Implementation of myocardial perfusion imaging in the early triage of patients with suspected acute coronary syndromes

The risk of overlooking an underlying acute coronary syndrome remains an important challenge in patients complaining of chest pain but who have a non-diagnostic ECG (CP). Indeed, myocardial scintigraphy associated with exercise testing (exercise SPET) represents a valuable tool for excluding coronary artery disease (CAD) especially in patients with CP and delayed presentation to the emergency department. We sought to implement diagnoses of CAD in the early triage of CP patients by exercise gated SPET and compare diagnoses with outcomes. A total of 306 consecutive patients presenting with CP were found to be free of CAD at first line work-up including clinical evaluation, markers of myocardial injury and echocardiogram. These patients were studied initially with exercise SPET, and those with perfusion defects underwent angiography, while those with normal scans were discharged and followed up. Patients with positive scans (34%, n=105) had documented coronary stenoses in 43% (n=45); patients with negative scans (66%, n=201) had evidence of non-fatal coronary events at 6 months in 1.5% (n=3). When imaging was analysed with gating by the presence of transmural perfusion defects associated with wall motion abnormalities (n=86), only one patient, among 19 excluded, was recognized as having coronary stenosis by angiography (SPET vs gated SPET: negative predictive value 98.5% and 98%, respectively, P=NS; diagnostic accuracy 79% and 85%, respectively; P< or =0.03). Therefore, implementation of myocardial perfusion imaging in the early triage of patients with suspected acute coronary syndromes was effectively obtained by early exercise gated SPET, especially in patients with transmural myocardial perfusion defects associated with wall motion abnormalities.     

Impact of acute chest pain Tc-99m sestamibi myocardial perfusion imaging on clinical management

BACKGROUND: Previous studies have demonstrated the high sensitivity and specificity of technetium 99m sestamibi scintigraphy during acute chest pain myocardial perfusion imaging. However, no study has shown that this technique would alter clinical management in practice. METHODS AND RESULTS: One hundred twenty consecutive patients were injected with Tc-99m sestamibi (22 mCi) during pain; single photon emission computed tomography was performed 1 to 6 hours later. The population included inpatients and those who arrived at the emergency department with chest pain deemed to be at intermediate risk for myocardial ischemia. The requesting physician completed a questionnaire before the study, indicating the likelihood of cardiac disease and proposed management had the test not been available. Follow-up management was evaluated from medical records. There was a 34% reduction in total admissions and 59% in planned admissions to the coronary care unit (P <.001). Conversely, 7 patients had discharge cancelled and 17 required coronary care purely because of abnormal acute rest myocardial perfusion imaging results. Coronary angiography was reduced by 40% in a selected subgroup. CONCLUSIONS: In our population, acute rest myocardial perfusion imaging reduced total admissions and altered resource utilization. This may result in more appropriate triage of individual patients in the management algorithm, as well as potential cost savings.     

Myocardial perfusion imaging versus biochemical markers in acute coronary syndromes

The assessment and appropriate clinical management of patients with acute chest pain and non-diagnostic electrocardiograms remain a continuing clinical problem. Accordingly, there is considerable interest in evaluating new strategies to improve early diagnostic accuracy in patients with possible acute myocardial ischaemia. Cardiac troponins (T and I) and acute rest myocardial perfusion imaging have similar sensitivities for detecting acute myocardial infarction. Whereas cardiac markers require 6-12 h to become positive, acute rest myocardial perfusion imaging immediately reflects the status of regional myocardial blood flow at the time of radiopharmaceutical injection. The measurement of cardiac troponins is particularly useful in the diagnosis and estimation of the degree of myocardial injury in those patients with a high likelihood of coronary artery disease and myocardial necrosis and for prognostication of adverse cardiac events in those patients with unstable angina. In contrast, the most appropriate use of acute rest myocardial perfusion imaging is in the setting of patients with acute ischaemic symptoms, non-diagnostic electrocardiogram and a low likelihood of myocardial necrosis, in which early imaging will assist in effective triage decisions.     

