Diagnostic performance of noninvasive myocardial perfusion imaging using single-photon emission computed tomography, cardiac magnetic resonance, and positron emission tomography imaging for the detection of obstructive coronary artery disease: a meta-analysis

Multi-modality imaging for the assessment of myocardial perfusion with emphasis on stress perfusion CT and MR imaging

High-quality and non-invasive diagnostic tools for assessing myocardial ischemia are necessary for therapeutic decisions regarding coronary artery disease. Myocardial perfusion has been studied using myocardial contrast echo perfusion, single-photon emission computed tomography, positron emission tomography, cardiovascular magnetic resonance, and, more recently, computed tomography. The addition of coronary computed tomography angiography to myocardial perfusion imaging improves the specificity and overall diagnostic accuracy of detecting the hemodynamic significance of coronary artery stenosis. This study reviews the benefits, limitations, and imaging findings of various imaging modalities for assessing myocardial perfusion, with particular emphasis on stress perfusion computed tomography and cardiovascular magnetic resonance imaging.

Diagnostic accuracy of stress myocardial perfusion imaging compared to invasive coronary angiography with fractional flow reserve meta-analysis

BACKGROUND

Hemodynamically significant coronary artery disease is an important indication for revascularization. Stress myocardial perfusion imaging is a noninvasive alternative to invasive fractional flow reserve for evaluating hemodynamically significant coronary artery disease. The aim was to determine the diagnostic accuracy of myocardial perfusion imaging by single-photon emission computed tomography, echocardiography, MRI, positron emission tomography, and computed tomography compared with invasive coronary angiography with fractional flow reserve for the diagnosis of hemodynamically significant coronary artery disease.

METHODS AND RESULTS

The meta-analysis adhered to the Preferred Reporting Items for Systematic Reviews and Meta-analyses statement. PubMed, EMBASE, and Web of Science were searched until May 2014. Thirty-seven studies, reporting on 4721 vessels and 2048 patients, were included. Meta-analysis yielded pooled sensitivity, pooled specificity, pooled likelihood ratios (LR), pooled diagnostic odds ratio, and summary area under the receiver operating characteristic curve. The negative LR (NLR) was chosen as the primary outcome. At the vessel level, MRI (pooled NLR, 0.16; 95% confidence interval [CI], 0.13-0.21) was performed similar to computed tomography (pooled NLR, 0.22; 95% CI, 0.12-0.39) and positron emission tomography (pooled NLR, 0.15; 95% CI, 0.05-0.44), and better than single-photon emission computed tomography (pooled NLR, 0.47; 95% CI, 0.37-0.59). At the patient level, MRI (pooled NLR, 0.14; 95% CI, 0.10-0.18) performed similar to computed tomography (pooled NLR, 0.12; 95% CI, 0.04-0.33) and positron emission tomography (pooled NLR, 0.14; 95% CI, 0.02-0.87), and better than single-photon emission computed tomography (pooled NLR, 0.39; 95% CI, 0.27-0.55) and echocardiography (pooled NLR, 0.42; 95% CI, 0.30-0.59).

CONCLUSIONS

Stress myocardial perfusion imaging with MRI, computed tomography, or positron emission tomography can accurately rule out hemodynamically significant coronary artery disease and can act as a gatekeeper for invasive revascularization. Single-photon emission computed tomography and echocardiography are less suited for this purpose.

Quantification of coronary flow reserve in patients with ischaemic and non-ischaemic cardiomyopathy and its association with clinical outcomes

AIMS

Patients with left ventricular systolic dysfunction frequently show abnormal coronary vascular function, even in the absence of overt coronary artery disease. Moreover, the severity of vascular dysfunction might be related to the aetiology of cardiomyopathy.We sought to determine the incremental value of assessing coronary vascular dysfunction among patients with ischaemic (ICM) and non-ischaemic (NICM) cardiomyopathy at risk for adverse cardiovascular outcomes.

METHODS AND RESULTS

Coronary flow reserve (CFR, stress/rest myocardial blood flow) was quantified in 510 consecutive patients with rest left ventricular ejection fraction (LVEF) ≤45% referred for rest/stress myocardial perfusion PET imaging. The primary end point was a composite of major adverse cardiovascular events (MACE) including cardiac death, heart failure hospitalization, late revascularization, and aborted sudden cardiac death.Median follow-up was 8.2 months. Cox proportional hazards model was used to adjust for clinical variables. The annualized MACE rate was 26.3%. Patients in the lowest two tertiles of CFR (CFR ≤ 1.65) experienced higher MACE rates than those in the highest tertile (32.6 vs. 15.5% per year, respectively, P = 0.004), irrespective of aetiology of cardiomyopathy.

CONCLUSION

Impaired coronary vascular function, as assessed by reduced CFR by PET imaging, is common in patients with both ischaemic and non-ischaemic cardiomyopathy and is associated with MACE.

Technical prerequisites and imaging protocols for dynamic and dual energy myocardial perfusion imaging

Coronary CT angiography (CCTA) is an established imaging technique used for the non-invasive morphological assessment of coronary artery disease. As in invasive coronary angiography, CCTA anatomical assessment of coronary stenosis does not adequately predict hemodynamic relevance. However, recent technical improvements provide the possibility of CT myocardial perfusion imaging (CTMPI). Two distinct CT techniques are currently available for myocardial perfusion assessment: static CT myocardial perfusion imaging (sCTMPI), with single- or dual-energy modality, and dynamic CT myocardial perfusion imaging (dCTMPI). The combination of CCTA morphological assessment and CTMPI functional evaluation holds promise for achieving a comprehensive assessment of coronary artery anatomy and myocardial perfusion using a single image modality.

