial ischemia. A major limitation of echocardiographic study interpretation, however, is the subjective visual analysis of endocardial motion and wall thickening, which is only semiquantitative. METHODS: To analyze whether T-DSE with the use or tissue Doppler imaging (TDI) during graded dobutamine infusion may be useful to detect and quantify stress-induced myocardial ischemia by changes in myocardial velocities, 70 patients undergoing coronary arteriography were studied with T-DSE and TDI. Midesophageal and transgastric short- and long-axis images were obtained at each level of dobutamine infusion. T-DSE was successful in 67 patients (96%). Baseline resting pulsed and color peak systolic (S) and early diastolic (E) velocities of the anterior, septal, lateral, and inferior walls were examined. RESULTS: Pulsed and color TDI correlated well at rest and after stress. Fifteen patients had a normal response to dobutamine, and 52 patients had inducible ischemia by two-dimensional criteria. In the normal group, there was a significant dose-dependent increase in S and E velocities. Compared with those in the normal group, patients with coronary artery disease (CAD) had lower resting S and E velocities and blunted S wave increase or E wave decrease during DSE. CONCLUSIONS: T-DSE with TDI is a feasible and accurate test for the quantitative assessment of patients with CAD who have impaired augmentation of systolic and diastolic myocardial velocities during dobutamine infusion.     

Use of myocardial backscatter as a quantitative tool for dobutamine echocardiography: feasibility,response to ischemia and accuracy compared with coronary angiography

Background: Integrated backscatter (IB) changes with ischemia, but most prior studies have involved parasternal imaging, which limited the number of evaluable segments. We sought to assess the efficacy and feasibility of IB from the apical views, and compare this to myocardial Doppler findings and wall motion analysis during dobutamine echocardiography. Methods and results: Forty-one patients undergoing dobutamine echocardiography had gray scale images and color myocardial Doppler acquired in three apical views. Cyclic variation IB (CVIB), time to peak IB (tIB, corrected for QT interval) and Doppler peak velocity (PV) in the same segment at rest and peak stress were assessed offline from digital cineloops at 80–120 frames/s. Significant coronary disease was defined by quantitative angiography as >50% stenosis. Analysis of the waveform in the apical views was feasible in 82% of segments. The backscatter curve was shown to be biphasic, with correlation of the first peak with peak tissue velocity, and significant regional variation. However, the response to normal segments was different with tissue Doppler (increased velocity) and backscatter (no change). Ischemia was associated with a lower peak tissue velocity and lower CVIB. Only resting tissue velocity and tIB (not CVIB) distinguished scar from ischemic segments. Using an optimal cutoff of <5.3 dB at rest achieved a sensitivity of 55%, a specificity of 76% and an accuracy of 75% when compared to angiography. The same cutoff at peak achieved a sensitivity of 58%, a specificity of 80% and an accuracy of 76%. Conclusions: CVIB and tissue velocity responses to stress are different, but both may be used to identify abnormal segments in patients with CAD. However, while measurement of CVIB is feasible in the apical views, the variability caused by anisotropy limits the accuracy of a single cutoff.     

大剂量多巴酚丁胺负荷超声心动图在分级心肌缺血中的应用价值

与冠脉造影对照检测临床疑为冠心病患者５５例，评估多巴酚丁胺负荷超声心动图检测冠脉狭窄程度及范围的应用价值。多巴酚丁胺输入中，左室舒张末期容积指数无明显变化；左室收缩末期容积指数于冠脉狭窄小于７４％及冠脉狭窄累及一支组降低，冠脉狭窄大于７４％和冠脉狭窄累及两支以上组增加；检测冠脉狭窄程度及范围的敏感性、特异性及准确度分别为７６％，７８％；８８％，８７％及８３％，８４％；对左前降支狭窄敏感。     

Assessment of menopause-induced myocardial changes by integrated backscatter during inotropic stimulation and atropine injection

