Is viability still viable after the STICH trial?

The Current State of Coronary Revascularization: Coronary Artery Bypass Graft Surgery Versus Percutaneous Coronary Interventions

PURPOSE OF REVIEW

The optimal revascularization strategy for coronary artery disease depends on various factors, such as disease complexity, patient characteristics, and preferences. Including a heart team in complex cases is crucial to ensure optimal outcomes. Decision-making between percutaneous coronary intervention and coronary artery bypass grafting must consider each patient's clinical profile and coronary anatomy. While current practice guidelines offer some insight into the optimal revascularization approach for the various phenotypes of coronary artery disease, the evidence to support either strategy continues to evolve and grow. Given the large amount of contemporary data on revascularization, this review aims to comprehensively summarize the literature on coronary artery bypass grafting and percutaneous coronary intervention in patients across the spectrum of coronary artery disease phenotypes.

RECENT FINDINGS

Contemporary evidence suggests that for patients with triple vessel disease, coronary artery bypass grafting is preferred over percutaneous coronary intervention due to better long-term outcomes, including lower rates of death, myocardial infarction, and target vessel revascularization. Similarly, for patients with left main coronary artery disease, both percutaneous coronary intervention and coronary artery bypass grafting can be considered, as they have shown similar efficacy in terms of major adverse cardiac events, but there may be a slightly higher risk of death with percutaneous coronary intervention. For proximal left anterior descending artery disease, both percutaneous coronary intervention and coronary artery bypass grafting are viable options, but coronary artery bypass grafting has shown lower rates of repeat revascularization and better relief from angina. The Synergy Between PCI with Taxus and Cardiac Surgery score can help in decision-making by predicting the risk of adverse events and guiding the choice between percutaneous coronary intervention and coronary artery bypass grafting. European and American guidelines both agree with including a heart team that can develop and lay out individualized, optimal treatment options with respect for patient preferences. The debate between coronary artery bypass grafting versus percutaneous coronary intervention in multiple different scenarios will continue to develop as technology and techniques improve for both procedures. Risk factors, pre, peri, and post-procedural complications involved in both revascularization strategies will continue to be mitigated to optimize outcomes for those patients for which coronary artery bypass grafting or percutaneous coronary intervention provide ultimate benefit. Methods to avoid unnecessary revascularization continue to develop as well as percutaneous technology that may allow patients to avoid surgical intervention when possible. With such changes, revascularization guidelines for specific patient populations may change in the coming years, which can serve as a limitation of this time-dated review.

2021 ACC/AHA/SCAI Guideline for Coronary Artery Revascularization: A Report of the American College of Cardiology/American Heart Association Joint Committee on Clinical Practice Guidelines

AIM

The guideline for coronary artery revascularization replaces the 2011 coronary artery bypass graft surgery and the 2011 and 2015 percutaneous coronary intervention guidelines, providing a patient-centric approach to guide clinicians in the treatment of patients with significant coronary artery disease undergoing coronary revascularization as well as the supporting documentation to encourage their use.

METHODS

A comprehensive literature search was conducted from May 2019 to September 2019, encompassing studies, reviews, and other evidence conducted on human subjects that were published in English from PubMed, EMBASE, the Cochrane Collaboration, CINHL Complete, and other relevant databases. Additional relevant studies, published through May 2021, were also considered.

STRUCTURE

Coronary artery disease remains a leading cause of morbidity and mortality globally. Coronary revascularization is an important therapeutic option when managing patients with coronary artery disease. The 2021 coronary artery revascularization guideline provides recommendations based on contemporary evidence for the treatment of these patients. The recommendations present an evidence-based approach to managing patients with coronary artery disease who are being considered for coronary revascularization, with the intent to improve quality of care and align with patients' interests.

Prevalence and Localization of Hibernating Myocardium Among Patients with Left Ventricular Dysfunction

OBJECTIVE

This study evaluated how much of the myocardium was hibernating in patients with left ventricle dysfunction and/or comorbidities who planned to undergo either surgical or interventional revascularization. Furthermore, this study also identified which irrigation areas of the coronary arteries presented more scar and hibernating tissue.

