Long-Term Follow-Up of Outcomes With F-18-Fluorodeoxyglucose Positron Emission Tomography Imaging–Assisted Management of Patients With Severe Left Ventricular Dysfunction Secondary to Coronary Disease

Outcomes of Percutaneous Revascularization in Severe Ischemic Left Ventricular Dysfunction

PURPOSE OF REVIEW

This article presents a comprehensive review of coronary revascularization versus optimal medical therapy (OMT) in patients with severe ischemic left ventricular dysfunction.

RECENT FINDINGS

The REVIVED-BCIS2 trial randomized 700 patients with extensive coronary artery disease and left ventricular (LV) ejection fraction (LVEF) ≤ 35% and viability in more than four dysfunctional myocardial segments to percutaneous coronary intervention (PCI) plus OMT versus OMT alone. Over a median duration of 41 months, there was no difference in the composite of all-cause mortality, heart failure hospitalization, or improvement in LVEF with PCI plus OMT versus OMT alone at 6 and 12 months, quality of life scores at 24 months, or fatal ventricular arrhythmia. The STICH randomized trial was conducted between 2002 and 2007, involving patients with LV dysfunction and coronary artery disease. The patients were assigned to either CABG plus medical therapy or medical therapy alone. At the 5-year follow-up, the trial showed that CABG plus medical therapy reduced cardiovascular disease-related deaths and hospitalizations but no reduction in all-cause mortality. However, a 10-year follow-up showed a significant decrease in all-cause mortality with CABG. The currently available evidence showed no apparent benefit of PCI in severe ischemic cardiomyopathy as compared to OMT, but that CABG improves outcomes in this patient population. The paucity of data on the advantages of PCI in this patient population underscores the critical need for optimization of medical therapy for better survival and quality of life until further evidence from RCTs is available.

Molecular Imaging of Heart Failure: An Update and Future Trends

Molecular imaging can detect and quantify pathophysiological processes underlying heart failure, complementing evaluation of cardiac structure and function with other imaging modalities. Targeted tracers have enabled assessment of various cellular and subcellular mechanisms of heart failure aiming for improved phenotyping, risk stratification, and personalized therapy. This review outlines the current status of molecular imaging in heart failure, accompanied with discussion on novel developments. The focus is on radionuclide methods with data from clinical studies. Imaging of myocardial metabolism can identify left ventricle dysfunction caused by myocardial ischemia that may be reversible after revascularization in the presence of viable myocardium. In vivo imaging of active inflammation and amyloid deposition have an established role in the detection of cardiac sarcoidosis and transthyretin amyloidosis. Innervation imaging has well documented prognostic value in predicting heart failure progression and arrhythmias. Tracers specific for inflammation, angiogenesis and myocardial fibrotic activity are in earlier stages of development, but have demonstrated potential value in early characterization of the response to myocardial injury and prediction of cardiac function over time. Early detection of disease activity is a key for transition from medical treatment of clinically overt heart failure towards a personalized approach aimed at supporting repair and preventing progressive cardiac dysfunction.

Phenotyping heart failure by nuclear imaging of myocardial perfusion, metabolism, and molecular targets

Nuclear imaging techniques can detect and quantify pathophysiological processes underlying heart failure, complementing evaluation of cardiac structure and function with other imaging modalities. Combined imaging of myocardial perfusion and metabolism can identify left ventricle dysfunction caused by myocardial ischaemia that may be reversible after revascularization in the presence of viable myocardium. High sensitivity of nuclear imaging to detect targeted tracers has enabled assessment of various cellular and subcellular mechanisms of heart failure. Nuclear imaging of active inflammation and amyloid deposition is incorporated into clinical management algorithms of cardiac sarcoidosis and amyloidosis. Innervation imaging has well-documented prognostic value with respect to heart failure progression and arrhythmias. Emerging tracers specific for inflammation and myocardial fibrotic activity are in earlier stages of development but have demonstrated potential value in early characterization of the response to myocardial injury and prediction of adverse left ventricular remodelling. Early detection of disease activity is a key for transition from broad medical treatment of clinically overt heart failure towards a personalized approach aimed at supporting repair and preventing progressive failure. This review outlines the current status of nuclear imaging in phenotyping heart failure and combines it with discussion on novel developments.