Estradiol has been considered as an L-type calcium channel blocker in animal studies. The concentration of estradiol decreases after menopause. Therefore, we hypothesized that human myocardial functional changes developed after menopause, and those changes could be evaluated through the use of cyclic variation of integrated backscatter (CVIBS). A total of 16 patients with menopause (native and surgical menopause), follicular stimulating hormone > 40 IU/L and estradiol < 20 pg/mL underwent dobutamine stress IBS examination (study group). Another 12 women with normal menstruation, follicular stimulating hormone < 40 IU/L and estradiol > 20 pg/mL were enrolled as a control group. All patients had a low likelihood of coronary artery disease and negative results of dobutamine stress echocardiography and (201)thallium scintigraphy. To avoid the phenomenon of anisotropy, the amplitude and phase of IBS were acquired only in the midanteroseptal segment from the parasternal short axis view. The baseline amplitudes of CVIBS differed between the control and study groups (5.9 +/- 1.2 dB vs. 8.1 +/- 2.1 dB; p = 0.007). The amplitudes during low-dose (20 microg/kg-min) and peak-dose (40 microg/kg-min) dobutamine infusion were also different between these 2 groups (5.7 +/- 0.9 dB vs. 8.4 +/- 1.7 dB; p < 0.001; 6.0 +/- 1.0 dB vs. 7.7 +/- 2.4 dB; p = 0.026). However, there were no significant differences in amplitudes between these two groups after atropine injection (control group 4.5 +/- 1.2 dB, study group 5.3 +/- 1.0 dB; p = NS). No significant differences of phase were found either at baseline or under dobutamine infusion between the two groups. Multivariate linear regression analysis showed that only menopause status associated significantly with the amplitudes at different doses of dobutamine infusion (p < 0.05). In conclusion, human myocardial functional changes are observed by CVIBS after menopause. Postmenopausal women have higher values of amplitude than premenopausal women. These phenomena persist during low and peak doses of dobutamine infusion, but are abolished by atropine injection.     

小剂量多巴酚丁胺负荷超声心动图试验对可逆性功能障碍心肌预测的新指标

目的：探讨小剂量多巴酚丁胺负荷超声心动图（DSE）试验中左心室功能EF值的变化,即ΔEF这一量化指标预测急性心肌梗死（AMI）后患者的功能障碍心肌是否可逆及其可恢复程度。方法：入选患者25例, 接受小剂量DSE检查,测定负荷试验各阶段的收缩功能EF值,25例患者亦接受冠脉造影,并择期行经皮经腔太动脉成形术（PTCA）治疗,根据病变血管的情况植入支架,在术后3．5－13个月之间复查小剂量DSE试验。结果：以小剂量DSE过程中EF增加值,即ΔEF大于等于15％作为衡量标准,预测可逆性功能障碍心肌的敏感性,特性和准确性分别为70．6％,75％和72％,此预测改善值与无改善值之间的差异有显著性意义（P＜0．05）,结论：ΔEF可以作为准确评价可逆性功能障碍心肌的指标,并且是一种定量测定方法。     

应用组织追踪法评价犬左室收缩功能的研究

目的应用超声心动图组织追踪法观察左室收缩功能改变对犬二尖瓣瓣环收缩期位移的影响.方法选用11只健康杂种犬,分别在基础状态时、静脉注射多巴酚丁胺后、静脉注射心得安后以及结扎冠状动脉左前降支,发生急性心肌缺血后,用组织追踪法在心尖四腔心切面、两腔心切面及心尖长轴切面测量二尖瓣瓣环6个不同位置的收缩期位移(DS);用M型超声心动图测量二尖瓣瓣环收缩期下移距离(DM);用超声心动图Simpson法测定左室射血分数(LVEF).结果在改变犬心肌整体收缩功能的过程中,用组织追踪法测量的二尖瓣瓣环6个不同位置的收缩期平均位移与用M型超声心动图测量的二尖瓣瓣环收缩期平均下移距离显著相关(r=0.94, P＜0.001);同时,二尖瓣瓣环收缩期平均DS与用超声心动图Simpson法测定的LVEF显著相关(r=0.92, P＜0.001);发生急性心肌缺血时,用组织追踪法测量的二尖瓣瓣环6个不同位置的收缩期平均位移与用超声心动图Simpson法测定的LVEF也呈显著相关(r=0.78, P＜0.001),但相关性相对较低.结论超声心动图组织追踪法测量二尖瓣瓣环收缩期位移可快速、直观、无创性地定量评价左室收缩功能.     

