Noninvasive Assessment Of Myocardial Perfusion Research Articles

Assessment of no-reflow phenomenon by myocardial contrast echocardiography in patients with acute myocardial infarction with ST-segment elevation

Abstract Funding Acknowledgements Type of funding sources: None. Background The noninvasive assessment of myocardial perfusion by echo contrast agents in patients with acute myocardial infarction with ST-segment elevation (STEMI) after successful revascularization is becoming a relevant clinical reality. Perfusion imaging techniques with myocardial contrast echocardiography (MCE) remains the least studied and most promising ultrasound technology for the diagnosis of no-reflow phenomenon. Purpose To study the echocardiographic and angiographic characteristics of the no-reflow phenomenon detected by MCE in patients with STEMI. Methods The study included 43 patients aged from 40 to 82 years in acute stage of myocardial infarction. Patients were divided into two groups: 32 patients characterized by sufficient myocardial reperfusion after revascularization according to MCE results and 11 patients were with the impaired perfusion. Results The patients with impaired perfusion demonstrated a greater size of the left ventricular (LV) asynergy (40.1 ± 2.2% vs 27.4 ± 8.5%, p < 0.001). LV dilatation (LV end-systolic volume 67.3 ± 20.3 ml vs 51.8 ± 17.2 ml, p = 0.015), impaired LV ejection fraction (39.5 ± 3.4% vs 47.2 ± 4.9%, p < 0.001), and significant mitral regurgitation (45.5% vs 3.1%, p = 0.011) with a decrease in DP/DT (979.9 ± 363.4 mmHg/s vs 1565.7 ± 502.8 mmHg/s, p < 0.001) was more often detected in this group. In more than a quarter of these patients, coronary angiography showed no perfusion disorders after revascularization. In the group with impaired perfusion by MCE, the single-vascular lesions (46.9% vs 9.1%, p = 0.033), the lesions of the anterior interventricular artery (90.9% vs 40.6%, p = 0.004), and acute occlusion (100% vs 68.8%, p = 0.043) were more often determined. Conclusion According to the results of MCE, the echo signs of LV dysfunction were more pronounced after successful revascularization in patients with STEMI and myocardial perfusion disorders. The SYNTAX score was twice higher in these patients compared to the patients with recovered perfusion. In addition, no-reflow phenomenon by MCE was observed in the most patients with anterior interventricular artery lesion.

From 201Tl to 99mTc-Sestamibi (perspective on “Technetium-99m Hexakis 2-Methoxyisobutyl Isonitrile: Human Biodistribution, Dosimetry, Safety, and Preliminary Comparison To Thallium-201 for Myocardial Perfusion Imaging” J Nucl Med. 1989;30:301–311)

In the 1980s, 201Tl scintigraphy helped to introduce noninvasive assessment of myocardial perfusion as an important clinical tool for the detection and management of coronary artery disease (CAD). Monovalent cations such as 201Tl exhibit pharmacokinetics that are very suitable for the assessment of

408 Stress Cardiac Magnetic Resonance With In-Line AI Quantitative Perfusion Mapping; Clinical Experience for Ischaemia and Microvascular Dyfunction

Adenosine Stress Perfusion Cardiac Magnetic Resonance (CMR) is a highly accurate technique for non-invasive assessment of myocardial perfusion, as shown in recent CEMARC, MR-INFORM, SPINS and GADACAD trials. Quantitative perfusion mapping using convoluted neural network artificial intelligence (AI) reconstruction has been proposed to improve accuracy and diagnostic performance. 33 consecutive stress scans CMR clinically referred for evaluation of angina pectoris, performed on a 1.5T Siemens Aera system. Standard sequence was a free-breathing motion corrected FLASH dynamic perfusion after 140mcg/kg adenosine, compared to an investigational work-in-progress myocardial blood flow (MBF) dual bolus technique with automatic arterial input function quantitated in ml/min/g using 16-segment AHA model. 22 scans referred for ischaemia, 11 for microvascular dysfunction. Level-3 expert reader blindly evaluated grey-scale dynamic perfusion imaging, and separately evaluated quantitative perfusion maps. Scans were categorised as ischaemia, microvascular, or normal coronary physiology. Diagnostic confidence was measured on a Likert rating scale from 1 (unconfident) to 3 (very confident). 31/33 scans (94%) had successful perfusion mapping, with 2 excluded due to artefact from arrythmia or failed motion correction. 20/22 scans referred for ischaemia (91%) mapping improved diagnostic confidence (score 2.03 vs 2.88, P<0.001). For all 11 (100%) microvascular dysfunction cases perfusion mapping was diagnostic over standard imaging. Quantitative perfusion mapping improves diagnostic confidence and allows accurate separation of ischaemic vs microvascular causes of angina.

