Poststress redistribution of thallium-201 in patients with coronary artery disease, with and without prior myocardial infarction

To elucidate patterns of thallium-201 redistribution with and without myocardial infarction, to determine the value of thallium-201 redistribution scintigrams in identifying additional ischemic myocardium in the presence of prior myocardial infarction and to delineate the relation of collateral vessels to redistribution, thallium-201 myocardial perfusion scintigraphy was performed immediately after exercise and 4 to 6 hours after exercise in 46 patients with coronary artery disease and 12 normal control subjects. Scintigrams were interpreted in the conventional visual manner as well as with use of computer-processed myocardial perfusion ratios. Normal control subjects demonstrated uniform thallium-201 distribution with regional perfusion ratios approximating unity in both the early and delayed scintigrams.

Of 27 patients with prior myocardial infarction, 5 (19 percent) had complete redistribution on delayed imaging, 17 (62 percent) had partial redistribution and 5 (19 percent) had no redistribution. Of 25 regions corresponding to electrocardiographlc evidence of infarction, 8 (32 percent) had total, 8 (32 percent) had partial and 9 (36 percent) had no redistribution. Collateral vessels were absent or of poor quality in seven of eight infarct areas with no redistribution; three of four infarct regions with normal early thallium uptake were supplied by collateral vessels of good quality. Of 12 regions supplied with good collateral vessels, 9 had complete redistribution, 2 partial and 1 no redistribution. In contrast, only 2 of 21 hypoperfused zones without redistribution (10 percent) were supplied by good collateral vessels. Of 19 patients without prior myocardial infarction, 10 (53 percent) had complete redistribution, 6 (31 percent) had partial redistribution and 3 (16 percent) had no redistribution. Of the 34 abnormal areas in the immediate postexercise image, 22 (65 percent) showed total redistribution, 3 (9 percent) showed partial redistribution and 9 (26 percent) showed no redistribution.

Thus, considerable overlap in redistribution scintigrams occurs in patients with coronary artery disesase with and without prior infarction; a high incidence rate of transient stress-induced hypoperfusion occurs in both infarcted and noninfarcted myocardium. Further, good quality collateral vessels afford redistribution, even to some areas of prior infarction. These data indicate that because delayed postexercise redistribution imaging may not discriminate between myocardial scar and ischemia resting scintigrams may be needed in a substantial number of patients.     

Noninvasive assessment of coronary artery bypass patency: Determination of myocardial thallium-201 washout rates*

This prospective study was undertaken to investigate the responseof thallium-201 washout rates to coronary artery bypass surgery.Thirty-four patients with coronary heart disease were studiedbefore and after coronary artery bypass grafting, 27 patientswith normal coronary arteries serving as controls. All patientsunderwent cardiac catheterization and thallium-201 serial imaging,including assessment of myocardial washout rates. Pre-operatively,thallium-201 washout rates yielded a considerably higher sensitivityin detection of coronary artery disease, without significantloss of specificity compared to qualitative evaluation of serialstatic thallium-201 scintigrams. Post-operatively, 50 of 57segments supplied by a patent graft showed normal washout rates,while in 9 out of 11 segments an occlusion of the graft wasindicated by decreased washout rates. Compared to pre- and post-operativequalitative interpretation of static thallium-201 images, thepostoperative assessment of washout rates increased both sensitivity(82% vs. 64%) and specificity (88% vs. 77%) for the evaluationof bypass graft patency. Thus, quantitative assessment of thallium-201washout rates improves the diagnostic reliability of noninvasivedetection of myocardial ischaemia with regard to the evaluationof coronary artery bypass graft patency.     

Early patency of the infarct-related artery after myocardial infarction preserves diastolic filling