Measurement of myocardial blood flow by cardiovascular magnetic resonance perfusion: comparison of distributed parameter and Fermi models with single and dual bolus

BACKGROUND

Mathematical modeling of cardiovascular magnetic resonance perfusion data allows absolute quantification of myocardial blood flow. Saturation of left ventricle signal during standard contrast administration can compromise the input function used when applying these models. This saturation effect is evident during application of standard Fermi models in single bolus perfusion data. Dual bolus injection protocols have been suggested to eliminate saturation but are much less practical in the clinical setting. The distributed parameter model can also be used for absolute quantification but has not been applied in patients with coronary artery disease. We assessed whether distributed parameter modeling might be less dependent on arterial input function saturation than Fermi modeling in healthy volunteers. We validated the accuracy of each model in detecting reduced myocardial blood flow in stenotic vessels versus gold-standard invasive methods.

METHODS

Eight healthy subjects were scanned using a dual bolus cardiac perfusion protocol at 3T. We performed both single and dual bolus analysis of these data using the distributed parameter and Fermi models. For the dual bolus analysis, a scaled pre-bolus arterial input function was used. In single bolus analysis, the arterial input function was extracted from the main bolus. We also performed analysis using both models of single bolus data obtained from five patients with coronary artery disease and findings were compared against independent invasive coronary angiography and fractional flow reserve. Statistical significance was defined as two-sided P value < 0.05.

RESULTS

Fermi models overestimated myocardial blood flow in healthy volunteers due to arterial input function saturation in single bolus analysis compared to dual bolus analysis (P < 0.05). No difference was observed in these volunteers when applying distributed parameter-myocardial blood flow between single and dual bolus analysis. In patients, distributed parameter modeling was able to detect reduced myocardial blood flow at stress (<2.5 mL/min/mL of tissue) in all 12 stenotic vessels compared to only 9 for Fermi modeling.

CONCLUSIONS

Comparison of single bolus versus dual bolus values suggests that distributed parameter modeling is less dependent on arterial input function saturation than Fermi modeling. Distributed parameter modeling showed excellent accuracy in detecting reduced myocardial blood flow in all stenotic vessels.

Contrast-free diagnosis and treatment of coronary artery disease guided by integrated cardiac imaging: concept and first clinical experience

The use of iodinated contrast media (ICM) remains a potential hazard for patients undergoing diagnostic cardiac imaging and percutaneous coronary intervention. In particular patients with history of prior adverse reaction to a contrast agent are at a high risk in case of re-exposure, even if designated premedication is administered. Based on a patient with recurrent angina pectoris and history of systemic anaphylactic reaction to ICM, we describe the logical stepwise approach from diagnostic imaging to safe and successful imaging guided percutaneous coronary intervention without the use of contrast agent.

Prognostic value of positron emission tomography myocardial perfusion imaging beyond traditional cardiovascular risk factors: Systematic review and meta-analysis

Background

Despite substantive growth in utilization of positron emission tomography (PET) myocardial perfusion imaging (MPI), evidence on its prognostic value is limited. We aimed to comprehensively evaluate the prognostic literature of PET perfusion measures according to the most recent American Heart Association recommendations for assessment of novel cardiovascular biomarkers.

Methods

We searched the literature for studies reporting associations of PET MPI measures and outcomes in patients with known or suspected coronary artery disease. We documented hazard ratios (HR) and 95% confidence intervals (CI) of association effects and quantitatively synthesized them with random-effects meta-analyses. Discrimination, calibration and risk reclassification after addition of PET MPI measures to standard prognostic models were documented.

Results

We identified 20 eligible studies with median n = 551 patients. In meta-analyses, the extents of ischemic and scarred myocardium were significantly associated with cardiac death. Meta-analyses of multivariate estimates for abnormal summed stress score ≥ 4 and myocardial perfusion reserve < 2 revealed significant associations with major adverse cardiovascular events [HR (95% CI) 2.30 (1.53–3.44) and 2.11 (1.33–3.36), respectively]. Changes in model discrimination, calibration or risk reclassification were reported in 5 studies (8 prognostic evaluations). There were marginal improvements in discrimination based on C index and no improvements in model calibration. Net reclassification index ranged from 9.8% to 14.2% and risk classification was significantly improved in 4/5 prognostic evaluations.

Conclusions

PET MPI measures were strongly associated with adverse patient outcomes. Risk classification was more consistently improved than discrimination and calibration after addition of PET MPI measures, but reporting of such metrics was overall limited.

Individualized cardiovascular risk assessment by cardiovascular magnetic resonance

Cardiovascular magnetic resonance (CMR) is gaining clinical importance in preventive medicine. Evidence on diagnostic accuracy and prognostic value, in addition to the development of faster imaging, increased availability of equipment and imaging expertise have led to a wide-spread use of CMR in a growing number of clinical indications. The first part of this review summarizes the role of CMR biomarkers for risk assessment focusing on the patients groups that benefit from the use of CMR. In the second part, the future directions for CMR are discussed and their role in prevention of cardiovascular disease.

Myocardial blood flow quantification for evaluation of coronary artery disease by positron emission tomography, cardiac magnetic resonance imaging, and computed tomography

The noninvasive detection of the presence and functional significance of coronary artery stenosis is important in the diagnosis, risk assessment, and management of patients with known or suspected coronary artery disease. Quantitative assessment of myocardial perfusion can provide an objective and reproducible estimate of myocardial ischemia and risk prediction. Positron emission tomography, cardiac magnetic resonance, and cardiac computed tomography perfusion are modalities capable of measuring myocardial blood flow and coronary flow reserve. In this review, we will discuss the technical aspects of quantitative myocardial perfusion imaging with positron emission tomography, cardiac magnetic resonance imaging, and computed tomography, and its emerging clinical applications.

