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.     

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.     

Insights into coronary artery disease gained from metabolic imaging

Positron emission tomography offers the possibility of evaluating and quantifying regional myocardial blood flow and metabolism. Used in patients with coronary artery disease, positron emission tomography has demonstrated sustained metabolic activity in regions with reduced blood flow and impaired contractile function, and it thereby enables differentiation between viable myocardium and myocardium that has succumbed to necrosis and scar formation. Viable myocardial regions identified by metabolic rather than functional or blood-flow criteria are frequently observed in patients after an acute coronary event and in patients with stable coronary artery disease. Positron emission tomography reflects either acute myocardial ischemia, "hibernation," as well as "myocardial stunning." Findings from metabolic imaging have proved useful in characterizing more accurately coronary artery disease and its functional consequences. These findings have been found equally useful for clinical management.     

Sex-Related Differences in the Extent of Myocardial Fibrosis in Patients With Aortic Valve Stenosis

ObjectivesThe aim of this study was to assess the effect of sex on myocardial fibrosis as assessed by using cardiac magnetic resonance (CMR) imaging in aortic stenosis (AS).BackgroundPrevious studies reported sex-related differences in the left ventricular (LV) remodeling response to pressure overload in AS. However, there are very few data regarding the effect of sex on myocardial fibrosis, a key marker of LV decompensation and adverse cardiac events in AS.MethodsA total of 249 patients (mean age 66 ± 13 years; 30% women) with at least mild AS were recruited from 2 prospective observational cohort studies and underwent comprehensive Doppler echocardiography and CMR examinations. On CMR, T1 mapping was used to quantify extracellular volume (ECV) fraction as a marker of diffuse fibrosis, and late gadolinium enhancement (LGE) was used to assess focal fibrosis.ResultsThere was no difference in age between women and men (age 66 ± 15 years vs 66 ± 12 years; p = 0.78). However, women presented with a better cardiovascular risk profile than men with less hypertension, dyslipidemia, diabetes, and coronary artery disease (all, p ≤ 0.10). As expected, LV mass index measured by CMR imaging was smaller in women than in men (p < 0.0001). Despite fewer comorbidities, women presented with larger ECV fraction (median: 29.0% [25th to 75th percentiles: 27.4% to 30.6%] vs. 26.8% [25th to 75th percentiles: 25.1% to 28.7%]; p < 0.0001) and similar LGE (median: 4.5% [25th–75th percentiles: 2.3% to 7.0%] vs. 2.8% [25th–75th percentiles: 0.6% to 6.8%]; p = 0.20) than men. In multivariable analysis, female sex remained an independent determinant of higher ECV fraction and LGE (all, p ≤ 0.05).ConclusionsWomen have greater diffuse and focal myocardial fibrosis independent of the degree of AS severity. These findings further emphasize the sex-related differences in LV remodeling response to pressure overload.     

Myocardial viability assessment and utility in contemporary management of ischemic cardiomyopathy

BackgroundIn clinical practice, we encounter ischemic cardiomyopathy (ICM) with underlying viable, dysfunctional myocardium on a regular basis. Evidence from the Surgical Treatment for Ischemic Heart failure (STICH) and its Extension Study is supportive of improved outcomes with coronary revascularization, irrespective of myocardial viable status. However, Dobutamine stress echocardiography (DSE) and single‐photon emission computed tomography (SPECT), used in STICH to assess myocardial viability may fail to distinguish hibernating myocardium from scar due to suboptimal image resolution and poor tissue characterization.HypothesisCardiac magnetic resonance (CMR) and positron emission tomography (PET) can precisely quantify myocardial scar and identify metabolically active, viable myocardium respectively. Unlike DSE and SPECT, CMR and PET allow examining myocardial status as a contiguous spectrum from viable to partially viable myocardium with varying degrees of subendocardial scar and nonviable myocardium with predominantly transmural scar, the therapeutic and prognostic determinants of ICM.MethodsUnder the guidance of CMR and PET imaging, myocardium can be distinguished viable from partially viable with subendocardial scar and predominantly transmural scar. In ICM, optimal medical therapy and coronary revascularization of viable/partially viable myocardium but not transmural scar may improve outcomes in patients with acceptable procedural risk.ResultsCoronary revascularization of partially viable and viable myocardial territory may improve clinical outcomes by preventing future ischemic, infarct events and further worsening of left ventricular remodeling and function.ConclusionsWhen deciding if coronary revascularization is appropriate in a patient with ICM, it is essential to take a patient‐tailored, comprehensive approach incorporating myocardial viability, ischemia, and scar data with others such as procedural risk, and patient''s comorbidities.     