Feasibility Study of Computational Fluid Dynamics Simulation of Coronary Computed Tomography Angiography Based on Dual-Source Computed Tomography.

BackgroundAdding functional features to morphological features offers a new method for non-invasive assessment of myocardial perfusion. This study aimed to explore technical routes of assessing the left coronary artery pressure gradient, wall shear stress distribution and blood flow velocity distribution, combining three-dimensional coronary model which was based on high resolution dual-source computed tomography (CT) with computational fluid dynamics (CFD) simulation.MethodsThree cases of no obvious stenosis, mild stenosis and severe stenosis in left anterior descending (LAD) were enrolled. Images acquired on dual-source CT were input into software Mimics, ICEMCFD and FLUENT to simulate pressure gradient, wall shear stress distribution and blood flow velocity distribution. Measuring coronary enhancement ratio of coronary artery was to compare with pressure gradient.ResultsResults conformed to theoretical values and showed difference between normal and abnormal samples.ConclusionsThe study verified essential parameters and basic techniques in blood flow numerical simulation preliminarily. It was proved feasible.

Primary Cardiac Involvement in Scleroderma and Role of Cardiac MRI

Systemic sclerosis (scleroderma) is a connective tissue disease characterized by vascular dysfunction and fibrosis that can affect multiple organ systems. We present case of primary cardiac involvement and the diagnostic role of cardiac MRI. Cardiovascular magnetic resonance imaging (MRI) is an accurate, quantitative method for the non-invasive assessment of myocardial perfusion. The presence of clinically apparent myocardial involvement in scleroderma portends a very poor prognosis. One study of US veterans found that clinical cardiac disease in scleroderma was associated with a 70% mortality rate at five years. Management of heart failure and conduction system abnormalities in scleroderma is similar to other cardiac disease. It includes afterload reduction, beta-blockade, defibrillator placement, etc. Patients with reduced cardiac function and normal coronary arteries may benefit from increased immune suppresion.

Cine‐ASL: A steady‐pulsed arterial spin labeling method for myocardial perfusion mapping in mice. Part I. Experimental study

Arterial spin labeling has been developed and used for the quantitative and completely noninvasive assessment of myocardial perfusion in vivo. Here we propose a novel arterial spin labeling method called cine-ASL, which is based on an electrocardiogram-gated steady-pulsed labeling approach combined with simultaneous readout over the cardiac cycle using cine-fast low-angle shot. This method led to shorter acquisition times than the previously used Look-Locker flow-sensitive alternating inversion recovery gradient-echo technique while preserving spatial resolution and robustness with respect to cardiac motion. High resolution perfusion mapping (in-plane resolution = 195 μm × 391 μm) was carried out with both techniques at 4.7 T in a group of 14 healthy mice. Mean perfusion values were 5.0 ± 0.8 mL g(-1) min(-1) with cine-ASL and 5.9 ± 1.4 mL g(-1) min(-1) with Look-Locker flow-sensitive alternating inversion recovery. In one animal, physiological stress was induced with higher anesthetic concentration to evaluate the response of both methods under vasodilation. Global myocardial perfusion increased from 5.6 to 16.0 mL g(-1) min(-1) with cine-ASL and from 6.3 to 18.7 mL g(-1) min(-1) with Look-Locker flow-sensitive alternating inversion recovery. Although this original scheme requires a separate T1 measurement to be fully quantitative, it improves arterial spin labeling sensitivity while maintaining compatibility with motion constraints in cardiac MRI in small rodents.

