Myocardial Viability Testing to Guide Coronary Revascularization

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.

Developing and evaluating a chronic ischemic cardiomyopathy in swine model by rest and stress CMR

A large animal model of chronic coronary artery disease (CAD) is crucial for the understanding the underlying pathophysiological processes of chronic CAD and consequences for cardiac structure and function. The goal of this study was to develop a chronic model of CAD in a swine model and to evaluate the changes of myocardial structure, myocardial motility, and myocardial viability during coronary stenosis. A total of 30 swine (including 24 experimental animals and 6 controls) were enrolled. The chronic ischemia model was constructed by using Ameroid constrictor in experimental group. The 24 experimental animals were further divided into 4 groups (6 animals in each group) and were sacrificed at 1, 2, 3 and 4 weeks after operation for pathological examination, respectively. Cardiac magnetic resonance (CMR) was performed preoperatively and weekly postoperatively until sacrificed both in experimental and control group. CMR cine images, rest/adenosine triphosphate (ATP) stress myocardial contrast perfusion and LGE were performed and analyzed. The rest wall thickening (WT) score was calculated from rest cine images. The MPRI (myocardial perfusion reserve index) and MPR (myocardial perfusion reserve) were calculated based on rest and stress perfusion images. Pathology staining including triphenyltetrazolium chloride, HE and picrosirus red staining were performed after swine were sacrificed and collagen volume fraction (CVF) was calculated. The time to formation of ischemic, hibernating, and infarcted myocardium was recorded. In experimental group, from 1w to 4w after surgery, the rest WT score decreased gradually from 35.2 ± 2.0%, 32.0 ± 2.9% to 30.5 ± 3.0% and finally 29.06 ± 1.78%, p < 0.001. Left ventricular ejection fraction was gradually impaired after modeling (58.9 ± 12.6%, 56.3 ± 10.1%, 55.3 ± 9.0%, 53.8 ± 9.9%, respectively). And the MPR and MPRI also decreased stepwise with extent of surgery time (MPRI dropped from 2.1 ± 0.4, 2.0 ± 0.2 to 1.8 ± 0.3 and finally 1.7 ± 0.1, p = 0.004; MPR dropped from 2.3 ± 0.4, 2.1 ± 0.2 to 1.9 ± 0.4 and finally 1.8 ± 0.1, p < 0.001). Stronger associations between MPR, MPRI and CVF were paralleled lower wall thickening scores in fibrosis-affected areas. The ischemic myocardium was first appeared in the first week after surgery (involving ten segments), hibernated myocardium was first appeared in the second week after surgery (involving seventeen segments). LGE was first appeared in eight swine in the third weeks after surgery (16 segments). At 4w after surgery, average 9.6 g scar tissue was found among 6 swine. At the same time, histological analysis established the presence of fibrosis and ongoing apoptosis in the infarcted area. In conclusion, our study provided valuable insights into the pathophysiological processes of chronic CAD and its consequences for cardiac structure and function in a large animal model through combining myocardial motion and stress perfusion.

Myocardial fibrosis in rheumatic heart disease: emerging concepts and clinical implications

Rheumatic heart disease (RHD) remains a significant cardiovascular burden in the world even though it is no longer common in affluent countries. Centuries of history surrounding this disease provide us with a thorough understanding of its pathophysiology. Infections in the throat, skin, or mucosa are the gateway for Group A Streptococcus (GAS) to penetrate our immune system. A significant inflammatory response to the heart is caused by an immunologic cascade triggered by GAS antigen cross-reactivity. This exaggerated immune response is primarily responsible for cardiac dysfunction. Recurrent inflammatory processes damage all layers of the heart, including the endocardium, myocardium, and pericardium. A vicious immunological cycle involving inflammatory mediators, angiotensin II, and TGF-β promotes extracellular matrix remodeling, resulting in myocardial fibrosis. Myocardial fibrosis appears to be a prevalent occurrence in patients with RHD. The presence of myocardial fibrosis, which causes left ventricular dysfunction in RHD, might be utilized to determine options for treatment and might also be used to predict the outcome of interventions in patients with RHD. This emerging concept of myocardial fibrosis needs to be explored comprehensively in order to be optimally utilized in the treatment of RHD.

The impact of viability assessment using cardiac MRI and echocardiogram on the outcome of revascularization in patients with multi-vessels coronary artery disease and moderate to severe ischemic cardiomyopathy

OBJECTIVES

To investigate the influence of viability assessment in the management of patients with ischemic cardiomyopathy (ICM).

