Long-Term Incremental Prognostic Value of Cardiovascular Magnetic Resonance After ST-Segment Elevation Myocardial Infarction

Ultrasound enhancing agents in cardiovascular imaging: expanding horizons beyond coronary arteries

From its inception as a two-dimensional snapshot of the beating heart, echocardiography has become an indelible part of cardiovascular diagnostics. The integration of ultrasound enhancing agents (UEAs) marks a pivotal transition, enhancing its diagnostic acumen beyond myocardial perfusion. These agents have refined echocardiography's capacity to visualize complex cardiac anatomy and pathology with unprecedented clarity, especially in non-coronary artery disease contexts. UEAs aid in detailed assessments of myocardial viability, endocardial border delineation in left ventricular opacification, and identification of intracardiac masses. Recent innovations in UEAs, accompanied by advancements in echocardiographic technology, offer clinicians a more nuanced view of cardiac function and blood flow dynamics. This review explores recent developments in these applications and future contemplated studies.

Cardiac Magnetic Resonance Evaluation of LV Remodeling Post-Myocardial Infarction: Prognosis, Monitoring and Trial Endpoints

Adverse left ventricular remodeling (ALVR) and subsequent heart failure after myocardial infarction (MI) remain a major cause of patient morbidity and mortality worldwide. Overt inflammation has been identified as the common pathway underlying myocardial fibrosis and development of ALVR post-MI. With its ability to simultaneously provide information about cardiac structure, function, perfusion, and tissue characteristics, cardiac magnetic resonance (CMR) is well poised to inform prognosis and guide early surveillance and therapeutics in high-risk cohorts. Further, established and evolving CMR-derived biomarkers may serve as clinical endpoints in prospective trials evaluating the efficacy of novel anti-inflammatory and antifibrotic therapies. This review provides an overview of post-MI ALVR and illustrates how CMR may help clinical adoption of novel therapies via mechanistic or prognostic imaging markers.

Long-Term Prognostic Value of Infarct Transmurality Determined by Contrast-Enhanced Cardiac Magnetic Resonance after ST-Segment Elevation Myocardial Infarction

The long-term prognostic significance of maximal infarct transmurality evaluated by contrast-enhanced cardiac magnetic resonance (CE-CMR) in ST-segment elevation myocardial infarction (STEMI) patients has yet to be determined. This study aimed to see if maximal infarct transmurality has any additional long-term prognostic value over other CE-CMR predictors in STEMI patients, such as microvascular obstruction (MVO) and intramyocardial hemorrhage (IMH). The study included 112 consecutive patients who underwent CE-CMR after STEMI to assess established parameters of myocardial injury as well as the maximal infarct transmurality. The primary clinical endpoint was the occurrence of major adverse cardiac events (MACE), which included all-cause death, non-fatal reinfarction, and new heart failure hospitalization. The MACE occurred in 10 patients over a median follow-up of 7.9 years (IQR, 5.8 to 9.2 years) (2 deaths, 3 nonfatal MI, and 5 heart failure hospitalization). Patients with MACE had significantly higher rates of transmural extent of infarction, infarct size >5.4 percent, MVO, and IMH compared to patients without MACE. In stepwise multivariable Cox regression analysis, the transmural extent of infarction defined as 75 percent or more of infarct transmurality was an independent predictor of the MACE after correction for MVO and IMH (hazard ratio 8.7, 95% confidence intervals [CIs] 1.1-71; p=0.043). In revascularized STEMI patients, post-infarction CE-CMR-based maximal infarct transmurality is an independent long-term prognosticator. Adding maximal infarct transmurality to CE-CMR parameters like MVO and IMH could thus identify patients at high risk of long-term adverse outcomes in STEMI.

Growth differentiation factor-15 as a negative predictor for microvascular obstruction in ST-segment elevation myocardial infarction after primary percutaneous coronary intervention

Growth differentiation factor-15 (GDF-15) is an anti-inflammatory cytokine with cardioprotective effects, but circulating GDF-15 concentration predicts adverse cardiovascular outcomes in clinical settings. Microvascular obstruction (MVO) formation contributed to poor prognosis in patients with ST-segment elevation myocardial infarction (STEMI) after primary percutaneous coronary intervention (pPCI). We aimed to investigate GDF-15 concentration in relation to cardiac magnetic resonance (CMR)-derived MVO in STEMI patients after pPCI, which might help better understand the role of GDF-15 in STEMI. GDF-15 levels at 6 h after pPCI and MVO extent at day 5 ± 2 after pPCI were measured in 74 STEMI patients (mean age 60.3 ± 12.8 years, 86.5% men). The adjusted association of GDF-15 with MVO was analyzed with MVO treated as a categorized variable (extensive MVO, defined as MVO extent ≥ 2.6% of left ventricular (LV)) and a continuous variable (MVO mass, % of LV), respectively, in multivariate logistic and linear regression models. 41.9% of the patients developed extensive MVO after pPCI. In multivariate analysis, the odds ratio (95% confidential interval (CI)) of each standard deviation (SD) increase in GDF-15 for developing extensive MVO was 0.46 (0.21, 0.82), p = 0.02). Consistently, when MVO was used a continuous variable, each SD increase in GDF-15 was associated with a substantially lower MVO mass (β - 0.42, standard error 0.19, p = 0.03). GDF-15 was a negative predictor for MVO in STEMI patients after pPCI. The observation was consistent with results from experiment studies, suggesting a potential protective effect of GDF-15 against cardiac injury.

Anterior-wall and non-anterior-wall STEMIs do not differ in long-term mortality: results from the augsburg myocardial infarction registry

Background

Different ST-segment elevation myocardial infarction (STEMI) localizations go along with dissimilarities in the size of the affected myocardium, the causing coronary vessel occlusion, and the right ventricular participation. Therefore, this study aims to clarify if there is any difference in long-term survival between anterior- and non-anterior-wall STEMI.

Methods

This study included 2,195 incident STEMI cases that occurred between 2009 and 2017, recorded by the population-based Augsburg Myocardial Infarction Registry, Germany. The study population comprised 1.570 men and 625 women aged 25-84 years at acute myocardial infarction. The patients were observed from the day of their first acute event with an average follow-up period of 4.3 years, (standard deviation: 3.0). Survival analyses and multivariable Cox regression analyses were performed to examine the association between infarction localizations and long-term all-cause mortality.

Results

Of the 2,195 patients, 1,118 had an anterior (AWS)- and 1,077 a non-anterior-wall-STEMI (NAWS). No significant associations of the STEMI localization with long-term mortality were found. When comparing AWS with NAWS, a hazard ratio of 0.91 [95% confidence interval: 0.75-1.10] could be calculated after multivariable adjustment. In contrast to NAWS, AWS was associated with a greater <28 day mortality, less current or former smoking and higher creatine kinase-myocardial band levels (CK-MB) and went along with a higher frequency of impaired left ventricular ejection fraction (<30%).

Conclusions

Despite pathophysiological differences between AWS and NAWS, and identified differences in multiple clinical characteristics, no significant differences in long-term mortality between both groups were observed.

The Canadian Cardiovascular Society Classification of Acute Atherothrombotic Myocardial Infarction Based on Stages of Tissue Injury Severity: An Expert Consensus Statement

Myocardial infarction (MI) remains a leading cause of morbidity and mortality. In atherothrombotic MI (ST-elevation MI and type 1 non-ST-elevation MI), coronary artery occlusion leads to ischemia. Subsequent cardiomyocyte necrosis evolves over time as a wavefront within the territory at risk. The spectrum of ischemia and reperfusion injury is wide: it can be minimal in aborted MI or myocardial necrosis can be large and complicated by microvascular obstruction and reperfusion hemorrhage. Established risk scores and infarct classifications help with patient management but do not consider tissue injury characteristics. This document outlines the Canadian Cardiovascular Society classification of acute MI. It is an expert consensus formed on the basis of decades of data on atherothrombotic MI with reperfusion therapy. Four stages of progressively worsening myocardial tissue injury are identified: (1) aborted MI (no/minimal myocardial necrosis); (2) MI with significant cardiomyocyte necrosis, but without microvascular injury; (3) cardiomyocyte necrosis and microvascular dysfunction leading to microvascular obstruction (ie, "no-reflow"); and (4) cardiomyocyte and microvascular necrosis leading to reperfusion hemorrhage. Each stage reflects progression of tissue pathology of myocardial ischemia and reperfusion injury from the previous stage. Clinical studies have shown worse remodeling and increase in adverse clinical outcomes with progressive injury. Notably, microvascular injury is of particular importance, with the most severe form (hemorrhagic MI) leading to infarct expansion and risk of mechanical complications. This classification has the potential to stratify risk in MI patients and lay the groundwork for development of new, injury stage-specific and tissue pathology-based therapies for MI.

