Thallium single photon emission computed tomography following thrombolysis: missing relation to left ventricular function

To address the question of whether infarct size after thrombolysis can comparably be estimated by thallium SPECT scintigraphy and contrast cineangiography, 32 patients in whom regional wall motion abnormality had been assessed by means of the "centerline" method, 10 to 21 days after infarction, underwent biphasic thallium SPECT scintigraphy with dipyridamole. There were no statistically significant correlations between left ventricular ejection fraction and the degree of hypokinesia in the infarct area on one hand, and thallium defect size in the early and late scintigram on the other. Hypokinesia was inversely correlated (r = -0.51) with the time interval from symptom onset to reperfusion, but no such correlation was found between thallium defect size and this parameter. In patients in whom reperfusion was achieved within 3 h of symptom onset, hypokinesia was significantly less (-1.11 +/- 0.6 standard deviations (SD] than in patients in whom reperfusion was achieved later (-2.16 +/- 0.8 SD; p less than 0.01). Thallium defect size, however, was not different in these two groups of patients. It is concluded that there is no close correlation between regional wall motion abnormality assessed subacutely after thrombolysis and infarct size determined by SPECT in the chronic state. Thus, impairment of left ventricular function may not be assessed from scintigraphic findings.     

Recovery of left ventricular function after myocardial infarction can be predicted immediately after thrombolysis by semiquantitative intracoronary thallium and technetium pyrophosphate scintigraphy

The accuracy with which intracoronary thallium and technetiumpyrophosphate scintigraphy during intra-coronary thrombolysispredicts myocardial salvage was studied in 58 patients withacute myocardial infarction by comparing the acute scintigraphicfindings with subsequent left ventricular function. Scintigramsobtained before and immediately after thrombolysis were interpretedby three independent observers using a scoring system. Regionalwall motion in the infarct area was determined from left ventricular(LV) cine angiograms using the center-line method. Patients with mild hypokinesis (hypokinesis –2 SD fromnormal) could be distinguished from those with severe hypokinesis(hypokinesis > – 2SD) using the prethrombolysis thalliumscore with an accuracy of 83%. Accuracy using the post-thrombolysisscore was 76%. When the post-thrombolysis thallium and technetiumpyrophosphate scores were combined, differentiation was possiblein 91% of all patients studied, and in 100% of patients withanterior myocardial infarction. Thus, analysis of combined thallium and technetium phyrophosphatescintigraphy accurately predicts recovery of LV function afterthrombolysis and may be helpful in deciding whether acute percutaneoustransluminal coronary angioplasty or bypass surgery should beperformed after thrombolysis.     

Changes in left ventricular regional asynchrony after intracoronary thrombolysis in patients with impending myocardial infarction

Ventriculograms obtained before and a mean (SD) of 4.3 (2.5) weeks after intracoronary thrombolysis in 23 patients who were treated within 3.5 (3.1) hours of the onset of pain were examined for changes in asynchronous left ventricular wall motion. Lysis was achieved in 19 patients, and in 16 the affected artery was still patent at restudy. Angiograms were digitised frame by frame. Left ventricular volumes, ejection fraction, and peak ejection rate were all unchanged after thrombolysis, whereas peak filling rate fell, whether or not patency was achieved or maintained. Regional wall motion was examined by means of isometric and contour plots. The area supplied by the affected coronary artery showed simple hypokinesis or akinesis in 10 cases, which was unchanged at the second study in nine and improved in one. The commonest manifestation of asynchrony was delayed inward motion during isovolumic relaxation. This was present in 12 cases with or without associated hypokinesis; after thrombolysis wall motion improved significantly in eight and returned to normal in six, significantly more frequently than it did in patients with simple hypokinesis. Dyskinesis (three patients) and hyperkinesis (five patients) resolved in all. Outward wall motion during isovolumic relaxation reverted to normal in four out of five cases, and outward motion during isovolumic contraction reverted to normal in five out of seven. The frequency of improvement was also increased when the circulation to the affected segment was not compromised by an important residual stenosis. Flow in the affected artery was re-established or maintained significantly less frequently when simple hypokinesis or akinesis was present at the first study. These observations provide further evidence that asynchronous wall motion early after acute myocardial infarction represents residual contractile activity, and suggest that knowledge of its presence and distribution may be useful in assessing patients on whom thrombolysis is performed.     

