Comparison of thallium-201 and technetium-99m methoxyisobutyl isonitrile.

Thallium-201 (201Tl) is a well-established radionuclide used in myocardial perfusion imaging for assessing the presence and prognostic significance of coronary artery disease. Recently, technetium-99m hexakis-2-methoxyisobutyl isonitrile (99mTc-sestamibi) has become available for the same diagnostic and prognostic procedures. This discussion compares the imaging characteristics and clinical applications of 201Tl with those of 99mTc-sestamibi. There is a strong diagnostic concordance between the 2 agents in symptomatic patients. Various comparative clinical trials have shown in numerous patients that both agents have a similar diagnostic yield in both planar and single-photon emission computed tomography (SPECT) imaging. Because of better image quality of the 99mTc agent, there is a trend toward better specificity and normalcy rate, in comparison to 201Tl. However, when using reinjection imaging protocols, 201Tl retains a unique place as an imaging agent to identify viable myocardium.     

Advances in imaging for assessment of ischemic heart disease

Cardiac imaging techniques continue to develop for the noninvasive detection and evaluation of patients with coronary artery disease. These techniques include single photon and positron emission tomography along with computed tomography and magnetic resonance imaging. The new myocardial perfusion tracers 99mTc-hexakis-2-methoxyisobutyl-isonitrile and 99mTc-teboroxime have recently come into general use for these purposes, and their role alongside that of more traditional agents is currently being defined using new imaging protocols and instrumentation. 99mTc-hexakis-2-methoxyisobutyl-isonitrile has also been documented as an important research tool for evaluating both at-risk myocardium and the degree of subsequent myocardial salvage following reperfusion therapies for acute myocardial infarction. Antimyosin antibody imaging is another emerging approach in the evaluation of patients with acute myocardial infarction. Metabolic imaging with 18F-fluoro-2-deoxyglucose using positron emission tomography to detect myocardial segments with compromised blood flow but preserved glucose metabolism is currently the best noninvasive method of identifying viable myocardium in patients with left ventricular dysfunction who may benefit from revascularization. Insights from these studies have led to development of the current 201Tl stress-rest reinjection protocols for viability evaluation using single photon emission computed tomography. Positron emission tomography, in combination with blood flow tracers using kinetic modeling, provides accurate estimates of coronary blood flow and flow reserve. The use of these new imaging techniques will allow increasingly accurate evaluation of patients with suspected and proven coronary artery disease in the future.     

Rest-redistribution 201-Tl single-photon emission CT imaging for determination of myocardial viability: relationship among viability, mode of therapy, and long-term prognosis.

BACKGROUND: The diagnosis of viable myocardium in the setting of ischemic left ventricular systolic dysfunction might indicate which patients have the greatest prognostic benefit from myocardial revascularization. Single-photon emission CT (SPECT) thallium-201 (201Tl) scintigraphy for the detection of viable myocardium is widely available in the community, but outcome data using this imaging modality are limited. METHODS: Thirty-seven patients (mean [+/- SD] age, 62+/-12 years) with ischemic left ventricular dysfunction (mean ejection fraction, 30+/-9%) initially referred for rest-redistribution SPECT thallium scintigraphy were evaluated 29+/-19 months after coronary bypass surgery (n = 15) or medical therapy alone (n = 22). The relationship among myocardial viability, mode of therapy, and long-term prognosis was evaluated. RESULTS: Significant myocardial viability (defined as a viability index [VI] of > 0.5) was present in 19 patients. Among patients with a VI > 0.5, the 48-month actuarial event-free survival was 89+/-10% for patients undergoing surgical revascularization, compared with 0% for the medical treatment subgroup (p = 0.005). In contrast, patients in the low-viability subgroup tended to have intermediate event-free survival rates, which were not statistically different for patients receiving either surgical (62+/-21%) or medical therapy (50+/-14%; p = 0.55). CONCLUSIONS: Survival is significantly more favorable for surgically revascularized patients with ischemic left ventricular dysfunction and myocardial viability as detected by SPECT 201Tl scintigraphy.     

