Serial Thallium-201 Myocardial Perfusion Scanning in Acute Myocardial Infarction*

Summary Serial myocardial perfusion scanning was performed in 30 patients with acute myocardial infarction. Scanning was commenced less than six hours after onset of symptoms in 12 patients, 6–24 hr in eight and 24–120 hr in ten. All 30 patients showed thallium defects corresponding to the ECG site of infarction. When initial and four-hour scans were compared, constant defects were present in ten patients and changing defects in 20. Of the 169 segments with defects on the initial scan, 117 (69%) remained constant, 41 (24%) improved, and 11 (7%) deteriorated. More defects changed in the patients scanned earlier (< 6hr) than in the patients scanned later (> 6hr) (42% vs 23% P < 0·025), and more defects changed in patients with subendocardial compared to transmural infarction (49% vs 26% P < 0·025). During a mean follow-up period of 18 months, seven patients died, two developed left ventricular failure, seven had angina and 14 remained asymptomatic. The non-survivors had significantly larger thallium defects than the survivors (55 ± 15% vs 37 ± 14%, P < 0·005). Serial change on thallium scanning was not related to the clinical course. Perfusion defects on serial thallium scanning are useful in detecting and localising early myocardial infarction and the size of defects is related to the subsequent clinical course. Changing perfusion defects on serial scanning suggesting peri-infarctional ischaemia are common, and make assessment of therapeutic interventions to limit infarct size difficult, but are not related to the clinical course.     

The Value of Exercise Electrocardiography and Exercise Thallium-201 Myocardial Perfusion Scanning in Determining the Presence of Single Vessel Coronary Artery Obstruction

Summary: In 39 patients with single vessel coronary artery disease and no previous myocardial infarction, exercise thallium-207 myocardial perfusion scanning and 12 lead exercise electrocardiography (ECG) were compared to see how reliably each method identified the site of coronary artery obstruction. Significant (≥ 70% diameter) stenosis was present in the left anterior descending (LAD) coronary artery in 21 patients, in the right coronary artery (RCA) in 14 patients and in the left circumflex (LCX) in four patients. Thallium defects on the scan in the septa1 (SEPT), anteroseptal (ANT SEPT) and anterior (ANT) segments correlated (P < 0.0005) with LAD disease and defects in the inferior (INF), posteroinferior (POST INF), and posterior (POST) segments correlated (P < 0.0005) with RCA or LCX disease. Exercise induced ST segment elevation in VI and/or AVL correlated with LAD disease. The site of ischaemic ST depression did not correlate with disease in any vessel. ST segment depression in leads L2, 3, AVF (67%) and in leads V4–6 (67%) was most sensitive for detecting patients with LAD disease and ST depression in leads V4–6 was most sensitive (56%) for detecting patients with RCA or LCX disease but neither differentiated LAD from RCAILCX disease.
During exercise induced ischaemia, the site of ST segment depression on the 12 lead exercise ECG will not identify the area of ischaemia in patients with single vessel disease but thallium defects will. In contrast to ST depression, ST elevation in V1 and/or AVL may identify LAD stenosis.     

Prospective evaluation of a rapid nanoparticle‐based lateral flow immunoassay (STic Expert® HIT) for the diagnosis of heparin‐induced thrombocytopenia

A rapid lateral flow immunoassay (LFIA) (STic Expert^® HIT), recently developed for the diagnosis of heparin‐induced thrombocytopenia (HIT), was evaluated in a prospective multicentre cohort of 334 consecutive patients. The risk of HIT was estimated by the 4Ts score as low, intermediate and high in 28·7%, 61·7% and 9·6% of patients, respectively. Definite HIT was diagnosed in 40 patients (12·0%) with positive results on both enzyme‐linked immunosorbent assay (Asserachrom^® HPIA IgG) and serotonin release assay. The inter‐reader reproducibility of results obtained was excellent (kappa ratio > 0·9). The negative predictive value of LFIA with plasma samples was 99·6% with a negative likelihood ratio (LR) of 0·03, and was comparable to those of the particle gel immunoassay (H/PF4‐PaGIA^®) performed in 124 cases. Positive predictive value and positive LR were 44·4% and 5·87, respectively, and the results were similar for serum samples. The probability of HIT in intermediate risk patients decreased from 11·2% to 0·4% when the LFIA result was negative and increased to 42·5% when it was positive. In conclusion, the STic Expert^® HIT combined with the 4Ts score is a reliable tool to rule out the diagnosis of HIT.     