Changes in left ventricular regional asynchrony after intracoronary thrombolysis in patients with impending myocardial infarction.

Ventriculograms obtained before and a mean (SD) of 4.3 (2.5) weeks after intracoronary thrombolysis in 23 patients who were treated within 3.5 (3.1) hours of the onset of pain were examined for changes in asynchronous left ventricular wall motion. Lysis was achieved in 19 patients, and in 16 the affected artery was still patent at restudy. Angiograms were digitised frame by frame. Left ventricular volumes, ejection fraction, and peak ejection rate were all unchanged after thrombolysis, whereas peak filling rate fell, whether or not patency was achieved or maintained. Regional wall motion was examined by means of isometric and contour plots. The area supplied by the affected coronary artery showed simple hypokinesis or akinesis in 10 cases, which was unchanged at the second study in nine and improved in one. The commonest manifestation of asynchrony was delayed inward motion during isovolumic relaxation. This was present in 12 cases with or without associated hypokinesis; after thrombolysis wall motion improved significantly in eight and returned to normal in six, significantly more frequently than it did in patients with simple hypokinesis. Dyskinesis (three patients) and hyperkinesis (five patients) resolved in all. Outward wall motion during isovolumic relaxation reverted to normal in four out of five cases, and outward motion during isovolumic contraction reverted to normal in five out of seven. The frequency of improvement was also increased when the circulation to the affected segment was not compromised by an important residual stenosis. Flow in the affected artery was re-established or maintained significantly less frequently when simple hypokinesis or akinesis was present at the first study. These observations provide further evidence that asynchronous wall motion early after acute myocardial infarction represents residual contractile activity, and suggest that knowledge of its presence and distribution may be useful in assessing patients on whom thrombolysis is performed.     

Quantitative regional wall motion analysis with early contrast ventriculography for the assessment of myocardium at risk in acute myocardial infarction

Background

Several techniques have been used to quantify the myocardium at risk, including measurement of regional ventricular function with contrast ventriculography and measurement of perfusion defect size with tomographic technetium-99m-sestamibi imaging. This study evaluates the correlation between these 2 techniques.

Methods

Twenty-three patients with angiographically documented coronary occlusion and acute myocardial infarctions (10 anterior, 13 inferior) were studied. All patients had contrast left ventriculography at the time of their acute angiogram before any revascularization therapy. Regional wall motion parameters measured with the centerline method were the severity, circumferential extent, and global circumferential extent of hypokinesis and the mean standardized motion in predefined areas. Technetium-99m-sestamibi was injected before reperfusion therapy with measurement of the myocardium at risk using single photon emission computed tomography imaging.

Results

The tomographic sestamibi-measured myocardium at risk was significantly greater for anterior infarctions compared with inferior infarctions (40% ± 18% vs 14.0 ± 8.5%, P = .0001). The only parameter of regional wall motion to show a significant difference by infarct location was global circumferential extent of hypokinesis (43% ± 25% vs 22% ± 15%, P = .02). The other parameters were not significantly different between anterior and inferior myocardial infarctions. For anterior infarctions, these parameters of regional wall motion correlated with myocardium at risk assessed with sestamibi: global circumferential extent of hypokinesis (r = .88, P < .01), circumferential extent of hypokinesis (r = .78, P < .01), mean standardized motion in predefined areas (r = -.74, P < .05), and severity of hypokinesis (r = -.70, P < .05). For inferior infarctions, there was no significant correlation between any of these parameters of regional wall motion and myocardium at risk assessed with sestamibi imaging.

Conclusion

The assessment of regional ventricular function with contrast ventriculography correlates with the area of myocardium at risk measured with tomographic technetium-99m-sestamibi for anterior, but not for inferior, myocardial infarctions. Therefore, these parameters of regional wall motion are a poor measure of the efficacy of reperfusion therapies.     

