Alternative Imaging Modalities in Ischemic Heart Failure (AIMI-HF) IMAGE HF Project I-A: study protocol for a randomized controlled trial

Exploratory analysis of predictors of ventricular aneurysm in a cohort of 291 patients with acute myocardial infarction

OBJECTIVE

In this study, we explored the determinants of ventricular aneurysm development following acute myocardial infarction (AMI), thereby prompting timely interventions to enhance patient prognosis.

METHODS

In this retrospective cohort analysis, we evaluated 297 AMI patients admitted to the First People's Hospital of Changzhou. The study was structured as follows. Comprehensive baseline data collection included hematological evaluations, ECG, echocardiography, and coronary angiography upon admission. Within 3 months post-AMI, cardiac ultrasounds were administered to detect ventricular aneurysm development. Univariate and multivariate logistic regression analysis were employed to pinpoint the determinants of ventricular aneurysm formation. Subsequently, a predictive model was formulated for ventricular aneurysm post-AMI. Moreover, the diagnostic efficacy of this model was appraised using the ROC curves.

RESULTS

In our analysis of 291 AMI patients, spanning an age range of 32-91 years, 247 were male (84.9%). At the conclusion of a 3-month observational period, the cohort bifurcated into two subsets: 278 patients without ventricular aneurysm and 13 with evident ventricular aneurysm. Distinguishing features of the ventricular aneurysm subgroup were markedly higher values for age, B-type natriuretic peptide(BNP), Left atrium(LA), Left ventricular end-diastolic dimension (LEVDD), left ventricular end systolic diameter (LVEWD), E-wave velocity (E), Left atrial volume (LAV), E/A ratio (E/A), E/e ratio (E/e), ECG with elevated adjacent four leads(4 ST-Elevation), and anterior wall myocardial infarction(AWMI) compared to their counterparts (p < 0.05). Among the singular predictive factors, total cholesterol (TC) emerged as the most significant predictor for ventricular aneurysm development, exhibiting an AUC of 0.704. However, upon crafting a multifactorial model that incorporated gender, TC, an elevated ST-segment in adjacent four leads, and anterior wall infarction, its diagnostic capability: notably surpassed that of the standalone TC, yielding an AUC of 0.883 (z = -9.405, p = 0.000) as opposed to 0.704. Multivariate predictive model included gender, total cholesterol, ST elevation in 4 adjacent leads, anterior myocardial infarction, the multivariate predictive model showed better diagnostic efficacy than single factor index TC (AUC: 0. 883 vs. 0.704,z =-9.405, p = 0.000), it also improved predictive power for correctly reclassifying ventricular aneurysm occurrence in patients with AMI, NRI = 28.42% (95% CI: 6.29-50.55%; p = 0.012). Decision curve analysis showed that the use of combination model had a positive net benefit.

CONCLUSION

Lipid combined with ECG model after myocardial infarction could be used to predict the formation of ventricular aneurysm and aimed to optimize and adjust treatment strategies.

Enhancing Prediction of Myocardial Recovery After Coronary Revascularization: Integrating Radiomics from Myocardial Contrast Echocardiography with Machine Learning

Introduction

Chronic coronary artery disease (CAD) management often relies on myocardial contrast echocardiography (MCE), yet its effectiveness is limited by subjective interpretations and difficulty in distinguishing hibernating from necrotic myocardium. This study explores the integration of machine learning (ML) with radiomics to predict functional recovery in dyskinetic myocardial segments in CAD patients undergoing revascularization, aiming to overcome these limitations.

Methods

This prospective study enrolled 55 chronic CAD patients, dividing into training (39 patients, 205 segments) and testing sets (16 patients, 68 segments). Dysfunctional myocardial segments were identified by initial wall motion scores (WMS) of ≥2 (hypokinesis or higher). Functional recovery was defined as a decrease of ≥1 grade in WMS during follow-up echocardiography. Radiomics features were extracted from dyssynergic segments in end-systolic phase MCE images across five cardiac cycles post- "flash" impulse and processed through a five-step feature selection. Four ML classifiers were trained and compared using these features and MCE parameters, to identify the optimal model for myocardial recovery prediction.