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.     

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.     

Cardiac MRI For Myocardial Ischemia

Proper assessment of the physiologic impact of coronary artery stenosis on the LV myocardium can affect patient prognosis and treatment decisions. Cardiac magnetic resonance imaging (CMR) assesses myocardial perfusion by imaging the myocardium during a first-pass transit of an intravenous gadolinium bolus, with spatial and temporal resolution substantially higher than nuclear myocardial perfusion imaging. Coupled with late gadolinium enhancement (LGE) imaging for infarction during the same imaging session, CMR with vasodilating stress perfusion imaging can qualitatively and quantitatively assess the myocardial extent of hypoperfusion from coronary stenosis independent of infarcted myocardium. This approach has been validated experimentally, and multiple clinical trials have established its diagnostic robustness when compared to stress single-photon emission computed tomography. In specialized centers, dobutamine stress CMR has been shown to have incremental diagnostic value above stress echocardiography due to its high imaging quality and ability to image the heart with no restriction of imaging window. This paper reviews the technical aspects, diagnostic utility, prognostic values, challenges to clinical adaptation, and future developments of stress CMR imaging.     

Left Ventricular Hypertrophy: The Relationship between the Electrocardiogram and Cardiovascular Magnetic Resonance Imaging

Conventional assessment of left ventricular hypertrophy (LVH) using the electrocardiogram (ECG), for example, by the Sokolow–Lyon, Romhilt–Estes or Cornell criteria, have relied on assessing changes in the amplitude and/or duration of the QRS complex of the ECG to quantify LV mass. ECG measures of LV mass have typically been validated by imaging with echocardiography or cardiovascular magnetic resonance imaging (CMR). However, LVH can be the result of diverse etiologies, and LVH is also characterized by pathological changes in myocardial tissue characteristics on the genetic, molecular, cellular, and tissue level beyond a pure increase in the number of otherwise normal cardiomyocytes. For example, slowed conduction velocity through the myocardium, which can be due to diffuse myocardial fibrosis, has been shown to be an important determinant of conventional ECG LVH criteria regardless of LV mass. Myocardial tissue characterization by CMR has emerged to not only quantify LV mass, but also detect and quantify the extent and severity of focal or diffuse myocardial fibrosis, edema, inflammation, myocarditis, fatty replacement, myocardial disarray, and myocardial deposition of amyloid proteins (amyloidosis), glycolipids (Fabry disease), or iron (siderosis). This can be undertaken using CMR techniques including late gadolinium enhancement (LGE), T1 mapping, T2 mapping, T2* mapping, extracellular volume fraction (ECV) mapping, fat/water‐weighted imaging, and diffusion tensor CMR. This review presents an overview of current and emerging concepts regarding the diagnostic possibilities of both ECG and CMR for LVH in an attempt to narrow gaps in our knowledge regarding the ECG diagnosis of LVH.     

Positron emission tomography to assess the haemodynamics of the coronary circulation.

Positron emission tomography (PET) allows the non-invasive measurement of absolute myocardial blood flow (ml/min/g of myocardium) in man. This has made possible the measurement of myocardial blood flow and the coronary vasodilator reserve (an index of the ability of the coronary microcirculation to dilate) in healthy volunteers to establish the normal values and ranges of these parameters. This technique allows the assessment of the functional significance of epicardial coronary stenoses as well as the investigation of the function of the coronary microcirculation in patients with and without coronary artery disease.     

Diagnostic value of contrast-enhanced magnetic resonance imaging and single-photon emission computed tomography for detection of myocardial necrosis early after acute myocardial infarction.