METHODS

At rest, Tc-99m MIBI SPECT and cardiac F-18 FDG PET/CT images collected between March 2009 and September 2016 from 65 patients (55 men, 10 women, mean age 64±12) were retrospectively analyzed in order to evaluate myocardial viability. The areas with perfusion defects that were considered metabolic were accepted as hibernating myocardium, whereas areas with perfusion defects that were considered non-metabolic were accepted as scar tissue.

RESULTS

Perfusion defects were observed in 26% of myocardium, on average 48% were associated with hibernation whereas other 52% were scar tissue. In the remaining Tc-99m MIBI images, perfusion defects were observed in the following areas in the left anterior descending artery (LAD; 31%), in the right coronary artery (RCA; 23%) and in the Left Circumflex Artery (LCx; 19%) irrigation areas. Hibernation areas were localized within the LAD (46%), LCx (54%), and RCA (64%) irrigation areas. Scar tissue was also localized within the LAD (54%), LCx (46%), and RCA (36%) irrigation areas.

CONCLUSION

Perfusion defects are thought to be the result of half hibernating tissue and half scar tissue. The majority of perfusion defects was observed in the LAD irrigation area, whereas hibernation was most often observed in the RCA irrigation area. The scar tissue development was more common in the LAD irrigation zone.

Early Diagnosis of Cardiovascular Diseases in Workers: Role of Standard and Advanced Echocardiography

Cardiovascular disease (CVD) still remains the main cause of morbidity and mortality and consequently early diagnosis is of paramount importance. Working conditions can be regarded as an additional risk factor for CVD. Since different aspects of the job may affect vascular health differently, it is important to consider occupation from multiple perspectives to better assess occupational impacts on health. Standard echocardiography has several targets in the cardiac population, as the assessment of myocardial performance, valvular and/or congenital heart disease, and hemodynamics. Three-dimensional echocardiography gained attention recently as a viable clinical tool in assessing left ventricular (LV) and right ventricular (RV) function, volume, and shape. Two-dimensional (2DSTE) and, more recently, three-dimensional speckle tracking echocardiography (3DSTE) have also emerged as methods for detection of global and regional myocardial dysfunction in various cardiovascular diseases and applied to the diagnosis of subtle LV and RV dysfunction. Although these novel echocardiographic imaging modalities have advanced our understanding of LV and RV mechanics, overlapping patterns often show challenges that limit their clinical utility. This review will describe the current state of standard and advanced echocardiography in early detection (secondary prevention) of CVD and address future directions for this potentially important diagnostic strategy.

Off-pump coronary artery bypass surgery outcomes in patients with ischaemic left ventricular systolic dysfunction with or without detected viable myocardium

OBJECTIVES

The prognostic value of myocardial viability before coronary bypass grafting remains controversial. The present study evaluated the effects of off-pump coronary artery bypass (OPCAB) grafting on patients with coronary artery disease (CAD) with or without viable myocardium (VM) preoperatively detected via nuclear imaging.

METHODS

A total of 115 consecutive patients with 3-vessel disease and impaired left ventricular ejection fraction (LVEF ≤ 45%) who underwent OPCAB grafting were recruited in this prospective study. The patients were divided into 2 groups based on myocardial viability, the non-viable myocardium (NVM, 55 patients) and VM (60 patients) groups. Positron emission tomography and radionuclide imaging examination were applied to evaluate the myocardium viability. A Kaplan-Meier analysis was conducted to evaluate the 1-year survival rate.

RESULTS

The preoperative data were similar between groups. An improvement in the LVEF was observed in both groups 12 months after OPCAB grafting (P < 0.05). A binary logistic regression revealed that NVM was an independent predictor of a 5% improvement in LVEF at 6 months (P = 0.012). The rate of main adverse cardiovascular and cerebrovascular events (MACCEs) rate at 1 year was similar between the 2 groups (P = 0.06). At 1 year, the death rates were 14.5% in the NVM group and 5% in the VM group (P = 0.17). A Cox regression analysis revealed that NVM and age were independent predictors of mortality [the hazard ratio for death associated with NVM and age were 1.62, 95% confidence interval (CI) = 1.16-2.89, P = 0.036 and 1.05, 95% CI = 0.98-1.12, P =0.025, respectively].