CT imaging of myocardial viability: experimental and clinical evidence

Over the last decade, imaging of myocardial viability has become a well-established indication in patients suffering from myocardial infarction. Myocardial viability imaging is routinely performed using (18)F-fluorodeoxyglucose positron emission tomography, single-photon emission computed tomography or magnetic resonance imaging. Only recently have several multi-slice spiral computed tomography (MSCT) techniques been evaluated for visualisation of myocardial infarction. This review describes the different concepts of MSCT viability imaging. MSCT assessment of myocardial morphology, myocardial perfusion imaging and delayed myocardial contrast enhancement are introduced, with the latter evolving as the key concept of MSCT viability imaging. Clinical relevance of the different MSCT techniques is described.     

Comparison of electrocardiographic-gated technetium-99m sestamibi single-photon emission computed tomographic imaging and rest-redistribution thallium-201 in the prediction of myocardial viability

Although the combined assessment of perfusion and function using rest electrocardiographic (ECG)-gated technetium-99m (Tc-99m) sestamibi single-photon emission computed tomographic (SPECT) imaging has been shown to improve sensitivity and accuracy over perfusion alone in the prediction of myocardial viability, no data are available comparing this technique with rest-redistribution thallium-201. Thirty patients with coronary artery disease and left ventricular dysfunction (ejection fraction < or = 40%) underwent rest-redistribution thallium-201 and rest ECG-gated Tc-99m sestamibi SPECT imaging before revascularization and rest ECG-gated Tc-99m sestamibi SPECT imaging at 1 or 6 weeks after revascularization. All thallium-201 and Tc-99m sestamibi images were interpreted by a consensus agreement of 3 experienced readers without knowledge of patient identity or time of imaging with Tc-99m sestamibi (before or after revascularization) using a 17-segment model. Concordance between techniques for the prediction of viability was 89% (kappa 0.556 +/- 0.109). With rest-redistribution thallium-201, sensitivity, specificity, positive predictive value, negative predictive value, and predictive accuracy were 95%, 59%, 88%, 78%, and 86%, respectively. With rest ECG-gated Tc-99m sestamibi SPECT imaging, sensitivity, specificity, positive predictive value, negative predictive value, and predictive accuracy were 96%, 55%, 87%, 80%, and 86%, respectively (p = NS vs rest-redistribution thallium-201). Although both techniques are comparable for detecting viable myocardium, rest ECG-gated Tc-99m sestamibi SPECT imaging allows direct assessment of both myocardial perfusion and ventricular function, which may be clinically useful in patients who require assessment of myocardial viability.     

Long-term prognostic value of 201Tl single-photon emission computed tomographic myocardial perfusion imaging after coronary stenting

BACKGROUND: The prognostic value of (201)Tl myocardial imaging has been demonstrated in several studies concerning patients with a known significant coronary artery disease. However, the evolution of a coronary stenosis after stenting is difficult to predict. This study was designed to assess the prognostic value of (201)Tl single-photon emission computed tomography (thallium SPECT) perfusion imaging in patients after intracoronary stenting. METHODS: One hundred fifty-two patients were studied. They were followed up during 40 +/- 13 (mean +/- SD) months after thallium SPECT. Stent-related events were studied after thallium stress testing and included cardiovascular death, myocardial infarction, and revascularization. Stress thallium imaging was performed 5 +/- 2 months after stenting, and ischemia was considered to be present if at least 2 contiguous segments were showing reversible defects. RESULTS: Only 3 (3%) among the 105 nonischemic patients had major cardiac events during the follow-up versus 13 (28%) of the 47 ischemic patients (P < .001) after thallium SPECT. The relative risk of major cardiac events for patients with significant ischemia was 10.5 compared with nonischemic patients (P < .001). Fourteen (30%) of the ischemic patients and 8 (8%) among the nonischemic patients underwent iterative revascularization (P < .001). Therefore, only 11 (10%) of the nonischemic patients had major cardiac events or revascularization compared with 24 (51%) of the ischemic patients (P < .001). CONCLUSIONS: Absence of ischemia on thallium SPECT imaging at 5 months after coronary stenting indicates a low risk for cardiovascular events or interventional procedure. These results may have important clinical implications in patient treatment.     