运动负荷201铊单光子发射型计算机断层显像判断经皮冠状动脉腔内成形术后再狭窄的价值

目的 :探讨运动负荷 2 0 1铊 (2 0 1 Tl)单光子发射型计算机断层显像 (Ex- 2 0 1 Tl SPECT)判断经皮冠状动脉腔内成形术(PTCA)后再狭窄的价值。　　方法 :对 PTCA术后 3～ 6个月的 12 8例患者 (心绞痛 74例 ,陈旧性心肌梗塞 5 4例 )进行 Ex- 2 0 1 Tl SPECT及运动负荷心电图 (Ex- ECG)。将左心室划分为 9个节段 ,采用 4级评分法对 2 0 1 Tl分布进行视觉评价 ,比较延迟像与负荷像的核素分布。　　结果 :12 8例冠心病患者 ,Ex- 2 0 1 Tl SPECT判断冠状动脉再狭窄的敏感性及特异性分别为 79%、89% ,明显高于 Ex-ECG(Ex- ECG 为 5 9%、6 8% ,Ex- ECG 为 5 2 %、74% ) ;心肌梗塞患者的 Ex- 2 0 1 Tl SPECT敏感性明显高于 Ex- ECG (P<0 .0 1) ,其特异性无显著差别。冠状动脉再狭窄程度越重 (狭窄 <10 0 % ) ,其检出率越高。　　结论 :Ex- 2 0 1 Tl SPECT使心肌显像对判断 PTCA术后再狭窄具有较大的临床应用价值。     

Comparison of dobutamine stress echocardiography and exercise stress Thallium-201 SPECT for detection of myocardial ischemia after acute myocardial infarction treated with thrombolysis

In order to compare the ability of dobutamine stress echocardiography (DSE) and exercise Thallium-201 SPECT to detect myocardial ischemia in patients with myocardial infarction (Ml) treated with thrombolysis, 43 prospectively selected patients with Ml treated with thrombolysis underwent within 1 month from Ml DSE, stress-redistribution-reinjection Thallium-201 SPECT and coronary angiography. The echocardiographic and scintigraphic images were analyzed for the presence of myocardial ischemia using a 11-segment left ventricular model. DSE and exercise Thallium-201 SPECT detected myocardial ischemia in the infarct zone in 72 and 72 (31/43) of patients and ischemia at a distance in 12 (5/43) and 19 (8/43) of patients with a concordance of 67 and 88 , respectively. A significant agreement between DSE and exercise Thallium SPECT was found in the evaluation of the extent of both myocardial necrosis and stress-induced myocardial ischemia. DSE and exercise Thallium SPECT showed similar sensitivity (79 vs 76), specificity (60 vs 60) and accuracy (77 vs 74) for detection of a critical stenosis of the infarct-related artery; there was also no significant difference between the tests in sensitivity, specificity and accuracy for detection of the multivessel disease.In conclusion, initially after thrombolyzed MI, DSE and exercise Thallium-201 SPECT detect myocardial ischemia in the infarct zone in a high proportion of patients and show a similar accuracy for the diagnosis of a critical stenosis of the infarct-related coronary artery and of the multivessel disease.     

Comparison of Technetium-99m Tetrofosmin and Thallium-201 Single-Photon Emission Computed Tomographic Imaging for Detection of Myocardial Perfusion Defects in Patients With Coronary Artery Disease