心肌灌注造影在多巴酚丁胺负荷前后早期诊断冠心病的临床研究

目的探讨心肌灌注造影(MCE)技术在大剂量多巴酚丁胺负荷前后早期诊断冠心病的价值.方法 对临床疑为冠心病患者38例,进行大剂量多巴酚丁胺负荷超声心动图试验,分别在静息状态和多巴酚丁胺负荷超声心动图试验终止时即刻行MCE检查.以冠状动脉造影为金标准将大剂量多巴酚丁胺负荷超声心动图前后心肌灌注状态目测法对冠心病的检出率进行比较.结果 多巴酚丁胺负荷超声心动图检查的38例患者中,9例(24%,9/38)达到峰值负荷水平,22例(58%,22/38)达到中级负荷水平.其中通过冠状动脉造影诊断的27例冠心病患者在多巴酚丁胺负荷前后,通过心肌灌注状态目测法诊断心肌缺血患者的例数分别为10例(37%,10/27)及24例(89%,24/27,χ2=15.565,P＜0.01).结论 大剂量多巴酚丁胺负荷超声心动图结合MCE可提高缺血心肌的检出率,发现隐匿性心肌缺血,为临床无创性诊断早期冠心病患者提供新方法.     

Effects of dobutamine on coronary flow velocity response and their relations to age

The purpose of this study was to assess the effects of low-dose dobutamine on left ventricular (LV) functional and coronary flow reserves using transthracic echocardiography. The study group consisted of 30 children aged from 5 months to 16 years (mean 4.8 +/- 4.4 years). Echocardiographic studies were repeated before and during dobutamine infusion (5 microg/kg per minute). The peak diastolic velocity in the left descending coronary artery (LAD) was recorded by pulsed-Doppler under the guidance of color Doppler flow mapping. The coronary flow velocity (CFV) response was calculated as the ratio of LAD peak flow velocity at dobutamine infusion to basal LAD peak flow velocity. Left ventricular contractility was calculated by two-dimensionally directed M-mode echocardiography. The rate-corrected mean velocity of circumferential fiber shortening (mVcfc) and LV end-systolic wall stress (ESS) were used as indices of contractility. Adequate spectral Doppler recordings of the LAD peak flow velocity for the assessment of CFV response were obtained in 26 of 30 patients (87%). The LAD peak flow velocity at dobutamine infusion increased significantly compared with the basal values. The CFV response in the younger children was low and increased significantly with age. The CFV response did not show significant correlations with the changes in heart rate, systolic blood pressure, rate-pressure product, nor ESS during dobutamine infusion. However, a significant relationship between the CFV response and the percent change of mVcfc was observed. In the present study using high frequency transthoracic echocardiography, we demonstrated the age-related changes in CFV response and LV functional reserve by dobutamine infusion. Responses of LV contractility and coronary flow to dobutamine are less sensitive in youngerchildren and increased with increasing age.     

小剂量多巴酚丁胺负荷超声心动图试验对急性心肌梗塞后患者梗塞相关动脉残存狭窄的诊断

目的　将小剂量多巴酚丁胺负荷超声心动图试验用于急性心肌梗塞后两周患者的研究。方法　根据美国超声协会推荐的心室壁 16节段划分法 ,推断引起室壁运动异常区域血流灌注异常的梗塞相关动脉 ,并与金标准冠状动脉造影结果相比较。结果　该试验对梗塞相关动脉残存狭窄诊断的敏感性及特异性分别为 80 %、78 8%。结论　小剂量DSE试验对梗塞相关动脉残存狭窄也有较好的诊断价值     

Cardiovascular response in patients with and without myocardial ischaemia during dobutamine echocardiography stress test for coronary artery disease