A patent infarct-related artery (IRA) following myocardial infarction has been associated with lower mortality, increased systolic function, decreased left ventricular remodeling, and electrical stability. The purpose of this study was to determine whether coronary artery patency early after myocardial infarction is associated with greater early diastolic filling than a closed artery. Radionuclide ventriculograms were performed at a central laboratory on 167 patients who received alteplase for an acute myocardial infarction and had infarct artery patency determined by cardiac catheterization. The peak early filling rate (PEFR) was assessed by 4 different methods: (1) PEFR (EDV/s)--normalized to the end-diastolic volume; (2) PEFR (SV/s)--normalized to the stroke volume; (3) PEFR (ml/s/m(2))--an absolute diastolic filling rate; and (4) PEFR (PER)--normalized to the peak ejection rate. Patients with a closed IRA (n = 16, Thrombolysis In Myocardial Infarction [TIMI] 0 or 1 flow) and patients with an open IRA (n = 151, TIMI 2 or 3 flow) had similar ages, ejection fractions, and cardiac volumes. However, among patients with an occluded IRA, the PEFR was decreased by 12% to 18% by the 4 measures of diastolic filling (3 of 4 methods, p <0.05). PEFR (EDV/s) was 1.69 +/- 0.9 in the occluded group versus 2.06 +/- 0.4 EDV/s in the open artery group (p = 0.005). By multivariate analysis, IRA patency was an independent predictor of the PEFR by all 4 methods. Early coronary artery patency after an acute myocardial infarction preserves diastolic filling. Improved diastolic function may in part explain part of the long-term benefits of a patent IRA after thrombolytic therapy when there is no documented improvement in the ejection fraction.     

Late arrhythmic events and patency of the infarct-related coronary artery in survivors of acute myocardial infarction.

In the present study we evaluated the influence of intravenous thrombolysis and patency of the infarct-related coronary artery on both markers of ventricular electrical instability and incidence of late arrhythmic events after acute myocardial infarction (AMI). Ninety one patients surviving a first AMI who consecutively performed coronary angiography were enrolled in the present study; 44 patients (48%) received thrombolysis, 47 patients (52%) were treated conventionally. Of 91 patients, 90 (99%) had signal-averaged electrocardiogram (SAECG), and 40 (44%) programmed ventricular stimulation. No significant difference was observed between thrombolytic-treated and control group in late potential rate, SAECG determinants and ventricular arrhythmia inducibility. Of 91 patients, 40 (44%) had occlusion of the infarct-related artery: of these, 15 (37%) had late potentials compared with 5 of 51 patients (9%) with a patent artery (p < 0.01). Mean left ventricular ejection fraction was not significantly different between the two groups (0.50 +/- 0.15 vs 0.55 +/- 0.12; p = NS). No significant difference was present between the two groups of patients with regard to inducibility of sustained ventricular tachyarrhythmias, however an odds ratio of 3.5 was observed in the group with a closed vessel.(ABSTRACT TRUNCATED AT 250 WORDS)     

Evaluation of thallium-201 imaging in nontransmural ischemia and infarction

To assess the validity of thallium-201 myocardial imaging in the diagnosis of non-transmural ischemia and infarction, the proximal left anterior descending coronary artery was partially occluded for 60 minutes with a balloon-tip catheter in intact anesthetized dogs in a basal state or during atrial pacing. In vivo sclntigrams of myocardium were compared with those obtained in the isolated heart and in the incised ventricle spread flat. None of the animals with partial occlusion wtth or without pacing demonstrated abnormal scintiscans in vivo. Removal of background by isolating the heart increased positive images to 30%; positive images were associated wtth an isotope count ratio between ischemlc and normal muscle of less than 0.67. Removal of superimposed nonischemic muscle in the heart enface increased image detection after pacing to 11 of 15. Since animals with subendocardlal scar failed to demonstrate a “cold area” in vivo, unfavorable geometry as well as extent and degree of ischemia appear to be important Thus, thallium radioactivity in superimposed and adjacent myocardium, as well as background, may limit the detection of nontransmural ischemia and scar.     

静脉溶栓冠脉再通对急性心肌梗死生存率的影响

目的：探讨静脉溶栓对急性心肌梗死存活率的影响。方法：对64例经静脉溶栓治疗的患,以临床血管再通为标准,对比分析再通组与未通组的存活率。结果：血管再通组存活率为97．6％,死亡率2．4％,未通组存活率为73％,死亡率27％,结论：急性心肌梗死静脉溶栓治疗是提高生存率的关键。     

Reverse and pseudo redistribution of thallium-201 in healed myocardial infarction and normal and negative thallium-201 washout in ischemia due to background oversubtraction