Results

Functional improvement was noted in 139 out of 273 dyskinetic segments (50.9%) following revascularization. Receiver Operating Characteristic (ROC) analysis determined that myocardial blood flow (MBF) was the most precise clinical predictor of recovery, with an area under the curve (AUC) of 0.770. Approximately 1.34 million radiomics features were extracted, with nine features identified as key predictors of myocardial recovery. The random forest (RF) model, integrating MBF values and radiomics features, demonstrated superior predictive accuracy over other ML classifiers. Validation of the RF model on the testing dataset demonstrated its effectiveness, evidenced by an AUC of 0.821, along with consistent calibration and clinical utility.

Conclusion

The integration of ML with radiomics from MCE effectively predicts myocardial recovery in CAD. The RF model, combining radiomics and MBF values, presents a non-invasive, precise approach, significantly enhancing CAD management.

Myocardial Viability Testing in the Management of Ischemic Heart Failure

Although major advances have occurred lately in medical therapy, ischemic heart failure remains an important cause of death and disability. Viable myocardium represents a cause of reversible ischemic left ventricular dysfunction. Coronary revascularization may improve left ventricular function and prognosis in patients with viable myocardium. Although patients with impaired left ventricular function and multi-vessel coronary artery disease benefit the most from revascularization, they are at high risk of complications related to revascularization procedure. An important element in selecting the patients for myocardial revascularization is the presence of the viable myocardium. Multiple imaging modalities can assess myocardial viability and predict functional improvement after revascularization, with dobutamine stress echocardiography, nuclear imaging tests and magnetic resonance imaging being the most frequently used. However, the role of myocardial viability testing in the management of patients with ischemic heart failure is still controversial due to the failure of randomized controlled trials of revascularization to reveal clear benefits of viability testing. This review summarizes the current knowledge regarding the concept of viable myocardium, depicts the role and tools for viability testing, discusses the research involving this topic and the controversies related to the utility of myocardial viability testing and provides a patient-centered approach for clinical practice.

PCI in Patients With Heart Failure: Current Evidence, Impact of Complete Revascularization, and Contemporary Techniques to Improve Outcomes

Coronary artery disease (CAD) is the most common cause of left ventricular systolic dysfunction (LVSD) and heart failure (HF). Revascularization with coronary artery bypass grafting (CABG) reduces all-cause mortality compared with medical therapy alone for these patients. Despite this, CABG is performed in a minority of patients with HF, partly due to patient unwillingness or inability to undergo major cardiac surgery and partly due to physician reluctance to refer for surgery due to high operative risk. Percutaneous coronary intervention (PCI) is a less-invasive method of revascularization that has the potential to reduce periprocedural complications compared with CABG in patients with HF. Recent advances in PCI technology and technique have made it realistic to achieve more complete revascularization with PCI in high-risk patients with HF, although no randomized controlled clinical trials (RCTs) of PCI in HF compared with either medical therapy or CABG have been performed. In this review, we discuss the currently available evidence for PCI in HF and the association between the extent of revascularization and clinical outcomes in HF. We also review recent advances in PCI technology and techniques with the potential to improve clinical outcomes in HF. Finally, we discuss emerging clinical trial evidence of revascularization in HF and the large, persistent evidence gaps that should be addressed with future clinical trials of revascularization in HF.

Myocardial viability testing: all STICHed up, or about to be REVIVED?

Patients with ischaemic left ventricular dysfunction frequently undergo myocardial viability testing. The historical model presumes that those who have extensive areas of dysfunctional-yet-viable myocardium derive particular benefit from revascularization, whilst those without extensive viability do not. These suppositions rely on the theory of hibernation and are based on data of low quality: taking a dogmatic approach may therefore lead to patients being refused appropriate, prognostically important treatment. Recent data from a sub-study of the randomized STICH trial challenges these historical concepts, as the volume of viable myocardium failed to predict the effectiveness of coronary artery bypass grafting. Should the Heart Team now abandon viability testing, or are new paradigms needed in the way we interpret viability? This state-of-the-art review critically examines the evidence base for viability testing, focusing in particular on the presumed interactions between viability, functional recovery, revascularization and prognosis which underly the traditional model. We consider whether viability should relate solely to dysfunctional myocardium or be considered more broadly and explore wider uses of viability testingoutside of revascularization decision-making. Finally, we look forward to ongoing and future randomized trials, which will shape evidence-based clinical practice in the future.