Utility of nuclear cardiovascular imaging in the cardiac intensive care unit

The contemporary Cardiac Intensive Care Unit (CICU) has evolved into a complex unit that admits a heterogeneous mix of patients with a wide range of acute cardiovascular diseases often complicated by multi-organ failure. Although electrocardiography (ECG) and echocardiography are well-established as first-line diagnostic modalities for assessing patients in the CICU, nuclear cardiology imaging has emerged as a useful adjunctive diagnostic modality. The versatility, safety and accuracy of nuclear imaging (e.g., perfusion, metabolism, inflammation) for the assessment of patient with coronary artery disease, ventricular arrhythmias, infiltrative cardiomyopathies, infective endocarditis and inflammatory aortopathies has been proven useful and now often incorporated into the best practices for the management of critically ill cardiac patients. Thus, clinicians must familiarize themselves with the value and current and future applications of nuclear imaging in the management of the cardiac patient in the CICU.

Myocardial Revascularization in Patients With Ischemic Cardiomyopathy: For Whom and How

Background Myocardial revascularization has been advocated to improve myocardial function and prognosis in ischemic cardiomyopathy (ICM). We discuss the evidence for revascularization in patients with ICM and the role of ischemia and viability detection in guiding treatment. Methods and Results We searched for randomized controlled trials evaluating the prognostic impact of revascularization in ICM and the value of viability imaging for patient management. Out of 1397 publications, 4 randomized controlled trials were included, enrolling 2480 patients. Three trials (HEART [Heart Failure Revascularisation Trial], STICH [Surgical Treatment for Ischemic Heart Failure], and REVIVED [REVascularization for Ischemic VEntricular Dysfunction]-BCIS2) randomized patients to revascularization or optimal medical therapy. HEART was stopped prematurely without showing any significant difference between treatment strategies. STICH showed a 16% lower mortality with bypass surgery compared with optimal medical therapy at a median follow-up of 9.8 years. However, neither the presence/extent of left ventricle viability nor ischemia interacted with treatment outcomes. REVIVED-BCIS2 showed no difference in the primary end point between percutaneous revascularization or optimal medical therapy. PARR-2 (Positron Emission Tomography and Recovery Following Revascularization) randomized patients to imaging-guided revascularization versus standard care, with neutral results overall. Information regarding the consistency of patient management with viability testing results was available in ≈65% of patients (n=1623). No difference in survival was revealed according to adherence or no adherence to viability imaging. Conclusions In ICM, the largest randomized controlled trial, STICH, suggests that surgical revascularization improves patients' prognosis at long-term follow-up, whereas evidence supports no benefit of percutaneous coronary intervention. Data from randomized controlled trials do not support myocardial ischemia or viability testing for treatment guidance. We propose an algorithm for the workup of patients with ICM considering clinical presentation, imaging results, and surgical risk.

Coronary Revascularization in Patients With Stable Coronary Artery Disease: The Role of Imaging

In the last decades, the effective management of some cardiovascular risk factors in the general population has led to a progressive decrease in the prevalence of coronary artery disease (CAD). Nevertheless, coronary heart disease remains the major cause of death in developed and developing countries and chronic coronary syndromes (CCS) are still a major target of utilization of non-invasive cardiac imaging and invasive procedures. Current guidelines recommend the use of non-invasive imaging in patients with CCS to identify subjects at higher risk to be referred for invasive coronary angiography and possible revascularization. These recommendations are challenged by two opposite lines of evidence. Recent trials have somewhat questioned the efficacy of coronary revascularization as compared with optimal medical therapy in CCS. As a consequence the role of imaging in these patients and in in patients with ischemic cardiomyopathy is under debate. On the other hand, real-life data indicate that a consistent proportion of patients undergo invasive procedure and are revascularized without any previous non-invasive imaging characterization. On top of this, the impact of COVID-19 pandemic on the sanitary systems caused a change in the current management of patients with CAD. In the present review we will discuss these conflicting data analyzing the evidence which has been recently accumulated as well as the gaps of knowledge which should still be filled.