While the interpolative background subtraction used in quantitative planar thallium scanning can significantly overestimate the background overlying the heart, the effects of background oversubtraction on quantitative analysis have not been well defined. A mathematical model that relates myocardial washout determined using interpolative background subtraction to true myocardial washout is presented. The model was validated using phantoms and applied to myocardial and pulmonary thallium kinetic data in 100 patients, 85 with and 15 without coronary artery disease. The model showed that when using interpolative background subtraction, measured washout equals true washout in normally perfused myocardium; however, depending on the relation between myocardial and pulmonary thallium clearance, myocardial washout in ischemic regions and areas of infarction can be substantially over- or underestimated. Based on generally accepted quantitative criteria, this incorrect washout determination can at times lead to misdiagnosis of infarction as ischemia and ischemia as normally perfused tissue. It can also cause both "reverse redistribution" and "pseudo redistribution" of thallium in myocardial infarction in the absence of a physiologic basis.     

急性心肌梗死后的延迟冠状动脉内支架植入治疗

目的　评估急性心肌梗死后梗死相关冠状动脉内支架植入的临床疗效。方法　 15 4例急性心肌梗死患者 ,平均年龄 (6 1± 12 )岁于发病后平均 13天行冠状动脉内支架术 ,所有患者常规服用肠溶阿司匹林和噻氯匹定。观察住院期和随访期的临床事件。结果　 15 4例患者共植入 173个支架 (平均 1 1个 /例 )。支架植入的指征 :选择性初发病变 (denovo)占 2 4 3 % ,急性或濒危闭塞占13 9% ,有发生闭塞高危因素的病变占 6 1 8%。所用支架主要为Nir支架 (2 6 % )、Multi Link支架(19% )、XT支架 (13% )、Crossflex支架 (10 % ) ,等等。支架植入时最大球囊充盈压力为 (12± 2 )大气压。平均残余狭窄 (7± 8) %。住院期间无一例死亡、心肌梗死和需重复再通治疗 ,但术后“微坏死(micronecrosis)”率为 1 3%。术后 6个月病死率为 3 9% ,Q波型或非Q波型心肌梗死率为 1 9% ,支架内再狭窄而行再次冠状动脉腔内成形术率 6 1%。总的无心脏事件存活率为 89 6 %。结论　心肌梗死后行冠状动脉内支架术是安全的 ,并能改善患者的近期预后 ,但其远期疗效尚需进一步研究。     

Reverse redistribution of thallium-201 myocardial single photon emission tomography and contractile reserve

The present study investigated the contractile reserve of myocardium exhibiting reverse redistribution (RRD) of thallium-201 (201Tl) after acute myocardial infarction. Forty patients experiencing their first acute myocardial infarction underwent resting 201Tl single-photon emission computed tomography (SPECT) and low-dose (5-10 microgxkg(-1)xmin(-1)) dobutamine stress echocardiography (DSE) within 4 weeks after the onset of infarction. The left ventricle was divided into 13 segments for analysis. The severity of defects in 201Tl SPECT and the extent of wall motion abnormality in DSE were visually assessed and scored. The sum of each defect score and wall motion score of infarct-related segments were defined as total defect score (TDS) and total wall motion score (TWM), respectively. Quantitative analysis of 201Tl uptake was also performed. Resting 201Tl SPECT revealed RRD in 16 patients (group RRD), fixed defect (FIX) in 23 patients (group FIX), and redistribution in one. There was a significant difference in improvement of TWM between rest and stress in TWM in both the RRD and FIX groups (p<0.0001, each case). The improvement of TWM with dobutamine was significantly greater in RRD than in FIX (1.6+/-1.0 vs 0.6+/-0.7, p=0.001). There was a positive correlation between the magnitude of RRD and improvement of TWM with dobutamine (r=0.48, p=0.002). Myocardium exhibiting RRD on 201Tl SPECT in patients with acute myocardial infarction has greater contractile reserve than that exhibiting a fixed defect.     

Reverse redistribution on exercise thallium scintigraphy: relationship to coronary patency and ventricular function after myocardial infarction.