Beyond stenosis detection: computed tomography approaches for determining the functional relevance of coronary artery disease

Coronary computed tomography angiography (CCTA) is an established imaging technique for the noninvasive assessment of coronary arteries. However, CCTA remains a morphologic technique with the same limitations as invasive coronary angiography in evaluating the hemodynamic significance of coronary stenosis. Different computed tomography (CT) techniques for the functional analysis of coronary lesions have recently emerged, including static and dynamic CT myocardial perfusion imaging and CT-based fractional flow reserve and transluminal attenuation gradient methods. These techniques hold promise for achieving a comprehensive appraisal of anatomic and functional aspects of coronary heart disease with a single modality.

Comparison of the Diagnostic Performance of Four Quantitative Myocardial Perfusion Estimation Methods Used in Cardiac MR Imaging: CE-MARC Substudy

PURPOSE

To compare the diagnostic performance of four tracer kinetic analysis methods to quantify myocardial perfusion from magnetic resonance (MR) imaging cardiac perfusion data sets in terms of their ability to lead to the diagnosis of myocardial ischemia.

MATERIALS AND METHODS

The study was approved by the regional ethics committee, and all patients gave written consent. A representative sample of 50 patients with suspected ischemic heart disease was retrospectively selected from the Clinical Evaluation of Magnetic Resonance Imaging in Coronary Heart Disease trial data set. Quantitative myocardial blood flow (MBF) was estimated from rest and adenosine stress MR imaging perfusion data sets by using four established methods. A matching diagnosis of both an inducible defect as assessed with single photon emission computed tomography and a luminal stenosis of 70% or more as assessed with quantitative x-ray angiography was used as the reference standard for the presence of myocardial ischemia. Diagnostic performance was evaluated with receiver operating characteristic (ROC) curve analysis for each method, with stress MBF and myocardial perfusion reserve (MPR) serving as continuous measures.

RESULTS

Area under the ROC curve with stress MBF and MPR as the outcome measures, respectively, was 0.86 and 0.92 for the Fermi model, 0.85 and 0.87 for the uptake model, 0.85 and 0.80 for the one-compartment model, and 0.87 and 0.87 for model-independent deconvolution. There was no significant difference between any of the models or between MBF and MPR, except that the Fermi model outperformed the one-compartment model if MPR was used as the outcome measure (P = .02).

CONCLUSION

Diagnostic performance of quantitative myocardial perfusion estimates is not affected by the tracer kinetic analysis method used.

Coronary flow reserve estimated by positron emission tomography to diagnose significant coronary artery disease and predict cardiac events

Coronary artery disease (CAD) is a major cause of death in Japan. Coronary angiography is useful to assess the atherosclerotic burden in CAD patients, but its ability to predict whether patients will respond favorably to optimal medical therapy and revascularization is limited. The measurement of the fractional flow reserve with angiography is a well-validated method for identifying ischemic vessels. However, neither an anatomical assessment nor a functional assessment can delineate microvasculature or estimate its function. The quantitative coronary flow reserve (CFR) estimated from sequential myocardial perfusion images obtained by positron emission tomography (PET) during stress provides an accurate index of hyperemic reactivity to vasodilatory agents in the myocardium. In fact, there is growing evidence that the CFR reflects disease activity in the entire coronary circulation, including epicardial coronary artery stenosis, diffuse atherosclerosis, and microvascular dilatory function. Importantly, reduced CFR is observed even in patients without flow-limiting coronary stenosis, and its evaluation can improve the risk stratification of patients at any stage of CAD. This review focuses on the application of CFR estimated by cardiac PET for the diagnosis and risk stratification of patients with CAD.

2014 korean guidelines for appropriate utilization of cardiovascular magnetic resonance imaging: a joint report of the korean society of cardiology and the korean society of radiology

Cardiac magnetic resonance (CMR) imaging is now widely used in several fields of cardiovascular disease assessment due to recent technical developments. CMR can give physicians information that cannot be found with other imaging modalities. However, there is no guideline which is suitable for Korean people for the use of CMR. Therefore, we have prepared a Korean guideline for the appropriate utilization of CMR to guide Korean physicians, imaging specialists, medical associates and patients to improve the overall medical system performances. By addressing CMR usage and creating these guidelines we hope to contribute towards the promotion of public health. This guideline is a joint report of the Korean Society of Cardiology and the Korean Society of Radiology.

[¹⁸F]-fluorodeoxyglucose PET imaging of atherosclerosis

[(18)F]-fluorodeoxyglucose PET ((18)FDG PET) imaging has emerged as a promising tool for assessment of atherosclerosis. By targeting atherosclerotic plaque glycolysis, a marker for plaque inflammation and hypoxia, (18)FDG PET can assess plaque vulnerability and potentially predict risk of atherosclerosis-related disease, such as stroke and myocardial infarction. With excellent reproducibility, (18)FDG PET can be a surrogate end point in clinical drug trials, improving trial efficiency. This article summarizes key findings in the literature, discusses limitations of (18)FDG PET imaging of atherosclerosis, and reports recommendations to optimize imaging protocols.