METHODS

This retrospective cohort study included all patients with ICM with moderate to severely reduced left ventricular ejection fraction (LVEF) who underwent viability assessment using cardiac magnetic resonance imaging (MRI) and echocardiogram as modalities of imaging. In addition, LVEF, modality of choice, and treatment plans were all extracted as main variables from the electronic database. One hundred 6 patients who met the inclusion criteria from December 2014 to December 2019 were included.

RESULTS

Posttreatment LVEF improved by 5% in the viable group compared to the nonviable group (p=0.016). Regardless of the treatment received, 6 (8.8%) patients in the viable group died due to cardiac causes after an 18-month follow-up period; in contrast, 7 (18.4%) patients died due to cardiac causes in the nonviable group. However, despite that difference, this was not statistically significant (p=0.153). Medical therapy alone was observed in 32 (84.2%) patients in the nonviable group compared to 32 (47.1%) in the viable group (p<0.001). Although the reduction in hospitalization for cardiac reasons was not statistically significant, the viable arm had 50% fewer hospitalizations than the nonviable arm (p=0.051).

CONCLUSION

Patients with viable myocardium had better outcomes in which LVEF significantly improved posttreatment. Additionally, there was a reduction in the number of hospitalizations for cardiac reasons in the viable group compared to the nonviable group, even though the difference was not statistically significant. However, further studies with a larger number of patients are needed to determine a definite conclusion.

Concomitant Mitral Valve Surgery Versus No Intervention in Patients with Moderate Ischemic Mitral Regurgitation Undergoing Coronary Artery Bypass Grafting: A Propensity Score Analysis

Objectives

Ischemic mitral valve regurgitation (IMR) in patients undergoing coronary artery bypass grafting (CABG) is associated with worse long-term outcomes. This study aimed to assess the impact of mitral valve repair with CABG in patients with moderate IMR.

Materials

This observational study enrolled 3,215 consecutive patients from the Juntendo CABG registry with moderate IMR and multivessel coronary artery disease who underwent CABG between 2002 and 2017.

Methods

The CABG alone and CABG with mitral valve surgery (MVs) groups were compared. The propensity score was calculated for each patient. Long-term all-cause death, cardiac death, and major adverse cardiac and cerebrovascular events (MACCEs) were compared.

Results

Our database had 101 patients who underwent CABG with moderate IMR. Propensity score matching selected 40 pairs for final analysis. MVs was associated with increased risks of postoperative atrial fibrillation, blood transfusion, and longer hospitalization. Long-term outcomes, including all-cause mortality, cardiac mortality, and the incidence of MACCEs were similar.

Conclusion

Surgical treatment of moderate IMR combined with CABG was related to increased risk of several non-fatal short-term complications when compared to CABG alone, with similar long-term outcomes. Further studies are needed to determine the effects of MVs in patients with moderate IMR and severe coronary artery disease.

Outcomes of Patients Undergoing Closed Traction CoronaryEndarterectomy: A Long-Term Single Center Study

Background-Coronary endarterectomy (CEA) is an option for treating severely diffused coronary artery diseases; however, many surgeons avoid performing it due to its complexity and reported controversial results. Therefore, we aimed to review the results of patients undergoing CEA within coronary artery bypass grafting (CABG). Methods-This is a retrospective observational study evaluating the results of patients undergoing CEA within CABG surgery between March 2003 and February 2018. Follow-up via active personal and/or telephone interviews was performed to evaluate long-term clinical outcomes. The study endpoints included early postoperative incidence of myocardial infarction or cardiac mortality, long-term survival, and freedom from major adverse cardiac and cerebrovascular events (MACCE). Results-A total of 326 patients were included in this study for evaluation. The patients' mean age was 67 years; 88% were male, and most presented with three-vessel disease, reporting a mean SYNTAX score of 33.1 ± 12. Approximately 5.5% (n = 18) of the patients had undergone previous CABG surgery. A total of 394 CEAs within a mean of 4.3 ± 1.1 grafts per patient were performed. The indication for CEA was either totally (n = 111, 28.2%) or sub-totally (n = 283, 71.8%) occluded coronary arteries. Early results included perioperative myocardial infarction in eight (2.4%), stroke in eight (2.4%), and in-hospital mortality in thirteen (4.0%) patients. Long-term clinical follow-up reported mortality in 27.6% and overall incidence of MACCE in 41.4% of the patients at the ten-year follow-up. Conclusions-Patients with severe and diffuse CAD are difficult candidates for surgical revascularization. CEA offers an option to allow complete revascularization, even in the case of chronic occlusion, when the myocardium is still viable. The closed traction CEA technique presented here is our preferred method; it achieves satisfactory short- and long-term results.