OBJECTIVE: To define prevalence, pathophysiology and relation to thrombolytic therapy of reverse redistribution (appearance of a new, or worsening of an existing, scintigraphic defect on 4 h delayed images compared with the stress thallium image). DESIGN: Randomized, double-blind, placebo-controlled trial. SETTING: Referral centre. PATIENTS: Sixty-three patients with acute myocardial infarction. INTERVENTIONS: Tomographic exercise thallium scintigraphy, radionuclide angiography, and quantitative coronary angiography. MAIN RESULTS: Tomographic exercise thallium scintigraphy performed at day 10 revealed fixed defects in 15 patients, reversible defects in 22 patients and reverse redistribution in 26 patients; no difference in treatment assignment (tissue plasminogen activator versus placebo) was found among the three groups. Left ventricular function was similar in patients with fixed or reversible defects and reverse redistribution; global ejection fraction was 48 +/- 14, 51 +/- 10 and 48 +/- 5%, respectively, and regional infarct ejection fraction was 36 +/- 15, 40 +/- 13 and 37 +/- 18%, respectively. However, nitroglycerin administration resulted in a significantly greater improvement in regional ejection fraction in reverse redistribution patients (5 +/- 4%) than that in patients with fixed defect (2 +/- 5%, P < 0.05) or reversible defects (3 +/- 5%, P < 0.05). The infarct-related artery had a greater cross-sectional area in reverse redistribution patients (1.5 +/- 1.42 mm2) compared with those with reversible defects (0.50 +/- 0.26 mm2, P < 0.05), but was similar to fixed defect patients (1.04 +/- 0.88). CONCLUSIONS: Reverse redistribution on tomographic thallium scintigraphy is a frequent phenomenon (occurring in 40% of patients following acute myocardial infarction) and is independent of thrombolytic therapy. Patients with reverse redistribution have a more widely patent infarct-related artery and similar ventricular function, but significantly greater functional improvement following nitroglycerin administration compared with those with reversible or fixed defects. These data suggest myocardial salvage within the infarct zone in some patients with reverse redistribution.     

Relationship between changes in ST segment elevation and patency of the infarct-related coronary artery in acute myocardial infarction

Forty-one patients with acute myocardial infarction and ST segment elevation were studied to determine the relationship between early changes in ST segment elevation, time to peak serum creatine kinase (CK), peak serum CK, left ventricular function, and patency of the infarct-related artery. ST segment elevation decreased by more than 40% within 8 hours of peak sigma ST in all patients with inferior infarction and in 10 of the 13 patients with anterior infarction and subtotal occlusion, but in none of the patients with anterior infarction and total occlusion (p = 0.003). The time to peak serum CK was related to the rate of decrease of ST segment elevation in patients with anterior (r = 0.59) and inferior (r = 0.71) infarction. In patients with anterior infarction, peak serum CK tended to be lower and left ventricular ejection fraction (EF) higher in those with rapid resolution of ST segment elevation than in those with persistent ST elevation (1721 +/- 1422 U/L vs 3285 +/- 1148 U/L, p less than 0.10, for peak CK; and 50.3 +/- 18.5% vs 41.2 +/- 12.8%, p = NS, for EF), but there was no difference in the patients with inferior infarction. Early resolution of ST segment elevation is an index of early spontaneous antegrade or collateral reperfusion in patients with acute myocardial infarction.     

Functional role of microvascular integrity in patients with infarct-related artery patency after acute myocardial infarction

AIMS: The study was set up to evaluate the functional role of post-infarctpreserved microvascular integrity. Low dose dobutamine echocardiographyand myocardial contrast echocardiography were used to studypatients before hospital discharge who had suffered a recentmyocardial infarction and had a patent infarct-related artery(TIMI flow grade 3). METHOD: In the dysfunctioning infarct area, the wall motion score indexwas calculated at baseline, during the dobutamine infusion andat the 3 month follow-up echocardiogram; contrast echocardiographywas performed at the time of coronary angiography, before hospitaldischarge. RESULTS: In patients with more than 50% of the dysfunctioning infarctarea opacified at contrast echocardiography (group A), regionalwall motion score index decreased, compared to baseline, duringthe dobutamine infusion (1·97 ± 0·78 vs2·5 ± 0·35 at baseline; P<0·001)and at follow-up echocardiography (1·83 ± 0·63vs 2·5 ± 0·35 at baseline; P<0·001).In patients with less extensive microvascular integrity as revealedby contrast echocardiography (group B), regional wall motionscore index did not decrease from baseline during either thedobutamine infusion (2·73 ± 0·21 vs 2·81± 0·20 at baseline; P=ns) or at follow-up (2·81± 0·20 vs 2·81 ± 0·20 atbaseline; P=ns). CONCLUSION: In patients with post-infarct dysfunctioning myocardium buta patent infarct-related artery, microvascular integrity, asassessed by myocardial contrast echocardiography, is an indicatorof myocardial viability in terms of preserved contractile reserve,as demonstrated by dobutamine infusion and functional recoveryat follow-up.     