Circulating Small Extracellular Vesicles Reflect the Severity of Myocardial Damage in STEMI Patients

Circulating small extracellular vesicles (sEVs) contribute to inflammation, coagulation and vascular injury, and have great potential as diagnostic markers of disease. The ability of sEVs to reflect myocardial damage assessed by Cardiac Magnetic Resonance (CMR) in ST-segment elevation myocardial infarction (STEMI) is unknown. To fill this gap, plasma sEVs were isolated from 42 STEMI patients treated by primary percutaneous coronary intervention (pPCI) and evaluated by CMR between days 3 and 6. Nanoparticle tracking analysis showed that sEVs were greater in patients with anterior STEMI (p = 0.0001), with the culprit lesion located in LAD (p = 0.045), and in those who underwent late revascularization (p = 0.038). A smaller sEV size was observed in patients with a low myocardial salvage index (MSI, p = 0.014). Patients with microvascular obstruction (MVO) had smaller sEVs (p < 0.002) and lower expression of the platelet marker CD41-CD61 (p = 0.039). sEV size and CD41-CD61 expression were independent predictors of MVO/MSI (OR [95% CI]: 0.93 [0.87-0.98] and 0.04 [0-0.61], respectively). In conclusion, we provide evidence that the CD41-CD61 expression in sEVs reflects the CMR-assessed ischemic damage after STEMI. This finding paves the way for the development of a new strategy for the timely identification of high-risk patients and their treatment optimization.

Translational large animal model of coronary microvascular embolism: characterization by serial cardiac magnetic resonance and histopathology

This study aimed to construct a large animal model of coronary microvascular embolism, and investigate whether it could mimic the clinical imaging phenotypes of myocardial hypoperfusion in patients with ST-segment elevation myocardial infarction (STEMI). Nine minipigs underwent percutaneous coronary embolization with microspheres, followed by cardiac magnetic resonance (CMR) on week 1, 2 and 4 post operation. Microvascular obstruction (MVO) was defined as the isolated hypointense core within the enhanced area on late gadolinium enhancement images, which evolved during a 4-week follow-up. Fibrotic fraction of the segments was measured by Masson trichrome staining using a panoramic analysis software. Iron deposit and macrophage infiltration were quantified based on Perl's blue and anti-CD163 staining, respectively. Seven out of 9 (77.8%) minipigs survived and completed all of the imaging follow-ups. Four out of 7 (57.1%) minipigs were identified as transmural infarct with MVO. The systolic wall thickening (SWT) of MVO zone was similar to that of infarct zone (P = 0.762). Histopathology revealed transmural deposition of collagen, with microvessels obstructed by microspheres. The fibrotic fraction of infarct with MVO segments was similar to that of infarct without MVO segments (P = 0.954). The fraction of iron deposit in infarct with MVO segments was higher than that of infarct without MVO segments (P < 0.05), but the fraction of macrophage infiltration between these two segments did not show statistical difference (P = 0.723). Large animal model of coronary microvascular embolism could mimic most clinical imaging phenotypes of myocardial hypoperfusion in patients with STEMI, demonstrated by serial CMR and histopathology.

Coronary microvascular dysfunction and cardiovascular disease: Pathogenesis, associations and treatment strategies

Coronary microvascular dysfunction (CMD) is a high-risk factor for a variety of cardiovascular events. Due to its complex aetiology and concealability, knowledge of the pathophysiological mechanism of CMD is still limited at present, which greatly restricts its clinical diagnosis and treatment. Studies have shown that CMD is closely related to a variety of cardiovascular diseases, can aggravate the occurrence and development of cardiovascular diseases, and is closely related to a poor prognosis in patients with cardiovascular diseases. Improving coronary microvascular remodelling and increasing myocardial perfusion might be promising strategies for the treatment of cardiovascular diseases. In this paper, the pathogenesis and functional assessment of CMD are reviewed first, along with the relationship of CMD with cardiovascular diseases. Then, the latest strategies for the treatment of CMD and cardiovascular diseases are summarized. Finally, urgent scientific problems in CMD and cardiovascular diseases are highlighted and future research directions are proposed to provide prospective insights for the prevention and treatment of CMD and cardiovascular diseases in the future.

Cardiovascular Magnetic Resonance from Fetal to Adult Life-Indications and Challenges: A State-of-the-Art Review

Cardiovascular magnetic resonance (CMR) imaging offers a comprehensive, non-invasive, and radiation-free imaging modality, which provides a highly accurate and reproducible assessment of cardiac morphology and functions across a wide spectrum of cardiac conditions spanning from fetal to adult life. It minimises risks to the patient, particularly the risks associated with exposure to ionising radiation and the risk of complications from more invasive haemodynamic assessments. CMR utilises high spatial resolution and provides a detailed assessment of intracardiac and extracardiac anatomy, ventricular and valvular function, and flow haemodynamic and tissue characterisation, which aid in the diagnosis, and, hence, with the management of patients with cardiac disease. This article aims to discuss the role of CMR and the indications for its use throughout the different stages of life, from fetal to adult life.

A novel risk stratification model for STEMI after primary PCI: global longitudinal strain and deep neural network assisted myocardial contrast echocardiography quantitative analysis

Background

In ST-segment elevation myocardial infarction (STEMI) with the restoration of TIMI 3 flow by percutaneous coronary intervention (PCI), visually defined microvascular obstruction (MVO) was shown to be the predictor of poor prognosis, but not an ideal risk stratification method. We intend to introduce deep neural network (DNN) assisted myocardial contrast echocardiography (MCE) quantitative analysis and propose a better risk stratification model.

Methods

194 STEMI patients with successful primary PCI with at least 6 months follow-up were included. MCE was performed within 48 h after PCI. The major adverse cardiovascular events (MACE) were defined as cardiac death, congestive heart failure, reinfarction, stroke, and recurrent angina. The perfusion parameters were derived from a DNN-based myocardial segmentation framework. Three patterns of visual microvascular perfusion (MVP) qualitative analysis: normal, delay, and MVO. Clinical markers and imaging features, including global longitudinal strain (GLS) were analyzed. A calculator for risk was constructed and validated with bootstrap resampling.

Results

The time-cost for processing 7,403 MCE frames is 773 s. The correlation coefficients of microvascular blood flow (MBF) were 0.99 to 0.97 for intra-observer and inter-observer variability. 38 patients met MACE in 6-month follow-up. We proposed A risk prediction model based on MBF [HR: 0.93 (0.91-0.95)] in culprit lesion areas and GLS [HR: 0.80 (0.73-0.88)]. At the best risk threshold of 40%, the AUC was 0.95 (sensitivity: 0.84, specificity: 0.94), better than visual MVP method (AUC: 0.70, Sensitivity: 0.89, Specificity: 0.40, IDI: -0.49). The Kaplan-Meier curves showed that the proposed risk prediction model allowed for better risk stratification.

Conclusion

The MBF + GLS model allowed more accurate risk stratification of STEMI after PCI than visual qualitative analysis. The DNN-assisted MCE quantitative analysis is an objective, efficient and reproducible method to evaluate microvascular perfusion.

Current Concepts and Future Applications of Non-Invasive Functional and Anatomical Evaluation of Coronary Artery Disease

Over the last decades, significant advances have been achieved in the treatment of coronary artery disease (CAD). Proper non-invasive diagnosis and appropriate management based on functional information and the extension of ischemia or viability remain the cornerstone in the fight against adverse CAD events. Stress echocardiography and single photon emission computed tomography are often used for the evaluation of ischemia. Advancements in non-invasive imaging modalities such as computed tomography (CT) coronary angiography and cardiac magnetic resonance imaging (MRI) have not only allowed non-invasive imaging of coronary artery lumen but also provide additional functional information. Other characteristics regarding the plaque morphology can be further evaluated with the latest modalities achieving a morpho-functional evaluation of CAD. Advances in the utilization of positron emission tomography (PET), as well as software advancements especially regarding cardiac CT, may provide additional prognostic information to a more evidence-based treatment decision. Since the armamentarium on non-invasive imaging modalities has evolved, the knowledge of the capabilities and limitations of each imaging modality should be evaluated in a case-by-case basis to achieve the best diagnosis and treatment decision. In this review article, we present the most recent advances in the noninvasive anatomical and functional evaluation of CAD.