Myocardial Viability Assessment Before Surgical Revascularization in Ischemic Cardiomyopathy: JACC Review Topic of the Week

Ischemic cardiomyopathy results from the combination of scar with fibrosis replacement and areas of dysfunctional but viable myocardium that may improve contractile function with revascularization. Observational studies reported that only patients with substantial amounts of myocardial viability had better outcomes following surgical revascularization. Accordingly, dedicated noninvasive techniques have evolved to quantify viable myocardium with the objective of selecting patients for this form of therapeutic intervention. However, prospective trials have not confirmed the interaction between myocardial viability and the treatment effect of revascularization. Furthermore, recent observations indicate that recovery of left ventricular function is not the principal mechanism by which surgical revascularization improves prognosis. In this paper, the authors describe a more contemporary application of viability testing that is founded on the alternative concept that the main goal of surgical revascularization is to prevent further damage by protecting the residual viable myocardium from subsequent acute coronary events.

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.

Multimodality imaging of myocardial viability: an expert consensus document from the European Association of Cardiovascular Imaging (EACVI)

In clinical decision making, myocardial viability is defined as myocardium in acute or chronic coronary artery disease and other conditions with contractile dysfunction but maintained metabolic and electrical function, having the potential to improve dysfunction upon revascularization or other therapy. Several pathophysiological conditions may coexist to explain this phenomenon. Cardiac imaging may allow identification of myocardial viability through different principles, with the purpose of prediction of therapeutic response and selection for treatment. This expert consensus document reviews current insight into the underlying pathophysiology and available methods for assessing viability. In particular the document reviews contemporary viability imaging techniques, including stress echocardiography, single photon emission computed tomography, positron emission tomography, cardiovascular magnetic resonance, and computed tomography and provides clinical recommendations for how to standardize these methods in terms of acquisition and interpretation. Finally, it presents clinical scenarios where viability assessment is clinically useful.

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.

[Myocardial revascularization in left ventricular dysfunction]

Left ventricular dysfunction due to adverse remodeling constitutes the underlying structural anatomical condition of heart failure and is the main and most severe sequela of long-term coronary artery disease, and it is the only pathology that can benefit from surgical myocardial revascularization. For its control, there are current medical treatment guidelines supported by the favorable results of contemporary clinical trials. However, in recent studies, there was no benefit of surgical revascularization in addition to optimal medical therapy when compared to optimal medical therapy alone. The identification of myocardial viability to guide revascularization was also not favorable. The results of the extension of these trials showed benefit of revascularization treatment, but the detection of viability remained unfavorable. Increased left ventricular ejection fraction, as a marker of benefit from revascularization, was not associated with lower mortality. There are many reasons why the known advantages of revascularization were not identified. Despite this discrepancies, myocardial revascularization and the identification of viability in these patients are supported and are usually indications for routine treatment.

Regional Distribution of Fluorine-18-Flubrobenguane and Carbon-11-Hydroxyephedrine for Cardiac PET Imaging of Sympathetic Innervation

OBJECTIVES

The aim of this study was to investigate the regional distribution of novel ¹⁸F-labeled positron emission tomographic (PET) tracer flubrobenguane (FBBG) (whose longer half-life could enable more widespread use) to assess myocardial presynaptic sympathetic nerve function in humans in comparison to [¹¹C]meta-hydroxyephedrine (HED).

BACKGROUND

The sympathetic nervous system (SNS) is vitally linked to cardiovascular regulation and disease. SNS imaging has shown prognostic value. HED is the most commonly used PET tracer for evaluation of sympathetic function in humans, but widespread clinical use is limited because of the short half-life of ¹¹C.