PET Cardiac Imaging (Perfusion, Viability, Sarcoidosis, and Infection)

Cardiovascular disease is the leading cause of death worldwide. Given the increased availability of radiopharmaceuticals, improved positron emission tomography (PET) camera systems and proven higher diagnostic accuracy, PET is increasingly utilized in the management of various cardiovascular diseases. PET has high temporal and spatial resolution, when compared to Single Photon Emission Computed Tomography. In clinical practice, hybrid imaging with sequential PET and Computed Tomography acquisitions (PET/CT) or concurrent PET and Magnetic Resonance Imaging are standard. This article will review applications of cardiovascular PET/CT including myocardial perfusion, viability, cardiac sarcoidosis/inflammation, and infection.

Molecular Imaging Using Cardiac PET/CT: Opportunities to Harmonize Diagnosis and Therapy

Purpose of Review

Current therapeutic strategies to mitigate heart failure progression after myocardial infarction involve support of endogenous repair through molecular targets. The capacity for repair varies greatly between individuals. In this review, we will assess how cardiac PET/CT enables precise characterization of early pathogenetic processes which govern ventricle remodeling and progression to heart failure.

Recent Findings

Inflammation in the first days after myocardial infarction predicts subsequent functional decline and can influence therapy decisions. The expansion of anti-inflammatory approaches to improve outcomes after myocardial infarction may benefit from noninvasive characterization using imaging. Novel probes also allow visualization of fibroblast transdifferentiation and activation, as a precursor to ventricle remodeling.

Summary

The expanding arsenal of molecular imaging agents in parallel with new treatment options provides opportunity to harmonize diagnostic imaging with precision therapy.

Myocardial Viability Imaging using Manganese-Enhanced MRI in the First Hours after Myocardial Infarction

Early measurements of tissue viability after myocardial infarction (MI) are essential for accurate diagnosis and treatment planning but are challenging to obtain. Here, manganese, a calcium analogue and clinically approved magnetic resonance imaging (MRI) contrast agent, is used as an imaging biomarker of myocardial viability in the first hours after experimental MI. Safe Mn2+ dosing is confirmed by measuring in vitro beating rates, calcium transients, and action potentials in cardiomyocytes, and in vivo heart rates and cardiac contractility in mice. Quantitative T1 mapping-manganese-enhanced MRI (MEMRI) reveals elevated and increasing Mn2+ uptake in viable myocardium remote from the infarct, suggesting MEMRI offers a quantitative biomarker of cardiac inotropy. MEMRI evaluation of infarct size at 1 h, 1 and 14 days after MI quantifies myocardial viability earlier than the current gold-standard technique, late-gadolinium-enhanced MRI. These data, coupled with the re-emergence of clinical Mn2+ -based contrast agents open the possibility of using MEMRI for direct evaluation of myocardial viability early after ischemic onset in patients.

Nuclear cardiology: state of the art

Radionuclide imaging remains an essential component of modern cardiology. There is overlap with the information from other imaging techniques, but no technique is static and new developments have expanded its role. This review focuses on ischaemic heart disease, heart failure, infection and inflammation. Radiopharmaceutical development includes the wider availability of positron emission tomography (PET) tracers such as rubidium-82, which allows myocardial perfusion to be quantified in absolute terms. Compared with alternative techniques, myocardial perfusion scintigraphy PET and single photon emission computed tomography (SPECT) have the advantages of being widely applicable using exercise or pharmacological stress, full coverage of the myocardium and a measure of ischaemic burden, which helps to triage patients between medical therapy and revascularisation. Disadvantages include the availability of expertise in some cardiac centres and the lack of simple SPECT quantification, meaning that global abnormalities can be underestimated. In patients with heart failure, despite the findings of the STICH (Surgical Treatment for Ischemic Heart Failure) trial, there are still data to support the assessment of myocardial hibernation in predicting when abolition of ischaemia might lead to improvement in ventricular function. Imaging of sympathetic innervation is well validated, but simpler markers of prognosis mean that it has not been widely adopted. There are insufficient data to support its use in predicting the need for implanted devices, but non-randomised studies are promising. Other areas where radionuclide imaging is uniquely valuable are detection and monitoring of endocarditis, device infection, myocardial inflammation in sarcoidosis, myocarditis and so on, and reliable detection of deposition in suspected transthyretin-related amyloidosis.