Diagnosis and management of ischemic cardiomyopathy: Role of cardiovascular magnetic resonance imaging

Coronary artery disease (CAD) represents an important cause of mortality. Cardiovascular magnetic resonance (CMR) imaging evolved as an imaging modality that allows the assessment of myocardial function, perfusion, contractile reserve and extent of fibrosis in a single comprehensive exam. This review highlights the role of CMR in the differential diagnosis of acute chest pain by detecting the location of obstructive CAD or necrosis and identifying other conditions like stress cardiomyopathy or myocarditis that can present with acute chest pain. Besides, it underlines the prognostic implication of perfusion abnormalities in the setting of acute chest pain. Furthermore, the review addresses the role of CMR to detect significant CAD in patients with stable CAD. It elucidates the accuracy and clinical utility of CMR with respect to other imaging modalities like single-photon emission computed tomography and positron emission tomography. Besides, the prognostic value of CMR stress testing is discussed. Additionally, it summarizes the available CMR techniques to assess myocardial viability and describes algorithm to identify those patient who might profit from revascularization those who should be treated medically. Finally, future promising imaging techniques that will provide further insights into the fundamental disease processes in ischemic cardiomyopathy are discussed.     

Myocardial thallium-201 scintigraphy for assessment of viability in patients with severe left ventricular dysfunction.

Many patients with ischemic heart disease and depressed left ventricular (LV) function have asynergic zones with sustained microcirculatory perfusion and myocardial metabolic activity that exhibit improved systolic function after coronary revascularization. The 2 predominant noninvasive techniques used to determine myocardial viability in patients with severely depressed LV function are thallium-201 (201Tl) scintigraphy and positron emission tomography (PET). Myocardial extraction of 201Tl is unaltered under experimental conditions of myocardial stunning or short-term hibernation (characterized by decreased flow and ischemic dysfunction). Akinetic or dyskinetic LV wall segments can exhibit normal or near normal 201Tl uptake as long as some residual flow is present. 201Tl scintigraphy can identify viable asynergic segments when performed on patients with severe coronary artery disease who are in the resting state. Many of these patients have initial resting defects that demonstrate delayed redistribution, or mild persistent defects that show improved perfusion and function after revascularization. There is a direct correlation between the extent of 201Tl uptake in zones of severe regional myocardial asynergy and the magnitude of improvement in resting LV ejection fraction after coronary bypass surgery. Rest 201Tl scintigraphy may help in the selection of patients with coronary artery disease and severely depressed LV function who would benefit the most from revascularization.     

Detecting viable myocardium and predicting functional improvement: comparisons of positron emission tomography, rest-redistribution thallium-201 single-photon emission computed tomography (SPECT), exercise thallium-201 reinjection SPECT, I-123 BMIPP SPECT and dobutamine stress echocardiography.

BACKGROUND: Low-dose dobutamine stress echocardiography (LDDE) has become a useful and safe method for identifying hibernating or stunned myocardium and for predicting improvement in wall motion after coronary revascularization. METHODS AND RESULTS: In the present study, fluorine-18 fluorodeoxyglucose positron emission tomography (FDG-PET), rest-redistribution thallium-201 ((201)Tl) single-photon emission computed tomography (RR-Tl SPECT), (123)I-15-(p-iodophenyl)-3-(R,S)-methyl pentadecanoic acid (BMIPP) and LDDE were performed in 30 patients with acute myocardial infarction (AMI) at 10+/-3 days after the onset of AMI. Also, exercise (201)Tl reinjection SPECT (RI-Tl SPECT) was performed at 14+/-2 days. Follow-up echocardiography was performed 5+/-3 months later in all patients after interventional therapy for the assessment of functional recovery. Of the 390 segments analyzed by echocardiography, 110 (28%) had abnormal wall motion. There were no significant differences between RR-Tl SPECT and LDDE in sensitivity, specificity, positive predictive value and negative predictive value using the chi(2)-test; however, in akinetic segments, there was a significant difference in sensitivity. Among FDG-PET, RI-Tl SPECT, BMIPP and LDDE, there were significant differences in 3 variables. In akinetic segments, LDDE is superior to RR-Tl SPECT in sensitivity and to FDG-PET in specificity. In hypokinetic segments, LDDE is superior to RI-Tl SPECT and BMIPP in sensitivity, and to FDG-PET and BMIPP in specificity. CONCLUSIONS: LDDE could detect functional recovery of viable myocardium in the early period of AMI and can be performed easily and safely.     