OBJECTIVES: This study sought to evaluate the diagnostic value of contrast-enhanced magnetic resonance imaging (CMR) and single-photon emission computed tomography (SPECT) for detection of myocardial necrosis after acute myocardial infarction (AMI). BACKGROUND: Single-photon emission computed tomography is widely accepted in the clinical setting for detection and estimation of myocardial infarction. Contrast-enhanced magnetic resonance imaging offers technical advantages and is therefore a promising new method for identification of infarcted tissue. METHODS: Seventy-eight patients with AMI were examined by CMR and SPECT 7 days after percutaneous coronary intervention. Contrast-enhanced magnetic resonance imaging and SPECT images were scored for presence and location of infarction using a 17-segment model. Results were compared with the peak troponin T level, electrocardiographic, and angiographic findings. RESULTS: Acute myocardial infarction was detected significantly more often by CMR than SPECT (overall sensitivity: 97% vs. 87%; p = 0.008). Sensitivity of CMR was superior to SPECT in detecting small infarction as assessed by the peak troponin T level <3.0 ng/ml (92 vs. 69%; p = 0.03), and infarction in non-anterior location (98% vs. 84%; p = 0.03). Non-Q-wave infarctions were more likely to be detected by CMR (sensitivity 85% vs. 46%; p = 0.06). While CMR offered high sensitivity for detection of AMI irrespective of the infarct-related artery, SPECT was less sensitive, particularly within the left circumflex artery territory. CONCLUSIONS: Contrast-enhanced magnetic resonance imaging is superior to SPECT in detecting myocardial necrosis after reperfused AMI because CMR detects small infarcts that were missed by SPECT independent of the infarct location. Thus, CMR is attractive for accurate detection and assessment of the myocardial infarct region in patients early after AMI.     

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.     

Metabolic and ultrastructural abnormalities during ischemia in canine myocardium: noninvasive assessment by positron emission tomography

Positron emission tomography allows the noninvasive assessment of regional myocardial blood flow and metabolism. The purpose of this study was to correlate N-13 ammonia uptake as a measure of regional blood flow and C-11 palmitate kinetics as a marker for fatty acid metabolism in ischemic canine myocardium using positron emission tomography. Furthermore, the metabolic results were compared with ultrastructural findings obtained in the same animal model. Regional ischemia was induced by balloon occlusion of the left anterior descending artery in a closed chest dog model. The three myocardial sites studied were the center and "border" of the ischemic segment as well as the control myocardium. C-11 palmitate uptake closely correlated with blood flow (r = 0.88). In the center of ischemia uptake of C-11 palmitate was decreased and clearance of C-11 activity significantly prolonged. In the "border" of the ischemic segment with only mild reduction of flow and C-11 palmitate uptake (approximately 20%) clearance halftime and residual activity were significantly different from control. The residual activity normalized for initial uptake of C-11 palmitate was highest in the "border" regions consistent with increased deposition of C-11 palmitate in lipid pools. The electron microscopic studies showed in 8 of 11 dogs lipid droplets as the only abnormality in corresponding segments with only mild reduction in microsphere blood flow. Thus, these data indicate the potential of metabolic imaging to characterize ischemia on a cellular level. Positron emission tomography provides a sensitive means to detect mild ischemia and to define extent and severity. Metabolic imaging may prove clinically useful to identify not only necrosis, but also myocardium at risk.     

Noncontrast Myocardial T1 Mapping by Cardiac Magnetic Resonance Predicts Outcome in Patients With Aortic Stenosis

Objectives

The aim of this study was to evaluate whether native T1 value of the myocardium on cardiac magnetic resonance (CMR) could predict clinical events in patients with significant aortic stenosis (AS).

Important Advances in Technology and Unique Applications Related to Cardiac Magnetic Resonance Imaging

Cardiac magnetic resonance has become a well-established imaging modality and is considered the gold standard for myocardial tissue viability assessment and ventricular volumes quantification. Recent technological hardware and software advancements in magnetic resonance imaging technology have allowed the development of new methods that can improve clinical cardiovascular diagnosis and prognosis. The advent of a new generation of higher magnetic field scanners can be beneficial to various clinical applications. Also, the development of faster acquisition techniques have allowed mapping of the magnetic relaxation properties T1, T2, and T2* in the myocardium that can be used to quantify myocardial diffuse fibrosis, determine the presence of edema or inflammation, and measure iron within the myocardium, respectively. Another recent major advancement in CMR has been the introduction of three-dimension (3D) phase contrast imaging, also known as 4D flow. The following review discusses key advances in cardiac magnetic resonance technology and their potential to improve clinical cardiovascular diagnosis and outcomes.     

Recent advances in cardiac positron emission tomography in the clinical management of the cardiac patient

Despite being primarily a research tool, positron emission tomography (PET) has seen slow but steady growth in the clinical management of the cardiac patient. The two major clinical applications of cardiac PET are regional myocardial perfusion imaging to determine the presence and severity of coronary artery disease and metabolic imaging to differentiate viable from nonviable myocardium in patients with ischemic left ventricular dysfunction. Indeed, PET with either nitrogen 13 ammonia or rubidium 82 may offer advantages over current single photon emission computed tomography approaches to assess myocardial perfusion. PETwith fluorine 18 fluorodeoxyglucose is considered the current gold standard for identifying viable myocardium. Finally, the use of PET to quantify myocardial perfusion, metabolism, and innervation has led to key insights into the role of altered microvascular function, substrate metabolism, and neuronal function in a variety of cardiac disease processes.     