Established and emerging cardiovascular magnetic resonance techniques for the assessment of stable coronary heart disease and acute coronary syndromes

Coronary heart disease (CHD) is a leading cause of death and disability worldwide. International guidelines recommend cardiovascular magnetic resonance (CMR) as an investigative option in those presenting with chest pain to inform diagnosis, risk stratify and determine the need for revascularization. CMR offers a unique method to assess global and regional cardiac function, myocardial perfusion, myocardial viability, tissue characterisation and proximal coronary anatomy all within a single study. This results in high diagnostic accuracy for the detection of significant coronary stenoses and an established role in the management of both stable CHD and acute coronary syndromes (ACS). The growing evidence base for the prognostic value of CMR, emerging advances in acquisition techniques, improvements in hardware and the completion of current major multi-centre clinical CMR trials will further raise its prominence in international guidelines and routine cardiological practice. This article will focus on the rapidly evolving role of the multi-parametric CMR examination in the assessment of patients with stable and unstable CHD.

2014 Korean guidelines for appropriate utilization of cardiovascular magnetic resonance imaging: a joint report of the Korean Society of Cardiology and the Korean Society of Radiology

Cardiac magnetic resonance (CMR) imaging is now widely used in several fields of cardiovascular disease assessment due to recent technical developments. CMR can give physicians information that cannot be found with other imaging modalities. However, there is no guideline which is suitable for Korean people for the use of CMR. Therefore, we have prepared a Korean guideline for the appropriate utilization of CMR to guide Korean physicians, imaging specialists, medical associates and patients to improve the overall medical system performances. By addressing CMR usage and creating these guidelines we hope to contribute towards the promotion of public health. This guideline is a joint report of the Korean Society of Cardiology and the Korean Society of Radiology.

Hemodynamic significance of coronary stenosis by vessel attenuation measurement on CT compared with adenosine perfusion MRI

PURPOSE

We assessed the association between corrected contrast opacification (CCO) based on coronary computed tomography angiography (cCTA) and inducible ischemia by adenosine perfusion magnetic resonance imaging (APMR).

METHODS

Sixty cardiac asymptomatic patients with extra-cardiac arterial disease (mean age 64.4 ± 7.7 years; 78% male) underwent cCTA and APMR. Luminal CT attenuation values (Hounsfield Units) were measured in coronary arteries from proximal to distal, with additional measurements across sites with >50% lumen stenosis. CCO was calculated by dividing coronary CT attenuation by descending aorta CT attenuation. A reversible perfusion defect on APMR was considered as myocardial ischemia.

RESULTS

In total, 169 coronary stenoses were found. Seven patients had 8 perfusion defects on APMR, with 11 stenoses in corresponding vessels. CCO decrease across stenoses with hemodynamic significance was 0.144 ± 0.112 compared to 0.047 ± 0.104 across stenoses without hemodynamic significance (P=0.003). CCO decrease in lesions with and without anatomical stenosis was similar (0.054 ± 0.116 versus 0.052 ± 0.101; P=0.89). Using 0.20 as preliminary CCO decrease cut-off, hemodynamic significance would be excluded in 82.9% of anatomical stenoses.

CONCLUSIONS

CCO decrease across coronary stenosis is associated with myocardial ischemia on APMR. CCO based on common cCTA data is a novel method to assess hemodynamic significance of anatomical stenosis.

Diagnostic accuracy of myocardial magnetic resonance perfusion to diagnose ischemic stenosis with fractional flow reserve as reference: systematic review and meta-analysis

OBJECTIVES

This paper systematically analyzed the performance of magnetic resonance (MR) perfusion to diagnose coronary artery disease (CAD) with fractional flow reserve (FFR) as the reference standard.

BACKGROUND

Myocardial MR perfusion has passed the stage of a research technique and has demonstrated the ability to detect functional or ischemic stenosis of coronary arteries. However, the evidence is limited to single-center studies and small sample sizes.

METHODS

We searched PubMed and Embase databases for all published studies that evaluated the accuracy of MR perfusion to diagnose CAD versus FFR. We used an exact binomial rendition of the bivariate mixed-effects regression model with test type as a random-effects covariate to synthesize the available data. Based on Bayes' theorem, the post-test probability was calculated to guide MR perfusion's clinical utility.

RESULTS

We identified 14 studies evaluating 1,073 arteries and 650 patients. The pooled sensitivity and specificity were 0.90 (95% confidence interval [CI]: 0.86 to 0.93) and 0.87 (95% CI: 0.82 to 0.90) at the patient level and 0.89 (95% CI: 0.83 to 0.92) and 0.86 (95% CI: 0.77 to 0.92) at the artery and territory levels, respectively. The area under the summary receiver-operating characteristic at the patient level was 0.95 (95% CI: 0.92 to 0.96) and 0.93 (95% CI: 0.91 to 0.95) at the artery and territory levels, respectively. MR perfusion could increase the post-test probability of CAD >80% in patients with a pre-test probability of >37% and can decrease post-test probability of CAD <20% with a pre-test probability of <72%.

CONCLUSIONS

With FFR as the reference standard, the diagnostic ability of MR perfusion to detect ischemic CAD is high.

Cardiac imaging to investigate suspected cardiac pain in the post-treadmill era

Symptomatic cardiovascular disease is one of the leading causes of hospital admissions in the UK; along with emergency attendances, over 100,000 patients are investigated using treadmill testing via rapid access chest pain clinics each year. With the introduction of new technologies, clinicians have a wide choice of investigations including nuclear perfusion scanning, dobutamine stress echocardiography, cardiac computed tomography and stress cardiac magnetic resonance imaging. These imaging modalities have their strengths and weaknesses, which depend not only on the pre-test likelihood of significant coronary artery disease but also the clinical characteristics of the patient. This article will review the differing imaging modalities, the patient experience, accuracy, prognostic data and future prospects for cardiac computed tomography and magnetic resonance imaging.