Cost effectiveness of adding CMR to evaluation of suspected coronary ischaemia

Summary To estimate the cost and diagnostic implications of using CMR alone instead of conventional TTE/TMET work-up to guide patient selection for angiography. Healthcare costs were derived from VHI’s hospital billing system. Background Patient selection for coronary angiography traditionally relies on clinical assessment, treadmill exercise testing (TMET) and transthoracic echocardiography (TTE). Cardiac Magnetic Resonance (CMR) is a relatively novel imaging study, which provides excellent non-invasive assessment of myocardial perfusion and is useful in risk stratification of patients with suspected coronary artery disease (CAD). Methods

SPECT Imaging for Detecting Coronary Artery Disease and Determining Prognosis by Noninvasive Assessment of Myocardial Perfusion and Myocardial Viability

Basic knowledge of active and passive transport mechanisms for concentrating monovalent cations in myocardial cells led to the investigation of the application of radioisotopes of potassium, thallium, rubidium, and ammonia to the in vivo noninvasive assessment of regional myocardial perfusion and viability utilizing gamma camera or positron emission tomographic (PET) imaging technology. Subsequently, technetium-99m (Tc-99m)-labeled isonitriles (sestamibi and tetrofosmin), which bind to mitochondrial membranes, emerged as superior imaging agents with single photon emission tomography (SPECT) imaging. When any of these imaging agents are injected intravenously during either exercise or pharmacologic stress, myocardial defects in tracer uptake represent either abnormal regional flow reserve or myocardial scar reflecting of coronary artery disease (CAD). The major clinical indications for stress SPECT or PET myocardial perfusion imaging are for detection of CAD as the cause of chest pain and risk stratification for prognostication. Patients with normal stress myocardial perfusion scans have an excellent prognosis with <1.0% annual rate future annual death or nonfatal infarction. The greater the extent and severity of ischemic perfusion defects (defects seen on stress images but improve on resting images), the greater the subsequent death or infarction rate during follow-up. Rest imaging alone is performed for determination of myocardial viability in patients with CAD and severe left ventricular dysfunction. Myocardial segments showing >50% uptake compared to normal uptake have a better long-term outcome with revascularization than with medical therapy with enhanced left ventricular function and improved survival. Other applications of SPECT imaging include the evaluation of cardiac sympathetic function, assessment of myocardial metabolism in health and disease, and molecular imaging of coronary atherosclerosis and myocardial stem cell therapy.

Minimizing liver uptake of cationic 99mTc radiotracers with ether and crown ether functional groups

Ischemia-related diseases, particularly coronary artery disease (CAD), account for the majority of deaths worldwide. Myocardial ischemia is a serious condition and the delay in reperfusion of ischemic tissues can be life-threatening. This is particular true in the aged population. Rapid and accurate early detection of myocardial ischemia is highly desirable so that various therapeutic regiments can be given before irreversible myocardial damage occurs. Myocardial perfusion imaging with radiotracers is an integral component in evaluations of patients with known or suspected CAD. (99m)Tc-Sestamibi and (99m)Tc-Tetrofosmin are commercial radiopharmaceuticals currently available for myocardial perfusion imaging. Despite their widespread clinical applications, both (99m)Tc-Sestamibi and (99m)Tc-Tetrofosmin do not meet the requirements of an ideal perfusion imaging agent, largely due to their high liver uptake. The intense liver uptake makes it difficult to interpret the heart activity in the inferior and left ventricular wall. Photon scattering from the high liver radioactivity accumulation remains a significant challenge for diagnosis of heart diseases. This review will summarize the most recent research efforts to minimize the liver uptake of cationic (99m)Tc radiotracers by using ether and crown ether-containing chelators. Fast liver clearance will shorten the duration of imaging protocols (< 30 min post-injection), and allow for early acquisition of heart images with high quality. Improvement of heart/liver ratio may permit better detection of the presence and extent of coronary artery disease. Identification of such a new radiotracer that allows for the improved noninvasive assessment of myocardial perfusion would be of considerable benefit in treatment of patients with suspected CAD.