METHODS

A total of 25 participants (n = 6 healthy; n = 14 ischemic cardiomyopathy, left ventricular [LV] ejection fraction [EF] = 34 ± 5%; and n = 5 nonischemic cardiomyopathy, EF = 33 ± 3%) underwent 2 separate PET imaging visits 8.7 ± 7.6 days apart. On 1 visit, participants underwent dynamic HED PET imaging. On a different visit, participants underwent dynamic FBBG PET imaging. The order of testing was random. HED and FBBG global innervation (retention index [RI] and distribution volume [DV]) and regional denervation (% nonuniformity) were quantified to assess regional presynaptic sympathetic innervations.

RESULTS

FBBG RI (r² = 0.72; ICC = 0.79; p < 0.0001), DV (r² = 0.62; ICC = 0.78; p < 0.0001), and regional denervation (r² = 0.97; ICC = 0.98; p < 0.0001) correlated highly with HED. Average LV RI values were highly similar between HED (7.3 ± 2.4%/min) and FBBG (7.0 ± 1.7%/min; p = 0.33). Post-hoc analysis did not reveal any between-tracer differences on a regional level (17-segment), suggesting equivalent regional distributions in both patients with and without ischemic cardiomyopathy.

CONCLUSIONS

FBBG and HED yield equivalent global and regional distributions in both patients with and without ischemic cardiomyopathy. ¹⁸F-labeled PET tracers, such as FBBG, are critical for widespread distribution necessary for multicenter clinical trials and to maximize patient impact.

Does myocardial viability detection improve using a novel combined 99mTc sestamibi infusion and low dose dobutamine infusion in high risk ischemic cardiomyopathy patients?

OBJECTIVE

Early identification of viable myocardium in ischemic cardiomyopathy (ICM) patients is essential for early intervention and better clinical outcome. 99mTechnetium (99mTc) sestamibi gated myocardial perfusion imaging (gMPI) is a well-established technique for myocardial viability evaluation. Detection of potentially viable segments is a predictor of hibernating myocardium. ICM patients with hibernation have a better prognosis after revascularization. We used a novel infusion technique to determine better viability detection preoperatively in challenging situations. Like thallium, does prolonged availability of sestamibi in circulation with additional low dose dobutamine steady infusion (DS Inf) facilitate improved myocardial viability?

METHODS

A total of 58 ICM patients with infarct and left ventricular ejection fraction (LVEF) <45% underwent 99mTc sestamibi bolus injection followed by slow intravenous infusion single-photon emission computed tomography (SPECT) using a 2 day protocol. After acquiring the second set of 99mTc sestamibi infusion images, a third SPECT gMPI was performed during DS Inf.

RESULTS

A 17-segment myocardial model was used; 52 of 58 patients (548/986 segments) demonstrated perfusion defects (nonviable myocardium) on bolus study. Only 24 patients demonstrated viable segments by standard bolus imaging protocol. The slow MIBI infusion study demonstrated 158 viable segments (12 ICM patients), while combined infusion (99mTc sestamibi+DS Inf) exhibited an additional 6 patients with improved myocardial viability. Thus, 18 high risk patients benefited by this novel infusion technique to demonstrate viable myocardium on SPECT. There was a significantly higher sensitivity (p=0.05) and positive predictive value (p=0.01) in viability identification with the combined DS Inf technique. In dysfunctional segments, the rate of concordance for detecting viability between infusion and bolus techniques was 65%. Paired t test showed statistically significant improvement in viability detection with combined infusion compared to the bolus study (p=0.001).

CONCLUSION

This novel infusion technique was shown to be feasible and incremental in viability detection in ICM patients with severe left ventricular dysfunction. It is a robust tool to guide revascularization, in high risk ICM patients. This study also showed that patients with large transmural MI demonstrated no significant improvement in myocardial perfusion status using either protocol.

Manganese-enhanced T1 mapping to quantify myocardial viability: validation with 18F-fluorodeoxyglucose positron emission tomography