Association of patency of the infarct-related coronary artery with plasma levels of plasminogen activator inhibitor activity in acute myocardial infarction.

To examine the fibrinolytic capacity in patients with acute myocardial infarction (AMI), baseline levels of plasma plasminogen activator inhibitor (PAI) activity and tissue-type plasminogen activator (t-PA) antigen were measured in 47 patients with Q-wave AMI who underwent emergent coronary angiography 3.0 +/- 0.2 hours after the symptom onset. They received intracoronary injection of urokinase if their infarct-related arteries were occluded. They were classified into 3 groups according to the patency of the infarct-related artery before and after thrombolytic therapy: the patent group (13 patients), the recanalized group (23 patients) and the occluded group (11 patients). The mean level of plasma PAI activity (IU/ml) was higher in patients with AMI as a whole than in the control group (12.8 +/- 1.6 vs 5.4 +/- 0.5, p less than 0.01). The level was lower in the patent group (3.0 +/- 1.1) and higher in the recanalized (18.6 +/- 2.2) and occluded (10.8 +/- 2.5) groups than in the control group (each p less than 0.01). The level was lower in the occluded than in the recanalized group (p less than 0.01) and 62% of the patients in the occluded group had levels within range of the control group. The mean level of plasma t-PA antigen (ng/ml) was higher in patients with AMI as a whole than in the control group (10.3 +/- 0.8 vs 5.8 +/- 0.3, p less than 0.01). There was no difference in the level among the 3 groups with AMI.(ABSTRACT TRUNCATED AT 250 WORDS)     

Correlations between redistribution areas observed on exercise thallium-201 myocardial SPECT images and the coronary collateral circulations in patients with myocardial infarction]

The significance of coronary collateral circulation for redistribution in the infarcted zone was evaluated in 16 patients with history of myocardial infarction and severe stenosis (> or = 90%) of the coronary artery. Redistribution areas were quantitatively measured using the redistribution ratios and redistribution indices on the infarction-redistribution map obtained by thallium-201 scintigraphy with single photon emission computed tomography. Coronary collateral findings were categorized in 4 classes according to the Rentrop's grading. There was good, positive linear correlation between the redistribution ratio (Y) and collateral grading (X) (Y = 0.21X + 0.10, r = 0.92, p < 0.01). The redistribution index (X) also correlated well with the collateral grading (Y) using a good, positive quadratic equation (Y = 0.32X2 + 0.24X + 0.04, r = 0.89, p < 0.01). These results suggest that the measurements of the redistribution areas in the ischemic zone in myocardial infarction correlated well with collateral perfusion. Collateral perfusion severer than Rentrop's grade 2 markedly reduces the severity of ischemia and increases redistribution areas.     

Correlation between infarct-related coronary artery patency and predischarge electrocardiographic patterns in patients with first anterior myocardial infarction who received thrombolytic therapy