Noninvasive imaging in coronary artery disease

Noninvasive cardiac imaging is widely used to evaluate the presence of coronary artery disease. Recently, with improvements in imaging technology, noninvasive imaging has also been used for evaluation of the presence, severity, and prognosis of coronary artery disease. Coronary CT angiography and MRI of coronary arteries provide an anatomical assessment of coronary stenosis, whereas the hemodynamic significance of a coronary artery stenosis can be assessed by stress myocardial perfusion imaging, such as SPECT/PET and stress MRI. For appropriate use of multiple imaging modalities, the strengths and limitations of each modality are discussed in this review.

Impact of co-morbidity on the risk of first-time myocardial infarction, stroke, or death after single-photon emission computed tomography myocardial perfusion imaging

The impact of co-morbidity on the cardiovascular risk after single-photon emission computed tomography myocardial perfusion imaging (SPECT MPI) remains unclear. We examined the association between a normal versus abnormal SPECT MPI scan on 10-year risk of myocardial infarction, stroke, and all-cause death, overall and according to co-morbidity level. We identified all patients without previous myocardial infarction or cerebrovascular disease, who had an SPECT MPI performed at Aarhus University Hospital Skejby during 1999 to 2011. We categorized the SPECT MPI scan as normal (no defects) or abnormal (reversible and/or fixed defects). Using nationwide medical registries, we obtained information on co-morbidity level (using Charlson co-morbidity index) and outcomes. We used Cox regression to compute hazard ratios with 95% confidence intervals (CIs), adjusting for gender, age, and co-morbidity level. Among 7,040 patients, 4,962 (70%) had normal scans and 2,078 (30%) abnormal scans. Patients with a normal versus abnormal scan had a 10-year risk of 5.7% versus 10.9% for myocardial infarction, 6.0% versus 7.8% for stroke, and 16.5% versus 29.0% for all-cause death. After adjustment, an abnormal scan was associated with increased risk of myocardial infarction (adjusted hazard ratio 1.73, 95% CI 1.37 to 2.18) and all-cause death (1.42, 95% CI 1.23 to 1.65) but not stroke (1.12, 95% CI 0.86 to 1.45). Co-morbidity level did not affect substantially the association between the scan result and the outcomes. In conclusion, independently of co-morbidity level, an abnormal SPECT MPI scan was associated with an increased 10-year risk of myocardial infarction and all-cause death but not stroke.

Multimodality Imaging in Ischemic Cardiomyopathy

Cardiac multimodality (hybrid) imaging can be obtained from a variety of techniques, such as nuclear medicine with single photon emission computed tomography (SPECT) and positron emission tomography (PET), or radiology with multislice computed tomography (CT), magnetic resonance (MR) and echography. They are typically combined in a side-by-side or fusion mode in order to provide functional and morphological data to better characterise coronary artery disease, with more proven efficacy than when used separately. The gained information is then used to guide revascularisation procedures. We present an up-to-date comprehensive overview of multimodality imaging already in clinical use, as well as a combination of techniques with promising or developing applications.

Baseline instantaneous wave-free ratio as a pressure-only estimation of underlying coronary flow reserve: results of the JUSTIFY-CFR Study (Joined Coronary Pressure and Flow Analysis to Determine Diagnostic Characteristics of Basal and Hyperemic Indices of Functional Lesion Severity-Coronary Flow Reserve)

BACKGROUND

Coronary flow reserve has extensive validation as a prognostic marker in coronary disease. Although pressure-only fractional flow reserve (FFR) improves outcomes compared with angiography when guiding percutaneous coronary intervention, it disagrees with coronary flow reserve classification 30% of the time. We evaluated whether baseline instantaneous wave-free ratio (iFR) could provide an improved pressure-only estimation of underlying coronary flow reserve.

METHODS AND RESULTS

Invasive pressure and flow velocity were measured in 216 stenoses from 186 patients with coronary disease. The diagnostic relationship between pressure-only indices (iFR and FFR) and coronary flow velocity reserve (CFVR) was compared using correlation coefficient and the area under the receiver operating characteristic curve. iFR showed a stronger correlation with underlying CFVR (iFR-CFVR, ρ=0.68 versus FFR-CFVR, ρ=0.50; P<0.001). iFR also agreed more closely with CFVR in stenosis classification (iFR area under the receiver operating characteristic curve, 0.82 versus FFR area under the receiver operating characteristic curve, 0.72; P<0.001, for a CFVR of 2). The closer relationship between iFR and CFVR was found for different CFVR cutoffs and was particularly marked in the 0.6 to 0.9 FFR range. Hyperemic FFR flow was similar to baseline iFR flow in functionally significant lesions (FFR ≤0.75; mean FFR flow, 25.8±13.7 cm/s versus mean iFR flow, 21.5±11.7 cm/s; P=0.13). FFR flow was higher than iFR flow in nonsignificant stenoses (FFR >0.75; mean FFR flow, 42.3±22.8 cm/s versus mean iFR flow, 26.1±15.5 cm/s; P<0.001).

CONCLUSIONS

When compared with FFR, iFR shows stronger correlation and better agreement with CFVR. These results provide physiological evidence that iFR could potentially be used as a functional index of disease severity, independently from its agreement with FFR.

Influence of spatial resolution on the accuracy of quantitative myocardial perfusion in first pass stress perfusion CMR

PURPOSE

High-resolution myocardial perfusion analysis allows for preserving spatial information with excellent sensitivity for subendocardial ischemia detection. However, it suffers from low signal-to-noise ratio. Commonly, spatial averaging is used to increase signal-to-noise ratio. This bears the risk of losing information about the extent, localization and transmurality of ischemia. This study investigates spatial-averaging effects on perfusion-estimates accuracy.