Gadolinium chelates are widely used in cardiovascular magnetic resonance imaging (MRI) as passive intravascular and extracellular space markers. Manganese, a biologically active paramagnetic calcium analogue, provides novel intracellular myocardial tissue characterisation. We previously showed manganese-enhanced MRI (MEMRI) more accurately quantifies myocardial infarction than gadolinium delayed-enhancement MRI (DEMRI). Here, we evaluated the potential of MEMRI to assess myocardial viability compared to gold-standard 18F-fluorodeoxyglucose (18F-FDG) positron emission tomography (PET) viability. Coronary artery ligation surgery was performed in male Sprague-Dawley rats (n = 13) followed by dual MEMRI and 18F-FDG PET imaging at 10-12 weeks. MEMRI was achieved with unchelated (EVP1001-1) or chelated (mangafodipir) manganese. T1 mapping MRI was followed by 18F-FDG micro-PET, with tissue taken for histological correlation. MEMRI and PET demonstrated good agreement with histology but native T1 underestimated infarct size. Quantification of viability by MEMRI, PET and MTC were similar, irrespective of manganese agent. MEMRI showed superior agreement with PET than native T1. MEMRI showed excellent agreement with PET and MTC viability. Myocardial MEMRI T1 correlated with 18F-FDG standard uptake values and influx constant but not native T1. Our findings indicate that MEMRI identifies and quantifies myocardial viability and has major potential for clinical application in myocardial disease and regenerative therapies.

Multimodality imaging in ischaemic heart failure

In heart failure, extensive evaluation with modern non-invasive imaging modalities is needed to assess causes, pathophysiology, and haemodynamics, to determine prognosis and consider therapeutic options. This systematic evaluation includes a stepwise assessment of left ventricular size and function, the presence and severity of coronary artery disease, mitral regurgitation, pulmonary hypertension, right ventricular dilation and dysfunction, and tricuspid regurgitation. Based on this imaging-derived information, the need for specific therapies besides optimised medical therapy can be determined. The need for revascularisation, implantation of an implantable cardiac defibrillator, and mitral or tricuspid valve repair or replacement, can be (partially) guided by non-invasive imaging. Importantly, randomised controlled trials on the use of non-inasive imaging to guide therapy are scarce in this field and most non-pharmacological therapies are based on expert-consensus, but whenever trials are available, they will be addressed in this paper.

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.

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.

N-Terminal Pro B-Type Natriuretic Peptide and High-Sensitivity Cardiac Troponin T Levels Are Related to the Extent of Hibernating Myocardium in Patients With Ischemic Heart Failure

BACKGROUND

Increased N-terminal pro b-type natriuretic peptide (NT-proBNP) and high-sensitivity cardiac troponin T (hs-cTnT) can identify patients with heart failure (HF) who are at increased risk of cardiac events. The relationship of these biomarkers to the extent of hibernating myocardium and scar has not been previously characterized in patients with ischemic left ventricular dysfunction and HF.

METHODS

Patients with ischemic HF meeting recruitment criteria and undergoing perfusion and fluorodeoxyglucose-positron emission tomography to define myocardial hibernation and scar were included in the study. A total of 39 patients (mean age 67 ± 8 years) with New York Heart Association class II-IV HF and ischemic cardiomyopathy (ejection fraction [EF], 27.9% ± 8.5%) were enrolled in the study.

RESULTS

Serum NT-proBNP and hs-cTnT levels were elevated in patients with ≥ 10% hibernating myocardium compared with those with < 10% (NT-pro-BNP, 7419.10 ± 7169.5 pg/mL vs 2894.6 ± 2967.4 pg/mL; hs-cTnT, 789.3 ± 1835.3 pg/mL vs 44.8 ± 78.9 pg/mL; P < 0.05). The overall receiver operating characteristic under the curve value for NT-proBNP and hs-cTnT to predict hibernating myocardium was 0.76 and 0.78, respectively (P < 0.05). The NT-proBNP (P = 0.02) and hs-cTnT (P < 0.0001) levels also correlated with hibernation, particularly in patients with ≥ 10% scar, independent of EF, age, and estimated glomerular filtration rate. No differences were noted in biomarker levels for patients with vs those without ≥ 10% scar.

CONCLUSIONS

NT-proBNP and hs-cTnT levels are elevated in patients with ischemic HF hibernation and are correlated with the degree of hibernation but not with the presence or extent of scar. Taken together, these data support the novel concept that NT-proBNP and hs-cTnT release in patients with ischemic HF reflects the presence and extent of hibernating myocardium.

Revascularization in Patients With Severe Left Ventricular Dysfunction: Is the Assessment of Viability Still Viable?