[Ischemic heart disease : More than just chronic CAD]

CLINICAL/METHODOLOGICAL ISSUE

Myocardial ischemia as a reduction in perfusion with therefore oxygen deficiency of vital cardiomyocytes. Thus primary and secondary prophylaxis of myocardial infarction and it's complications.

STANDARD RADIOLOGICAL METHODS

Adenosine-regadenoson stress magnetic resonance imaging (AR-stress MRI), computed tomography coronary angiography (CTCA).

METHODOLOGICAL INNOVATIONS

Non-invasive stress testing using AR-stress MRI to exclude relevant obstructive coronary artery disease (CAD).

PERFORMANCE

Meta-analysis: The diagnosis of obstructive CAD at the coronary artery level has a pooled sensitivity of 87.7% and a specificity of 88.6%. Diagnostic accuracy is better than single photon emission computed tomography (SPECT; AUC 0.89 vs. 0.74).

ACHIEVEMENTS

AR-stress MRI can be used to assess myocardial ischemia in the setting of obstructive CAD. Current clinical guidelines for myocardial revascularization have strengthened the use of stress MRI in patients with intermediate risk of CAD and stable symptoms. Cardiac MR imaging using late gadolinium enhancement (LGE) is considered gold standard for myocardial viability assessment in vivo. Both viability and ischemia are considered prognostic factors for major adverse cardiac events.

PRACTICAL RECOMMENDATIONS

AR-stress MRI is used to diagnose myocardial ischemia in combination with viability imaging (LGE). Dobutamine-atropine (DoA) stress MRI is an alternative in the setting of contraindications for AR or specific clinical questions.

Complete Revascularization and One-Year Survival with Good Neurological Outcome in Patients Resuscitated from an Out-of-Hospital Cardiac Arrest

Background. The survival benefit of complete versus infarct-related artery (IRA)-only revascularization during the index hospitalization in patients resuscitated from an out-of-hospital cardiac arrest (OHCA) with multivessel disease is unknown. Methods. We considered all the OHCA patients prospectively enrolled in the Lombardia Cardiac Arrest Registry (Lombardia CARe) from 1 January 2015 to 1 May 2021 who underwent coronary angiography (CAG) at the Fondazione IRCCS Policlinico San Matteo (Pavia). Patients’ prehospital, angiographical and survival data were reviewed. Results. Out of 239 patients, 119 had a multivessel coronary disease: 69% received IRA-only revascularization, and 31% received a complete revascularization: 8 during the first procedure and 29 in a staged-procedure after a median time of 5 days [IQR 2.5−10.3]. The complete revascularization group showed significantly higher one-year survival with good neurological outcome than the IRA-only group (83.3% vs. 30.4%, p < 0.001). After correcting for cardiac arrest duration, shockable presenting rhythm, peak of Troponin-I, creatinine on admission and the need for circulatory support, complete revascularization was independently associated with the probability of death and poor neurological outcome [HR 0.3 (95%CI 0.1−0.8), p = 0.02]. Conclusions. This observation study shows that complete myocardial revascularization during the index hospitalization improves one-year survival with good neurological outcome in patients resuscitated from an OHCA with multivessel coronary disease.

Myocardial extracellular volume quantified by cardiac magnetic resonance predicts left ventricular aneurysm following acute myocardial infarction

OBJECTIVE

This study aimed to investigate the correlation between increased extracellular matrix estimated by cardiac magnetic resonance (CMR) and left ventricular aneurysm after acute myocardial infarction.

METHODS

A total of 175 patients from 3 centers with an isolated left anterior descending culprit vessel underwent CMR examinations within 1 week and at a 6-month follow-up. Of these, 92 were identified to have left ventricular aneurysms (LVAs): 74 with functional aneurysm and 18 with anatomical aneurysm. The predictive significance of acute extracellular volume (ECV), left gadolinium enhancement (LGE), and other characteristics were analyzed using binary logistic regression analysis.

RESULTS

Patients with LVA were more likely to present with left ventricular adverse remodeling (LVAR) than those without (p = 0.009). With optimal cutoff values of 30.90% for LGE and 33% for ECV to discriminate LVA from non-LVA, the area under the curve (AUC) by receiver operator characteristic curve (ROC) analysis was 0.92 (95% CI: 0.87-0.96; p < 0.001) and 0.93 (95% CI: 0.88-0.96; p < 0.001), respectively. ECV was significantly better than LGE at discriminating between functional and anatomical LVA (p < 0.001). Both acute LGE and ECV were predictors of LVA, with an odds ratio of 1.35 (95% CI: 1.21-1.52, p < 0.001) and 1.23 (95% CI: 1.13-1.33, p < 0.001), respectively, by multivariable logistic regression analysis.

CONCLUSIONS

Acute LGE and ECV of the myocardium provided predictive significance for LVA. The discriminative significance of ECV for functional versus anatomical LVA was better than the discriminative significance of LGE.

KEY POINTS

• Patients with LVA were more likely to present with LVAR. • Acute LGE and ECV of the myocardium provided the strongest predictive significance for LVA. • The discriminative significance of ECV for functional versus anatomical LVA was better than that of LGE.

Diagnostic performance of cardiac magnetic resonance segmental myocardial strain for detecting microvascular obstruction and late gadolinium enhancement in patients presenting after a ST-elevation myocardial infarction

Background

Microvascular obstruction (MVO) and Late Gadolinium Enhancement (LGE) assessed in cardiac magnetic resonance (CMR) are associated with adverse outcome in patients with ST-elevation myocardial infarction (STEMI). Our aim was to analyze the diagnostic performance of segmental strain for the detection of MVO and LGE.

Methods

Patients with anterior STEMI, who underwent additional CMR were enrolled in this sub-study of the CARE-AMI trial. Using CMR feature tracking (FT) segmental circumferential peak strain (SCS) was measured and the diagnostic performance of SCS to discriminate MVO and LGE was assessed in a derivation and validation cohort.

Results

Forty-eight STEMI patients (62 ± 12 years old), 39 (81%) males, who underwent CMR (i.e., mean 3.0 ± 1.5 days) after primary percutaneous coronary intervention (PCI) were included. All patients presented with LGE and in 40 (83%) patients, MVO was additionally present. Segments in all patients were visually classified and 146 (19%) segments showed MVO (i.e., LGE+/MVO+), 308 (40%) segments showed LGE and no MVO (i.e., LGE+/MVO–), and 314 (41%) segments showed no LGE (i.e., LGE–). Diagnostic performance of SCS for detecting MVO segments (i.e., LGE+/MVO+ vs. LGE+/MVO–, and LGE–) showed an AUC = 0.764 and SCS cut-off value was –11.2%, resulting in a sensitivity of 78% and a specificity of 67% with a positive predictive value (PPV) of 30% and a negative predictive value (NPV) of 94% when tested in the validation group. For LGE segments (i.e., LGE+/MVO+ and LGE+/MVO– vs. LGE–) AUC = 0.848 and SCS with a cut-off value of –13.8% yielded to a sensitivity of 76%, specificity of 74%, PPV of 81%, and NPV of 70%.

Conclusion

Segmental strain in STEMI patients was associated with good diagnostic performance for detection of MVO+ segments and very good diagnostic performance of LGE+ segments. Segmental strain may be useful as a potential contrast-free surrogate marker to improve early risk stratification in patients after primary PCI.

The role of cardiac magnetic resonance imaging in defining the prognosis of patients with acute <i>ST</i>-segment elevation myocardial infarction. Part 2. Assessment of the disease prognosis

Currently the incidence of congestive heart failure after ST-segment elevation myocardial infarction (STEMI) tends to increase. Reperfusion therapy is still the only effective method to reduce an infarct size. Therefore, there is a high unmet need of novel cardioprotective treatments that would improve outcomes in such patients. Recent advances in cardiovascular magnetic resonance (CMR) methods enabled the identification of certain new infarct characteristics associated with the development of heart failure and sudden cardiac death. These characteristics can help identify new groups of high risk patients and used as a targets for novel cardioprotective treatments. This part of the review summarizes novel CMR-based characteristics of myocardial infarction and their role in the prognostic stratification of STEMI patients.