放射性核素心肌灌注显像在急性冠状动脉综合征中的临床应用

近年来,急性冠状动脉综合征(ACS)在临床上越来越受到重视。应用放射性核素心肌灌注显像(MPI)可以对常规方法不能明确诊断的急性胸痛患者排除或确诊ACS作出迅速、准确判断,其诊断的灵敏度和阴性预测值均很高。MPI还有助于评价心肌缺血和梗死灶的范围和程度,对ACS患者进行危险分层,为ACS的预后判断和疗效评估提供重要信息。     

Impact of myocardial perfusion imaging with PET and (82)Rb on downstream invasive procedure utilization, costs, and outcomes in coronary disease management.

We hypothesized that PET myocardial perfusion imaging with (82)Rb (PET MPI), would reduce downstream utilization of diagnostic arteriography, compared with SPECT, in patients matched for pretest likelihood of coronary disease (pCAD). PET MPI is more accurate for assessment of impaired coronary flow reserve compared with SPECT MPI, potentially reducing the demand for subsequent arteriography, percutaneous trans-coronary intervention, and coronary artery bypass grafting (CABG), with attendant cost savings, while avoiding a negative impact on coronary events. METHODS: The frequency of diagnostic arteriography, revascularization, costs, and 1-y clinical outcomes in 2,159 patients studied with PET MPI was compared with 2 control groups studied with SPECT MPI matched to the PET group by pCAD: an internal control group of 102 patients and an external SPECT control group of 5,826 patients. CAD management costs were approximated with realistic global fee estimates. RESULTS: Arteriography rates were 0.34 and 0.31 for the external and internal control SPECT groups and 0.13 for the patients studied with PET (P < 0.0001). pCAD averaged 0.39 in patients studied with PET MPI, and in the external SPECT control group, and 0.37 in the internal SPECT controls. Revascularization rates were 0.13 and 0.11 for external and internal SPECT patients and 0.06 for the PET group (P < 0.0001; P < 0.01), with a cost savings of 30% noted for PET patients, with no significant difference in cardiac death or myocardial infarction at 1-y follow-up. CONCLUSION: PET MPI in patients with intermediate pCAD results in a >50% reduction in invasive coronary arteriography and CABG, a 30% cost savings, and excellent clinical outcomes at 1 y compared with SPECT.     

Inappropriate utilization of SPECT myocardial perfusion imaging on the USA-Mexico border

Background

The American College of Cardiology/American Society of Nuclear Cardiology published revised appropriate use criteria (AUC) for SPECT MPI in 2009. We assessed adherence to these guidelines and factors associated with inappropriate utilization at the University Medical Center.

Methods

The AUC was applied retrospectively to 420 SPECT MPI studies. Two-sample t test, Fisher’s exact test, and multivariable logistic regression models were used for analysis.

Results

There were 322 appropriate (86%) and 54 (14%) inappropriate studies. The odds of having an inappropriate test increased with younger age (P < .001) and female gender (P < .001). Subjects with diabetes (P = .007) and chest pain (P < .001) were less likely to have an inappropriate test. Academic outpatients were three times more likely to have an inappropriate study (P = .123), while community PCPs were 5.6 times (P = .011) and community cardiologists eight times more likely to order inappropriate tests (P = .031).

Conclusions

Inappropriate SPECT MPI in low risk younger women is an important issue on the USA-Mexico border. Initiatives to reduce inappropriate SPECT MPI should focus on a few indications and evaluation of cardiovascular symptoms in younger age women in outpatient/community practices.     

Myocardial edema imaging in acute coronary syndromes

Acute coronary syndromes (ACS) continue to be the most common morbid condition of industrialized nations. The advent of and technical improvements in revascularization and medical therapy have led to a steady decline in mortality rates. However, many patients who suffer unstable angina or myocardial infarction require further testing and risk stratification to guide therapeutic selection and prognosis assignment. Myocardial edema imaging with cardiac magnetic resonance (CMR) affords the ability to define the amount of myocardium at risk, refine estimates of prognosis and provide guidance for therapies with excellent sensitivity compared with standard clinical markers. This review will discuss the rationale for edema imaging, how it is performed using CMR, and potential clinical applications.     