MULTIMODAL LOGIT MODEL FOR PREDICTING THE EFFICIENCY OF MYOCARDIAL REVASCULARIZATION BY THE METHOD OF CORONARY ARTERY BYPASS GRAFTING IN PATIENTS WITH CORONARY HEART DISEASE

OBJECTIVE

building of a mathematical logit model for possible prediction of the outcome of surgical treatment bythe method of coronary artery bypass grafting (CABG) in patients of different groups with coronary heart disease(CHD) based on myocardial viability (MV) assessment.

MATERIAL AND METHODS

To implement the set clinical tasks, 62 patients with coronary heart disease with preservedsystolic function and systolic dysfunction were examined. The mean age of the subjects was (59.6 ± 8.2) years. 35(56 %) patients had a variant of heart failure (HF) with an ejection fraction (EF) of 45 % or less. 27 (44 %) patientshad EF of 46 % or more. 5 (8.0 %) patients denied myocardial infarction (MI). Myocardial scintigraphy (MSG) wasperformed on Infinia Hawkeye combined gamma-camera (GE, USA) with integrated CT. The studies were performedin SPECT and SPECT / CT with ECG synchronization (Gated SPECT) modes. 99mTc-MIBI with an activity of 555-740 MBqwas used. MSG was performed in the dynamics of treatment (before CABG and after CABG) according to One Day Restprotocol. A total of 124 scintigraphic studies were performed.

RESULTS

Samples of patients studied «before» and «after» the treatment were compared using nonparametricWilcoxon test (Wilcoxon Matched Pairs Test). A multivariate regression model, that reflects a statistically significanteffect on the treatment response (MV after treatment) of such cardiac activity indicators as LV EF (%), coronary bedlesion area and MV level (%) before treatment, was built. The above-described regression relationship between thethree above-defined functional factors of cardiac activity before treatment and the therapeutic effect in the formof the change in MV can be construed as a diagnostic model that predicts the treatment outcome.

CONCLUSIONS

This scientific study allows to build logit models to predict the expected outcome of coronary heartdisease surgical treatment in patients of different groups. The presented multivariate regression model is characterised by a sufficiently high for biostatistical studies adjusted coefficient of determination (Adjusted R2 = 0,893 (F = 173,4; p < 0,001)).

Validity of resting strain/strain rate in prediction of myocardial viability

To evaluate the validity of the resting strain/strain rate measurements in predicting myocardial viability taking delayed enhancement cardiac magnetic resonance imaging as the gold standard. A cohort of 60 patients at three months followed up after acute myocardial infarction were recruited for this study. Resting echocardiography with offline analysis of deformation indices and gadolinium contrast enhanced cardiac magnetic resonance imaging were applied for all patients. For the final assessment, 268 segments with significant resting wall motion abnormalities were presented. Resting longitudinal strain was significantly (p < 0.05) higher in viable, compared with non-viable segments in all the studied individual myocardial segments (apical inferior, mid antro-lateral, mid-inferolateral, mid inferoseptum, and all other segments). Likewise, resting longitudinal strain rate was significantly (p < 0.05) higher in viable, compared with non-viable segments in almost all studied individual myocardial segments apart from apical inferior, mid inferolateral and basal antro-septum (p = 0.245, p = 0.098, p = 0.097 respectively). Resting Strain and Resting Strain rate could be used as accurate predictors of myocardia viability following acute myocardial infarction.

Evaluating the role of left ventricle global longitudinal strain in myocardial perfusion defect assessment

Myocardial perfusion defect, assessed with single photon emission computed tomography (SPECT), is useful for patient management and risk stratification. Left ventricle Global Longitudinal Strain (LV GLS) has gained interest for observing subclinical LV dysfunction. We aimed to investigate the utility of LV GLS in evaluating myocardial perfusion defect. A retrospective study of all patients who underwent SPECT and LV GLS at Tel Aviv Sourasky medical center. Overall, 86 patients were included. LV GLS and SPECT correlated in the base and apex sections for infraction, and in the apex only for ischemia. Adjusted analysis showed a significant correlation between LV GLS of both the mid and apical section and infarction by SPECT, but no association with ischemia. No associations were found by arterial supply territory. A sub-analysis of patients without left bundle branch block (LBBB) strengthened the correlations, with a 58-70% higher chance of both fixed and reversible defects for every 1-unit decrease LV GLS in the mid and apical sections. LV GLS effectively evaluated the presence of infarction by SPECT in the mid and apical sections, particularly in patients without LBBB. Due to its high availability, LV GLS may have a role in evaluating myocardial perfusion defect.