Radionuclide imaging of myocardial perfusion and viability in assessment of acute myocardial infarction

Technical advances in radionuclide imaging have important implications for the management of patients with acute myocardial infarction. Single-photon emission computerized tomography with thallium 201 (TI-201) offers greater accuracy than planar imaging in detecting, localizing and sizing myocardial perfusion defects. Use of single-photon emission computerized tomography with TI-201 should allow for a more accurate assessment of prognosis after myocardial infarction. A new radiopharmaceutical, technetium 99-m methoxyisobutyl isonitrile, provides a number of advantages over TI-201, including higher quality images, lack of redistribution, and the ability to assess first-pass ventricular function. Applications of TI-201 and technetium 99-m methoxyisobutyl isonitrile include assessment of arterial patency and myocardial salvage immediately after thrombolytic therapy, detection of resting ischemia after thrombolytic therapy, targeting of subsets of patients for further intervention, and predischarge assessment to predict the future course of patients after an acute myocardial infarction.     

Positron emission tomography for assessment of viability

PURPOSE OF REVIEW: The recent success of magnetic resonance imaging for viability assessment has raised questions about the future role of positron emission tomography and older imaging modalities in the assessment of viability. Recent information, however, indicates that positron emission tomography will remain a valuable tool. RECENT FINDINGS: The primary positron emission tomography tracer used for assessment of viability is 18F-fluorodeoxyglucose, a glucose analogue that exhibits enhanced uptake in ischemic tissue. The finding of enhanced 18F-fluorodeoxyglucose uptake and a relative reduction in perfusion is considered the positron emission tomography correlate of myocardial hibernation. The mismatch pattern has been shown to identify patients with improvement in systolic function, heart failure symptoms, and prognosis with revascularization. Mismatch identifies a subset of patients with vulnerable myocardium who have a higher likelihood of a cardiac event compared with those without significant mismatch. Delay in revascularization may pose extra risk for those with mismatch. Positron emission tomography and magnetic resonance imaging demonstrate a close correlation in the detection of viable myocardium. The development of combined positron emission tomography/computed tomography scanners can reduce imaging time and improve functional-anatomic correlations. SUMMARY: Positron emission tomography imaging utilizing 18F-fluorodeoxyglucose and perfusion tracers provides valuable diagnostic and prognostic information in patients with ischemic left ventricular dysfunction and has comparable accuracy to competing technologies for detection of viability.     

Contrast-enhanced magnetic resonance and thallium scintigraphy in the detection of myocardial viability: a prospective comparative study

The aim of the present study was to prospectively compare contrast-enhanced magnetic resonance imaging (CE-MRI) with single-photon emission tomography using (201)Thallium chloride (SPECT Tl) in the detection of myocardial viability. Patients with chronic coronary artery disease and systolic dysfunction defined by an ejection fraction (EF) 相似文献   

The Current Role of Viability Imaging to Guide Revascularization and Therapy Decisions in Patients With Heart Failure and Reduced Left Ventricular Function