Normal Variants and Pitfalls in Cardiac PET/CT

Positron emission tomography and/or computed tomography (PET/CT) MPI is a powerful imaging modality for the assessment of cardiovascular diseases. It offers several advantages over single-photon emission computed tomography (SPECT) MPI including robust attenuation correction and absolute quantification of radiotracer activity. PET MPI has a large evidence base and is the only clinical tool to evaluate coronary microvascular dysfunction. In addition, the clinical use and evidence base for 2-deoxy-2-[¹⁸F]fluoro-D-g1ucose (¹⁸F-FDG) cardiac PET imaging for inflammation and metabolism imaging is rising exponentially. In order to gain from the advances of this sophisticated quantitative technique, a high-quality scan is critical. It is important for readers to recognize a poor-quality scan, identify artifacts contributing to the poor image quality, and understand how to correct them prior to reporting the results. In this review, we will discuss some normal variants and pitfalls in cardiac PET/CT radionuclide MPI, myocardial viability, and inflammation imaging.

Coronary revascularisation in patients with ischaemic cardiomyopathy

Heart failure resulting from ischaemic heart disease is associated with a poor prognosis despite optimal medical treatment. Despite this, patients with ischaemic cardiomyopathy have been largely excluded from randomised trials of revascularisation in stable coronary artery disease. Revascularisation has multiple potential mechanisms of benefit, including the reversal of myocardial hibernation, suppression of ventricular arrhythmias and prevention of spontaneous myocardial infarction. Coronary artery bypass grafting is considered the first-line mode of revascularisation in these patients; however, evidence from the Surgical Treatment of Ischaemic Heart Failure (STICH) trial showed a reduction in mortality, though this only became apparent with extended follow-up due to an excess of early adverse events in the surgical arm. There is currently no randomised controlled trial evidence for percutaneous coronary intervention in patients with ischaemic cardiomyopathy; however, the REVIVED-BCIS2 trial has recently completed recruitment and will address this gap in the evidence. Future directions include (1) clinical trials of revascularisation in patients hospitalised with heart failure, (2) defining the role of viability and ischaemia testing in heart failure, (3) studies to enhance the understanding of the mechanistic effects of revascularisation and (4) generating models to refine pre- and post-revascularisation risk prediction.

Multimodality Imaging of Myocardial Viability

PURPOSE OF REVIEW

Myocardial viability is an important pathophysiologic concept which may have significant clinical impact in patients with left ventricular dysfunction due to ischemic heart disease. Understanding the imaging modalities used to assess viability, and the clinical implication of their findings, is critical for clinical decision-making in this population.

RECENT FINDINGS

The ability of dobutamine echocardiography, single-photon emission computed tomography, positron emission tomography, and cardiac magnetic resonance imaging to predict functional recovery following revascularization is well-established. Despite different advantages and disadvantages for each imaging modality, each modality has demonstrated reasonable performance characteristics in identifying viable myocardium. Recent data, however, has called into question whether this functional recovery leads to improved clinical outcomes. Although the assessment of viability can be used to aid in clinical decision-making prior to revascularization, its broad application to all patients is limited by a lack of data confirming improvement in clinical outcomes. Thus, viability assessments may be best applied to select patients (such as those with increased surgical risk) and integrated with clinical, laboratory, and imaging data to guide clinical care. Future research efforts should be aimed at establishing the impact of viability on clinical outcomes.