Role of cardiac magnetic resonance imaging in troponinemia syndromes

Cardiac magnetic resonance imaging (MRI) is an evolving technology, proving to be a highly accurate tool for quantitative assessment. Most recently, it has been increasingly used in the diagnostic and prognostic evaluation of conditions involving an elevation in troponin or troponinemia. Although an elevation in troponin is a nonspecific marker of myocardial tissue damage, it is a frequently ordered investigation leaving many patients without a specific diagnosis. Fortunately, the advent of newer cardiac MRI protocols can provide additional information. In this review, we discuss several conditions associated with an elevation in troponin such as myocardial infarction, myocarditis, Takotsubo cardiomyopathy, coronavirus disease 2019 related cardiac dysfunction and athlete’s heart syndrome.

Impact of Obesity on Microvascular Obstruction and Area at Risk in Patients After ST-Segment-Elevation Myocardial Infarction: A Magnetic Resonance Imaging Study

BACKGROUND

Better survival for overweight and obese patients after ST-segment elevation myocardial infarction (STEMI) has been demonstrated. The association between body mass index (BMI), microvascular obstruction (MVO), and area at risk (AAR) after STEMI was evaluated.

METHODS

A prospective observational study was performed to enrolled patients undergoing primary percutaneous coronary intervention (pPCI) for STEMI and cardiac magnetic resonance was performed within 5-7 days. Patients were classified as normal weight (18.5 ≤BMI <24.0 kg/m²), overweight (24.0 ≤BMI <28.0 kg/m²), or obese (BMI ≥28 kg/m²).

RESULTS

Among 225 patients undergoing pPCI, 67 (30.00%) were normal weight, 113 (50.22%) were overweight, and 45 (20.00%) were obese. BMI ≥28 kg/m² was significantly associated with less risk of MVO when compared with a normal BMI after multivariable adjustment (overweight: HR 0.29, 95% CI 0.13-0.68, p = 0.004). Compared with normal weight patients, obese and overweight patients tend to have larger hearts (greater left ventricular end-diastolic volume [LVEDV] and left ventricular [LV] mass). In adjusted analysis, increased BMI was significantly associated with a smaller AAR. In addition, obese patients had a smaller AAR (β = -0.252, 95% CI -20.298- -3.244, p = 0.007) and AAR, % LV mass (β = -0.331, 95% CI -0.211- -0.062, p < 0.001) than normal weight patients.

CONCLUSION

Obesity (BMI ≥28 kg/m²) is independently associated with lower risks of MVO and a smaller AAR, % LV mass than normal weight patients among subjects undergoing pPCI for STEMI.

Feasibility of late gadolinium enhancement (LGE) in ischemic cardiomyopathy using 2D-multisegment LGE combined with artificial intelligence reconstruction deep learning noise reduction algorithm

BACKGROUND

Despite the low spatial resolution of 2D-multisegment late gadolinium enhancement (2D-MSLGE) sequences, it may be useful in uncooperative patients instead of standard 2D single segmented inversion recovery gradient echo late gadolinium enhancement sequences (2D-SSLGE). The aim of the study is to assess the feasibility and comparison of 2D-MSLGE reconstructed with artificial intelligence reconstruction deep learning noise reduction (NR) algorithm compared to standard 2D-SSLGE in consecutive patients with ischemic cardiomyopathy (ICM).

METHODS

Fifty-seven patients with known ICM referred for a clinically indicated CMR were enrolled in this study. 2D-MSLGE were reconstructed using a growing level of NR (0%,25%,50%,75%and 100%). Subjective image quality, signal to noise ratio (SNR) and contrast to noise ratio (CNR) were evaluated in each dataset and compared to standard 2D-SSLGE. Moreover, diagnostic accuracy, LGE mass and scan time were compared between 2D-MSLGE with NR and 2D-SSLGE.

RESULTS

The application of NR reconstruction ≥50% to 2D-MSLGE provided better subjective image quality, CNR and SNR compared to 2D-SSLGE (p < 0.01). The best compromise in terms of subjective and objective image quality was observed for values of 2D-MSLGE 75%, while no differences were found in terms of LGE quantification between 2D-MSLGE versus 2D-SSLGE, regardless the NR applied. The sensitivity, specificity, negative predictive value, positive predictive value and accuracy of 2D-MSLGE NR 75% were 87.77%,96.27%,96.13%,88.16% and 94.22%, respectively. Time of acquisition of 2D-MSLGE was significantly shorter compared to 2D-SSLGE (p < 0.01).

CONCLUSION

When compared to standard 2D-SSLGE, the application of NR reconstruction to 2D-MSLGE provides superior image quality with similar diagnostic accuracy.

Impact of COVID-19 pandemic restrictions on ST-elevation myocardial infarction: a cardiac magnetic resonance imaging study

AIMS

The severity of myocardial tissue damage following ST-elevation myocardial infarction (STEMI) strongly determines short- and long-term prognosis. This study explored the impact of the coronavirus disease 2019 (COVID-19) pandemic and associated public health restrictions on infarct severity.

METHODS AND RESULTS

STEMI patients treated with primary percutaneous coronary intervention (PCI) and included in the prospective Magnetic Resonance Imaging in Acute ST-Elevation Myocardial Infarction (MARINA-STEMI) cohort study from 2015- 2020 (n = 474) were categorized according to (i) timeframes with and without major public health restrictions in 2020, and (ii) timeframes of major public health restrictions during 2020 and during the corresponding timeframes between 2015-2019. Myocardial damage was evaluated by cardiac magnetic resonance imaging. During major public health restrictions in 2020 (n = 48), there was an increase in infarct size (22 [IQR 12-29] vs. 14 [IQR 6-23]%, P < 0.01), a higher frequency (77% vs. 52%, P < 0.01) and larger extent of microvascular obstruction (1.5 [IQR 0.1-11.4] vs. 0.2 [IQR 0.0-2.6]%, P < 0.01) and a higher rate of intramyocardial haemorrhage (56% vs. 34%, P = 0.02) as compared to the phases without major restrictions in 2020 (n = 101). These findings were confirmed in adjusted analysis and were consistent when comparing patients admitted in 2020 versus patients admitted in the "pre-pandemic" era (2015-2019). Patient characteristics were comparable between groups, except for a significantly longer total ischemia time (P < 0.01) and higher frequency of pre-PCI Thrombolysis in Myocardial Infarction (TIMI) flow 0 during times of major restrictions (P = 0.03).

CONCLUSION

This study provides novel mechanistic insights demonstrating a significant increase in myocardial damage in STEMI patients admitted during the COVID-19 pandemic with a temporal relation to major public health restrictions.

Cardiac Magnetic Resonance Tissue Characterization in Ischemic Cardiomyopathy

Ischemic cardiomyopathy (ICM) is one of the most common causes of congestive heart failure. In patients with ICM, tissue characterization with cardiac magnetic resonance imaging (CMR) allows for evaluation of myocardial abnormalities in acute and chronic settings. Myocardial edema, microvascular obstruction (MVO), intracardiac thrombus, intramyocardial hemorrhage, and late gadolinium enhancement of the myocardium are easily depicted using standard CMR sequences. In the acute setting, tissue characterization is mainly focused on assessment of ventricular thrombus and MVO, which are associated with poor prognosis. Conversely, in chronic ICM, it is important to depict late gadolinium enhancement and myocardial ischemia using stress perfusion sequences. Overall, with CMR's ability to accurately characterize myocardial tissue in acute and chronic ICM, it represents a valuable diagnostic and prognostic imaging method for treatment planning. In particular, tissue characterization abnormalities in the acute setting can provide information regarding the patients that may develop major adverse cardiac event and show the presence of ventricular thrombus; in the chronic setting, evaluation of viable myocardium can be fundamental for planning myocardial revascularization. In this review, the main findings on tissue characterization are illustrated in acute and chronic settings using qualitative and quantitative tissue characterization.

Advances in Ultrasound Therapeutics

PURPOSE OF REVIEW

High mechanical index impulses from a diagnostic transducer are utilized in myocardial perfusion imaging, but can also be utilized therapeutically in three cardiovascular applications: (a) thrombus dissolution (sonothrombolysis), (b) improving microvascular flow in ischemic territories (sonoperfusion), and (c) targeted drug and nucleic acid delivery. The targeted therapeutic effect appears to be based on acoustic cavitation of the intravascular microbubbles which results in endothelial shear and pore formation, as well as mechanical destruction of thrombi.

RECENT FINDINGS

Within the last 5 years, clinical trials have been performed in acute myocardial infarction demonstrating successful reductions in myocardial infarct size with sonothrombolysis added to current guideline-based treatment. In patients with severe peripheral arterial disease, brief improvements in calf microvascular blood flow have been observed for 1 h after 10 min of sonoperfusion therapy. Targeted ultrasound therapies are developing for prevention of microvascular obstruction in acute coronary syndromes and peripheral vascular disease.