Noninvasive Assessment of Myocardial Perfusion

Noninvasive assessment of myocardial perfusion is important in the diagnosis and risk stratification of patients with known or suspected coronary artery disease (CAD). Although single-photon emission computed tomography (SPECT) is most commonly used, multiple modalities including myocardial contrast echocardiography (MCE), positron emission tomography (PET), cardiac MRI (CMR), and cardiac computed tomography (CT) have emerged as promising techniques. This article will critically evaluate the strengths and weakness of these modalities for evaluating myocardial perfusion. Myocardial perfusion is a highly regulated process that includes epicardial vessels, resistance vessels, and the endothelium. Endothelial dysfunction is an early manifestation of vascular disease and plays a role in the development of CAD.1 In normal coronaries, sympathetic stimulation causes a flow-mediated endothelium-dependent release of nitric oxide resulting in epicardial and arteriolar vasodilation. With endothelial dysfunction, vasoconstriction from acetylcholine predominates, resulting an attenuation or absence of the normal flow-mediated vasodilation.2 When coronary arteries are narrowed by atherosclerotic disease, coronary autoregulation attempts to normalize myocardial blood flow by reducing the resistance of distal perfusion beds to preserve adequate myocardial oxygen supply.3 A stenosis must exceed 85% to 90% of luminal diameter before significant reductions in resting blood flow occur.4 However, under vasodilator stimulus, maximal coronary flow has been shown to decrease with stenosis of >45% (Figure 1).4 This has been demonstrated clinically using quantitative PET myocardial perfusion imaging (MPI).5,6 Because perfusion is an early change in the ischemic cascade,7 stress modalities that assess coronary perfusion reserve have a higher sensitivity in detecting flow-limiting stenoses than analysis of stress-induced wall motion abnormalities or ECG changes alone.8 Abnormal coronary flow reserve with vasodilator stress in the absence of a significant coronary stenosis occurs and has been attributed to microvascular and/or endothelial dysfunction.9 Figure 1. Relationship between percent diameter stenosis and …

Diagnostik der koronaren Herzkrankheit – Teil 2: Belastungs-EKG und Myokardperfusionsszintigraphie

The principle of exercise stress test and myocardial perfusions scintigraphy (MPS) is based on the detection of exercise-induced myocardial ischaemia by ECG and non-invasive assessment of myocardial perfusion respectively, MPS being the more sensitive method. The exercise stress test is the method of choice in patients with a normal resting ECG and good exercise tolerance, whereas MPS is a suitable test for patients with abnormal resting ECG and/or exercise intolerance. Stressors for MPS included exercise, pharmacological stress, or a combination. Both exercise stress test and MPS are suitable for the evaluation of patients with chest pain and intermediate pre-test probability of significant coronary artery disease. For patients with high pre-test probability, both tests are helpful for risk stratification. Neither test makes sense for the evaluation of patients with chest pain and low pre-test probability of significant coronary artery disease or unselected asymptomatic patients.

Preliminary Data on the Diagnostic Accuracy of Rubidium-82 Cardiac PET Perfusion Imaging for the Evaluation of Ischemia in a Pediatric Population

Evaluation of myocardial perfusion is sometimes necessary in children with congenital heart disease or acquired coronary artery abnormalities. Limited information is available regarding the clinical utility of myocardial perfusion imaging in children. PET imaging with rubidium-82 may provide a convenient clinical means of assessing regional circulatory compromise in pediatric patients with small hearts, due to its improved spatial resolution. Clinically indicated cardiac PET studies obtained in 22 pediatric patients were reviewed by two blinded observers and assigned myocardial perfusion scores using a standard 17-segment model. PET results were correlated with coronary angiography, available in 15 cases, to determine the accuracy of PET scanning for evaluating compromise of the myocardial circulation. Reversible defects consistent with myocardial ischemia were present in 6 of 15 (40%) PET cases. The sensitivity and specificity of cardiac PET for the detection of significant coronary artery disease were 100% and 82%, respectively. The positive predictive value of cardiac PET was 67%, while the negative predictive value was 100%. Cardiac PET imaging with rubidium-82 appears promising for the noninvasive assessment of myocardial perfusion in the pediatric population. The findings from this small series suggest that prospective study in a larger patient cohort merits consideration.