Clinical characteristics and outcomes of patients with severe left ventricular dysfunction undergoing cardiac MRI viability assessment prior to revascularization

Coronary artery bypass grafting improves survival in patients with ischemic cardiomyopathy, however, these patients are at high risk for morbidity and mortality. The role of viability testing to guide revascularization in these patients is unclear. Cardiac magnetic resonance imaging (CMR) has not been studied adequately in this population despite being considered a reference standard for infarct imaging. We performed a multicenter retrospective analysis of patients (n = 154) with severe left ventricular systolic dysfunction [ejection fraction (EF) < 35%] on CMR who underwent CMR viability assessment prior to consideration for revascularization. Using the AHA16-segment model, percent total myocardial viability was determined depending on the degree of transmural scar thickness. Patients with or without revascularization had similar clinical characteristics and were prescribed similar medical therapy. Overall, 43% of patients (n = 66) experienced an adverse event during the median 3 years follow up. For the composite outcome (death, myocardial infarction, heart failure hospitalization, stroke, ventricular tachycardia) patients receiving revascularization were less likely to experience an adverse event compared to those without revascularization (HR 0.53, 95% CI 0.33-0.86, p = 0.01). Patients with > 50% viability on CMR had a 47% reduction in composite events when undergoing revascularization opposed to medical therapy alone (HR 0.53, p = 0.02) whereas patients with a viability < 50% were 2.7 times more likely to experience an adverse event (p = 0.01). CMR viability assessment may be an important tool in the shared decision-making process when considering revascularization options in patients with severe ischemic cardiomyopathy.

OUTSMART HF: A Randomized Controlled Trial of Routine Versus Selective Cardiac Magnetic Resonance for Patients With Nonischemic Heart Failure (IMAGE-HF 1B)

Background:

Cardiac magnetic resonance (CMR) is a recommended imaging test for patients with heart failure (HF); however, there is a lack of evidence showing incremental benefit over transthoracic echocardiography. Our primary hypothesis was that routine use of CMR will yield more specific diagnoses in nonischemic HF. Our secondary hypothesis was that routine use of CMR will improve patient outcomes.

Methods:

Patients with nonischemic HF were randomized to routine versus selective CMR. Patients in the routine strategy underwent echocardiography and CMR, whereas those assigned to selective use underwent echocardiography with or without CMR according to the clinical presentation. HF causes was classified from the imaging data as well as by the treating physician at 3 months (primary outcome). Clinical events were collected for 12 months.

Results:

A total of 500 patients (344 male) with mean age 59±13 years were randomized. The routine and selective CMR strategies had similar rates of specific HF causes at 3 months clinical follow-up (44% versus 50%, respectively; P =0.22). At image interpretation, rates of specific HF causes were also not different between routine and selective CMR (34% versus 30%, respectively; P =0.34). However, 24% of patients in the selective group underwent a nonprotocol CMR. Patients with specific HF causes had more clinical events than those with nonspecific caused on the basis of imaging classification (19% versus 12%, respectively; P =0.02), but not on clinical assessment (15% versus 14%, respectively; P =0.49).

Conclusions:

In patients with nonischemic HF, routine CMR does not yield more specific HF causes on clinical assessment. Patients with specific HF causes from imaging had worse outcomes, whereas HF causes defined clinically did not.

Registration:

URL: https://www.clinicaltrials.gov ; Unique identifier: NCT01281384.

Jeopardized Myocardium Defined by Late Gadolinium Enhancement Magnetic Resonance Imaging Predicts Survival in Patients With Ischemic Cardiomyopathy: Impact of Revascularization