CONCLUSIONS

The MACCEs and mortality rates of the NVM group were higher than those of the VM group. However, OPCAB surgery improved LVEF, regardless of myocardium status. Therefore, the assessment of myocardial viability might not be the sole deciding factor in decision-making process regarding OPCAB surgery.

Updates on Stress Imaging Testing and Myocardial Viability With Advanced Imaging Modalities

OPINION STATEMENT

Non-invasive stress testing plays a key role in diagnosis and risk stratification in patients with coronary artery disease. Technical advances in CT, MRI, and PET have lead to increased utility of these modalities in myocardial perfusion imaging. The aim of the review is to provide a succinct update on CT, PET, and MRI for myocardial stress perfusion imaging.

Intra-procedural determination of viability by myocardial deformation imaging: a randomized prospective study in the cardiac catheter laboratory

BACKGROUND

The benefit of revascularization for functional recovery depends on the presence of viable myocardial tissue.

OBJECTIVE

Myocardial deformation imaging allows determination of myocardial viability.

METHODS

In a first approach, we assessed the optimal cutoff value to determine preserved viability by layer-specific echocardiographic myocardial deformation imaging at rest and low-dose dobutamine (DSE) echocardiography: regional endocardial circumferential strain (eCS) <-19% at rest was as accurate as eCS at DSE. In a main study, 123 patients (66% men, age 59 ± 6 years) with relevant coronary stenoses and corresponding severe regional myocardial dysfunction were included and randomized in 2 groups after coronary angiography: group A: intra-procedural myocardial deformation imaging in the cardiac catheter laboratory (CLab), determination of myocardial viability by regional eCS <-19%, in case of positive viability immediate coronary intervention in the same session. Group B: two-step determination of myocardial viability by cardiovascular magnetic resonance (CMR), in case of positive viability coronary intervention. After 18 months follow-up an analysis of the endpoints regarding cardiovascular events, left ventricular (LV) function, and comparison of cost was performed.

RESULTS

Group A (N = 61) and group B (N = 62) showed no differences concerning localization of the coronary stenosis, comorbidities, or medical therapy. Cardiovascular events at 18-month follow-up were as follows: group A 13% (N = 10) vs. group B 14% (N = 9, p = 0.288); improvement of LV function: group A: +7 ± 2% vs. group B: +7 ± 3%, p = 0.963; costs: group A: 3096 Dollar vs. group B: 6043 Dollar, p < 0.001.

CONCLUSION

Intra-procedural determination of myocardial viability by myocardial deformation imaging in the CLab is feasible, safe, and cost effective and may become an emerging alternative to the current practice of two-stage viability diagnostics.

Prognostic value of cardiac power output to left ventricular mass in patients with left ventricular dysfunction and dobutamine stress echo negative by wall motion criteria

AIMS

Cardiac power output to left ventricular mass (power/mass) is an index of myocardial efficiency reflecting the rate at which cardiac work is delivered with respect to the potential energy stored in the left ventricular mass. In the present study, we sought to investigate the capability of power/mass assessed at peak of dobutamine stress echocardiography to predict mortality in patients with ischaemic cardiomyopathy and no inducible ischaemia.