Comparison of acute rest myocardial perfusion imaging and serum markers of myocardial injury in patients with chest pain syndromes

BACKGROUND: Newer diagnostic modalities such as serum markers and acute rest myocardial perfusion imaging (MPI) have been evaluated diagnostically in patients with chest pain in the emergency department (ED), but never concurrently. We compared these two modalities in distinguishing patients in the ED with symptomatic myocardial ischemia from those with non-cardiac causes. METHODS: Serum markers and acute technetium-99m sestamibi/tetrofosmin rest MPI were obtained in 75 patients admitted to the ED with chest pain and nondiagnostic electrocardiograms. Venous samples were drawn at admission and 8 to 24 hours later for total creatine kinase, CK-MB fraction, troponin T, troponin I, and myoglobin. Three nuclear cardiologists performed blinded image interpretation. Coronary artery disease (CAD) was confirmed either by diagnostic testing or by the occurrence of myocardial infarction (MI). RESULTS: Acute rest MPI results were abnormal in all 9 patients with MI. An additional 26 patients had objective evidence of CAD confirmed by diagnostic testing. The sensitivity of acute rest MPI for objective evidence of CAD was 73%. Serum troponin T and troponin I were highly specific for acute MI but had low sensitivity at presentation. Individual serum markers had very low sensitivity for symptomatic myocardial ischemia alone. In the multivariate regression model, only acute rest MPI and diabetes were independently predictive of CAD. CONCLUSION: At the time of presentation and 8 to 24 hours later, acute rest MPI has a better sensitivity and similar specificity for patients with objective evidence of CAD when compared with serum markers.     

可疑冠心病患者核素显像与CT冠状动脉造影对比分析

Objective The aim of this study was to analyze the relationship between myocardial perfusion imaging (MPI) and computed tomography coronary artefiography (CTCA) in diagnosis of patients with suspected coronary artery disease (CAD).Methods Forty patients with suspected CAD underwent invagive coronary angiography(CAG),MPI and CTCA within 2 months.The results of myocardial perfusion imaging were classified as normal or abnormal[reversible and(or)fixed defects] ;The CTCA studies were classified as normal,non-obstructive(＜50% stenosis)CAD,or obstructive CAD.Taking the results of CAG as"gold standard",the findings of MPI and CTCA were comparatively analyzed.Concordant and discordant results between MPI and CTCA were statistically analyzed using Kappa test.P＜0.05 Was considered statistically significant.Results Aboat 90.1% patients with normal CTCA also showed normal MPI.However,only 44.8% patients with abnormal CTCA showed corresponding perfusion abnormalities on MPI.Conversely,61.5% patients with normal MPI had abnormal CTCA.Compared with CAG,the sensitivity,specificity and accuracy of CTCA were 96.4%(27/28),83.3%(10/12) and 92.5%(37/40),and those of MPI were 46.4%(13/28),91.7%(11/12)and 60.0%(24/40) respectively.Conclusions MPI and CTCA provide different but complementary information in diagnosis of patients with suspected CAD.Their clinical value and application should be practically combined.     

可疑冠心病患者核素显像与CT冠状动脉造影对比分析

目的探讨核素心肌灌注显像（MPI）和CT冠状动脉造影（CTCA）2种无创性检查方法在可疑冠心病（CAD）患者诊断中的关系。方法对40例可疑冠心病患者行冠状动脉造影（CAG）、MPI和CTCA检查,均在2个月内进行。MPI结果分为正常和异常[可逆性和（或）不可逆性心肌缺血];CTCA结果分为正常、轻度（狭窄〈50％）和中度及其以上狭窄（至少1支主要血管或主要分支血管狭窄程度≥50％）。以CAG结果为“金标准”,对40例患者的MPI和CTCA结果进行对比分析。结果CTCA正常者中,90．1％的患者MPI正常;CTCA异常者中,55．2％的患者MPI正常;而MPI正常者中,61．5％的患者CTCA均有不同程度的狭窄。与CAG比较,CTCA的灵敏度、特异性和准确性高,分别为96．4％（27／28）、83．3％（10／12）和92．5％（37／40）。结论MPI和CTCA在可疑冠心病患者的诊断中提供了不同但却互补的信息,两者应合理联合应用。     

Evaluation of patients with suspected acute coronary syndromes in the emergency department