Coronary Artery Disease

Early and accurate diagnostic testing is a critical factor in the detection and optimal management of coronary artery disease (CAD); thus, noninvasive cardiac imaging has become a central tool for CAD evaluation. Currently, tests used for evaluating CAD include conventional resting and stress electrocardiogram, echocardiography, and myocardial perfusion imaging--the most widely used imaging test for evaluation of suspected myocardial ischemia. Emerging techniques for noninvasive assessment of myocardial perfusion and coronary angiography include cardiac computed tomography, cardiac magnetic resonance imaging, and positron emission tomography. The distinctive pathophysiology of atherosclerosis can be used together with imaging techniques to diagnose and assess risk for CAD. Imaging modalities for cardiac risk stratification include a diverse array of tools, such as noninvasive tests that visualize presymptomatic atherosclerosis to sophisticated radionuclide protocols that identify myocardial viability. Of the noninvasive imaging tests, gated SPECT is the most accurate method for risk stratification of CAD. Myocardial perfusion imaging with SPECT has improved accuracy and image quality such that a shift from diagnostic to prognostic use has occurred. Radionuclide myocardial perfusion imaging has played an important role in CAD evaluation since the introduction of thallium-201 (Tl-201) in the 1970s. Although Tl-201 has high sensitivity, specificity, and reproducibility, it also has physical properties that limit its use and affect image quality. Currently, Tc-99m tetrofosmin and sestamibi are the most commonly used agents for a variety of resting and stress protocols, both have similar diagnostic accuracy profiles. The field of nuclear cardiology has grown steadily over the past few decades, as more practitioners recognize its clinical applications and value in managing cardiovascular disease. There is abroad spectrum of noninvasive and invasive testing available for the diagnosis and management of patients with cardiovascular disease. Advances in computer technology have made sophisticated devices, such as the gated SPECT, a routine part of cardiology.

Intravenous myocardial contrast echocardiography for the diagnosis of coronary artery disease

Myocardial contrast echocardiography is a recently developed technique that permits the noninvasive assessment of myocardial perfusion. Myocardial contrast enhancement from microbubbles characteristically reflects the myocardial blood volume. The analysis of microbubble kinetics using quantitative myocardial contrast echocardiography permits the evaluation of myocardial blood flow both at rest and during pharmacological stress. Myocardial contrast echocardiography has been shown to have good concordance with single photon emission computed tomography for the localization of perfusion abnormalities. As a result of its better spatial resolution and the fact that it tracks myocardial blood flow changes, it seems to have higher sensitivity for the detection of angiographically significant coronary artery disease, while maintaining similar specificity to single photon emission computed tomography. Low mechanical index imaging techniques (real-time myocardial contrast echocardiography) have the advantage of permitting simultaneous analysis of wall motion and perfusion, which is particularly important during dobutamine stress. Myocardial perfusion analysis using real-time myocardial contrast echocardiography has been shown to have higher sensitivity and diagnostic accuracy than wall motion analysis for the detection of coronary artery disease. Quantitative myocardial contrast echocardiography seems to overcome the expertise requirements for appropriate interpretation of myocardial perfusion images, and may have been demonstrated to be an accurate supplemental technique for estimating the severity of coronary artery disease. Recent technological advances have positioned myocardial contrast echocardiography as a safe and feasible technique for the evaluation of myocardial perfusion. The analysis of myocardial perfusion using myocardial contrast echocardiography has higher diagnostic accuracy than wall motion analysis for detecting coronary artery disease.

Assessment of Ischemic Heart Disease Using Magnetic Resonance First-Pass Perfusion Imaging

Cardiovascular magnetic resonance (MR) perfusion imaging has matured to a point where it can be routinely applied to assess patients with coronary artery disease and ischemic cardiomyopathy. The method has been compared to invasive, catheter-based as well as other noninvasive imaging modalities (echocardiography, single-photon emission computed tomography [SPECT], and positron emission tomography [PET]) for the evaluation of patients with coronary artery disease. Besides qualitative evaluation of MR perfusion images, an absolute quantification of global, regional and transmural myocardial perfusion is possible. A relative or absolute myocardial perfusion reserve has been determined noninvasively with MR perfusion imaging, and can provide good agreement with the invasive assessment. Based on the perfusion reserve, the severity of an epicardial coronary stenosis can be evaluated in patients with known or suspected coronary artery disease. Besides the absence of radiation exposure, MR perfusion imaging offers good temporal and excellent spatial resolution. In particular, the spatial resolution increases the sensitivity and specificity for the detection of coronary artery disease. New parameters such as the "endo-/epimyocardial resting perfusion ratio", may under some circumstances sufficiently enhance the sensitivity for detecting an abnormal perfusion, and thus avoid potentially harmful and expensive stress testing in patients with suspected ischemic heart disease. New revascularization modalities such as therapeutic angiogenesis need to be matched by sensitive imaging tools to prove their benefits. Thus, the optimization of therapeutic angiogenesis may profit from the diagnostic advantages provided by MR perfusion imaging. Furthermore, MR might yield new insights into the pathophysiology of cardiac diseases such as "syndrome X", or might help in the repetitive assessment of heart transplant recipients, possibly obviating the need for further invasive testing. The breadth of cardiac MRI allows the combined noninvasive assessment of myocardial perfusion, function, as well as myocardial viability. The combination gives MRI a unique and strong position in the field of noninvasive diagnostic cardiology.