Summary. Dobutamine is widely used in cardiac stress testing for coronary artery disease and myocardial viability. To assess the systemic cardiovascular response during dobutamine echocardiography stress testing, we investigated nine patients without myocardial ischaemia (group 1, aged 48 to 72 years) and nine patients with myocardial ischaemia during the test (group 2, aged 53 to 73 years), by use of Doppler/echocardiography and subclavian artery pulse trace calibrated with brachial artery pressures. Peripheral resistance, total arterial compliance, and aortic characteristic impedance were estimated using a 3-element windkessel model of the systemic circulation. During infusion of dobutamine up to 40 μg kg^-1 min^-1, arterial pressure was maintained near baseline levels, whereas heart rate and cardiac index increased, more so in group 1 (mean: 89 and 79%) than in group 2 (58 and 52%; P<0.05 vs. group 1). Peripheral resistance was decreased by ≥32% at peak stress, whereas characteristic impedance was maintained at or above baseline in both groups, and total arterial compliance was not significantly altered. The cardiovascular response in group 2 was not influenced by the wall motion abnormalities. Thus, in these patients the inotropic, chronotropic, and vasodilatory effects of dobutamine balanced the ischaemic impairment of left ventricular function during the stress test.     

Spontaneous delayed recovery of perfusion after thrombolyzed acute myocardial infarction: is it predictable before discharge?

In patients with thrombolyzed acute myocardial infarction, early assessment of the final infarct size is difficult because spontaneous recovery of perfusion and function of the left ventricle may be delayed. This study was undertaken to evaluate the ability of predischarge low-dose dobutamine echocardiography to predict late spontaneous recovery of perfusion assessed by single-photon emission computed tomography after acute myocardial infarction. We prospectively studied 53 consecutive patients with myocardial infarction treated with thrombolysis. Low-dose dobutamine echocardiography and resting (99m)Tc-sestamibi single-photon emission computed tomography (MIBI SPECT) were performed 4 +/- 2 days after infarction. A follow-up SPECT study was carried out in 45 patients after 6 months. Myocardial recovery was defined as a reduction of SPECT defect size by more than 10% at follow-up compared with the early study. In 25 of the 45 patients, the size of the left ventricular perfusion defect decreased significantly from 42% +/- 16% to 27% +/- 10% (group 1), whereas in the remaining 20 patients it showed no significant change (group 2). Predischarge low-dose dobutamine echocardiography showed a significant improvement in wall motion score index compared with baseline in group 1, from 1.62 +/- 0.28 to 1.41 +/- 0.24, P <.001, whereas in group 2 this index remained without significant change. Predischarge low-dose dobutamine echocardiography is an accurate tool for prediction of late recovery of myocardial perfusion after acute myocardial infarction treated with thrombolysis.     

Use of peak systolic strain as an index of regional left ventricular function: comparison with tissue Doppler velocity during dobutamine stress and myocardial ischemia.

OBJECTIVES: The goals of this study were to examine peak systolic strain as an index of regional function in an animal model of inotropic stress and ischemia, and to compare these results with peak systolic myocardial tissue Doppler velocity (MDV). BACKGROUND: Myocardial tissue Doppler velocity is an objective measure of regional left ventricular responses to inotropic stimulation and ischemia, but it is affected by tethering from adjacent segments and translational movement. Myocardial Doppler strain (epsilon, relative change in length) is a more local measure of contractility, which can now be derived noninvasively from MDV. METHODS: Eight dogs underwent graded dobutamine infusion followed by coronary occlusion. Epicardial 2-dimensional echocardiography and color MDV of the left ventricle were obtained and digitized from the short-axis view at baseline and with dobutamine doses of 2, 4, and 8 microg/kg per minute. These were repeated 0, 10, 20, 45, and 90 seconds after occlusion of the left anterior descending artery (LAD) (n = 3) or circumflex coronary artery (n = 5). Dobutamine was continued at 8 microg/kg per minute during coronary occlusion. The peak systolic radial MDV (cm/s) and systolic strain (epsilon(s), percent thickening) in the anterior and posterior walls were measured off-line at each stage. RESULTS: Dobutamine caused an increase in MDV (P =.0001) and epsilon(s) (P =.09) above baseline values. Coronary occlusion caused a reduction in wall motion; after 45 seconds, all nonperfused segments were hypokinetic. There was a corresponding decrease in MDV and epsilon(s), but this occurred earlier for epsilon(s), and the difference between ischemic and nonischemic segments was greater for epsilon(s) than for MDV (P <. 03). Nonischemic regions trended to an increase in epsilon(s) (compensatory hyperkinesis), whereas MDV trended downward, probably reflecting the global decrease in left ventricular function. CONCLUSION: Both MDV and epsilon(s) increase with dobutamine and decrease during ischemia. epsilon(s) appears to respond to local ischemia earlier than MDV, perhaps because it is a more local measure. Thus epsilon(s) may prove to be an accurate parameter for the clinical recognition of regional ischemia.     