The Relationship between Collateral Blood Flow and Infarct Zone Regional Wall Motion in Patients with Recent Acute Myocardial Infarction

After acute myocardial infarction (AMI), the most significant prognostic determinants of myocardial viability and function are deterioration degree of the distal myocardial microcirculation and collateral flow. Quantification of coronary collateral circulation is possible by using intracoronary pressure measurement techniques. We hypothesized that quantitatively determined coronary wedge pressure (CWP) and collateral flow index (CFI) may be useful in order to designate regional left ventricular function and indirectly viability after MI. In this study, we investigated the relationships between angiographically quantified wall motion scores and CWP and CFI in patients with recent AMI and treated with thrombolytic therapy. Forty patients early after myocardial infarction with 60% residual stenosis in infarct related artery (IRA) after thrombolysis, who underwent PTCA and/or stent implantation for this culprit lesion, were included in this study. None of the patients had significant stenosis in other coronary arteries. Angiographic ventricular wall motion scoring (WMS) was performed semi quantitatively according to coronary artery surgery study criteria. After angiography, fiberoptic pressure monitoring guide wire (pressure wire, Radi) was positioned distal to the stenosis to be dilated. During complete occlusion with balloon inflation distal pressure recorded as CWP. CFI was determined as the ratio of simultaneously measured CWP to aortic pressure. The mean values of CWP, CFI and mean WMS were 18.1 ± 7.9 mmHg, 0.18 ± 0.09 and 3.15 ± 0.8, respectively. The CWP (r: –0.86) and CFI (r: –0.84) values correlated well with WMS determined in the infarcted territory. We concluded that collateral circulation in the infarcted region is related to the left ventricular regional function. Presence of adequate and intact collateral network in the infarct related segments diminishes microvascular damage translating into preserved left ventricular regional functions.     

Thallium-201/technetium-99m pyrophosphate overlap in patients with acute myocardial infarction after thrombolysis: prediction of depressed wall motion despite thallium uptake

Intracoronary thallium-201/technetium-99m pyrophosphate planar scintigraphy was performed in 60 patients with acute myocardial infarction undergoing intracoronary thrombolysis to predict salvage of myocardium immediately after thrombolysis. In eight patients a significant overlap of new thallium uptake and technetium pyrophosphate accumulation was found after thrombolysis. Intravenous planar thallium scintigraphy revealed thallium uptake in the region of overlap in all patients; circumferential profile analysis showed no difference in the thallium scintigrams before and after technetium injections. Both findings indicate that overlap is not the result of scattering of technetium into the thallium window. Emission computed tomography revealed thallium/technetium pyrophosphate uptake in identical slices and regions. Regional wall motion in the area of overlap remained depressed in all patients, in contrast to patients with similar thallium uptake without overlap. These data suggest that thallium/technetium pyrophosphate overlap reflects the close proximity of viable and necrotic myocardial cells and predicts depressed wall motion after thrombolysis.     

The effect of intracoronary thrombolysis with streptokinase on myocardial thallium distribution and left ventricular function assessed by blood-pool scintigraphy

In order to evaluate the effect of coronary recanalization inacute myocardial infarction, thallium scintigrams were madeon admission in 23 patients in whom thrombolysis was attemptedand in 27 patients treated conventionally. The scintigrams wererepeated immediately after the procedure or after 3 h in thecontrol group. No significant differences were apparent betweenthe initial thallium uptake in treated patients or controls.Some degree of thallium redistribution occurred in 43 out of50 patients. The degree of redistribution was greater in patientswith open or recanalized arteries (redistribution 35%, s.d.24% of initial defect) than in patients in whom the artery remainedoccluded (17%, s.d. 12%). No differences were apparent in sixpatients between the late scintigrams and a third series ofimages made after an additional injection of thallium. Globalleft ventricular function was analysed in 30 patients with anteroseptalinfarction and in 35 patients with inferior wall infarction.Ejection fractions were lower in patients with anterior wallinfarction. Between one and seven days after admission, ejectionfractions were similar in patients with open or occluded arteriesin pilot studies and in randomized patients with inferior wallinfarction after thrombolysis or conventional treatment. Inpatients with anterior wall infarction, left ventricular ejectionfraction after streptokinase (45%, s.d. 7%) was greater thanafter conventional treatment (38%, s.d. 12%). Analysis of segmentalleft ventricular function suggests that this difference is duein part to the improvement of segmental function in the non-infarctedareas. No differences were observed between ejection fractionsmeasured early (1–7 days) or late (10–20 days) aftermyocardial infarction. The data show considerable overlap between patients treatedwith streptokinase and those treated conventionally. Furtherrandomized trials are needed to determine whether thrombolysisin acute myocardial infarction does indeed result in permanentimprovement of myocardial function.     