METHODS AND RESULTS

One-hundred eleven patients (95 males; age 68 ± 10 years) with 35 ± 7% mean left ventricular ejection fraction and a dobutamine stress echocardiography (up to 40 µg/kg/min) negative by wall motion criteria formed the study population. Power/mass at peak stress was obtained as the product of a constant (K = 2.22 × 10^-1) with cardiac output and the mean arterial pressure divided by left ventricular mass to convert the units to W/100 g. Patients were followed up for a median of 29 months (inter-quartile range 16-72 months). All-cause mortality was the only accepted clinical end point. Mean peak-stress power/mass was 0.70 ± 0.31 W/100 g. During follow-up, 29 deaths (26%) were registered. With a receiver operating characteristic analysis, a peak-stress power/mass ≤0.50 W/100 g [area under curve 0.72 (95% CI 0.63; 0.80), sensitivity 59%, specificity 80%] was the best value for predicting mortality. Univariate prognostic indicators were age, male sex, peak-stress ejection fraction, peak-stress stroke volume, peak-stress cardiac output, peak-stress cardiac power output ≤1.48 W, and peak-stress power/mass ≤0.50 W/100 g. At multivariate analysis, age (HR 1.08, 95% CI 1.04; 1.14; P = 0.004) and peak-stress power/mass ≤0.50 W/100 g (HR 4.05, 95% CI 1.36; 12.00; P = 0.01) provided independent prognostic information. Three-year mortality was 14% in patients with peak-stress power/mass >0.50 W/100 g and 47% in those with peak-stress power/mass ≤0.50 W/100 g (log-rank 20.4; P < 0.0001).

CONCLUSION

Power/mass assessed at peak of dobutamine stress echocardiography allows effective prognostication in patients with ischaemic cardiomyopathy and test result negative by wall motion criteria. In particular, a peak-stress power/mass ≤50 W/100 g is a strong and multivariable predictor of mortality.

Systematic review and modelling of the cost-effectiveness of cardiac magnetic resonance imaging compared with current existing testing pathways in ischaemic cardiomyopathy

BACKGROUND

Cardiac magnetic resonance imaging (CMR) is increasingly used to assess patients for myocardial viability prior to revascularisation. This is important to ensure that only those likely to benefit are subjected to the risk of revascularisation.

OBJECTIVES

To assess current evidence on the accuracy and cost-effectiveness of CMR to test patients prior to revascularisation in ischaemic cardiomyopathy; to develop an economic model to assess cost-effectiveness for different imaging strategies; and to identify areas for further primary research.

DATA SOURCES

Databases searched were: MEDLINE including MEDLINE In-Process & Other Non-Indexed Citations Initial searches were conducted in March 2011 in the following databases with dates: MEDLINE including MEDLINE In-Process & Other Non-Indexed Citations via Ovid (1946 to March 2011); Bioscience Information Service (BIOSIS) Previews via Web of Science (1969 to March 2011); EMBASE via Ovid (1974 to March 2011); Cochrane Database of Systematic Reviews via The Cochrane Library (1996 to March 2011); Cochrane Central Register of Controlled Trials via The Cochrane Library 1998 to March 2011; Database of Abstracts of Reviews of Effects via The Cochrane Library (1994 to March 2011); NHS Economic Evaluation Database via The Cochrane Library (1968 to March 2011); Health Technology Assessment Database via The Cochrane Library (1989 to March 2011); and the Science Citation Index via Web of Science (1900 to March 2011). Additional searches were conducted from October to November 2011 in the following databases with dates: MEDLINE including MEDLINE In-Process & Other Non-Indexed Citations via Ovid (1946 to November 2011); BIOSIS Previews via Web of Science (1969 to October 2011); EMBASE via Ovid (1974 to November 2011); Cochrane Database of Systematic Reviews via The Cochrane Library (1996 to November 2011); Cochrane Central Register of Controlled Trials via The Cochrane Library (1998 to November 2011); Database of Abstracts of Reviews of Effects via The Cochrane Library (1994 to November 2011); NHS Economic Evaluation Database via The Cochrane Library (1968 to November 2011); Health Technology Assessment Database via The Cochrane Library (1989 to November 2011); and the Science Citation Index via Web of Science (1900 to October 2011). Electronic databases were searched March-November 2011.