This review describes the current evidence and controversies for viability imaging to direct revascularization decisions and the impact on patient outcomes. Balancing procedural risks and possible benefit from revascularization is a key question in patients with heart failure of ischemic origin (IHF). Different stages of ischemia induce adaptive changes in myocardial metabolism and function. Viable but dysfunctional myocardium has the potential to recover after restoring blood flow. Modern imaging techniques demonstrate different aspects of viable myocardium; perfusion (single-photon emission computed tomography [SPECT], positron emission tomography [PET], cardiovascular magnetic resonance [CMR]), cell metabolism (PET), cell membrane integrity and mitochondrial function (201Tl and 99mTc-based SPECT), contractile reserve (stress echocardiography, CMR) and scar (CMR). Observational studies suggest that patients with IHF and significant viable myocardium may benefit from revascularization compared with medical treatment alone but that in patients without significant viability, revascularization appears to offer no survival benefit or could even worsen the outcome. This was not supported by 2 randomized trials (Surgical Treatment for Ischemic Heart Failure [STICH] and PET and Recovery Following Revascularization [PARR] -2) although post-hoc analyses suggest that benefit can be achieved if decisions had been strictly based on viability imaging recommendations. Based on current evidence, viability testing should not be the routine for all patients with IHF considered for revascularization but rather integrated with clinical data to guide decisions on revascularization of high-risk patients with comorbidities.     

Assessment of myocardial viability by radionuclide and echocardiographic techniques: is it simply a sensitivity and specificity issue?

PURPOSE OF REVIEW: The assessment of myocardial viability provides important information that may guide therapeutic decisions in patients with coronary artery disease and left ventricular dysfunction. This review describes methods for assessing myocardial viability using single-photon emission computed tomography, with an emphasis on how to optimize the detection of viable myocardium using current techniques. Relevant comparisons of radionuclide techniques with echocardiographic methods are also discussed. RECENT FINDINGS: The basis for the assessment of myocardial viability using radionuclides is reviewed briefly. Radionuclide techniques provide important prognostic information that may affect the decision on if patients with coronary artery disease should be revascularized or treated medically. Data suggest that dobutamine stress echocardiography may underestimate viability in certain patients. Radionuclide techniques that assess both radiotracer uptake and ventricular function can provide a comprehensive approach to detect viable myocardium in most patients. SUMMARY: The methods for assessing myocardial viability using single-photon emission computed tomography are accurate, reproducible, and widely available. Viability testing should be considered in patients with known coronary artery disease and left ventricular dysfunction. Further studies are warranted to assess the affect of viability assessment on clinical outcomes.     

PET imaging with FDG to guide revascularization in patients with systolic heart failure

The assessment of myocardial viability is important in the management of patients with coronary artery disease and left ventricular systolic dysfunction. There are several different imaging modalities currently available for the identification of viable myocardium: dobutamine stress echocardiography, single photon emission computed tomography, delayed-enhancement cardiac magnetic resonance imaging, and F-18 fluorodeoxyglucose positron emission tomography. The goal of viability imaging is to determine the likelihood of recovery of systolic function after revascularization. Positron emission tomography with F-18 fluorodeoxyglucose (FDG-PET) provides information about perfusion as well as myocardial metabolism, requires meticulous patient preparation, and is currently the gold standard imaging modality for the assessment of myocardial viability. Viability imaging for the purposes of predicting which patients will have improvement in left ventricular systolic function is supported under current guidelines, but the results of the recent STICH-viability substudy have created uncertainty about the incremental benefit. This review article will provide a summary of the currently available imaging modalities with an emphasis on FDG-PET and discuss the clinical relevance of viability imaging in light of the STICH-viability substudy.     

Evaluation of salvaged myocardium after acute myocardial infarction using single photon emission computed tomography after 201Tl-glucose-insulin infusion.