Mild Therapeutic Hypothermia Alters Hemostasis in ST Elevation Myocardial Infarction Patients

Background and Rationale: Mild therapeutic hypothermia (MTH) is a concept to reduce infarct size and improve outcome after ST-segment elevation myocardial infarction (STEMI). In the STATIM trial, we investigated MTH as an additional therapy for STEMI patients. In the intention-to-treat set, 101 patients were included. No difference in primary and secondary endpoints measured by cardiac magnetic resonance imaging was found. Platelet activation and plasmatic coagulation are key in the pathophysiology of STEMI. In the present study, we investigated the effect of MTH on primary and secondary hemostasis in STEMI patients.

Methods and Results: Platelet function and morphology were assessed by routine blood count, aggregometry testing, and flow cytometry. Soluble platelet markers were determined by enzyme-linked immunosorbent assay (ELISA) testing. Plasmatic coagulation was measured throughout the study. Platelet count remained unchanged, irrespective of treatment, whereas platelet size decreased in both patient groups. Platelet aggregometry indicated increased platelet reactivity in the MTH group. Furthermore, higher adenosine diphosphate (ADP) plasma levels were found in MTH patients. Expression of glycoprotein IIb/IIIa was increased on platelets of STEMI patients treated with MTH. Lower patient temperatures correlated with longer clotting times and resulted in reduced pH. Lower pH values were positively correlated with longer clotting times.

Conclusion: Present data indicate longer clotting times and higher platelet reactivity in STEMI patients treated with MTH. These changes did not correspond to clinical bleeding events or larger infarct size.

Image Quality and Reliability of a Novel Dark-Blood Late Gadolinium Enhancement Sequence in Ischemic Cardiomyopathy

PURPOSE

The aim of this study was to assess the reliability of a 2D dark-blood phase-sensitive late gadolinium enhancement sequence (2D-DBPSLGE) compared with 2D phase-sensitive inversion recovery late gadolinium enhancement sequence (2D-BBPSLGE) in patients with ischemic cardiomyopathy (ICM).

MATERIALS AND METHODS

A total of 73 patients with a clinical history of ICM were prospectively enrolled. The following endpoints were evaluated: (a) comparison of image quality between 2D-BBPSLGE and 2D-DBPSLGE for differentiation between blood pool-late gadolinium enhancement (LGE), remote myocardium-LGE, and blood pool-remote myocardium; (b) diagnostic accuracy of 2D-DBPSLGE compared with gold standard 2D-BBPSLGE for the evaluation of infarcted segments; (c) diagnostic accuracy of 2D-DBPSLGE for the evaluation of microvascular obstruction (MVO); (d) comparison of transmurality index between 2D-BBPSLGE and 2D-DBPSLGE; (e) comparison of papillary muscle hyperenhancement between 2D-BBPSLGE and 2D-DBPSLGE; inter-reader agreement for depiction of hyperenhanced segments in both LGE sequences. Data were analyzed using paired t test, Wilcoxon test, and McNemar test, and η coefficient and intercorrelation coefficient (ICC).

RESULTS

Image quality was superior for 2D-DBPSLGE for differentiation of blood pool-LGE (P<0.001). 2D-DBPSLGE, compared with 2D-BBPSLGE, showed a sensitivity, specificity, positive predictive value, negative predictive value, and diagnostic accuracy of 96.93%, 99.89%, 99.71%, 98.78, and 99.04%, respectively. Concerning MVO detection, 2D-DBPSLGE showed a sensitivity, specificity, positive predictive value, negative predictive value, and diagnostic accuracy of 66.67%, 100.00%, 100.00%, 80.95%, and 86.21%, respectively. 2D-DBPSLGE underestimated the transmurality (P=0.007) and identified papillary muscle hyperenhancement (P<0.001). Both LGE sequences showed comparable interobserver agreement for the evaluation of infarcted areas (2D-BBPSLGE: ICC 0.99;2D-DBPSLGE: ICC 0.99).

CONCLUSIONS

Compared with 2D-BBPSLGE, 2D-DBPSLGE sequences provide better differentiation between LGE and blood-pool, while underestimating LGE trasmurality and the presence of MVO.

Culprit site extracellular DNA and microvascular obstruction in ST-elevation myocardial infarction

AIMS

Extracellular chromatin and deoxyribonuclease (DNase) have been identified as important players of thrombosis, inflammation and homeostasis in a murine model. We previously demonstrated that activated neutrophils release neutrophil extracellular traps (NETs) at the culprit site in ST elevation myocardial infarction (STEMI), which significantly contribute to extracellular chromatin burden, and are associated with larger infarcts. To understand the correlation between neutrophil activation, extracellular chromatin and infarct size (IS), we investigated these parameters in a porcine myocardial infarction model, and at different time points and sites in a prospective STEMI trial with cardiac magnetic resonance (CMR) endpoints.

METHODS AND RESULTS

In a prospective STEMI trial (NCT01777750), 101 STEMI patients were included and blood samples were obtained from first medical contact until 6 months after primary percutaneous coronary intervention (pPCI) including direct sampling from the culprit site. CMR was performed 4 ± 2 days and 6 months after pPCI. Neutrophil counts, markers of extracellular chromatin and inflammation were measured. Double-stranded DNA (dsDNA), citrullinated histone 3, nucleosomes, myeloperoxidase, neutrophil elastase and interleukin (IL)-6 were significantly increased, while DNase activity was significantly decreased at the culprit site in STEMI patients. High neutrophil counts and dsDNA levels at the culprit site correlated with high microvascular obstruction (MVO) and low ejection fraction (EF). High DNase activity at the culprit site correlated with low MVO and high EF.In correspondence, dsDNA correlated with IS in the porcine myocardial infarction model. In porcine infarcts, neutrophils and extracellular chromatin were detected in congested small arteries corresponding with MVO. Markers of neutrophil activation, extracellular chromatin, DNase activity and CMR measurements correlated with markers of systemic inflammation C-reactive protein and IL-6 in patients.

CONCLUSIONS

NETs and extracellular chromatin are important determinants of MVO in STEMI. Rapid degradation of extracellular chromatin by DNases appears to be crucial for microvascular patency and outcome.

TRANSLATIONAL PERSPECTIVE

We show that NETs and extracellular DNA obstruct microvessels in the porcine myocardial infarction model and is connected to increased infarct size. We are able to prove this observation in human STEMI patients. DNase is capable to counteract these effects. Extracellular DNA could be a new treatment target in STEMI.

Early or deferred cardiovascular magnetic resonance after ST-segment-elevation myocardial infarction for effective risk stratification

AIMS

In ST-segment-elevation myocardial infarction (STEMI), cardiovascular magnetic resonance (CMR) holds the potentiality to improve risk stratification in addition to Thrombolysis in Myocardial Infarction (TIMI) risk score. Nevertheless, the optimal timing for CMR after STEMI remains poorly defined. We aim at comparing the prognostic performance of three stratification strategies according to the timing of CMR after STEMI.

METHODS AND RESULTS

The population of this prospective registry-based study included 492 reperfused STEMI patients. All patients underwent post-reperfusion (median: 4 days post-STEMI) and follow-up (median: 4.8 months post-STEMI) CMR. Left ventricular (LV) volumes, function, infarct size, and microvascular obstruction extent were quantified. Primary endpoint was a composite of all-death and heart failure (HF) hospitalization. Baseline-to-follow-up percentage increase of LV end-diastolic (EDV; ΔLV-EDV) ≥20% or end-systolic volumes (ESV; ΔLV-ESV) ≥15% were tested against outcome. Three multivariate models were developed including TIMI risk score plus early post-STEMI (early-CMR) or follow-up CMR (deferred-CMR) or both CMRs parameters along with adverse LV remodelling (paired-CMRs). During a median follow-up of 8.3 years, the primary endpoint occurred in 84 patients (47 deaths; 37 HF hospitalizations). Early-CMR, deferred-CMR, and paired-CMR demonstrated similar predictive value for the primary endpoint (C-statistic: 0.726, 0.728, and 0.738, respectively; P = 0.663). ΔLV-EDV ≥20% or ΔLV-ESV ≥15% were unadjusted outcome predictors (hazard ratio: 2.020 and 2.032, respectively; P = 0.002 for both) but lost their predictive value when corrected for other covariates in paired-CMR model.