REVIEW METHODS

The systematic review selected studies that assessed the clinical effectiveness and cost-effectiveness of CMR to establish the role of CMR in viability assessment compared with other imaging techniques: stress echocardiography, single-photon emission computed tomography (SPECT) and positron emission tomography (PET). Studies had to have an appropriate reference standard and contain accuracy data or sufficient details so that accuracy data could be calculated. Data were extracted by two reviewers and discrepancies resolved by discussion. Quality of studies was assessed using the QUADAS II tool (University of Bristol, Bristol, UK). A rigorous diagnostic accuracy systematic review assessed clinical and cost-effectiveness of CMR in viability assessment. A health economic model estimated costs and quality-adjusted life-years (QALYs) accrued by diagnostic pathways for identifying patients with viable myocardium in ischaemic cardiomyopathy with a view to revascularisation. The pathways involved CMR, stress echocardiography, SPECT, PET alone or in combination. Strategies of no testing and revascularisation were included to determine the most cost-effective strategy.

RESULTS

Twenty-four studies met the inclusion criteria. All were prospective. Participant numbers ranged from 8 to 52. The mean left ventricular ejection fraction in studies reporting this outcome was 24-62%. CMR approaches included stress CMR and late gadolinium-enhanced cardiovascular magnetic resonance imaging (CE CMR). Recovery following revascularisation was the reference standard. Twelve studies assessed diagnostic accuracy of stress CMR and 14 studies assessed CE CMR. A bivariate regression model was used to calculate the sensitivity and specificity of CMR. Summary sensitivity and specificity for stress CMR was 82.2% [95% confidence interval (CI) 73.2% to 88.7%] and 87.1% (95% CI 80.4% to 91.7%) and for CE CMR was 95.5% (95% CI 94.1% to 96.7%) and 53% (95% CI 40.4% to 65.2%) respectively. The sensitivity and specificity of PET, SPECT and stress echocardiography were calculated using data from 10 studies and systematic reviews. The sensitivity of PET was 94.7% (95% CI 90.3% to 97.2%), of SPECT was 85.1% (95% CI 78.1% to 90.2%) and of stress echocardiography was 77.6% (95% CI 70.7% to 83.3%). The specificity of PET was 68.8% (95% CI 50% to 82.9%), of SPECT was 62.1% (95% CI 52.7% to 70.7%) and of stress echocardiography was 69.6% (95% CI 62.4% to 75.9%). All currently used diagnostic strategies were cost-effective compared with no testing at current National Institute for Health and Care Excellence thresholds. If the annual mortality rates for non-viable patients were assumed to be higher for revascularised patients, then testing with CE CMR was most cost-effective at a threshold of £20,000/QALY. The proportion of model runs in which each strategy was most cost-effective, at a threshold of £20,000/QALY, was 40% for CE CMR, 42% for PET and 16.5% for revascularising everyone. The expected value of perfect information at £20,000/QALY was £620 per patient. If all patients (viable or not) gained benefit from revascularisation, then it was most cost-effective to revascularise all patients.

LIMITATIONS

Definitions and techniques assessing viability were highly variable, making data extraction and comparisons difficult. Lack of evidence meant assumptions were made in the model leading to uncertainty; differing scenarios were generated around key assumptions.

CONCLUSIONS

All the diagnostic pathways are a cost-effective use of NHS resources. Given the uncertainty in the mortality rates, the cost-effectiveness analysis was performed using a set of scenarios. The cost-effectiveness analyses suggest that CE CMR and revascularising everyone were the optimal strategies. Future research should look at implementation costs for this type of imaging service, provide guidance on consistent reporting of diagnostic testing data for viability assessment, and focus on the impact of revascularisation or best medical therapy in this group of high-risk patients.

FUNDING

The National Institute of Health Technology Assessment programme.