Asynchronous left ventricular wall motion early after coronary thrombosis

To study regional wall motion early in the development of acute myocardial infarction, left ventriculograms performed in 24 patients before thrombolysis and within 3.5(1.2) (mean (SD] hours of the onset of pain were digitised frame by frame. Isometric and contour plots of regional wall motion were constructed. In 19 patients (seven with anterior descending, eight with right, and four with circumflex disease) thrombosis was demonstrated on an underlying stenosis. In 10 patients the two remaining coronary arteries were normal, and in nine, one or both showed important disease. Mean values of global indices of left ventricular function, including end diastolic volume, ejection fraction, peak ejection and filling rates, and cavity shape changes were all within normal limits, though end systolic volume was significantly raised. Total systolic amplitude of wall motion was normal in the affected area in all but seven patients (four with anterior descending, two with right, and one with circumflex thrombosis). Dyskinesis of more than 2 mm was seen in only three patients, all with thrombosis of the anterior anterior descending coronary artery, and hyperkinesis was present in four. The commonest abnormality of wall motion was hypokinesis during ejection followed by prolonged inward motion during isovolumic relaxation, which was seen in four patients with anterior descending, seven with right, and three with circumflex artery thrombosis. This was preceded by outward motion during isovolumic contraction and delayed inward motion during ejection in eight with right or circumflex thrombosis. Five of six patients without thrombosis had simple hypokinesis or dyskinesis without asynchrony. Disease of other coronary arteries did not affect the pattern of wall motion seen after right or circumflex coronary artery occlusion but it reduced the incidence of delayed inward motion along the free wall after thrombosis of anterior descending artery. Thus early after acute coronary thrombosis asynchronous wall motion is commoner than simple hypokinesis or dyskinesis. Its persistence suggests that in the setting of coronary artery thrombosis in man, residual contractile activity may persist for up to six hours after the onset of symptoms.     

Asynchronous left ventricular wall motion early after coronary thrombosis.

To study regional wall motion early in the development of acute myocardial infarction, left ventriculograms performed in 24 patients before thrombolysis and within 3.5(1.2) (mean (SD] hours of the onset of pain were digitised frame by frame. Isometric and contour plots of regional wall motion were constructed. In 19 patients (seven with anterior descending, eight with right, and four with circumflex disease) thrombosis was demonstrated on an underlying stenosis. In 10 patients the two remaining coronary arteries were normal, and in nine, one or both showed important disease. Mean values of global indices of left ventricular function, including end diastolic volume, ejection fraction, peak ejection and filling rates, and cavity shape changes were all within normal limits, though end systolic volume was significantly raised. Total systolic amplitude of wall motion was normal in the affected area in all but seven patients (four with anterior descending, two with right, and one with circumflex thrombosis). Dyskinesis of more than 2 mm was seen in only three patients, all with thrombosis of the anterior anterior descending coronary artery, and hyperkinesis was present in four. The commonest abnormality of wall motion was hypokinesis during ejection followed by prolonged inward motion during isovolumic relaxation, which was seen in four patients with anterior descending, seven with right, and three with circumflex artery thrombosis. This was preceded by outward motion during isovolumic contraction and delayed inward motion during ejection in eight with right or circumflex thrombosis. Five of six patients without thrombosis had simple hypokinesis or dyskinesis without asynchrony. Disease of other coronary arteries did not affect the pattern of wall motion seen after right or circumflex coronary artery occlusion but it reduced the incidence of delayed inward motion along the free wall after thrombosis of anterior descending artery. Thus early after acute coronary thrombosis asynchronous wall motion is commoner than simple hypokinesis or dyskinesis. Its persistence suggests that in the setting of coronary artery thrombosis in man, residual contractile activity may persist for up to six hours after the onset of symptoms.     