BACKGROUND: GIK-201Tl imaging reportedly improves the detection of viable myocardium, so the present study evaluated whether it can detect myocardial viability after acute myocardial infarction (AMI). METHODS AND RESULTS: Resting 201Tl and 99mTc-pyrophosphate (PYP) dual single photon emission computed tomography (SPECT) and 201Tl SPECT after 201Tl with GIK (10% glucose, insulin 5 U, and KCl 10 mmol) infusion (GIK-201Tl) were performed in 25 AMI patients within 10 days of admission. GIK-201Tl SPECT images were obtained immediately and 4 h after infusion. Left ventriculography (LVG) was performed within 3 weeks and at 6 months when follow-up 201Tl SPECT was also performed. From 20 SPECT segments, both the summed defect score (RDS) and the number of defect segments (ES) were calculated. The infarcted area was defined as 99mTc-PYP uptake segments. Wall motion was estimated in 7 LVG segments. The ES of R-201Tl (5.5 +/- 2.8), immediate GIK-201Tl (4.0 +/- 2.3), and 4-h GIK-201Tl (5.6 +/- 2.7) were lower than that of 99mTc-PYP (7.5 +/- 4.1) (p<0.05), and the ES had significantly declined 6 months later on 201Tl (3.5 +/- 2.8) (p<0.05). Although the RDS of R-201Tl (11.3 +/- 7.9) and 4-h GIK-201Tl (11.2 +/- 6.3) were greater than at the 6-month 201Tl (7.1 +/- 6.5), immediate GIK-201Tl (7.4 +/- 6.5) was equivalent to follow-up 201Tl. The sensitivity of immediate GIK-201Tl was highest among the imaging methods. CONCLUSION: To detect myocardial viability after AMI, early imaging with GIK-201Tl is more useful than resting 201Tl imaging.     

Low-dose dobutamine radionuclide ventriculography for prediction of myocardial viability: quantitative analysis of regional left ventricular function

BACKGROUND: It is important to distinguish viable myocardium from necrotic tissue in order to decide upon therapy in patients with ischemic heart disease. HYPOTHESIS: We verified the hypothesis that quantitative analysis of regional left ventricular function using low-dose dobutamine radionuclide ventriculography (RNV) can sensitively predict myocardial viability and compared its usefulness with thallium-201 (201Tl) single-photon emission computed tomography (201Tl-SPECT). METHODS: Radionuclide ventriculography at rest and during low-dose dobutamine infusion (5 micrograms/kg/min), 201Tl-SPECT, and coronary angiography were performed in 51 subjects with severe ischemia-related stenosis of coronary arteries and 3 subjects without coronary artery disease. 201Tl uptake was assessed as normal (control), low perfusion (LP), or defect. We compared the response of regional function to dobutamine with the regional 201Tl uptake. The accuracy of both methods for identifying viable myocardium was investigated in 17 patients who underwent successful coronary revascularization, with a resulting improvement in wall motion. RESULTS: The increase in regional ejection fraction (delta r-EF) in response to dobutamine was significantly greater in the control (12 +/- 6%) and LP (16 +/- 11%) regions than in the defect (5 +/- 10%) regions. The increase in one-third regional ejection fraction (delta r-1/3EF) was also significantly higher in the control (14 +/- 7%) and LP (10 +/- 8%) regions than in the defect regions (5 +/- 6%). We defined myocardial viability as a delta r-EF > 5% or a delta r-1/3EF > 2%. The sensitivity and specificity of the delta r-EF for identification of myocardial viability were 91.4 and 55.5%, respectively. The sensitivity and specificity of the delta r-1/3EF were 91.4 and 66.6%, respectively; the corresponding values for 201Tl SPECT were 74.2 and 77.8%. CONCLUSION: Low-dose dobutamine RNV with quantitative analysis of regional left ventricular function was more sensitive for identification of viable myocardium than 201Tl-SPECT.     

Myocardial perfusion imaging in ischemic heart disease anno 1990

The field of radionuclide myocardial perfusion imaging is in a rapid state of change. Stress-rest myocardial imaging is important not only for the detection of coronary artery disease but also for prognostic stratification of patients. In particular, assessment of myocardial viability in patients with left ventricular dysfunction is a recent focus of investigation. Single-photon emission computed tomography has become widely accepted as the preferred (albeit challenging) imaging modality for myocardial perfusion imaging. Silent myocardial ischemia and its clinical significance continues to be an intriguing aspect of the clinical manifestation of coronary artery disease. Myocardial perfusion imaging is an invaluable independent method to unravel this problem. Dipyridamole was approved for pharmacologic vasodilation in conjunction with myocardial perfusion imaging. At the same time, direct infusion of adenosine was proposed as an alternative method of effecting vasodilatory stress. In 1990, several new technetium-99m-labeled myocardial perfusion imaging agents have been introduced (teboroxime and hexakis-2-methoxyisobutyl-isonitrile [sestaMIBI]) that may have a profound impact on imaging techniques and applications of myocardial perfusion imaging.     