Myocardial viability assessment is typically reserved for patients with coronary artery disease and significant left ventricular dysfunction. In this setting, there is myocardial adaptation to an altered physiological state that is potentially reversible. Imaging can characterize different parameters of cardiac function; however, despite previously published appraisals of different imaging modalities, there is still uncertainty regarding the role of these tests in clinical practice. The purpose of this review is to reflect on the physiological basis of myocardial viability, discuss the imaging tests available that characterize myocardial viability, and summarize the current published reports on the use of these tests in clinical practice.

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.

The role of nuclear cardiac imaging in risk stratification of sudden cardiac death

Sudden cardiac death (SCD) represents a significant portion of all cardiac deaths. Current guidelines focus mainly on left ventricular ejection fraction (LVEF) as the main criterion for SCD risk stratification and management. However, LVEF alone lacks both sensitivity and specificity in stratifying patients. Recent research has provided interesting data which supports a greater role for advanced cardiac imaging in risk stratification and patient management. In this article, we will focus on nuclear cardiac imaging, including left ventricular function assessment, myocardial perfusion imaging, myocardial blood flow quantification, metabolic imaging, and neurohormonal imaging. We will discuss how these can be used to better understand SCD and better stratify patient with both ischemic and non-ischemic cardiomyopathy.

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

Background—

Whether viability imaging can impact long-term patient outcomes is uncertain. The PARR-2 study (Positron Emission Tomography and Recovery Following Revascularization) showed a nonsignificant trend toward improved outcomes at 1 year using an F-18-fluorodeoxyglucose positron emission tomography (PET)–assisted strategy in patients with suspected ischemic cardiomyopathy. When patients adhered to F-18-fluorodeoxyglucose PET recommendations, outcome benefit was observed. Long-term outcomes of viability imaging–assisted management have not previously been evaluated in a randomized controlled trial.

Methods and Results—

PARR-2 randomized patients with severe left ventricular dysfunction and suspected CAD being considered for revascularization or transplantation to standard care (n= 195) versus PET-assisted management (n=197) at sites participating in long-term follow-up. The predefined primary outcome was time to composite event (cardiac death, myocardial infarction, or cardiac hospitalization). After 5 years, 105 (53%) patients in the PET arm and 111 (57%) in the standard care arm experienced the composite event (hazard ratio for time to composite event =0.82 [95% confidence interval 0.62–1.07]; P =0.15). When only patients who adhered to PET recommendations were included, the hazard ratio for the time to primary outcome was 0.73 (95% confidence interval 0.54–0.99; P =0.042).

Conclusions—

After a 5-year follow-up in patients with left ventricular dysfunction and suspected CAD, overall, PET-assisted management did not significantly reduce cardiac events compared with standard care. However, significant benefits were observed when there was adherence to PET recommendations. PET viability imaging may be best applied when there is likely to be adherence to imaging-based recommendations.

Clinical Trial Registration—

URL: http://www.clinicaltrials.gov . Unique identifier: NCT00385242.

Myocardial Viability: From Proof of Concept to Clinical Practice

Ischaemic left ventricular (LV) dysfunction can arise from myocardial stunning, hibernation, or necrosis. Imaging modalities have become front-line methods in the assessment of viable myocardial tissue, with the aim to stratify patients into optimal treatment pathways. Initial studies, although favorable, lacked sufficient power and sample size to provide conclusive outcomes of viability assessment. Recent trials, including the STICH and HEART studies, have failed to confer prognostic benefits of revascularisation therapy over standard medical management in ischaemic cardiomyopathy. In lieu of these recent findings, assessment of myocardial viability therefore should not be the sole factor for therapy choice. Optimization of medical therapy is paramount, and physicians should feel comfortable in deferring coronary revascularisation in patients with coronary artery disease with reduced LV systolic function. Newer trials are currently underway and will hopefully provide a more complete understanding of the pathos and management of ischaemic cardiomyopathy.

