Myocardial Viability on Cardiac Magnetic Resonance

[Prediction of myocardial contractility after coronary bypass surgery according to preoperative contrast-enhanced magnetic resonance imaging and echocardiography]

OBJECTIVE

To establish the criteria for reversibility of myocardial contractility in patients with coronary artery disease (CAD) after coronary artery bypass grafting considering data of cardiac magnetic resonance imaging (MRI) and echocardiography.

MATERIAL AND METHODS

We studied the results of coronary artery bypass grafting in 186 patients with CAD complicated by reduced left ventricular ejection fraction (<30%). All patients underwent cardiac MRI and echocardiography before surgery. Immediate and long-term results were evaluated according to echocardiography and MRI data.

RESULTS

We confirmed the previously established predictors of improvement in left ventricular contractility: diastolic IVST ≥10.5 mm and PWT ≥9.5 mm, score of LV myocardium damage according to MRI with delayed contrast enhancement (p<0.05). Multivariate analysis makes it possible to calculate prognostic index and obtain information about further myocardial contractility after revascularization with an error of 6%.

CONCLUSION

Echocardiography and contrast-enhanced cardiac MRI are valuable to assess morphological and functional state of the left ventricle in patients with ischemic cardiomyopathy and preoperatively determine functional reserve of the myocardium.

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.

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.

Effect of Myocardial Viability Assessed by Cardiac Magnetic Resonance on Survival in Patients With Severe Left Ventricular Dysfunction

Background: Myocardial viability assessment in revascularization of ischemic heart failure remains controversial. This study evaluated the prognostic utility of cardiac magnetic resonance (CMR) late gadolinium enhancement (LGE) in ischemic heart failure.

Methods and Results: This study retrospectively analyzed subjects with ischemic heart failure and left ventricular ejection fraction (LVEF) ≤35%, who underwent CMR at a single center in 2004–2014 before undergoing coronary artery bypass grafting (CABG) or optimal medical therapy (OMT). Analyses were stratified by treatment. Myocardial segments were deemed non-viable if LGE exceeded 50% wall thickness. Overall and anterior viability were assessed. Outcomes were all-cause mortality, cardiovascular (CV) mortality and major adverse CV events. Among 165 subjects (mean (±SD) age 57.5±8.5 years, 152 males), 79 underwent CABG and 86 received OMT. A greater number of non-viable segments was significantly associated with higher all-cause and CV mortality in the CABG group (adjusted hazard ratios 1.17 [95% confidence interval {CI} 1.01–1.37; P=0.04] and 1.25 [95% CI 1.01–1.56; P=0.045], respectively), but not in the OMT (P>0.05) group. Anterior wall viability did not affect outcomes.

Conclusions: The extent of myocardial viability assessed by LGE appeared to identify patients with a differential survival benefit from CABG in this retrospective, small cohort study. These findings raise interesting hypotheses that need to be validated in larger prospective studies.

Microencapsulated Insulin-Like Growth Factor-1 therapy improves cardiac function and reduces fibrosis in a porcine acute myocardial infarction model

Insulin-like growth factor-1 (IGF-1) has demonstrated beneficial effects after myocardial infarction (MI). Microencapsulation of IGF-1 could potentially improve results. We aimed to test the effect of an intracoronary (IC) infusion of microencapsulated IGF-1 in a swine acute MI model. For that purpose IC injection of a 10 ml solution of 5 × 106 IGF-1 loaded microspheres (MSPs) (n = 8, IGF-1 MSPs), 5 × 106 unloaded MSPs (n = 9; MSPs) or saline (n = 7; CON) was performed 48 hours post-MI. Left ventricular ejection fraction (LVEF), indexed ventricular volumes and infarct size (IS) were determined by cardiac magnetic resonance at pre-injection and 10 weeks. Animals were euthanized at 10 weeks, and myocardial fibrosis and vascular density were analysed. End-study LVEF was significantly greater in IGF-1 MSPs compared to MSPs and CON, while ventricular volumes exhibited no significant differences between groups. IS decreased over time in all groups. Collagen volume fraction on the infarct area was significantly reduced in IGF-1 MSPs compared to CON and MSPs. Vascular density analysis of infarct and border zones showed no significant differences between groups. In conclusion, the IC injection of 5 × 106 IGF-1 loaded MSPs in a porcine acute MI model successfully improves cardiac function and limits myocardial fibrosis, which could be clinically relevant.

Assessment of myocardial viability by cardiac MRI

PURPOSE OF REVIEW

Left ventricular systolic dysfunction because of coronary artery disease is common, and ascertaining which patients will benefit from revascularization can be challenging. Viability testing is an accepted means by which to base this decision, with multiple noninvasive imaging modalities available for this purpose. This review aims to highlight the key role of cardiac magnetic resonance in myocardial viability assessment, with a focus on its unique strengths over other imaging modalities.

RECENT FINDINGS

Transmural extent of hyperenhancement with late gadolinium imaging has been shown to be greater acutely in ST elevation myocardial infarction patients undergoing primary percutaneous coronary intervention and regress at follow-up studies. An explanation for this reported phenomenon and an argument against redefining CMR viability criteria in the acute setting will be offered.

SUMMARY

Although not universally available, cardiac magnetic resonance is an exceptionally powerful and well tolerated imaging modality that should be considered when viability testing will influence patient management. Although observational outcomes data suggest a promising prognostic role for viability, randomized studies in this area are needed.

Advances in MRI Applications to Diagnose and Manage Cardiomyopathies

PURPOSE OF REVIEW

The prevalence of heart failure continues to rise, and imaging characterization of the cardiomyopathic process is important for identifying myocardial disease, initiating appropriate treatment, and improving outcomes. We aimed to summarize recent advances in cardiac magnetic resonance imaging (CMR) applications for the diagnosis, characterization, and implications on management of various cardiomyopathies.

RECENT FINDINGS

Parametric mapping by CMR has emerged as an important advancement in quantification of myocardial fibrosis, increased extracellular space, and myocardial edema. In addition, improved assessment of myocardial function with myocardial strain assessment may provide early identification of patients at risk and determining responsiveness to therapeutic interventions. Novel MRI techniques and the advent of artificial intelligence may help to uncover important mechanistic insights into the cardiomyopathic process. Innovative CMR techniques continue to evolve, and it will be of interest to determine how these advances can be incorporated into clinical practice to improve diagnosis, treatment, and management of patients with cardiomyopathies.

Cardiac Magnetic Resonance and Myocardial Viability: Why Is It so Important?

For a better assessment of ischemic heart diseases, myocardial viability should be quantified. Current studies underline the importance and the evolution of several techniques and methods used in the evaluation of myocardial viability. Taking into account these considerations, the aim of this manuscript was to present the recent points of view regarding myocardial viability and its clinical significance in patients with ischemic cardiomyopathies and left ventricular dysfunction. On the other hand, the manuscript points out the role of magnetic resonance imaging (MRI), one of the most useful noninvasive imaging techniques, in the assessment of myocardial viability. By comparing the advantages and disadvantages of cardiac MRI, its usefulness can be better appreciated by the clinician. In the following years, it is considered that MRI will be an indispensable imaging tool in the assessment of ischemic heart disease, guiding interventions for revascularization and long-term risk stratification in patients with stable angina or myocardial infarction.