Usefulness and pitfalls in myocardial perfusion SPECT for detecting and assessing coronary artery disease

Thallium-201(Tl) is the dominant agent employed for myocardial perfusion imaging for detection of coronary artery disease, assessment of myocardial viability and prognostication. Technetium-99m(Tc) labeled radionuclides have been used as excellent alternatives to Tl. This paper will review the usefulness and pitfall in myocardial perfusion single photon emission computed tomography(SPECT) in patients with coronary artery disease. From a practical standpoint, we should know what are clinical questions, clinical status of patients(history and exercise ability of patients, obesity) and diagnostic accuracy of each diagnostic protocol and the performance in the nuclear laboratory. Myocardial perfusion defects during stress SPECT are produced by a heterogeneity in coronary blood flow, which depends on severity of coronary stenosis and consequent abnormalities in flow reserve. Certain factors can affect sensitivity and specificity of Tl SPECT for detection of coronary artery disease. Accurate determination of myocardial viability is vitally important for clinical decision making for patients with left ventricular(LV) dysfunction who will most benefit from revascularization. Hibernated myocardium may result in profound regional LV dysfunction in absence of necrosis. The various approach such as stress-redistribution-reinjection imaging, rest-redistribution imaging and rest-redistribution 24 hours delayed imaging has been utilized to assess myocardial viability with Tl. Alternatively, quantitative assessment of 99mTc-methoxy-isobutyl isonitrile(MIBI) and tetrofosmin uptake reflect the degree of viability. At the present time one of the most important clinical applications of exercise myocardial perfusion SPECT is the assessment of prognosis for patients with suspected and documented coronary artery disease. Patients with normal stress perfusion SPECT have a low event rate and excellent prognosis. Stress perfusion imagings have been widely used to stratify patients into different risk groups in the United State.     

Clinical outcome of patients with advanced coronary artery disease after viability studies with positron emission tomography.

OBJECTIVE. The aim of this study was to determine the prognostic significance of perfusion-metabolism imaging in patients undergoing positron emission tomography for myocardial viability assessment. BACKGROUND. Positron emission tomography using nitrogen-13 ammonia and 18fluorodeoxyglucose to assess myocardial blood flow and metabolism has been shown to predict improvement in wall motion after coronary artery revascularization. The prognostic implications of metabolic imaging in patients with advanced coronary artery disease have not been investigated. METHODS. Eighty-two patients with advanced coronary artery disease and impaired left ventricular function underwent positron emission tomographic imaging between August 1988 and March 1990 to assess myocardial viability before coronary artery revascularization. RESULTS. Forty patients underwent successful revascularization. Patients who exhibited evidence of metabolically compromised myocardium by positron emission tomography (decreased blood flow with preserved metabolism) who did not undergo subsequent revascularization were more likely to experience a myocardial infarction, death, cardiac arrest or late revascularization due to development of new symptoms than were the other patient groups (p less than 0.01). Concordantly decreased flow and metabolism in segments of previous infarction did not affect outcome in patients with or without subsequent revascularization. Those with a compromised myocardium who did undergo revascularization were more likely to experience an improvement in functional class than were patients with preoperative positron emission tomographic findings of concordant decrease in flow and metabolism. CONCLUSIONS. Positron emission tomographic myocardial viability imaging appears to identify patients at increased risk of having an adverse cardiac event or death. Patients with impaired left ventricular function and positron emission tomographic evidence for jeopardized myocardium appear to have the most benefit from a revascularization procedure.