Objectives. We compared dipyridamole technetium-99m (Tc-99m) tetrofosmin and thallium-201 (Tl-201) single-photon emission computed tomographic (SPECT) imaging with respect to the detection rate of perfusion abnormalities in 26 patients with angiographic coronary artery disease (CAD).Background. Experimental studies have shown that myocardial extraction of Tc-99m tetrofosmin is lower than that of Tl-201 at high flow rates, resulting in less severe defects with vasodilator stress. It is uncertain whether this results in a lower sensitivity than Tl-201 for detecting coronary stenoses with vasodilator stress in patients.Methods. Twenty-six patients with CAD underwent both dipyridamole Tl-201 and Tc-99m tetrofosmin SPECT. Tomographic images were scored for initial defects and the presence of reversibility. Defect magnitude was computer quantitated.Results. Of the 26 patients, 25 had defects on both Tl-201 and Tc-99m tetrofosmin SPECT images. Of 340 segments analyzed, 102 had defects by Tl-201 and 92 by Tc-99m tetrofosmin (p = NS). Whereas Tl-201 detected 27 fixed defects in 12 patients, Tc-99m tetrofosmin identified 37 fixed defects in 14 patients (p = NS). In contrast, Tl-201 identified more reversible and partially reversible defects than did Tc-99m tetrofosmin (89 vs. 55, p = 0.002). The average defect magnitude (percent normal) was similar for defects concordantly graded as fixed (38 ± 3.0% for Tl-201 vs. 42 ± 4% [mean ± SEM] for Tc-99m tetrofosmin, p = NS). The average defect magnitude for defects concordantly graded as completely reversible was significantly more severe on Tl-201 than on Tc-99m tetrofosmin (49 ± 3% vs. 58 ± 3%) SPECT images. A significantly greater defect magnitude for Tl-201 was also found for defects concordantly classified as partly reversible (30 ± 4% for Tl-201 vs. 45 ± 5% for Tc-99m tetrofosmin).Conclusions. With dipyridamole stress, 1) at least one defect was seen on both Tl-201 and Tc-99m tetrofosmin SPECT images; 2) Tc-99m tetrofosmin SPECT identified fewer reversible defects than did Tl-201, but showed a similar number of fixed defects; 3) the magnitude of reversible defects seen on Tc-99m tetrofosmin images was less, whereas fixed defects were similar for both tracers; 4) reversible defects seen on Tl-201 and not on Tc-99m tetrofosmin SPECT images were predominantly regions perfused by mild coronary stenoses.     

负荷心肌灌注显像在心肌桥临床应用中的研究进展

负荷心肌灌注显像通过检测核素在心肌的分布,明确心肌缺血的部位和程度,因此,它能够评价冠状动脉心肌桥是否影响心肌供血及影响程度。负荷心肌灌注显像具有敏感性及特异性较高,且相对价廉、安全无创等优点,在评价心肌桥导致的心肌缺血及缺血的程度范围、判断预后及指导下一步治疗中具有重要的临床价值及应用前景。     

The Diagnostic Value of ST Segment Analysis in Ambulatory ECG Monitoring Evaluated Using Bayes' Theorem in Patients Screened for Coronary Artery Disease

Background: The diagnostic value of ambulatory ECG monitoring in screening for coronary artery disease has been studied in diverse and usually small groups of patients. There are no studies evaluating the diagnostic value of Holter recorded ST depression using the Bayes' theorem of probability, which accounts for the prevalence of the disease in prespecified populations. Purpose: Applying the Bayes' theorem, this study aimed to examine the diagnostic value of Holterrecorded 1-mm ST depression in patients screened for coronary artery disease (CAD) and to identify groups of patients who may benefit from diagnostic ST segment monitoring in ambulatory ECG recordings. Methods: The ST segment analysis was performed in 24-hour ambulatory ECG monitoring of 460 subjects (375 males; aged 35–65, mean 48.6 years), who were screened for CAD and had coronary angiography. The Bayes' formulae were used to calculate the predictive value of ST segment monitoring (posttest likelihood of CAD) in comparison to pretest likelihood of the disease based on age, gender, and symptoms. Results: The 1-mm ST depression was identified in the ambulatory ECG monitoring in 203 (44%) patients. CAD was angiographically confirmed in 279 (61%) patients. The 1-mm ST depression had 54% sensitivity, 71% specificity, 74% positive predictive value, and 50% negative predictive value for CAD. The Bayes' theorem analysis with adjustment for pretest likelihood of the disease in relation to age, gender, and symptoms showed that 1-mm ST segment depression is significant diagnostically in patients with pretest likelihood of the disease exceeding 75%, i.e., in males aged 35–45 years and females aged 56–65 years, both with typical angina. In other groups of patients regardless of the symptoms, age, and gender, detection of ST segment depression does not improve the diagnostic process. A negative result (absence of ST segment depression) can be helpful, confirming the absence of CAD in patients with 15%–25% pretest likelihood of the disease, i.e., in females aged 35–45 years with atypical angina pains and in males aged 46–55 years with nonanginal chest pains. Conclusions: Based on our observations, the 1-mm ST segment depression detected on 24-hour ambulatory ECG monitoring indicates a high likelihood of CAD in patients with < 75% pretest likelihood of the disease. ST segment analysis in other age and gender relative groups of patients, regardless of the nature of their symptoms, does not significantly improve diagnosis process.     