Clinical utility of contrast echocardiography in the management of patients with acute myocardial infarction

The extensive use of myocardial contrast echocardiography (MCE) in patients with acute myocardial infarction has provided critical information regarding the perfusion-contraction mismatch that is observed in post-ischaemic dysfunctioning segments. ‘No-reflow’ phenomena, microvascular stunning, and the relation between microvascular integrity and inotropic reserve within the infarct zone represent areas in which NICE could provide useful information. Rapid technological progress has been made in echocardiographic imaging (harmonic and ultraharmonic imaging, real-time perfusion imaging), and new ultrasound contrast agents such as SonoVue (Bracco, Milan, Italy) have been introduced into the market. These have rendered non-invasive assessment of myocardial perfusion a clinical reality, and thus demonstrate the potential role of NICE in assessing myocardial salvage after reperfusion therapy and suggest that routine NICE use in a coronary care unit may be possible.

Novel method for assessing myocardial perfusion: visualization and measurement of intramyocardial coronary blood flow in the entire left ventricular wall using contrast enhanced, high frequency Doppler echocardiography.

Using a high frequency ultrasonic transducer, intramyocardial coronary blood flow (IM-CBF) can be visualized and evaluated during hemodynamic changes in the anterior wall and septum of the left ventricle (LV). We tested the hypothesis that detection and quantitative measurement of IM-CBF of entire LV segments are feasible using a high frequency ultrasonic transducer in conjunction with intravenous contrast injection in vivo. A 3 - 8 MHz transducer was used to image and measure IM-CBF in 10 anesthetized dogs. We obtained a color Doppler image of IM-CBF in the LV short-axis view after intravenous Levovist injection (25 mg/ml). The IM-CBF velocity was recorded using spectral Doppler in the antero-septal and infero-posterior wall of closed chest dogs and in the entire LV after opening the chest. A significant increase in IM-CBF velocity was observed in all LV regions after adenosine 5'- triphosphate (ATP) administration. After Levovist(TM) injection, the visualization of IM-CBF was improved and the spectral Doppler pattern of coronary flow velocity was clarified compared to baseline. IM-CBF was assessed in the antero-septal region of the LV before and after left anterior descending coronary artery occlusion. A high frequency ultrasonic transducer in conjunction with intravenous contrast injection improved IM-CBF visualization, enabling quantitative evaluation of the intramyocardial coronary circulation in the entire LV after coronary occlusion and hyperemia. This study may represent a step towards noninvasive assessment of myocardial perfusion before and after coronary reperfusion.

Noninvasive assessment of myocardial perfusion: preliminary results in patients with acute myocardial infarction

A many years of study and research, the noninvasive assessment of myocardial perfusion by echocontrast agents is becoming a clinical reality.1–9 The use of some firstand second-generation contrast agents (Levovist, Schering AG, Berlin, Germany; and Optison, Mallinckrodt Medical, Northampton, MA) on humans has been recently approved in Europe and the United States. The fast, technologic progress of echocardiographic imaging explains the growing interest in this new methodology. Before starting on this scientific journey, however, it is necessary to have the information with which to avoid all the pitfalls previously observed with other perfusion techniques. Several technical details relating to both imaging instrumentation and contrast agents require consideration to obtain an appropriate myocardial opacification by intravenous contrast media injection.

Noninvasive assessment of myocardial perfusion in mice: a contrast echocardiography study

Noninvasive assessment of myocardial perfusion in mice: a contrast echocardiography study

Noninvasive Assessment of Myocardial Perfusion in Mice: A Contrast Echocardiography Study

Noninvasive Assessment of Myocardial Perfusion in Mice: A Contrast Echocardiography Study