CONCLUSION

In STEMI patients, early-, deferred-, or paired-CMR were equivalent stratification strategies for outcome prediction. Adverse LV remodelling parameters were not independent prognosticators.

Exploratory echocardiographic strain parameters for the estimation of myocardial infarct size in ST-elevation myocardial infarction

Background

Outcome after ST‐elevation myocardial infarction (STEMI) can be most reliably estimated by cardiac magnetic resonance (CMR) imaging. However, CMR is expensive, laborious, and has only limited availability. In comparison, transthoracic echocardiography (TTE) is widely available and cost‐efficient.

Hypothesis

TTE strain parameters can be used as surrogate markers for CMR‐measured parameters after STEMI.

Methods

TTE strain analysis was performed of patients included in a controlled, prospective STEMI trial (NCT01777750) 4 ± 2 days after the event. Longitudinal peak strain (LPS), post‐systolic shortening, early systolic lengthening, early systolic lengthening time, and time to peak shortening were measured, and index parameters were computed. Global longitudinal strain (GLS) and ejection fraction (EF) were compiled. Parameters were correlated with CMR‐measured variables 4 ± 2 days after STEMI.

Results

In 70 STEMI patients, high quality CMR and TTE data were available. Highest correlation with CMR‐measured infarct size was observed with GLS (r = 0.577, p < 0.0001), LPS (r = 0.571, p < 0.0001), and EF (r = −0.533, p < 0.0001). Highest correlation with CMR‐measured area at risk was observed with GLS (r = 0.666, p < 0.0001), LPS (0.661, p < 0.0001) and early systolic lengthening index (r = 0.540, p < 0.0001). Receiver operating characteristics for the detection of large infarcts (quartile with highest infarct size) showed the highest area under the curve for LPS, GLS, EF, and myocardial dysfunction index. Multiple linear regression displayed the best association between GLS and infarct size.

Conclusion

Exploratory strain parameters significantly correlate with CMR‐measured area at risk and infarct size and are of potential interest as endpoint variables in clinical trials.

Global Circumferential Strain by Cardiac Magnetic Resonance Tissue Tracking Associated With Ventricular Arrhythmias in Hypertrophic Cardiomyopathy Patients

Background: Hypertrophic cardiomyopathy (HCM) is prone to myocardial heterogeneity and fibrosis, which are the substrates of ventricular arrhythmias (VAs). Cardiac magnetic resonance tissue tracking (CMR-TT) can quantitatively reflect global and regional left ventricular strain from different directions. It is uncertain whether the change of myocardial strain detected by CMR-TT is associated with VAs. The aim of the study is to explore the differential diagnostic value of VAs in HCM by CMR-TT.

Materials and Methods: We retrospectively included 93 HCM patients (38 with VAs and 55 without VAs) and 30 healthy cases. Left ventricular function, myocardial strain parameters and percentage of late gadolinium enhancement (%LGE) were evaluated.

Results: Global circumferential strain (GCS) and %LGE correlated moderately (r = 0.51, P < 0.001). HCM patients with VAs had lower left ventricular ejection fraction (LVEF), global radial strain (GRS), GCS, and global longitudinal strain (GLS), but increased %LGE compared with those without VAs (P < 0.01 for all). %LGE and GCS were indicators of VAs in HCM patients by multivariate logistic regression analysis. HCM patients with %LGE >5.35% (AUC 0.81, 95% CI 0.70–0.91, P < 0.001) or GCS >-14.73% (AUC 0.79, 95% CI 0.70–0.89, P < 0.001) on CMR more frequently had VAs. %LGE + GCS were able to better identify HCM patients with VAs (AUC 0.87, 95% CI 0.79–0.95, P < 0.001).

Conclusion: GCS and %LGE were independent risk indicators of VAs in HCM. GCS is expected to be a good potential predictor in identifying HCM patients with VAs, which may provide important values to improve risk stratification in HCM in clinical practice.

Impact of manual thrombectomy on microvascular obstruction in STEMI patients

OBJECTIVE

To assess the effect of manual thrombectomy (MT) on microvascular obstruction (MVO) using cardiac magnetic resonance (CMR) in ST-segment elevation myocardial infarction (STEMI) patients undergoing primary percutaneous coronary intervention (PCI).

METHODS AND RESULTS

Three hundred and eighty-three patients admitted for STEMI and undergoing CMR fulfilled the inclusion criteria and were categorized into two groups (did or did not undergo MT). The two primary endpoints were the occurrence and extent of MVO, analyzed as a categorical variable and as a semicontinuous variable. Among the 383 patients, 49.1% exhibited MVO. Both the incidence of MVO and the median number of segments presenting with MVO were significantly higher in the MT group than in the no-MT group, (59.5 vs. 38.9%, p < .001) and (1.5 [0;4] vs. 0 [0;2], p < .001). Analysis stratified on coronary thrombus grade showed similar results, only in patients with a high thrombus burden (60.7 vs. 43.5%, p = .004, and 2 [0;4] vs. 0 [0;3], p = .001. When adjusting for baseline differences, MT remained a determinant of MVO occurrence and extent (odds ratio, OR 1.802 [95% confidence interval, CI 1.080-3.009], p = .024) and β = .137, p = .024) in patients with a high thrombus grade.

CONCLUSION

In STEMI patients, MT was associated with the occurrence and extent of MVO, on CMR, especially in patients with a high thrombus burden.

Appropriate use criteria for cardiovascular magnetic resonance imaging (CMR): SIC-SIRM position paper part 1 (ischemic and congenital heart diseases, cardio-oncology, cardiac masses and heart transplant)

Cardiac magnetic resonance (CMR) has emerged as new mainstream technique for the evaluation of patients with cardiac diseases, providing unique information to support clinical decision-making. This document has been developed by a joined group of experts of the Italian Society of Cardiology and Italian society of Radiology and aims to produce an updated consensus statement about the current state of technology and clinical applications of CMR. The writing committee consisted of members and experts of both societies who worked jointly to develop a more integrated approach in the field of cardiac radiology. Part 1 of the document will cover ischemic heart disease, congenital heart disease, cardio-oncology, cardiac masses and heart transplant.

The shifted balance of arginine metabolites in acute myocardial infarction patients and its clinical relevance

The arginine metabolism as a target for cardioprotection in patients with ST-segment elevation myocardial infarction (STEMI) remains insufficiently understood. Arginine, ornithine, citrulline, asymmetric dimethylarginine (ADMA) and proline plasma levels were measured using liquid chromatography and tandem mass spectrometry in 70 consecutive STEMI patients upon admission and at 6-month follow-up and were compared with left ventricular function, volumes, and infarct characteristics determined by cardiac magnetic resonance imaging, and with 5-year clinical outcomes. Baseline median concentration of arginine was higher by 49% (P = 0.002) when compared to 6-month measurements and was correlated with an ischemia risk area (R = 0.34, P = 0.004) and infarct size (R = 0.33, P = 0.006). Following ischemia median citrulline/arginine index decreased when compared with 6-month result (P = 0.002), while citrulline/ornithine and arginine/ADMA ratios maintained unchanged indicating a shift of arginine metabolism from nitric oxide synthase (NOS) towards arginase. The 6-month arginine concentration reached the area under the ROC curve of 0.67 (95% confidence interval 0.54–0.81) for prediction of death, myocardial infarction or heart failure hospitalization and its value of < 29 µM was associated with lower event free survival (P = 0.02). In STEMI patients, during ischemia conversion of elevated plasma arginine was shifted from NOS towards arginase. Decreased 6-month arginine concentrations were associated with worse long-term outcomes.

SCMR Position Paper (2020) on clinical indications for cardiovascular magnetic resonance

The Society for Cardiovascular Magnetic Resonance (SCMR) last published its comprehensive expert panel report of clinical indications for CMR in 2004. This new Consensus Panel report brings those indications up to date for 2020 and includes the very substantial increase in scanning techniques, clinical applicability and adoption of CMR worldwide. We have used a nearly identical grading system for indications as in 2004 to ensure comparability with the previous report but have added the presence of randomized controlled trials as evidence for level 1 indications. In addition to the text, tables of the consensus indication levels are included for rapid assimilation and illustrative figures of some key techniques are provided.

Myocardial perfusion assessment in the infarct core and penumbra zones in an in-vivo porcine model of the acute, sub-acute, and chronic infarction

OBJECTIVES

To assess the longitudinal changes of microvascular function in different myocardial regions after myocardial infarction (MI) using myocardial blood flow derived by dynamic CT perfusion (CTP-MBF), and compare CTP-MBF with the results of cardiac magnetic resonance (CMR) and histopathology.