Background The prognostic impact of jeopardized myocardium ( JM ) in patients with advanced ischemic cardiomyopathy ( ICM ) is unclear. We hypothesized that JM is an independent predictor of mortality in patients with advanced ICM . Methods and Results Patients with ICM who underwent cardiac magnetic resonance imaging between January 2002 and January 2013 were included in our study. JM was identified as a vascular territory with <50% myocardial scarring on cardiac magnetic resonance imaging and with >70% stenosis in a major coronary vessel that was not subsequently revascularized. A propensity score was developed for revascularization. A multivariable Cox proportional hazards model was used to evaluate the association of JM with all-cause mortality. We evaluated 631 patients over a mean follow-up of 5.1 years. Overall, 336 patients underwent subsequent revascularization during the follow-up period, among whom 23% had remaining JM , while 295 patients were medically treated (57% with JM ). There were 204 deaths (32%). On multivariable analysis, JM (hazard ratio, 1.88; 95% confidence interval, 1.38-2.55 [ P<0.001]) was independently associated with all-cause mortality after adjusting for multiple other factors. The risk associated with the presence of JM increased by 5% for every 10-unit increase in left ventricular end-systolic volume index. Conclusions JM is an independent and incremental predictor of mortality in patients with advanced ICM . Patients undergoing revascularization with residual JM had similar risk of mortality compared with medically treated patients with JM . The risk associated with JM significantly increased in the presence of worsening adverse left ventricular remodeling. Cardiac magnetic resonance viability assessment may provide important risk stratification in patients with ICM .

Impact of hibernating and viable myocardium on improvement in perfusion and left ventricular ejection fraction after coronary artery bypass graft

OBJECTIVES

The association between the extent and degree of perfusion-metabolism mismatch and improvement in perfusion and left ventricular ejection fraction (LVEF) after revascularization was assessed. The secondary aim was to identify the best precoronary artery bypass graft surgery (pre-CABG) PET parameter, if any, to predict the improvement in the perfusion and LVEF after CABG.

METHODS AND RESULTS

Overal, 31 patients (mean age: 58+8.3 years) with ischemic left ventricle dysfunction underwent NH3 and F-FDG PET for the assessment of myocardial viability. CABG was performed in these patients and after a mean interval of 3 months, NH3 PET was repeated. The percentages of viable myocardium (VM), hibernating myocardium, degree of mismatch, and LVEF in pre-CABG PET were calculated. These were compared, the median [INCREMENT]LVEF and percent increase in perfusion being 5 (interquartile range: 3-9) and 78.7 (interquartile range: 51.3-100), respectively. No significant association was observed between the severity or extent of perfusion defect/mismatch and improvement in perfusion or LVEF after CABG. Patients with at least 65% VM predicted a 5-unit increase in LVEF at 88.9% sensitivity (P=0.1).

CONCLUSION

There was no significant relation between the severity and extent of perfusion-metabolism mismatch with improvement in perfusion and LVEF after CABG. After CABG for ischemic left ventricle dysfunction, VM shows a tendency toward better improvement in LVEF.

Viability testing to guide myocardial revascularisation in patients with heart failure

Myocardial revascularisation has the potential to restore ventricular function and improve survival in patients with heart failure due to underlying coronary artery disease. Viability testing is routinely used to identify which patients are likely to benefit, given that revascularisation may entail substantial procedural risk. However, while the concept of viability testing and revascularisation of patients with ‘hibernating myocardium’ is strongly supported by observational series, randomised studies have failed to demonstrate clear benefit. This divergence in the evidence base is reflected in current European and US guidelines, in which viability testing has a class II recommendation. In this article, we review the current evidence for routine viability testing prior to revascularisation of patients with heart failure, outline its use in clinical practice and discuss ongoing trials in the field.

Limited prognostic value of myocardial viability assessment in patients with coronary artery diseases and severe left ventricular dysfunction

Background

Myocardial viability assessment is typically performed in patients with coronary artery disease (CAD) and severe left ventricular (LV) dysfunction to identify those who might benefit from revascularization and assist in decision making process. However, the prognostic value of myocardial viability testing remains a debating issue.

