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

Utility of coronary revascularization in patients with ischemic left ventricular dysfunction

BACKGROUND

Revascularization in patients with left ventricular (LV) dysfunction has been a subject of ongoing uncertainty and conflicting results. This is further complicated by factors including viability, severity of LV dysfunction, and method of revascularization using percutaneous coronary intervention (PCI) versus coronary-artery bypass grafting (CABG).

OBJECTIVES

The purpose of this meta-analysis is to evaluate the association of coronary revascularization with outcomes in patients with ischemic LV dysfunction.

METHODS

A literature search was conducted for studies reporting on cardiovascular outcomes after revascularization compared to optimal medical therapy (OMT) in patients with ischemic LV dysfunction.

RESULTS

A total of 23 studies with 10,110 participants met inclusion criteria. Revascularization was significantly associated with lower all-cause mortality and CV mortality compared to OMT. The association was statistically significant regardless of severity of LV dysfunction or method of revascularization. Subgroup analysis demonstrated that revascularization was significantly associated with lower all-cause and CV mortality compared to OMT for patients with viable myocardium and mixed cohorts with variable viability, but not patients without viable myocardium. Revascularization was not associated with a significant difference in risk of heart failure (HF) hospitalization or acute myocardial infarction (AMI) compared to OMT.

CONCLUSIONS

Revascularization in patients with ischemic LV dysfunction is associated with lower risk of all-cause and CV mortality independent of severity of LV dysfunction or method of revascularization. Revascularization is not associated with lower risk of mortality in patients without evidence of viable myocardium and is not associated with lower risk of AMI or HF hospitalization.

Assessment of Myocardial Viability in Ischemic Cardiomyopathy With Reduced Left Ventricular Function Undergoing Coronary Artery Bypass Grafting

BACKGROUND

We aim to provide a comprehensive review of the current state of knowledge of myocardial viability assessment in patients undergoing coronary artery bypass grafting (CABG), with a focus on the clinical markers of viability for each imaging modality. We also compare mortality between patients with viable myocardium and those without viability who undergo CABG.

METHODS

A systematic database search with meta-analysis was conducted of comparative original articles (both observations and randomized controlled studies) of patients undergoing CABG with either viable or nonviable myocardium, in EMBASE, MEDLINE, Cochrane database, and Google Scholar, from inception to 2022. Imaging modalities included were dobutamine stress echocardiography (DSE), cardiac magnetic resonance (CMR), single-photon emission computed tomography (SPECT), and positron emission tomography (PET).

RESULTS

A total of 17 studies incorporating a total of 2317 patients were included. Across all imaging modalities, the relative risk of death post-CABG was reduced in patients with versus without viability (random-effects model: odds ratio: 0.42; 95% confidence interval: 0.29-0.61; p < 0.001). Imaging for myocardial viability has significant clinical implications as it can affect the accuracy of the diagnosis, guide treatment decisions, and predict patient outcomes. Generally, based on local availability and expertise, either SPECT or DSE should be considered as the first step in evaluating viability, while PET or CMR would provide further evaluation of transmurality, perfusion metabolism, and extent of scar tissue.

CONCLUSION

The assessment of myocardial viability is an essential component of preoperative evaluation in patients with ischemic heart disease undergoing surgical revascularization. Careful patient selection and individualized assessment of viability remain paramount.

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.

Outcomes of Coronary Artery Bypass Grafting in Patients With Poor Myocardial Viability: A Systematic Review and Meta-Analysis of the Last Decade

OBJECTIVES

Our objective is to assess whether the presence of myocardial viability is a predictor of mortality among patients undergoing coronary artery bypasss grafting (CABG) through a systematic review meta-analysis.

METHODS

Comprehensive review of EMBASE and PubMed in accordance with PRISMA guidelines, including studies of patients undergoing CABG with assessment of myocardial viability and recorded long-term mortality, age and sex. Studies were restricted to the last decade, and data were stratified by imaging modality (magnetic resonance imaging [MRI] or nuclear medicine). Random-effects model for assessing pooled effect, heterogeneity assessment using Chi-square and I² statistics, publication bias assessed by funnel plots and Egger's test.