Myocardial viability imaging using a novel non-breath-hold cardiac MRI protocol: a comparative assessment with 18F-FDG PET

Background

Delayed contrast enhancement on cardiac magnetic resonance imaging is a well-established MRI technique for the evaluation of myocardial tissue viability. A comprehensive cardiac MRI protocol for myocardial viability comprises of multiple breath hold sequences to provide information regarding chamber volumes, myocardial mass, and function in addition to viability. However, its routine use is limited mainly by lengthy acquisition time and patient’s inability to hold breath in multiple breath hold sequences. The important question to which the referring cardiologists/cardiac surgeons are seeking answer is that “What are the viable vascular territories that will benefit from revascularization?” In this study, we have analyzed the utility of non-breath-hold rapid delayed contrast-enhanced cardiac MR imaging protocol for myocardial viability assessment with 18-flourodeoxyglucose positron emission tomography (18F-FDG PET) as the reference standard.

Results

Forty patients of ischemic heart disease who met the inclusion criteria were included. All patients underwent both 18F-FDG PET and delayed contrast-enhanced cardiac magnetic resonance imaging as per the non-breath-hold protocol. In this free-breathing protocol, the breath hold cine sequences were omitted and, after localizers, post-contrast scans were obtained with a time gap of 15 min post-contrast administration. A total number of 680 myocardial segments and corresponding 120 vascular territories were assessed. MRI and 18F-FDG PET images were analyzed using a 17-segment model as proposed by AHA. Sensitivity, specificity, positive predictive value, and negative predictive value of non-breath-hold rapid delayed contrast-enhanced cardiac MR imaging protocol for assessing myocardial viability (on segment analysis) was 95.5%, 65.59%, 88.0%, and 84.72%, respectively, and of vascular territory analysis were 96.77%, 92.59%, 97.83%, and 89.29%, respectively, in relation to 18F-FDG PET used as the reference standard. Spearman’s rank correlation coefficient is 0.62.

Conclusion

This modified non-breath-hold delayed contrast-enhanced cardiac MR imaging protocol is a reliable tool to answer the clinically relevant question of myocardial viability with a significant reduction in acquisition time and overcomes the limiting need of breath hold.

Can the degree of coronary collateralization be used in clinical routine as a valid angiographic parameter of viability?

The success rate of percutaneous coronary artery intervention (PCI) of chronic total occlusion (CTO) lesions have increased in the recent years. However, improvement of function is only possible when significant myocardial viability is present. One of the most important factors of maintaining myocardial viability is the opening and development of collaterals. Our hypothesis was that with a higher degree of collaterals more viable myocardium is present. In 38 patients we compared the degree of collaterals, evaluated with a conventional coronary angiogram (CCA) and graded by the Rentrop classification to transmural extent of the scar obtained in a viability study with magnetic resonance (MRI). We found a statistically significant association of the degree of collaterals determined with Rentrop method and transmural extent of the scar as measured by CMR (p = 0.001; Tau = -0.144). Additionally, associations showed an increase in the ratio between viable vs. non-viable myocardium with the degree of collaterals. Our study suggests that it may be beneficial to routinely grade the collaterals at angiography in patients with CTO as an assessment of myocardial viability.

The duration of early systolic lengthening may predict ischemia from scar tissue in patients with chronic coronary total occlusion lesions

In this study, we aimed to investigate the predictive value of early systolic lengthening duration in differentiating myocardial ischemia from scar tissue in patients with chronic coronary total occlusion. A total of 69 patients were included in the study. The participating patients were divided into two groups as 35 patients with ischemia and 34 patients with scar tissue based on the results of the myocardial perfusion scintigraphy. In the scar group compared to the ischemia group; LVEF, GLS, SRS', and the duration of early systolic lengthening were significantly lower; whereas, EDV, ESV, and WMSI were significantly higher in the scar group compared to the ischemia group. In the multivariate logistic regression test, LVEF (OR 1.150, 95% CI 1.044-1.268, p = 0.005) and duration of early systolic lengthening (OR 1.021, 95% CI 1.004-1.039, p = 0.016) were determined as independent predictive parameters for ischemia detected by myocardial perfusion scintigraphy. Duration of early systolic lengthening obtained by speckle tracking echocardiography in patients with chronic total occlusion lesions may be useful in differentiating ischemia from scar tissue detected in myocardial perfusion scintigraphy. Prolonged duration of early systolic lengthening in patients with chronic total occlusion lesions was related to the presence of ischemia detected by myocardial perfusion scintigraphy.