METHODS

The CTP scanning was performed in a MI porcine model 1 day (n = 15), 7 days (n = 10), and 3 months (n = 5) following induction surgery. CTP-MBF was measured in the infarcted myocardium, penumbra, and remote myocardium, respectively. CMR perfusion and histopathology were performed for validation.

RESULTS

From baseline to follow-up scans, CTP-MBF presented a stepwise increase in the infarcted myocardium (68.51 ± 11.04 vs. 86.73 ± 13.32 vs. 109.53 ± 26.64 ml/100 ml/min, p = 0.001) and the penumbra (104.92 ± 29.29 vs. 120.32 ± 24.74 vs. 183.01 ± 57.98 ml/100 ml/min, p = 0.008), but not in the remote myocardium (150.05 ± 35.70 vs. 166.66 ± 38.17 vs. 195.36 ± 49.64 ml/100 ml/min, p = 0.120). The CTP-MBF correlated with max slope (r = 0.584, p < 0.001), max signal intensity (r = 0.357, p < 0.001), and time to max (r = - 0.378, p < 0.001) by CMR perfusion. Moreover, CTP-MBF defined the infarcted myocardium on triphenyl tetrazolium chloride staining (AUC: 0.810, p < 0.001) and correlated with microvascular density on CD31 staining (r = 0.561, p = 0.002).

CONCLUSION

CTP-MBF could quantify the longitudinal changes of microvascular function in different regions of the post-MI myocardium, which demonstrates good agreement with contemporary CMR and histopathological findings.

KEY POINTS

• The CT perfusion-based myocardial blood flow (CTP-MBF) could quantify the microvascular impairment in different myocardial regions after myocardial infarction (MI) and track its recovery over time. • The assessment of CTP-MBF is in good agreement with contemporary cardiac MRI and histopathological findings, which potentially facilitates a rapid approach for pathophysiological insights following MI.

Predictive Value of Fasting Blood Glucose for Microvascular Obstruction in Nondiabetic Patients with ST-Segment Elevation Myocardial Infarction after Primary Percutaneous Coronary Intervention

Background

The relationship between fasting blood glucose (FBG) and microvascular obstruction (MVO) after primary percutaneous coronary intervention (PCI) remains unclear in nondiabetic patients with ST-segment elevation myocardial infarction (STEMI). This study aimed to determine the predictive value of FBG in MVO in nondiabetic STEMI patients.

Methods

A total of 108 nondiabetic STEMI patients undergoing primary PCI were enrolled in this study. The patients were classified into either the MVO group or non-MVO group based on cardiac magnetic resonance imaging (CMR).

Results

FBG in the MVO group was higher than in the non-MVO group. Univariate analysis showed that FBG, peak high-sensitive troponin T (TnT), pre-PCI thrombolysis in myocardial infarction (pre-PCI TIMI) flow, left ventricular ejection fraction (LVEF), infarction size, left ventricular end-diastolic diameter (LVEDd), left ventricular end-diastolic volume (LVEDV), and global longitudinal strain (GLS) were likely predictive factors of MVO. After adjustment for other parameters, FBG, peak TnT, LVEF, and LVEDV remained independent predictors for MVO.

Conclusion

FBG was independently associated with MVO in nondiabetic STEMI patients.

Head-to-head comparison of multiple cardiovascular magnetic resonance techniques for the detection and quantification of intramyocardial haemorrhage in patients with ST-elevation myocardial infarction

Objectives

T2*-weighted (T2*w) is deemed as a reference standard for post-infarction intramyocardial haemorrhage (IMH). However, high proportion of T2* images is affected by off-resonance artefacts hampering image interpretation. Diagnostic accuracy and precision of alternative techniques for IMH diagnosis and quantification have been seldomly investigated.

Methods and results

Between April 2016 and May 2017, 50 ST-segment elevation myocardial infarction patients (66% male, 57 ± 17 years) and 15 healthy controls (60% male, 58 ± 13) were consecutively enrolled. Subjects underwent head-to-head comparison of single mid-infarct slice acquired on black-blood T2-weighted short-TI-inversion recovery (T2w-STIR), bright-blood T2prep-steady-state-free precession (T2prep-SSFP), and T2/T1 maps for IMH diagnosis and quantification against T2*w. All images were graded for quality (grade 1: very poor; grade 4: excellent) and diagnostic confidence (Likert scale, 1: very unsure and 5: highly confident). Reduced relaxation time/hypointense region (hypocore) embedded in infarct-related oedema on T2 map, T1 map, and T2w-STIR had the best overall diagnostic accuracy (per-subject: 91%, 86%, and 86%, respectively; per segment: 95%, 93%, and 93%, respectively). By mixed-effects analysis, image quality, and diagnostic confidence were higher for T2 map and T1 maps than T2*w (p < 0.05 for both scores). For IMH quantification, hypocore on T2 map and T1 map strongly correlated (Spearman’s r > 0.7, p < 0.001 for both) with IMH extent on T2*w and presented an overall excellent agreement on Bland-Altman analysis. By linear mixed model analysis, absolute hypocore size did not differ among T1-, T2 map, and T2*w. T2/T1 maps had the best intra- and inter-observer reproducibility among CMR techniques.

Conclusion

Hypocore on T2/T1 map is the best alternative technique to T2*w for diagnosing and quantifying IMH in post-STEMI patients.

Key Point

• Mapping techniques are the best alternatives for diagnosing post-infarction intramyocardial haemorrhage.

• Mapping techniques are valuable tools for imaging intramyocardial haemorrhage.

Electronic supplementary material

The online version of this article (10.1007/s00330-020-07254-1) contains supplementary material, which is available to authorized users.

A radiomic nomogram for prediction of major adverse cardiac events in ST-segment elevation myocardial infarction

OBJECTIVES

This study was conducted to establish and validate a non-contrast T1 map-based radiomic nomogram for predicting major adverse cardiac events (MACEs) in patients with acute ST-segment elevation myocardial infarction (STEMI) undergoing percutaneous coronary intervention (PCI).

METHODS

This retrospective study included 157 consecutive patients (training sets, 109 patients; test sets, 48 patients) with acute STEMI undergoing PCI. An open-source radiomics software was used to segment the myocardium on the non-contrast T1 mapping and extract features. A radiomic signature was constructed to predict MACEs using the least absolute shrinkage and selection operator method. The performance of the radiomic nomogram for predicting MACEs in both the training and test sets was evaluated by its discrimination, calibration, and clinical usefulness.

RESULTS

The radiomic signature showed a good prognostic ability in the training sets with an AUC of 0.94 (95% CI, 0.86 to 1.00) and F1 score of 0.71, which was confirmed in the test sets with an AUC of 0.90 (95% CI, 0.74 to 1.00) and F1 score of 0.62. The nomogram consisting of the radiomic scores and cardiac troponin I showed good discrimination ability in the training and test sets with AUCs of 0.96 (95% CI, 0.91 to 1.00; F1 score, 0.71) and 0.94 (95% CI, 0.83 to 1.00; F1 score, 0.70), respectively.

CONCLUSIONS

The non-contrast T1 map-based radiomic nomogram is a useful tool for the prediction of MACEs in patients with acute STEMI undergoing PCI that can assist clinicians for optimised risk stratification of individual patients.

KEY POINTS

• Radiomic signature improved MACE prediction in acute STEMI patients. • T1 mapping-derived radiomic signature outperformed conventional cardiac MRI parameters in predicting MACEs in acute STEMI patients. • The non-contrast T1 mapping-based radiomic nomogram can be used for prediction of MACEs and improvement of risk stratification in acute STEMI.

Diagnostic Utility of the Simplified Perfusion Fraction for Identifying Myocardial Injury in Patients With Reperfused ST-segment Elevation Myocardial Infarction

BACKGROUND

Acute myocardial infarction (AMI) is a disease with high morbidity and mortality worldwide and the evaluation of myocardial injury and perfusion status following myocardial ischemia and reperfusion is of clinical value.

PURPOSE

To assess the diagnostic utility of simplified perfusion fraction (SPF) in differentiating salvage and infarcted myocardium and its predictive value for left ventricular remodeling in patients with reperfusion ST-segment elevation myocardial infarction (STEMI).

STUDY TYPE

Prospective.

POPULATION

Forty-one reperfused STEMI patients and 20 healthy volunteers.