Methods

Positron Emission Tomography using ¹⁸F-fluorodeoxyglucose (¹⁸FDG-PET) was performed in 81 patients with ischemic LV dysfunction [ejection fraction (EF) ≤35%] for myocardial viability assessment prior to coronary artery bypass surgery. Fifty-three of them received finally coronary artery bypass grafting and were divided into two groups according to the extent of myocardial scar: one group with scar burden ≥10% (n=30) and the other with scar burden <10% (n=23). The remaining patients were contraindicated for CABG and received optimal medical treatment (OMT, n=28). All patients were followed up and the primary endpoint was all-cause mortality and the secondary endpoint was a composite of all-cause mortality and major adverse cardiovascular and cerebrovascular events (MACCE).

Results

¹⁸FDG-PET revealed a different profile of myocardial viability among three groups with respect to the extent of myocardial scar, the hibernating myocardium (both P<0.01), some echocardiographic parameters such as left ventricular diastolic dimension (LVDD) and EF were also significantly different (both P<0.05). Nevertheless, the baseline prevalence of comorbidities and functional classifications were comparable. The per-procedural parameters were not significantly different between two CABG groups. In a median follow-up time of 32 months, Kaplan Meier analysis uncovered no significant difference in terms of overall survival (P=0.74) and MACCE-free survival (P=0.66) among three groups.

Conclusions

Myocardial viability assessment using ¹⁸FDG-PET is of limited prognostic value in patients with CAD and severe LV dysfunction. In patients with substantial myocardial scar burden despite the existence of considerable hibernating myocardium, functional recovery following surgical revascularization is not necessarily translated to survival benefits.

Can Functional Testing for Ischemia and Viability Guide Revascularization?

Cardiac imaging procedures are a cornerstone of the diagnosis and management of patients with cardiac disease. The optimal management of the patient with stable ischemic heart disease or ischemic heart failure often rests on the totality of symptom burden, patient risk, and disease severity, whether assessed anatomically or functionally. Recent trials have demonstrated the power of flow measurements to direct revascularization as well as the strengths and limitations of ischemia and viability/hibernation imaging as markers of risk to direct interventions. They have also highlighted the challenges in evaluating imaging or functional testing to direct therapies, because imaging does not directly affect outcome itself, rather it affects the management decisions that may result in a positive outcome. Ongoing studies with randomized designs, such as FAME 3 (Fractional Flow Reserve versus Angiography for Multivessel Evaluation), ISCHEMIA (International Study of Comparative Health Effectiveness with Medical and Invasive Approaches), and AIMI-HF (Alternative Imaging Modalities in Ischemic Heart Failure) (IMAGE-HF [Imaging Modalities to Assist with Guiding Therapy in The Evaluation of Patients with Heart Failure]), will provide the highest level of evidence to support practice changes that may further clarify the role of cardiac imaging in the evaluation of these patients and result in improved patient outcomes.

Myocardial Viability: Survival Mechanisms and Molecular Imaging Targets in Acute and Chronic Ischemia

Myocardial responses to acute ischemia/reperfusion and to chronic ischemic conditions have been studied extensively at all levels of organization. These include subcellular (eg, mitochondria in vitro); intact, large animal models (eg, swine with chronic coronary stenosis); as well as human subjects. Investigations in humans have used positron emission tomographic metabolic and myocardial blood flow measurements, assessment of gene expression and anatomic description of myocardium obtained at the time of coronary artery revascularization, ventricular assist device placement, or heart transplantation. A multitude of genetic, molecular, and metabolic pathways have been identified, which may promote either myocyte survival or death or, most interestingly, both. Many of these potential mediators in both acute ischemia/reperfusion and adaptations to chronic ischemic conditions involve the mitochondria, which play a central role in cellular energy production and homeostasis. The present review is focused on operative survival mechanisms and potential myocardial viability molecular imaging targets in acute and chronic ischemia, especially those which impact mitochondrial function.

Multi-modality imaging: Bird's-eye view from the 2014 American Heart Association Scientific Sessions

A large number of studies were presented at the 2014 American Heart Association Scientific Sessions. In this review, we will summarize key studies in nuclear cardiology, computed tomography, echocardiography, and cardiac magnetic resonance imaging. This brief review will be helpful for readers of the Journal who are interested in being updated on the latest research covering these imaging modalities.