The aim of this study was to investigate the correlation between the ST-segment and T-wave patterns in predischarge electrocardiogram and patency of left anterior descending coronary artery in patients with a first anterior myocardial infarction (AMI). One hundred and fifty-six of 175 consecutive patients who were admitted to our clinic between January 2000 and September 2002 due to a first episode of transmural AMI and who received thrombolytic therapy were enrolled. Coronary angiography was performed by the Judkins method on the 6th–10th day after the acute infarction. The corrected TIMI frame count (CTFC) was estimated according to the previously described method. According to the combination of the ST-segment and T-wave morphology on the day (6–10) of cardiac catheterization, patients were classified into four groups: group A, ST elevation 0.1mV and negative T waves; group B, ST elevation 0.1mV and negative T waves; group C, ST elevation 0.1mV and positive T waves; and group D, ST elevation 0.1mV and positive T waves. Of the 99 patients with negative T waves, 47 (48%) had CTFC 27, 32 (32%) CTFC between 27 and 40, 15 (15%) CTFC 40–100, and 5 (5%) CTFC 100. Of the 57 patients with positive T waves, CTFC was 27 in 14 (25%), between 27 and 40 in 17 (30%), 40–100 in 11 (19%), and 100 in 15 (26%) (P 0.001). From the 76 patients with an isoelectric ST segment, 38 (50%) had CTFC 27, 29 (38%) CTFC between 27 and 40, 8 (11%) CTFC 40–100, and 1 (1%) CTFC 100. Of the 80 patients with an elevated ST segment, 23 (29%) had CTFC 27, 20 (25%) CTFC between 27 and 40, 18 (23%) CTFC 40–100, and 19 (23%) CTFC 100 (P 0.001). Use of the combination of two electrocardiographic parameters (ST segment and T waves) also indicated that there were significant differences between groups A and D, and groups B and D (P 0.001 and P 0.05, respectively). Development of an isoelectric ST segment with negative T waves may indicate a better degree of reperfusion after AMI. In contrast, patients in whom ST-segment elevation and positive T waves remain at discharge from the coronary care unit have a higher probability of a nonpatent left anterior descending artery.     

Inducible ventricular arrhythmias and patency of infarct-related artery in survivors of acute myocardial infarction.

BACKGROUND: Patency of infarct-related artery in patients who suffered an acute myocardial infarction (AMI) has been shown to be associated with improved survival. Ventricular tachyarrhythmias induced by programmed electrical stimulation may be predictive of arrhythmic events and sudden death. HYPOTHESIS: The study was undertaken to assess the possible effect of a patent infarct-related coronary artery on induced ventricular tachyarrhythmias during programmed ventricular stimulation in survivors of AMI. METHODS: In this prospective study, programmed electrical stimulation was performed before hospital discharge (14 +/- 2 days) in 79 patients who survived an AMI. Patients were subdivided into two groups: Group I with patent infarct-related coronary artery (n = 64) and Group 2 with occluded infarct-related artery (n = 15) at coronary angiography performed at 14 +/- 2 days. These two groups were comparable in terms of mean left ventricular ejection fraction, location of infarct-related artery, number of diseased vessels, peak creatine kinase value, and infarct location. RESULTS: Ventricular arrhythmias were induced in 21 patients ( 32.6%) of Group I and 4 patients (26.6%) of Group 2. This difference was not statistically significant. CONCLUSION: This study suggests that ventricular arrhythmias induced by programmed ventricular stimulation in survivors of AMI did not differ whether the infarct-related artery was patent or occluded. Other factors may play a role in electrical instability as assessed by programmed ventricular stimulation.     

Effect of eating on thallium-201 myocardial redistribution after myocardial ischemia

To determine whether eating a high-carbohydrate meal between initial and delayed postexercise thallium-201 (Tl-201) imaging affects detection of Tl-201 redistribution during exercise stress testing, 16 patients with stable angina performed 2 Tl-201 treadmill exercise stress tests within a 14-day interval. Immediately after initial postexercise imaging, patients either drank a commercially available instant breakfast preparation for the intervention test or drank an equivalent volume of water for the control test. Comparable exercise workloads were achieved by exercising patients to the same heart rate for both tests. The order of the 2 (intervention and control) tests were randomized. All patients had at least 1 region of Tl-201 myocardial redistribution on either their eating or control test scans, although only 7 of the 16 had positive treadmill exercise test responses. Forty-six regions showing Tl-201 myocardial redistribution were identified in all 144 regions examined. Significantly more of these regions were identified on control test scans than on eating test scans: 11 of 46 on both test scans, 6 of 46 only on eating test scans and 29 of 46 only on control scans (p less than 0.001). Consistent with results of the quantitative regional analysis, the percentage of Tl-201 clearance over 4 hours in the 46 Tl-201 myocardial redistribution regions was 39 +/- 8% for the eating tests and 29 +/- 8% for control tests (mean +/- standard deviation, p less than 0.003). In 4 patients diagnosis of transient ischemia would have been missed because their 14 Tl-201 myocardial redistribution regions were detected only on the control test scans.(ABSTRACT TRUNCATED AT 250 WORDS)