RESULTS

Meta-analysis of contemporary data (January 2010 to October 2020) yielded 3,621 manuscripts of which 92 were relevant, and 6 appropriate for inclusion with 993 patients. Pooled analysis showed that patients with non-viable myocardium undergoing CABG are at 1.34 times the risk of mortality compared to those with viable myocardium (95% CI 1.01-1.79, p=0.05). Subgroup analysis of the MRI or nuclear medicine modalities was not statistically significant and there was no confounding by age or sex in meta-regression. There was significant heterogeneity in imaging modality and diagnostic criteria, but heterogeneity between study findings was low with an I² statistic of 29%. The risk of publication bias was moderate on the Newcastle-Ottawa Scale), but not statistically significant (Egger's Test coefficient=1.3, 95%CI -0.35-2.61, p=0.10).

CONCLUSIONS

There is a multitude of methods for assessing cardiac viability for coronary revascularisation surgery, making meta-analyses fraught with limitations. Our meta-analysis demonstrates that the finding of non-viable myocardium can not be used draw conclusions for risk assessment in coronary surgery.

Improving Terminology to Describe Coronary Artery Procedures: JACC Review Topic of the Week

Coronary artery disease (CAD) is treated with medical therapy with or without percutaneous coronary intervention (PCI) or coronary artery bypass grafting (CABG). The latter 2 options are commonly referred to as "myocardial revascularization" procedures. We reason that this term is inappropriate because it is suggestive of a single treatment effect of PCI and CABG (ie, the reestablishment of blood flow to ischemic myocardium) and obscures key mechanisms, such as the improvement in coronary flow capability in the absence of ongoing ischemia, the reperfusion in the presence of ischemia, and the prevention of myocardial infarction from CAD progression. We review the current evidence on the topic and suggest the use of a purely descriptive terminology ("invasive treatment by PCI or CABG") which has the potential to improve clinical decision making and guide future trial design.

Myocardial Viability Testing by Positron Emission Tomography: Basic Concepts, Mini-Review of the Literature and Experience From a Tertiary PET Center

Ischemic heart disease ranges in severity from slightly reduced myocardial perfusion with preserved contractile function to chronic occlusion of coronary arteries with myocardial cells replaced by acontractile scar tissue-ischemic heart failure (iHF). Progression towards scar tissue is thought to involve a period in which the myocardial cells are acontractile but still viable despite severely reduced perfusion. This state of reduced myocardial function that can be reversed by revascularization is termed "hibernation." The concept of hibernating myocardium in iHF has prompted an increasing amount of requests for preoperative patient workup, but while the concept of viability is widely agreed upon, no consensus on clinical testing of hibernation has been established. Therefore, a variety of imaging methods have been used to assess hibernation including morphology based (MRI and ultrasound), perfusion based (MRI, SPECT, or PET) and/or methods to assess myocardial metabolism (PET). Regrettably, the heterogeneous body of literature on the subject has resulted in few robust prospective clinical trials designed to assess the impact of preoperative viability testing prior to revascularization. However, the PARR-2 trial and sub-studies has indicated that >5% hibernating myocardium favors revascularization over optimized medical therapy. In this paper, we review the basic concepts and current evidence for using PET to assess myocardial hibernation and discuss the various methodologies used to process the perfusion/metabolism PET images. Finally, we present our experience in conducting PET viability testing in a tertiary referral center.

Dobutamine echocardiography for assessment of viability in the current era

PURPOSE OF REVIEW

Studies from the 1990s and early 2000s documented the utility of dobutamine echocardiography for the prediction of functional recovery and prognosis with revascularization. The results of The Surgical Treatment of Ischemic Heart Failure (STICH) trial called into question the value of viability assessment using dobutamine echocardiography. The purpose of this review is to re-examine the literature on dobutamine echocardiography, put into context the STICH results, and provide insight into the current role of dobutamine echocardiography viability testing.

RECENT FINDINGS

In contrast to the results of previous nonrandomized trials, the STICH trial showed that patients with viability defined by nuclear perfusion imaging or dobutamine echocardiography did not have improved survival with CABG compared with optimal medical therapy. Viability by dobutamine echocardiography was defined as the presence of contractile reserve in at least five segments with baseline dysfunction. The results of dobutamine echocardiography studies published before and after initiation of the STICH trial suggest that the definition of viability utilized in that trial may be suboptimal for assessment of improvement in global function and prognosis in patients undergoing revascularization. Assessment of global contractile reserve using wall motion score (WMS) or ejection fraction may be superior to utilization of a binary definition of viability confined to assessment of contractile reserve in a fixed number of segments because these indices provide information on both the magnitude and extent of contractile reserve of the entire left ventricle (LV).

SUMMARY

Assessment of WMS or ejection fraction with dobutamine echocardiography may be the optimal means of evaluating the impact of viability on prognosis.Video abstract http://links.lww.com/HCO/A56.