Pre-ejectional left ventricular wall motions studied on conscious dogs using Doppler myocardial imaging: relationships with indices of left ventricular function

Duration of the pre-ejection period is a sensitive index of myocardial function. Our purpose was to document normal pre-ejectional left ventricular (LV) wall motions at rest and under dobutamine using Doppler myocardial imaging (DMI), and to correlate posterior wall velocities with indices of LV systolic function. M-mode recordings of both walls were imaged on eight conscious dogs chronically instrumented. Subendocardial pre-ejectional velocities were digitized and measured every 3.8 ms. DMI analysis consisted of sign recognition, velocity measurement, duration and timing from the Q wave of the electrocardiogram. Isovolumic contraction time (Ict) was represented by the time interval from onset to peak of the first derivative of LV pressure. Conventional Doppler labelling of velocity signs, positive toward and negative away from the transducer, was applied to the direction of encoded wall motions. For physiological understanding, wall motions of both walls were also labelled inward and outward with respect to the left ventricular cavity center. In each wall, PEP was shown as several colored strips, each strip representing the period of time that the wall was moving in one direction. Changes in velocity sign corresponding to changes in direction of motion were opposed in each wall (p < 0.001), featuring successive inward and outward wall motions. There was a markedly sustained inward motion during Ict. Its velocity amplitude increased with dobutamine. There was a positive correlation between velocities of the inward motion contemporaneous of Ict and ejection fraction (r = 0.72, p < 0.003). Values of Ict respectively drawn from DMI and from hemodynamics were also significantly correlated (r = 0.85, p < 0.007). Thus, the inward motion evidenced by DMI during Ict appears promising to assess myocardial function and effect of drugs.     

Aortic Doppler velocity measurement and cardiac function in the fetal lamb

Aortic haemodynamic parameters, and Doppler waveforms in particular, were investigated in acute experiments with fetal lambs. Cardiovascular changes were produced by central infusion of the drugs esmolol and dopamine. Pulsed Doppler waveforms were obtained from the descending thoracic aorta, simultaneous with recordings of pulsatile aortic volume flow rate, diameter and blood pressure. The relation between Doppler-derived velocities and the corresponding full vessel lumen velocities was shown to be fairly linear and consistent across different animals. The aortic volume flow per beat decreased with esmolol (p < 0.003, repeated measures ANOVA); the Doppler and vessel lumen mean velocities also decreased, whether measured only at peak systole or over the full cardiac cycle (at most p < 0.003). With dopamine the aortic flow per beat increased (p < 0.001), as did the Doppler and vessel lumen mean velocities (at most p < 0.02). An inverse relation between the aortic flow per beat and the peripheral resistance was observed. To identify inotropic changes in the presence of vascular effects, a theoretical model based on cardiac power output changes was implemented. The data were divided into three groups, according to whether the model did or did not identify a definite inotropic effect (positive or negative). The Doppler velocity changes for these three groups were different (p < 0.0001). The mean Doppler velocity increased by 7 cm s⁻¹ in the positive inotropic effect group, and decreased by 4 cm s⁻¹ in the negative group. The aortic flow parameters of the human fetus are very similar to those of the fetal lamb. Decreased aortic velocities have been reported in human fetal compromise, and the results of this study support the hypothesis that this can be evidence of impaired fetal cardiac function.