Prognostic value of thallium-201 single-photon emission computed tomographic myocardial perfusion imaging according to extent of myocardial defect: Study in 1,926 patients with foilow-up at 33 months

Objectives. This study was designed to assess the prognostic value of thallium-201 single-photon emission computed tomographic (thallium SPECT) perfusion imaging in patients evaluated for stable angina pectoris and to examine the relation, if any, between the preface and extent of myocardial defect and future fatal or nonfatal cardiovascular events (revascularization, secondary myocardial infarction).Background. Compared with planar scintigraphy, thallium SPECT enables better evaluation of the extent of mayocardial perfusion defect. However, its prognostic value has not yet been studied in a large population of patients.Methods. Between 1987 and 1989 we studied 3,193 patients. After exclusion of patients with unstable angina, myocardial infarction during the previous month or earlier revascularization, 1,926 patients were followed up for 33 ± 10 (mean ± SD) months after stress thallium SPECT imaging (performed after exercise in 1,121 patients or during dipyridamole infusion in 805 patients). Thallium SPECT imaging of the left ventricle was divided into six segments.Results. After normal thallium SPECT imaging (715 patients), the annual total and cardiovascular mortality rates were, respectively, 0.42%/year and 0.10%/year and were significantly higher after abnormal thallium SPECT imaging (respectively, 2.1%, relative risk 5, p = 0.012; 1.5%, relative risk 15, p < 0.0001 [log-rank test]). There was a significant relation between the number of abnormal segments and cardiovascular mortality during follow-up (p < 0.02) or the occurrence of nonfatal events (p < 0.001). The extent of defect on the initial scan provided the best SPECT variable for long-term prognosis. Thallium SPECT imaging provided additive prognostic information compared with other clinical variables (gender, previous myocardial infarction) and exercise electrocardiogram.Conclusions. In patients with stable angina, normal thallium SPECT imaging indicates a low risk patient, and the extent of myocardial defect is an important prognostic predictive factor.     

Radionuclide assessment of stunned myocardium by alterations in perfusion, metabolism and function

A method for the diagnosis of stunned myocardium has not yet been established, although it has been retrospectively demonstrated in patients after intracoronary thrombolysis, unstable angina, and coronary revascularization. In this study, radionuclide cardiac imaging was carried out to evaluate the existence of stunned myocardium. 1) Gated blood pool scanning was performed in patients undergoing intracoronary thrombolysis both at the time of reperfusion (Rp) and 10 days later. In the Rp less than 4 h group, about half of the initially abnormal segments showed complete improvement on quantitative wall motion analysis, which was more than in the Rp greater than 4 h and control groups. 2) In patients with acute myocardial ischemia, the correlation between thallium perfusion and regional wall motion was assessed semiquantitatively. In unstable angina, 5.8% of the ventricular wall segments showed dissociation between perfusion and wall motion (well-perfused asynergy). These segments had abnormal wall motion although perfusion was maintained, and were thought to be areas of stunned myocardium. 3) Fourteen dogs were studied using thallium and 123I-beta-methyliodophenyl pentadecanoic acid (BMIPP) fatty acid imaging to evaluate the relationship of perfusion to metabolism. In the reperfusion model, mismatching of the pattern of thallium and BMIPP uptake was observed. Reperfused myocardium probably has an increased triglyceride content, which is related to the degree of myocardial viability. In conclusion, stunned myocardium may be correctly diagnosed acutely on the basis of alterations in its perfusion, metabolism, and function by using radionuclide cardiac imaging.     

Reversal of rest asynergy during exercise in patients with coronary artery disease

The diagnosis of ischemic heart disease by radionuclide ventriculography (RNV) is performed on the basis of an abnormal response of the left ventricular ejection fraction and the occurrence, or aggravation, of regional wall motion abnormality during exercise. However, the abnormal wall motion observed by RNV at rest is improved in some patients with coronary artery disease during exercise. We examined the clinical features of such patients who showed a paradoxical response of regional wall motion. The left ventricle was divided into 4 segments: anteroseptal, apical, inferior and posterolateral. The degree of wall motion of each segment was classified into 5 grades and scored according to a 5 point system: 4 = normokinesis, 3 = hypokinesis, 2 = severe hypokinesis, 1 = akinesis and 0 = dyskinesis. The wall motion score (WMS) was calculated as the sum of each segment score. If the WMS increased by 2 points or more during exercise, the case was defined as having shown significant improvement of wall motion. Improvement in WMS was found in 26 (12%) of 209 serial patients who underwent exercise RNV, exercise thallium myocardial scintigraphy and coronary angiography. Clinically, half of these patients had a variant form of angina pectoris. With respect to coronary lesions in the segments with reversible asynergy, 12 patients had 0 vessel disease, 8 had lesions with stenosis of less than 75% and 3 showed an adequate collateral circulation. Redistribution found on the exercise thallium myocardial scintigram at the same sites of improved wall motion was identified in only 1 patient. An analysis of patients with paradoxical improvement of wall motion during exercise suggests the involvement of coronary spasm, an improvement of coronary flow reserve, such as could be produced by regression or recanalization of the main lesions, or establishment of significant collateral circulation.     