METHODS

Perfusion data were obtained from patients and healthy volunteers. Spatial averaging was performed on voxel-based data in transmural and angular direction to reduce resolution to 50, 20, and 10% of its original value. Fit quality assessment method is used to measure the fraction of modeled information and remaining unmodeled information in the residuals.

RESULTS

Fraction of modeled information decreased in patients as resolution reduced. This decrease was more evident for Fermi and exponential in transmural direction. Fermi and exponential showed significant difference at 50% resolution (Fermi P < 0.001, exponential P =0.0014). No significant differences were observed for autoregressive-moving-average model (P = 0.081). At full resolution, autoregressive-moving-average model has the lowest fraction of residual information (0.3). Differences were observed comparing ischemic regions perfusion-estimates coefficient of variation at transmural and angular direction.

CONCLUSION

Angular averaging preserves more information compared to transmural averaging. Reducing resolution level below 50% at transmural and 20% at angular direction results in losing information about transmural perfusion differences. Maximum voxel size of 2 × 2 mm(2) is necessary to avoid loss of physiological information due to spatial averaging.

Update on cardiac imaging techniques 2012

Cardiac imaging is one of the basic pillars of modern cardiology. The potential list of scenarios where cardiac imaging techniques can provide relevant information is simply endless so it is impossible to include all relevant new features of cardiac imaging published in the literature in 2012 in the limited format of a single article. We summarize the year's most relevant news on cardiac imaging, highlighting the ongoing development of myocardial deformation and 3-dimensional echocardiography techniques and the increasing use of magnetic resonance imaging and computed tomography in daily clinical practice.

Quantification of myocardial perfusion using cardiac magnetic resonance imaging correlates significantly to rubidium-82 positron emission tomography in patients with severe coronary artery disease: a preliminary study

INTRODUCTION

Aim was to compare absolute myocardial perfusion using cardiac magnetic resonance imaging (CMRI) based on Tikhonov's procedure of deconvolution and rubidium-82 positron emission tomography (Rb-82 PET).

MATERIALS AND METHODS

Fourteen patients with coronary artery stenosis underwent rest and adenosine stress imaging by 1.5-Tesla MR Scanner and a mCT/PET 64-slice Scanner. CMRI were analyzed based on Tikhonov's procedure of deconvolution without specifying an explicit compartment model using our own software. PET images were analyzed using standard clinical software. CMRI and PET data was compared with Spearman's rho and Bland-Altman analysis.

RESULTS

CMRI results were strongly and significantly correlated with PET results for the absolute global myocardial perfusion differences (r=0.805, p=0.001) and for global myocardial perfusion reserve (MPR) (r=0.886, p<0.001). At vessel territorial level, CMRI results were also significantly correlated with absolute PET myocardial perfusion differences (r=0.737, p<0.001) and MPR (r=0.818, p<0.001). Each vessel territory had similar strong correlation for absolute myocardial perfusion differences (right coronary artery (RCA): r=0.787, p=0.001; left anterior descending artery (LAD): r=0.796, p=0.001; left circumflex artery (LCX): r=0.880, p<0.001) and for MPR (RCA: r=0.895, p<0.001; LAD: r=0.886, p<0.001; LCX: r=0.886, p<0.001).

CONCLUSION

On a global and vessel territorial basis, CMRI-measured absolute myocardial perfusion differences and MPR were strongly and significantly correlated with the Rb-82 PET findings.

New insights from major prospective cohort studies with cardiac nuclear imaging

For more than two decades, radionuclide imaging has prevailed as a cornerstone in the diagnosis and treatment of patients with cardiac disease. From this experience, large cohort studies have emerged that demonstrate the prognostic value of cardiac radionuclide imaging in a variety of patient groups and conditions. Myocardial perfusion imaging has accrued the most robust evidence for accurate and independent risk stratification over traditional clinical variables. In a variety of patient populations, the presence of myocardial ischemia is a strong predictor of cardiac events on follow-up. In patients with heart failure, smaller observations have similarly established the prognostic value of viability imaging and imaging of cardiac sympathetic activity. The present review provides a summary of recent cohort studies with radionuclide imaging and a critical appraisal of their clinical implications. Its purpose is to put the available evidence into a clinical context, analyze its potential impact on patient management and identify gaps in knowledge and unanswered questions to be addressed in future randomized trials.

Evaluation of left ventricular diastolic function with a dedicated cadmium-zinc-telluride cardiac camera: comparison with Doppler echocardiography

AIMS

To evaluate the relationships between measures of left ventricular (LV) filling dynamics at cadmium-zinc-telluride (CZT) imaging and indexes of LV diastolic function at transthoracic echocardiography.

METHODS AND RESULTS

Two hundred and forty-seven patients underwent myocardial perfusion imaging at rest and after stress with a low-dose CZT protocol and a baseline transthoracic echocardiography study. All patients were submitted to invasive or computed coronary angiography. The peak filling rate (PFR) and the time to PFR (TPFR) were derived from gated CZT images as measures of LV filling dynamics. LV diastolic function was also evaluated at echocardiography and the presence of significantly increased LV filling pressures determined. Increased LV filling pressures at transthoracic echocardiography were evident in 103 (42%) patients. Interestingly, independently from the presence of coronary artery disease, there was a strict correlation between the presence and severity of LV diastolic dysfunction at echocardiography and CZT-derived measures of filling dynamics, i.e., PFR (P = 0.001) and TPFR (P = 0.001). At receiving operating characteristic analysis, a composite index of reduced PFR (≤2.11 end-diastolic volume s(-1)) and increased TPFR (>234 ms) showed a sensitivity of 84% and a specificity of 67% in unmasking the presence of elevated LV filling pressures at echocardiography.