A Machine-Learning Framework to Identify Distinct Phenotypes of Aortic Stenosis Severity

ObjectivesThe authors explored the development and validation of machine-learning models for augmenting the echocardiographic grading of aortic stenosis (AS) severity.BackgroundIn AS, symptoms and adverse events develop secondarily to valvular obstruction and left ventricular decompensation. The current echocardiographic grading of AS severity focuses on the valve and is limited by diagnostic uncertainty.MethodsUsing echocardiography (ECHO) measurements (ECHO cohort, n = 1,052), we performed patient similarity analysis to derive high-severity and low-severity phenogroups of AS. We subsequently developed a supervised machine-learning classifier and validated its performance with independent markers of disease severity obtained using computed tomography (CT) (CT cohort, n = 752) and cardiovascular magnetic resonance (CMR) imaging (CMR cohort, n = 160). The classifier’s prognostic value was further validated using clinical outcomes (aortic valve replacement [AVR] and death) observed in the ECHO and CMR cohorts.ResultsIn 1,964 patients from the 3 multi-institutional cohorts, 1,346 (68%) subjects had either nonsevere or discordant AS severity. Machine learning identified 1,117 (57%) patients as having high-severity and 847 (43%) as having low-severity AS. High-severity patients in CT and CMR cohorts had higher valve calcium scores and left ventricular mass and fibrosis, respectively than the low-severity group. In the ECHO cohort, progression to AVR and progression to death in patients who did not receive AVR was faster in the high-severity group. Compared with the conventional classification of disease severity, machine-learning–based severity classification improved discrimination (integrated discrimination improvement: 0.07; 95% confidence interval: 0.02 to 0.12) and reclassification (net reclassification improvement: 0.17; 95% confidence interval: 0.11 to 0.23) for the outcome of AVR at 5 years. For both ECHO and CMR cohorts, we observed prognostic value of the machine-learning classifications for subgroups with asymptomatic, nonsevere or discordant AS.ConclusionsMachine learning can integrate ECHO measurements to augment the classification of disease severity in most patients with AS, with major potential to optimize the timing of AVR.     

Imaging Heart Failure: Current and Future Applications

A variety of cardiac imaging tests are used to help manage patients with heart failure (HF). This article reviews current and future HF applications for the major noninvasive imaging modalities: transthoracic echocardiography (TTE), single-photon emission computed tomography (SPECT), positron emission tomography (PET), cardiovascular magnetic resonance (CMR), and computed tomography (CT). TTE is the primary imaging test used in the evaluation of patients with HF, given its widespread availability and reliability in assessing cardiac structure and function. Recent developments in myocardial strain, 3-dimensional TTE, and echo contrast appear to offer superior diagnostic and prognostic information. SPECT imaging is a common method employed to detect ischemia and viability in patients with HF; however, PET offers higher diagnostic accuracy for both. Ongoing study of sympathetic and molecular imaging techniques may enable early disease detection, better risk stratification, and ultimately targeted treatment interventions. CMR provides high-quality information on cardiac structure and function and allows the characterization of myocardial tissue. Myocardial late gadolinium enhancement allows the determination of HF etiology and may predict patient outcomes and treatment response. Cardiac CT has become a reliable means for detecting coronary artery disease, and recent advances have enabled concurrent myocardial function, perfusion, and scar analyses. Overall, available imaging methods provide reliable measures of cardiac performance in HF, and recent advances will allow detection of subclinical disease. More data are needed demonstrating the specific clinical value of imaging methods and particularly subclinical disease detection in large-scale, clinical settings.     

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.     

正电子发射断层扫描与X线断层扫描在冠状动脉性心脏病中的应用和进展

冠状动脉粥样硬化性心脏病是许多国家首要的死亡原因,正电子发射断层扫描可以清晰地显示心肌灌注,室壁运动和心肌活性,成为诊断冠状动脉粥样硬化性心脏病的重要手段。而正电子发射断层扫描和多层螺旋X线断层扫描仪的融合,把钙化积分和无创性的X线断层扫描仪血管造影加入心肌灌注显像和代谢显像,为冠状动脉粥样硬化性心脏病的诊断提供形态和功能方面的信息。