Long-term function in the remote region after myocardial infarction: importance of significant coronary stenoses in the non-infarct-related artery.

BACKGROUND--Left ventricular (LV) function is the most important determinant of outcome after a myocardial infarction. Global LV function after a myocardial infarction is affected not only by wall motion in the infarct zone but also by regional function in the contralateral territory. It was hypothesised that the presence of significant stenoses in coronary arteries supplying the contralateral territory might influence the ability of this region to compensate for damaged myocardium after a myocardial infarction. METHODS AND RESULTS--79 patients treated with thrombolysis for acute myocardial infarction had coronary and ventricular angiograms within 24 h and at a mean follow up of 12 months after myocardial infarction. Wall motion in the contralateral territory was analysed and scored by the centre line method and the change over time was correlated with the presence or absence of significant (> 70%) diameter stenoses in the non-infarct-related artery. Mean (SD) contralateral territory motion worsened, from 0.74 (1.78) to -1.55 (2.06) SD chord (p < 0.001) in 40 patients with stenoses, whereas contralateral territory motion improved from -0.02 (2.4) to 0.63 (2.21) SD chord (p < 0.05) in the 39 patients without coronary stenoses. The same pattern was present whether or not the infarct artery was patent. The global left ventricular ejection fraction at 12 months was also related to contralateral territory motion (r = 0.71, p < 0.001) and to the presence of coronary stenoses (54 (15)% in those with coronary stenoses and 62 (16)% in those without, p < 0.05). CONCLUSION--The results demonstrate that significant stenoses in arteries supplying the non-infarct territory adversely affect global and regional left ventricular function after a transmural infarction. Non-infarct artery anatomy should be considered in intervention strategies to improve left ventricular function after acute myocardial infarction.     

Dipyridamole magnetic resonance imaging: a comparison with thallium-201 emission tomography.

Limitation of space and motion artefact make magnetic resonance imaging during dynamic exercise difficult. Pharmacological stress with dipyridamole can be used as an alternative to exercise for thallium scanning. Forty patients with a history of angina and an abnormal exercise electrocardiogram were studied by dipyridamole thallium myocardial perfusion tomography and dipyridamole magnetic resonance wall motion imaging with a cine gradient refocused sequence. Images for both scans were obtained in the oblique horizontal and vertical long axis and short axis planes before and after pharmacological stress with dipyridamole. The myocardium was divided into nine segments for direct comparison of perfusion with wall motion. Segments were assessed visually into grades--normal, hypokinesis or reduced perfusion, and akinesis or very reduced perfusion. After dipyridamole there were reversible wall motion abnormalities in 24 (62%) of 39 patients with coronary artery disease and 24 (67%) of 36 patients with reversible thallium defects. The site of wall motion deterioration was always the site of a reversible thallium defect. Thallium defects affecting more than two segments were always associated with wall motion deterioration but most single segment thallium defects were undetected by magnetic resonance imaging. There was a significant correlation between detection of wall motion abnormality, the angiographic severity of coronary artery disease, and the induction of chest pain by dipyridamole. There were no significant differences in ventricular volume or ejection fraction changes after dipyridamole between the groups with and without detectable reversible wall motion changes but the normalised magnetic resonance signal intensity of the abnormally moving segments was significantly less than the signal intensity of the normal segments. In nine patients the change was apparent visually and it was maximal in the subendocardial region. Magnetic resonance imaging of reversible wall motion abnormalities in patients with coronary artery disease is feasible during pharmacological stress with dipyridamole and may be associated with a reduced magnetic resonance signal. The failure to show wall motion abnormalities in all cases of reversible thallium defects may be because the defect was small or because dipyridamole caused perfusion defects in the absence of myocardial ischaemia.     