CONCLUSIONS

CZT-derived measures of LV filling dynamics correlate with echocardiographic parameters of diastolic function and may identify the presence of increased LV filling pressures.

Direct comparison of cardiovascular magnetic resonance and single-photon emission computed tomography for detection of coronary artery disease: a meta-analysis

Objective

To use direct comparative studies or randomised controlled trials to compare the accuracy of cardiac magnetic resonance (CMR) and single-photon emission computed tomography (SPECT) for the detection of obstructive coronary artery disease (CAD).

Materials and Methods

Various databases were searched for original articles published prior to June 2013. Studies were selected that performed both CMR and SPECT in the same or randomised patients to detect CAD and that presented sufficient data to allow construction of contingency tables. For each study, the true-positive, false-positive, true-negative, and false-negative values were extracted or derived, and 2×2 contingency tables were constructed. To reduce heterogeneity, the meta-analysis was carried out in two parts: (1) coronary territory-based analysis and (2) patient-based analysis.

Results

10 studies (5 studies based on patient, 4 studies based on coronary territory, and 1 study based on both) were included in the meta-analysis with a total of 1727 patients. The methodological quality was moderate. For part (1), the summary estimates were as follows: for CMR based on patient–a sensitivity of 0.79 (95% confidence interval: 0.72–0.84) and a specificity of 0.75 (0.65–0.83); for SPECT based on patient–a sensitivity of 0.70 (0.59–0.79) and a specificity of 0.76 (0.66–0.83). For part (2), the summary estimates for CMR based on coronary territory were a sensitivity of 0.80 (0.73–0.85) and a specificity of 0.87 (0.81–0.91), and the summary estimates for SPECT based on coronary territory were a sensitivity of 0.67 (0.60–0.72) and a specificity of 0.80 (0.75–0.84).

Conclusions

Compared with SPECT, CMR is more sensitive to detect CAD on a per-patient basis. Nonetheless, large scale, well-designed trials are necessary to assess its clinical value on a per-coronary territory basis.

Diagnostic performance of low-dose rest/stress Tc-99m tetrofosmin myocardial perfusion SPECT using the 530c CZT camera: quantitative vs visual analysis

BACKGROUND

We set out to develop normal databases and prospectively validate abnormality criteria for a low-dose Tc-99m tetrofosmin myocardial perfusion SPECT protocol using the 530c CZT camera.

METHODS

All patients received 6 mCi rest/20 mCi stress doses of Tc-99m tetrofosmin. Rest and stress images were obtained over 7-9 and 5-7 minutes according to the chest size. Low-dose CT of the chest was obtained on a standalone CT scanner. Forty patients with very low likelihood (LLK) of coronary artery disease (CAD) were used to define the normal count distributions. The abnormality criteria were prospectively validated in 55 patients who had coronary angiography and in 40 patients with LLK of CAD.

RESULTS

The results for quantitative non-attenuation-corrected (AC) and AC analysis and visual analysis were as follows: sensitivity of 79%, 85%, and 92% (P = NS) and specificity of 44%, 75%, and 56% (P = NS), respectively. The normalcy rates for quantitative non-AC and AC analyses and visual analysis were 95%, 98%, and 98% (P = NS).

CONCLUSIONS

We have developed non-AC and AC normal databases for low-dose rest/stress Tc-99m tetrofosmin myocardial perfusion SPECT protocol using the 530c CZT camera. The per-patient diagnostic performance of quantitative analyses is not significantly different from visual analysis by an experienced reader.

Cardiac magnetic resonance imaging findings and the risk of cardiovascular events in patients with recent myocardial infarction or suspected or known coronary artery disease: a systematic review of prognostic studies

The goal of this study was to review the prognostic value of cardiac magnetic resonance (CMR) imaging findings for future cardiovascular events in patients with a recent myocardial infarction (MI) and patients with suspected or known coronary artery disease (CAD). Although the diagnostic value of CMR findings is established, the independent prognostic association with future cardiovascular events remains largely unclear. Studies published by February 2013, identified by systematic MEDLINE and EMBASE searches, were reviewed for associations between CMR findings (left ventricular ejection fraction [LVEF], wall motion abnormalities [WMA], abnormal myocardial perfusion, microvascular obstruction, late gadolinium enhancement, edema, and intramyocardial hemorrhage) and hard events (all-cause mortality, cardiac death, cardiac transplantation, and MI) or major adverse cardiovascular events (MACE) (hard events and other cardiovascular events defined by the authors of the evaluated papers). Fifty-six studies (n = 25,497) were evaluated. For patients with recent MI, too few patients were evaluated to establish associations between CMR findings and hard events. LVEF (range of adjusted hazard ratios [HRs]: 1.03 to 1.05 per % decrease) was independently associated with MACE. In patients with suspected or known CAD, WMA (adjusted HRs: 1.87 to 2.99), inducible perfusion defects (adjusted HRs: 3.02 to 7.77), LVEF (adjusted HRs: 0.72 to 0.82 per 10% increase), and infarction (adjusted HRs: 2.82 to 9.43) were independently associated with hard events, and the presence of inducible perfusion defects was associated with MACE (adjusted HRs: 1.76 to 3.21). The independent predictor of future cardiovascular events for patients with a recent MI was LVEF, and the predictors for patients with suspected or known CAD were WMA, inducible perfusion defects, LVEF, and presence of infarction.

CV imaging: what was new in 2012?