Individual risk prediction model for incident cardiovascular disease: A Bayesian clinical reasoning approach

Background

A Bayesian clinical reasoning model was developed to predict an individual risk for cardiovascular disease (CVD) for desk-top reference.

Methods

Three Bayesian models were constructed to estimate the CVD risk by sequentially incorporating demographic features (basic), six metabolic syndrome components (metabolic score) and conventional risk factors (enhanced model). By considering clinical weights (regression coefficients) of each model as normal distribution, individual risk can be predicted making allowance for uncertainty of clinical weights. A community-based cohort that enrolled 64,489 participants free of CVD at baseline and followed up over five years to ascertain newly diagnosed CVD cases during the period through 2000 to 2004 was used for the illustration of the three proposed models (full empirical data are available from website http://homepage.ntu.edu.tw/~chenlin/CVD_prediction_data.rar).

Results

The proposed models can be applied to predicting the CVD risk with any combination of risk factors. For a 47-year-old man, the five-year risk for CVD with the basic model was 11.2% (95% CI: 7.8%–15.6%). His metabolic syndrome score, leading to 1.488 of likelihood ratio, enhanced the risk for CVD up to 15.8% (95% CI: 11.0%–21.5%) and put him in highest deciles. As with the habit of smoking over 2 packs per-day and family history of CVD, yielding the likelihood ratios of 1.62 and 1.47, respectively, the risk was further raised to 30.9% (95% CI: 20.7%–39.8%).

Conclusions

We demonstrate how to make individual risk prediction for CVD by incorporating routine information with a sequential Bayesian clinical reasoning approach.     

A Clinical Tool to Identify Candidates for Stress-First Myocardial Perfusion Imaging

ObjectivesThis study sought to develop a clinical model that identifies a lower-risk population for coronary artery disease that could benefit from stress-first myocardial perfusion imaging (MPI) protocols and that can be used at point of care to risk stratify patients.BackgroundThere is an increasing interest in stress-first and stress-only imaging to reduce patient radiation exposure and improve patient workflow and experience.MethodsA secondary analysis was conducted on a single-center cohort of patients undergoing single-photon emission computed tomography (SPECT) and positron emission tomography (PET) studies. Normal MPI was defined by the absence of perfusion abnormalities and other ischemic markers and the presence of normal left ventricular wall motion and left ventricular ejection fraction. A model was derived using a cohort of 18,389 consecutive patients who underwent SPECT and was validated in a separate cohort of patients who underwent SPECT (n = 5,819), 1 internal cohort of patients who underwent PET (n=4,631), and 1 external PET cohort (n = 7,028).ResultsFinal models were made for men and women and consisted of 9 variables including age, smoking, hypertension, diabetes, dyslipidemia, typical angina, prior percutaneous coronary intervention, prior coronary artery bypass graft, and prior myocardial infarction. Patients with a score ≤1 were stratified as low risk. The model was robust with areas under the curve of 0.684 (95% confidence interval [CI]: 0.674 to 0.694) and 0.681 (95% CI: 0.666 to 0.696) in the derivation cohort, 0.745 (95% CI: 0.728 to 0.762) and 0.701 (95% CI: 0.673 to 0.728) in the SPECT validation cohort, 0.672 (95% CI: 0.649 to 0.696) and 0.686 (95% CI: 0.663 to 0.710) in the internal PET validation cohort, and 0.756 (95% CI: 0.740 to 0.772) and 0.737 (95% CI: 0.716 to 0.757) in the external PET validation cohort in men and women, respectively. Men and women who scored ≤1 had negative likelihood ratios of 0.48 and 0.52, respectively.ConclusionsA novel model, based on easily obtained clinical variables, is proposed to identify patients with low probability of having abnormal MPI results. This point-of-care tool may be used to identify a population that might qualify for stress-first MPI protocols.     