FIELD STRENGTH/SEQUENCE

3.0T MRI. The MR examination included cine, T₂ -short tau inversion recovery (T₂ -STIR), first pass perfusiong (FPP)，phase sensitive inversion recovery (PSIR), and diffusion-weighted imaging (DWI).

ASSESSMENT

SPF values among different myocardium regions (infarcted, salvaged, remote, and MVO) and stages of reperfused STEMI patients as well as normal controls were measured. The diagnostic utility of SPF values in differentiating salvaged and infarcted myocardium was assessed.

STATISTICAL ANALYSIS

Independent t-test and the Mann-Whitney U-test. Logistic regression.

RESULTS

SPF values in healthy controls were not significantly different than SPF values in the remote myocardium of patients (40.09 ± 1.47% vs. 40.28 ± 1.93%, P = 0.698). In reperfusion STEMI patients, SPF values were lower in infarcted myocardium compared to remote and salvaged myocardium (32.15 ± 2.36% vs. 40.28 ± 1.93%, P < 0.001; 32.15 ± 2.36% vs. 36.68 ± 2.71%, P < 0.001). SPF values of infarcted myocardium showed a rebound increase from acute to convalescent stages (32.15 ± 2.36% vs. 34.69 ± 3.69%, P < 0.001). When differentiating infarcted and salvaged myocardium, SPF values demonstrated an area under the curve (AUC) of 0.89 (sensitivity 85.4%, specificity 80.5%, cutoff 34.42%). Lower SPF values were associated with lower odds ratio (OR = 0.304) of left ventricular remodeling after adjusting for potential confounders with a confidence interval (CI) of 0.129-0.717, P = 0.007.

DATA CONCLUSION

SPF might be able to differentiate salvaged and infarcted myocardium and is a strong predictor of left ventricular remodeling in reperfused STEMI patients. Level of Evidence 2 Technical Efficacy Stage 2.

Long-term Prognostic Value of Cardiac MRI Left Atrial Strain in ST-Segment Elevation Myocardial Infarction

Background Left atrial (LA) dysfunction is associated with morbidity and mortality. To the knowledge of the authors, the relationship of LA strain to long-term prognosis in participants with ST-segment elevation myocardial infarction (STEMI) is unknown. Purpose To evaluate LA strain as a long-term outcome predictor in STEMI in a prospective, multicenter cardiac MRI cohort. Materials and Methods Participants with STEMI who underwent primary percutaneous coronary intervention and cardiac MRI from 10 sites (EARLY-MYO-CMR registry, clinical trial number NCT03768453) were included. The parent study took place between August 2013 and December 2018. LA longitudinal strain and strain rate parameters were derived from cine cardiac MRI by using an in-house semiautomated method. Major adverse cardiac events (MACEs) were defined as cardiovascular death, myocardial reinfarction, hospitalization for heart failure, and stroke. The association between LA performance and MACE was evaluated by using time-dependent receiver operating characteristic analysis, Kaplan-Meier analysis, and multivariable Cox regression analysis. Results A total of 321 participants (median age, 59 years; age range, 27-75 years; 90% men) were included in this study. During median follow-up of 3.7 years, MACE occurred in 76 participants (23.7%). Participants with impaired reservoir (≤22%) and conduit strain (≤10%) had a higher risk of MACE than those with reservoir strain greater than 22% and conduit strain greater than 10% (P < .001). Reservoir strain (hazard ratio, 0.84; 95% confidence interval: 0.77, 0.91; P < .001) and conduit strain (hazard ratio, 0.81; 95% confidence interval: 0.73, 0.89; P < .001) were independent predictors for MACE after adjustment for known risk factors. Finally, LA reservoir and conduit strains provided incremental prognostic value over traditional outcome predictors (Uno C statistic comparing models, 0.75 vs 0.68; P = .04). Conclusion Assessment of left atrial strain, as a measure of left atrial function, provided incremental prognostic information to established predictors in ST-segment elevation myocardial infarction. © RSNA, 2020 Online supplemental material is available for this article. See also the editorial by Kawel-Boehm and Bremerich in this issue.

Event-Free Survival Following Successful Percutaneous Intervention in Acute Myocardial Infarction Depends on Microvascular Perfusion

Background:

Although small trials have detected microvascular obstruction (MVO) with variable frequency following restoration of epicardial blood flow, the independent impact of abnormal microvascular perfusion (MVP) in predicting patient outcome following emergent percutaneous coronary intervention in acute ST-segment–elevation myocardial infarction is unknown. The study aims to determine the impact of abnormal MVP following successful epicardial recanalization in ST-segment–elevation myocardial infarction.

Methods:

MVP was analyzed by low mechanical index ultrasound imaging within 48 hours of emergent percutaneous coronary intervention in 297 patients with acute ST-segment–elevation myocardial infarction who had restoration of Thrombolysis in Myocardial Infarction grade 3 flow in the infarct vessel. Patients were divided into normal segmental replenishment (normal MVP) after high mechanical index impulses versus delayed replenishment but normal plateau intensity (delayed MVP) and both delayed replenishment and reduced plateau intensity (MVO by definition). Demographic variables, left ventricular ejection fraction change, and 5-year follow-up of death, recurrent myocardial infarction, and congestive heart failure were analyzed.

Results:

MVO was seen in 115 patients (39%), delayed MVP in 124 (42%), and normal MVP in 58 patients (19%). Patients with MVO had significant lower left ventricular ejection fraction change (39±12%) at hospital discharge compared with delayed MVP (50±10%; P =0.003) and normal MVP (57±8%; P <0.0001) groups. The MVO group also did not have an improvement in left ventricular ejection fraction change at 3-month follow-up (36±12% versus 37±13%; P =0.18). Both delayed MVP and MVO were independent predictors of adverse events at follow-up (hazard ratio, 21 [CI, 4–116]; P =0.001 and hazard ratio, 30 [CI, 5–183]; P <0.0001, respectively).

Conclusions:

Reduced or absent MVP following successful percutaneous coronary intervention in acute ST-segment–elevation myocardial infarction is common and associated with significantly worse outcome even with Thrombolysis in Myocardial Infarction 3 flow in the infarct vessel.

Intravenously delivered mesenchymal stem cells prevent microvascular obstruction formation after myocardial ischemia/reperfusion injury

Microvascular obstruction (MVO) after primary percutaneous coronary intervention (pPCI) is identified as an independent risk factor for poor prognosis in patients with acute myocardial infarction (AMI). The inflammatory response induced by ischemia and reperfusion (I/R) injury is considered one of the main mechanisms of MVO. Mesenchymal stem cells (MSCs) are a unique stromal cell type that confers an immunomodulatory effect in cardiac disease. The present study aimed to investigate whether immediate intravenous delivery of MSCs could be used as a potential therapeutic method to attenuate MVO formation. A cardiac catheterization-induced porcine model of myocardial I/R injury was established, and allograft MSCs were immediately delivered intravenously. Cardiac magnetic resonance (CMR) imaging was performed on days 2 and 7 after the operation to determine the infarct area, MVO, and cardiac function. The pigs with allograft MSCs showed decreased MVO and infarct size, as well as an improved left ventricular ejection fraction (LVEF). Histological analysis revealed decreased myocyte area, fibrosis, and inflammatory cell infiltration in the peri-infarct zone of pigs with allograft MSCs. Moreover, the concentrations of interleukin-1β (IL-1β), interleukin-6 (IL-6) and C-reactive protein (CRP) in the serum were reduced in the allograft MSC group compared to the control group. Flow cytometry indicated decreased natural killer (NK) cells in the peripheral blood and ischemic heart tissue in the pigs with allograft MSCs. In summary, allograft MSCs delivered intravenously and immediately after myocardial I/R injury can attenuate MVO formation in a porcine model through a decline in the number of NK cells in the myocardium.

Role of Cardiac Magnetic Resonance to Improve Risk Prediction Following Acute ST-Elevation Myocardial Infarction

Cardiac magnetic resonance (CMR) imaging allows comprehensive assessment of myocardial function and tissue characterization in a single examination after acute ST-elevation myocardial infarction. Markers of myocardial infarct severity determined by CMR imaging, especially infarct size and microvascular obstruction, strongly predict recurrent cardiovascular events and mortality. The prognostic information provided by a comprehensive CMR analysis is incremental to conventional risk factors including left ventricular ejection fraction. As such, CMR parameters of myocardial tissue damage are increasingly recognized for optimized risk stratification to further ameliorate the burden of recurrent cardiovascular events in this population. In this review, we provide an overview of the current impact of CMR imaging on optimized risk assessment soon after acute ST-elevation myocardial infarction.