Echocardiography, single-photon emission computed tomography (SPECT), positron emission tomography (PET), cardiac magnetic resonance, and cardiac computed tomography can be used for anatomic and functional imaging of the heart. All 4 methods are subject to continuous improvement. Echocardiography benefits from the more widespread availability of 3-dimensional imaging, strain and strain rate analysis, and contrast applications. SPECT imaging continues to provide very valuable prognostic data, and PET imaging, on the one hand, permits quantification of coronary flow reserve, a strong prognostic predictor, and, on the other hand, can be used for molecular imaging, allowing the analysis of extremely small-scale functional alterations in the heart. Magnetic resonance is gaining increasing importance as a stress test, mainly through perfusion imaging, and continues to provide very valuable prognostic information based on late gadolinium enhancement. Magnetic resonance coronary angiography does not substantially contribute to clinical cardiology at this point in time. Computed tomography imaging of the heart mainly concentrates on the imaging of coronary artery lumen and plaque and has made substantial progress regarding outcome data. In this review, the current status of the 5 imaging techniques is illustrated by reviewing pertinent publications of the year 2012.

Clinical implications of referral bias in the diagnostic performance of exercise testing for coronary artery disease

BACKGROUND

Exercise testing with echocardiography or myocardial perfusion imaging is widely used to risk-stratify patients with suspected coronary artery disease. However, reports of diagnostic performance rarely adjust for referral bias, and this practice may adversely influence patient care. Therefore, we evaluated the potential impact of referral bias on diagnostic effectiveness and clinical decision-making.

METHODS AND RESULTS

Searching PubMed and EMBASE (1990-2012), 2 investigators independently evaluated eligibility and abstracted data on study characteristics and referral patterns. Diagnostic performance reported in 4 previously published meta-analyses of exercise echocardiography and myocardial perfusion imaging was adjusted using pooled referral rates and Bayesian methods. Twenty-one studies reported referral patterns in 49 006 patients (mean age 60.7 years, 39.6% women, and 0.8% prior history of myocardial infarction). Catheterization referral rates after normal and abnormal exercise tests were 4.0% (95% CI, 2.9% to 5.0%) and 42.5% (36.2% to 48.9%), respectively, with odds ratio for referral after an abnormal test of 14.6 (10.7 to 19.9). After adjustment for referral, exercise echocardiography sensitivity fell from 84% (80% to 89%) to 34% (27% to 41%), and specificity rose from 77% (69% to 86%) to 99% (99% to 100%). Similarly, exercise myocardial perfusion imaging sensitivity fell from 85% (81% to 88%) to 38% (31% to 44%), and specificity rose from 69% (61% to 78%) to 99% (99% to 100%). Summary receiver operating curve analysis demonstrated only modest changes in overall discriminatory power but adjusting for referral increased positive-predictive value and reduced negative-predictive value.

CONCLUSIONS

Exercise echocardiography and myocardial perfusion imaging are considerably less sensitive and more specific for coronary artery disease after adjustment for referral. Given these findings, future work should assess the comparative ability of these and other tests to rule-in versus rule-out coronary artery disease.

Molecular imaging of myocardial infarction

Myocardial infarction (MI), and subsequent heart failure, remains a major healthcare problem in the western and developing world and leads to substantial morbidity and mortality. After MI, the ability of the myocardium to recover is closely associated with a complex immune response that often leads to adverse remodeling of the ventricle, and poor prognosis. Currently used clinical imaging modalities allow the assessment of anatomy, perfusion, function, and viability but do not provide insights into specific biological processes. In contrast, novel non-invasive imaging methods, using targeted imaging agents, allow imaging of the molecular processes underlying the post-MI immune cell response, and subsequent remodeling. Therefore, this may have significant diagnostic, prognostic, and therapeutic value, and may help to improve our understanding of post-infarct remodeling, in vivo. Imaging modalities such as magnetic resonance imaging, single-photon emission computed tomography, and positron emission tomography have been used in concert with radiolabelled and (super) paramagnetic probes to image each phase of the immune response. These probes, which target apoptosis, necrosis, neutrophils, monocytes, enzymes, angiogenesis, extracellular matrix, and scar formation have been assessed and validated pre-clinically. Translating this work to the bedside in a cost-effective, clinically beneficial manner remains a significant challenge. This article reviews these new imaging techniques as well as the corresponding pathophysiology.

PET/MRI: current state of the art and future potential for cardiovascular applications

Positron emission tomography-magnetic resonance imaging (PET/MRI) is emerging as a novel diagnostic modality with exciting potential for a role in multiple cardiovascular applications. The combination of the high sensitivity of PET tracers with the excellent spatial resolution and tissue characterization of cardiac MRI will provide complementary information in a variety of cardiac pathologies. While initial efforts have focused on the combination of MRI and PET for assessment of coronary artery disease, cardiomyopathy, viability, and inflammation, this new technology holds enormous potential for molecular cardiovascular imaging. This article will review the development of PET/MRI, review the current research, and discuss potential future applications.

Integrating anatomical and functional imaging for the assessment of coronary artery disease

Coronary artery disease (CAD) is a leading cause of morbidity and mortality. Invasive cardiac angiography with fractional flow reserve measurement allows for the anatomical and functional assessment of CAD. Given the invasive nature of invasive cardiac angiography and the risks of procedure-related complications, research has focused upon noninvasive methods for anatomical and functional measures of CAD. As such, there is growing interest in the development of hybrid imaging because it may provide incremental diagnostic information over each imaging modality alone. We will provide an overview of the evidence to date on the anatomical and functional stratification of CAD and current hybrid techniques.