To Revascularise or Not To Revascularise, That Is the Question: the Diagnostic and Management Conundrum of Ischaemic Cardiomyopathy

Ischaemic cardiomyopathy is an important cardiovascular condition that has differing pathophysiological substrates and clinical manifestations. Contemporary management involves the administration of heart failure pharmacotherapy and device therapy where indicated, which has good prognostic data to support it. Whilst the role of revascularisation is clear in those patients presenting with an acute coronary syndrome or angina, the role in those patients presenting either incidentally, with predominant heart failure symptoms, or in those presenting with acute heart failure with an associated elevated troponin is less well defined and lacks randomised outcome data to support its adoption. The aim of this review is therefore to discuss the challenges in the diagnosis of ischaemic cardiomyopathy with a review of the existing imaging modalities that can facilitate, and to revisit the variety of clinical presentations that can occur, with particular emphasis on the contemporary role of revascularisation in these cohorts of patients.

Comprehensive evaluation of hibernating myocardium: use of noninvasive imaging

Ischemic heart failure is probably the most challenging issue in cardiology today, posing an enormous medical and financial burden on our society. Conceptually, it represents a maladaptive cardiac remodeling due to acute and/or chronic coronary artery disease with varying degrees of left ventricular dilatation and dysfunction. Although therapeutic options have improved overall survival over the years, mortality rates remain high, and in daily practice cardiologists not infrequently face the therapeutic dilemma whether a revascularization procedure will lead to symptomatic and prognostic benefit for the patient. Simple, straightforward guidelines are lacking because of the complexity of the disease. Moreover, the issue of viability imaging grounded on observational and retrospective studies has recently been challenged by the publication of prospective, randomized trials (eg, STICH and PARR trial) showing no benefit of revascularization nor of preprocedural viability assessment in those patients. These contradictory findings have obliged us to inquire whether viability imaging is still relevant and what is needed to make it more appropriate.

Role of viability imaging in the post-STICH era

PURPOSE OF REVIEW

Recent results from prospective randomized controlled trials examining the management of patients with ischemic cardiomyopathy (ICM) have questioned both the added value of revascularization over contemporary optimal medical therapy (OMT) and the use of viability testing as a gate-keeper to revascularization. The purpose of this review is to summarize recent trial evidence before discussing future perspectives in the field.

RECENT FINDINGS

The Surgical Treatment of Ischemic Heart Failure (STICH) trial, PPAR-2 trial and Heart Failure Revascularisation Trial have all reported their results within the past 5 years. None of these trials found revascularization superior to OMT in improving survival of ICM patients. Additionally, the STICH trial's viability substudy suggested that pretreatment viability testing was not beneficial.

SUMMARY

ICM patients remain a clinical conundrum. The numerous limitations of the recent RCTs have led to uncertainty about optimal management. Revascularization continues to be offered to patients with evidence of myocardial viability. Further studies are required to answer the outstanding questions in the management of patients with ICM.

Computed tomographic coronary angiography for patients with heart failure (CTA-HF): a randomized controlled trial (IMAGE HF Project 1-C)

BACKGROUND

The prevalence of heart failure (HF) is rising in industrialized and developing countries. Though invasive coronary angiography (ICA) remains the gold standard for anatomical assessment of coronary artery disease in HF patients, alternatives are being sought. Computed tomographic coronary angiography (CTA) has emerged as an accurate non-invasive diagnostic tool for coronary artery disease (CAD) and has been demonstrated to have prognostic value. Whether or not CTA can be used in HF patients is unknown. Acknowledging the aging population, the growing prevalence of HF and the increasing financial burden of healthcare, we need to identify non-invasive diagnostic tests that are available, safe, accurate and cost-effective.

METHODS/DESIGN

The proposed study aims to provide insight into the efficacy of CTA in HF patients. A multicenter randomized controlled trial will enroll 250 HF patients requiring coronary anatomical definition. Enrolled patients will be randomized to either CTA or ICA (n = 125 per group) as the first test to define coronary anatomy. The primary outcomes will be collected to determine downstream resource utilization. Secondary outcomes will include the composite clinical events and major adverse cardiac events. In addition, the accuracy of CTA for detecting coronary anatomy and obstruction will be assessed in patients who subsequently undergo both CTA and ICA. It is expected that CTA will be a more cost-effective strategy for diagnosis: yielding similar outcomes with fewer procedural risks and improved resource utilization.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT01283659. Team grant #CIF 99470.