Clinical positron emission tomography/magnetic resonance imaging applications

Although clinical positron emission tomography (PET)/computed tomography (CT) applications were obvious and have completely replaced PET in oncology, clinical applications of PET/magnetic resonance (MR) are currently not clearly defined. This is due to the lack of clinical data, which is mainly because PET/MR technology is not clinically mature at this point. Open issues are technical and concern ease of obtaining PET attenuation correction maps, dealing with, for example, MR surface coil metal in the PET field-of-view and appropriate workflows leading to a cost-effective examination. All issues can be circumvented by using a shuttle-connected PET/CT-MR system, but the penalty is that simultaneous PET and MR imaging are not possible and potential motion between examinations may occur. Clinically, some systems installed worldwide start to have a reasonable bulk of clinical data. Preliminary results suggest that in oncology, PET/MR may have advantages over PET/CT in head and neck imaging. In liver imaging, more PET-positive lesions are seen on MR than on CT, but that does not mean that PET/MR is superior to PET/CT. Possibly in some settings where a contrast-enhanced PET/CT is needed to be diagnostic, PET/MR can be done without contrast media. Although PET/CT has virtually no role in brain imaging, this may be an important domain for PET/MR, particularly in dementia imaging. The role of PET/MR in the heart is as yet undefined, and much research will have to be done to elucidate this role. At this point, it is also not clear where the simultaneity afforded by a fully integrated PET/MR is really needed. Sequential data acquisition even on separate systems and consecutive software image fusion may well be appropriate. With the increasing installed base of systems, clinical data will be forthcoming and define more clearly where there is clinical value in PET/MR at an affordable price.

Noninvasive assessment myocardial viability: current status and future directions

Observations of reversibility of cardiac contractile dysfunction in patients with coronary artery disease and ischemia were first made more than 40 years ago. Since that time a wealth of basic science and clinical data has been gathered exploring the mechanisms of this phenomenon of myocardial viability and relevance to clinical care of patients. Advances in cardiac imaging techniques have contributed greatly to knowledge in the area, first with thallium-201 imaging, then later with Tc-99m-based tracers for SPECT imaging and metabolic tracers used in conjunction with positron emission tomography (PET), most commonly F-18 FDG in conjunction with blood flow imaging with N-13 ammonia or Rb-82 Cl. In parallel, stress echocardiography has made great progress also. Over time observational studies in patients using these techniques accumulated and were later summarized in several meta-analyses. More recently, cardiac magnetic resonance imaging (CMR) has contributed further information in combination with either late gadolinium enhancement imaging or dobutamine stress. This review discusses the tracer and CMR imaging techniques, the pooled observational data, the results of clinical trials, and ongoing investigation in the field. It also examines some of the current challenges and issues for researchers and explores the emerging potential of combined PET/CMR imaging for myocardial viability.

The year 2012 in the European Heart Journal-Cardiovascular Imaging: Part I

The new multi-modality cardiovascular imaging journal, European Heart Journal - Cardiovascular Imaging, was started in 2012. During its first year, the new Journal has published an impressive collection of cardiovascular studies utilizing all cardiovascular imaging modalities. We will summarize the most important studies from its first year in two articles. The present 'Part I' of the review will focus on studies in myocardial function, myocardial ischaemia, and emerging techniques in cardiovascular imaging.

Assessing the available techniques for testing myocardial viability: what does the future hold?

Left ventricular dysfunction in the setting of severe coronary artery disease poses a major diagnostic and therapeutic dilemma. While this clinical scenario is generally associated with poor outcomes, some but not all patients benefit from coronary revascularization. For example, patients with severe, transmural myocardial infarctions may derive little or no functional benefit from revascularization, as the underlying myocardium is irreversibly scarred. Furthermore, these patients may be exposed to high procedural risks with a low likelihood of deriving any perceivable benefit. Conversely, hibernating myocardium reflects a substrate whereby the nonfunctioning myocytes are chronically ischemic but may be viable. Existing data are somewhat inconclusive with regard to the benefits of performing viability testing in patients with ischemic cardiomyopathy. While this testing may predict regional and global functional myocardial recovery, the ability of viability studies to predict survival and prognosis remains unproven in prospective studies to date. Yet, viability testing may still be a valuable tool to guide therapeutic options in selected patients. A variety of noninvasive viability tests are available and newer technologies, such as PET and cardiac MRI, are likely to advance the scientific field in years to come.