Dipyridamole magnetic resonance imaging: a comparison with thallium-201 emission tomography

Limitation of space and motion artefact make magnetic resonance imaging during dynamic exercise difficult. Pharmacological stress with dipyridamole can be used as an alternative to exercise for thallium scanning. Forty patients with a history of angina and an abnormal exercise electrocardiogram were studied by dipyridamole thallium myocardial perfusion tomography and dipyridamole magnetic resonance wall motion imaging with a cine gradient refocused sequence. Images for both scans were obtained in the oblique horizontal and vertical long axis and short axis planes before and after pharmacological stress with dipyridamole. The myocardium was divided into nine segments for direct comparison of perfusion with wall motion. Segments were assessed visually into grades--normal, hypokinesis or reduced perfusion, and akinesis or very reduced perfusion. After dipyridamole there were reversible wall motion abnormalities in 24 (62%) of 39 patients with coronary artery disease and 24 (67%) of 36 patients with reversible thallium defects. The site of wall motion deterioration was always the site of a reversible thallium defect. Thallium defects affecting more than two segments were always associated with wall motion deterioration but most single segment thallium defects were undetected by magnetic resonance imaging. There was a significant correlation between detection of wall motion abnormality, the angiographic severity of coronary artery disease, and the induction of chest pain by dipyridamole. There were no significant differences in ventricular volume or ejection fraction changes after dipyridamole between the groups with and without detectable reversible wall motion changes but the normalised magnetic resonance signal intensity of the abnormally moving segments was significantly less than the signal intensity of the normal segments. In nine patients the change was apparent visually and it was maximal in the subendocardial region. Magnetic resonance imaging of reversible wall motion abnormalities in patients with coronary artery disease is feasible during pharmacological stress with dipyridamole and may be associated with a reduced magnetic resonance signal. The failure to show wall motion abnormalities in all cases of reversible thallium defects may be because the defect was small or because dipyridamole caused perfusion defects in the absence of myocardial ischaemia.     

Assessment of thallium scintigraphy and echocardiography during dobutamine infusion for the detection of coronary artery disease

Dobutamine infusion was performed in 16 patients following cardiac catheterization, and non-invasive assessment was performed with thallium SPECT and echocardiography. Dobutamine thallium scintigraphy was abnormal in 93% of patients with significant coronary artery disease. In addition, individual epicardial vessel involvement was identified by a corresponding perfusion defect with 88% sensitivity and 93% specificity. Dobutamine echocardiography revealed segmental wall motion abnormalities in 62% of patients with significant coronary disease. However, in six patients baseline segmental wall motion abnormalities on echocardiography improved during dobutamine infusion. Dobutamine thallium SPECT is a safe and useful test for the detection and localization of coronary artery disease. Dobutamine echocardiography is less useful in screening for coronary disease, but may detect areas of abnormally functioning myocardium having retained viability. © 1993 Wiley-Liss, Inc.     

Evaluation of myocarditis using T1-201 myocardial scintigraphy with bull's eye functional map

In order to evaluate myocardial damage in a patient with myocarditis, rest thallium-201 myocardial single photon emission computed tomography (SPECT) was performed in 15 patients with myocarditis. For qualitative and semiquantitative analysis, Bull's eye functional maps were made up with SPECT images. In the functional map, the abnormal area, where T1 uptake is less than mean-2SD of the T1 uptake of normal subjects, is generally distributed in the myocarditis group. But focal and sequential abnormal areas were recognized more often in the clinically severe cases. Abnormal area tended to be observed commonly at the antero-septal wall, but it was uncommon at the lateral wall. Extent score, i.e. degree of extension of abnormal area, and severity score, i.e. degree of abnormality, were in good negative correlation with left ventricular ejection fraction (r = 0.6, r = 0.7). Furthermore, existence of abnormal area was in good correlation with the left ventricular regional wall motion. Abnormal area existed 100% in the akinetic region, 71% in the region of severe hypokinesis, and 27% in the region of hypokinesis. Abnormal area occupied 30% of the normokinetic region in the myocarditis group, which was a higher rate than in the normal control group (p less than 0.05). It was suggested that latent myocardial damage existed in the normokinetic myocardium with myocarditis. Thus, rest T1-201 SPECT with Bull's eye map is useful for clinical diagnosis in patients with myocarditis.     