Patients complaining of chest pain (CP) who visit the emergency department (ED) represent the second cause of consultation in this department, and 20-30% of hospital admissions for medical reasons. These patients form a somewhat heterogeneous group with many different aetiologies and degrees of severity. In this setting, the clinical objectives include the prompt identification of patients with acute coronary syndromes (ACSs), the prompt evaluation of the immediate risk (i.e., initial risk stratification) of cardiovascular complications in order to tailor the treatment for each individual patient and to make the best use of hospital resources, and the prompt identification of patients with other potentially severe diseases. The diagnosis of ACS in patients coming to the ED for CP or any equivalent angina is one of the most difficult diagnostic challenges facing physicians in the ED. The correct diagnosis and risk stratification of these patients has clinical consequences, as well as very important legal and economic implications. The only methodology with a clear clinical impact on diagnosis, risk stratification and initial management is clinical evaluation based on data obtained by questioning the patient, carrying out a physical examination, and interpreting the results of a standard 12-lead electrocardiogram (ECG). Nevertheless, its combined diagnostic efficiency for ACS is imperfect and additional strategies are emerging which include serial ECG, the detection of serum biochemical markers of myocardial necrosis, exercise testing, and radionuclide myocardial perfusion imaging.     

The additive value of gated SPET myocardial perfusion imaging in patients with known and suspected coronary artery disease

In myocardial perfusion scintigraphy, the clinical significance of fixed defects presents some difficulty. In this study, we evaluated whether additional information on left ventricular function assessed by quantitative gated single-photon emission computed tomography (gated SPET) would increase the diagnostic yield of the study in such patients. We studied 55 patients with a previous myocardial infarction and 20 patients without a previous myocardial infarction using gated SPET 99Tc(m)-tetrofosmin myocardial perfusion imaging. Each patient had to have a persistent perfusion defect consisting of at least three contiguous segments in the same vascular territory. The left ventricle was divided into 20 segments which were analysed for perfusion and wall thickening on a 4-point severity scale. Of the 55 patients with myocardial infarction, 19 (35%) patients showed preserved wall thickening in the region of the previous infarction with fixed perfusion abnormalities, which suggested residual myocardial viability. In the 20 patients without myocardial infarction, preserved wall thickening was seen in 10 (50%) patients with fixed perfusion defects, suggesting an attenuation artefact. Conversely, in 16 (29%) patients in the myocardial infarction group and two (10%) patients in the non-myocardial infarction group normal perfusion was associated with severely diminished wall thickening possibly due to stunning. We found an excellent correlation between wall thickening and left ventricular ejection fraction both for the patients with myocardial infarction and the patients without myocardial infarction (r = 0.86 and r = 0.82, respectively, both P<0.0001). A reasonable correlation between perfusion and left ventricular ejection fraction was found for the patients with myocardial infarction (r = 0.41, P = 0.002), and a non-significant correlation for the patients without myocardial infarction (r = 0.37, P = 0.1). Quantitative gated SPET myocardial imaging allows the detection of residual wall thickening in patients with a previous myocardial infarction who show severe fixed perfusion defects. In patients without myocardial infarction, gated SPET imaging allows differentiation between an attenuation artefact and a fixed perfusion defect due to coronary artery disease. In addition, gated SPET may show diminished ventricular function in normally perfused segments possibly due to myocardial stunning. The addition of gated SPET myocardial perfusion imaging increases diagnostic confidence and may have direct clinical implications for optimal patient management.     

Reconciling discordant myocardial perfusion imaging and coronary angiography

A common clinical conundrum presents itself in the discordance between nuclear stress testing and invasive coronary angiography (ICA) in the patient presenting with angina. A patient with an abnormal perfusion scan and “normal coronary angiography” may result in the patient’s symptoms being dismissed as “non-cardiac.” Alternatively, a patient with a “normal perfusion study,” who nonetheless undergoes ICA and is found to have significant coronary artery disease may confound efforts to risk stratify and potentially treat patients with angina. This paper will review the current evidence to explain these apparent paradoxical scenarios.     

核素心肌显像在冠心病处理决策中的合理应用及其原理

核素心肌显像在冠心病诊断、危险度分层及预后判断方面积累了大量资料,并可据此制定冠心病的有效处理策略。在ACC/AHA(美国心脏病学会/美国心脏协会)有关冠心病和核心脏病学指南中,核素心肌显像的上述作用得到了充分肯定。合理应用该技术可以提高我们对冠心病诊断处理的整体水平,并使有限的医疗资源得到更合理利用,目前这在我国显得十分迫切和必要。