三磷酸腺苷负荷~(99m)锝—甲氧基异丁基异腈门控心肌灌注显像在评价心肌桥引起心肌缺血患者中的临床价值

目的:探讨三磷酸腺苷(ATP)负荷99m锝—甲氧基异丁基异腈(99mTc-MIBI)门控心肌灌注显像(G-MPI)对评价心肌桥患者心肌缺血的程度、部位及心功能的临床价值。方法:选择58例以冠状动脉造影或冠状动脉计算机断层血管造影术(CTA)明确诊断为心肌桥的患者,行ATP负荷99mTc-MIBI G-MPI检查,将左心室心肌短轴及垂直长轴像划分为13个节段,应用目测法按0~3分4阶法半定量评价左心室心肌各节段核素分布情况,计算左心室负荷总积分,判定心肌桥患者心肌缺血的程度及部位,并与心肌桥的严重程度进行对比。同时分析ATP负荷99mTc-MIBI G-MPI得出的左心室射血分数(LVEF)与经胸彩色多普勒超声心动图获得的LVEF的相关性。结果:ATP负荷99mTc-MIBI G-MPI对心肌桥患者心肌缺血的检出率为82.76%,动态心电图的检出率为56.10%,前者明显高于后者(P0.05)。ATP负荷99mTc-MIBI G-MPI显像中冠状动脉左前降支支配区域核素分布异常为258个节段(63.55%),冠状动脉左回旋支支配区域核素分布异常为82个节段(47.13%),右冠状动脉支配区域核素分布异常为74个节段(42.53%),冠状动脉左前降支支配区域核素分布异常节段数明显高于左回旋支及右冠状动脉(P0.0125)。在58例心肌桥患者,ATP负荷99mTc-MIBI G-MPI定量分析中得出的静息状态下LVEF为(69.59±4.13)%,经胸彩色多普勒超声心动图测得的LVEF为(63.22±4.12)%,二者差异无统计学意义(P0.05),且呈明显正相关性(r=0.555,P0.05)。结论:ATP负荷99mTc-MIBI GMPI可以较直观准确地评价心肌桥患者的心肌缺血程度、部位及左心功能,对临床治疗具有一定的指导价值。     

Anti Platelet Agents for Strokes and Myocardial Infarction: A Critical Appraisal of Recent Clinical Trials*

Abstract: Attempts at prevention of arterial thrombosis with platelet inhibitors have been the subject of a number of major trials in recent years. These trials were prompted by earlier observations that aspirin takers seemed to fare better after acute myocardial infarction and were further stimulated by the recent growth of knowledge about the role of vascular and platelet prostaglandins. The trials have sought to establish that aspirin (ASA), sulphinpyrazone and dipyridamole may prevent thrombosis in the form of recurrence of transient ischaemic attack (TIA) and stroke or reduce the recurrence rate and mortality after acute myocardial infarction. No single trial has provided conclusive evidence although there is a strong suggestion of some benefit from ASA. With further understanding of PG metabolism and the effects of inhibitors new approaches are likely to emerge in the near future .     

钾—温氧合血持续顺灌心肌保护、不降温体外循环冠状动脉搭桥术

应用温血顺灌心肌保护法进行连续54例冠状动脉搭桥术,全部获得成功.54例中,男性45例,女性9例,年龄平均55.41±12.31岁(41～71岁),术前合并心肌梗塞者30例,合并高血压26例.选择性冠状动脉造影显示单支病变2例,2支病变11例,3支病变41例,左室射血分数平均为56.93±18.36%.CPB时间:141.7±52.5分,升主动脉阻断时间:83.5±24.2分.全部病例均未行人工降温,鼻咽温度因室温不同波动在33.5～37.0℃之间(平均36.5℃).每例搭桥数1～4根不等,全组平均2.44根.作者介绍了温血灌注的操作方法,讨论了应用该方法进行冠状动脉搭桥术的优越性.指出,单独应用温血顺灌亦能为冠状动脉搭桥术提供良好的心肌保护.本文还就温血持续灌注对术野及血钾的影响进行了探讨.