Comparison of exercise radionuclide angiography with thallium SPECT imaging for detection of significant narrowing of the left circumflex coronary artery.

Although quantitation of exercise thallium tomograms has enhanced the noninvasive diagnosis and localization of coronary artery disease, the detection of stenosis of the left circumflex coronary artery remains suboptimal. Because posterolateral regional wall motion during exercise is well assessed by radionuclide angiography, this study determined whether regional dysfunction of the posterolateral wall during exercise radionuclide angiography is more sensitive in identifying left circumflex disease than thallium perfusion abnormalities assessed by single-photon emission computed tomography (SPECT). One hundred ten consecutive patients with CAD were studied, of whom 70 had a significant stenosis of the left circumflex coronary artery or a major obtuse marginal branch. Both regional function and segmental thallium activity of the posterolateral wall were assessed using visual and quantitative analysis. Left ventricular regional function was assessed objectively by dividing the left ventricular region of interest into 20 sectors; the 8 sectors corresponding to the posterolateral free wall were used to assess function in the left circumflex artery distribution. Similarly, using circumferential profile analysis of short-axis thallium tomograms, left ventricular myocardial activity was subdivided into 64 sectors; the 16 sectors corresponding to the posterolateral region were used to assess thallium perfusion abnormalities in the left circumflex artery territory. Qualitative posterolateral wall motion analysis detected 76% of patients with left circumflex coronary artery stenosis, with a specificity of 83%, compared with only 44% by qualitative thallium tomography (p less than 0.001) and a specificity of 92%. Whereas quantitation of thallium activity increased the sensitivity for detecting left circumflex coronary artery stenosis to 80% with a specificity of 55%, it did not achieve statistical significance when compared with qualitative wall motion analysis.(ABSTRACT TRUNCATED AT 250 WORDS)     

The oxygen consumption paradox of “stunned myocardium” in dogs

Summary The contractile state of the heart is a major determinant of myocardial oxygen consumption. Since regional myocardial contractility can be severely impaired following a transient coronary occlusion, post-ischemic myocardium is frequently assumed to consume less oxygen. To test this assumption, regional myocardial function and oxygen consumption were studied in ancsthetized dogs during 2 h of myocardial reperfusion following either a 15-min (Group I) or 4-h (Group II) left anterior descending coronary artery occlusion. Both groups developed similar post-ischemic regional dysfunction characterized by paradoxical motion (negative shortening). Measured as a percent of baseline segment shortening, anterior wall function in Group I (n=8) and Group II (n=5) at 30 min of reperfusion was –33±11% and –34±16% (p=NS) and at 120 min was –23±9% and –40±16% (p=NS). However, the two groups showed a marked difference in regional myocardial oxygen consumption during reperfusion. Despite the abnormal wall motion, regional oxygen consumption in Group I at 30 and 120 min of reperfusion was unchanged from pre-ischemic levels as measured as a percent of bascline: 104±20% (p=NS) and 111±21% (p=NS). In contrast, regional oxygen consumption in Group II was markedly depressed from bascline at 30 and 120 min of reperfusion: 42±7% (p<.01) and 40±8% (p<.01). To determine whether the dissociation between regional myocardial oxygen consumption and function in Group I was related to mitochondrial uncoupling, six additional dogs were studied. Tissue samples were obtained from post-ischemic myocardium after 120 min of reperfusion following a 15-min coronary artery occlusion, and compared to non-ischemic myocardium. There were no differences in the in vitro mitochondrial respiratory rates or oxidative phosphorylation capacity between the post-ischemic and non-ischemic myocardium. Therefore, in the post-ischemic myocardium, significant depressions in regional contractility may not be associated with falls in oxygen consumption. Following a 15-min coronary artery occlusion, the injured myocardium maintains a paradoxically high oxygen consumption with normal mitochondrial function despite decreased contractility and abnormal wall motion.Grant Support: Dr. Dean was a Fellow of the American Heart Association. Dr. Nicklas is supported by the NIH Clinical Investigator Award, HL 011170.