Cardiac magnetic resonance derived late microvascular obstruction assessment post ST-segment elevation myocardial infarction is the best predictor of left ventricular function: a comparison of angiographic and cardiac magnetic resonance derived measurements. Int J Cardiovasc Imaging. 2012;28:1971-1981. [PMID: 22310980 DOI: 10.1007/s10554-012-0021-9]

Index of Microcirculatory Resistance to predict microvascular obstruction in STEMI: A systematic review and meta-analysis

BACKGROUND

Microvascular obstruction (MVO) is an independent predictor of adverse cardiac events after ST-elevation myocardial infarction (STEMI). The Index of Microcirculatory Resistance (IMR) may be a useful marker of MVO, which could simplify the care pathway without the need for Cardiac Magnetic Resonance (CMR). We assessed whether the IMR can predict MVO in STEMI patients.

METHODS AND RESULTS

We conducted a systematic review and meta-analysis, including articles where invasive IMR was performed post primary percutaneous coronary intervention (PCI) in addition to MVO assessment with cardiac MRI. We searched PubMed, Scopus, Embase, and Cochrane databases from inception until January 2023. Baseline characteristics, coronary physiology and cardiac MRI data were extracted by two independent reviewers. The random-effects model was used to pool the data. Among 15 articles identified, nine articles (n = 728, mean age 61, 81% male) contained IMR data stratified by MVO. Patients with MVO had a mean IMR of 41.2 [95% CI 32.4-50.4], compared to 25.3 [18.3-32.2] for those without. The difference in IMR between those with and without MVO was 15.1 [9.7-20.6]. Meta-regression analyses demonstrated a linear relationship between IMR and TIMI grade (β = 0.69 [0.13-1.26]), as well as infarct size (β = 1.18 [0.24-2.11]) or ejection fraction at 6 months (β = -0.18 [-0.35 to -0.01]).

CONCLUSION

In STEMI, patients with MVO had 15-unit higher IMR than those without. IMR also predicts key prognostic endpoints such as infarct size, MVO, and long-term systolic function.

Coronary No-Reflow after Primary Percutaneous Coronary Intervention-Current Knowledge on Pathophysiology, Diagnosis, Clinical Impact and Therapy

Coronary no-reflow (CNR) is a frequent phenomenon that develops in patients with ST-segment elevation myocardial infarction (STEMI) following reperfusion therapy. CNR is highly dynamic, develops gradually (over hours) and persists for days to weeks after reperfusion. Microvascular obstruction (MVO) developing as a consequence of myocardial ischemia, distal embolization and reperfusion-related injury is the main pathophysiological mechanism of CNR. The frequency of CNR or MVO after primary PCI differs widely depending on the sensitivity of the tools used for diagnosis and timing of examination. Coronary angiography is readily available and most convenient to diagnose CNR but it is highly conservative and underestimates the true frequency of CNR. Cardiac magnetic resonance (CMR) imaging is the most sensitive method to diagnose MVO and CNR that provides information on the presence, localization and extent of MVO. CMR imaging detects intramyocardial hemorrhage and accurately estimates the infarct size. MVO and CNR markedly negate the benefits of reperfusion therapy and contribute to poor clinical outcomes including adverse remodeling of left ventricle, worsening or new congestive heart failure and reduced survival. Despite extensive research and the use of therapies that target almost all known pathophysiological mechanisms of CNR, no therapy has been found that prevents or reverses CNR and provides consistent clinical benefit in patients with STEMI undergoing reperfusion. Currently, the prevention or alleviation of MVO and CNR remain unmet goals in the therapy of STEMI that continue to be under intense research.

A Narrative Review of the Classical and Modern Diagnostic Methods of the No-Reflow Phenomenon

The incidence of the no-reflow (NR) phenomenon varies depending on the diagnostic criteria used. If just the angiographic criteria are considered (i.e., a degree of thrombolysis in myocardial infarction ≤2), it will be found that the incidence of NR is quite low; on the other hand, when the myocardial NR is taken into account (i.e., a decrease in the quality of myocardial reperfusion expressed by the degree of myocardial blush), the real incidence is higher. Thus, the early establishment of a diagnosis of NR and the administration of specific treatment can lead to its reversibility. Otherwise, regardless of the follow-up period, patients with NR have a poor prognosis. In the present work, we offer a comprehensive perspective on diagnostic tools for NR detection, for improving the global management of patients with arterial microvasculature damage, which is a topic of major interest in the cardiology field, due to its complexity and its link with severe clinical outcomes.

Value of Fast MVO Identification From Contrast-Enhanced Cine (CE-SSFP) Combined With Myocardial Strain in Predicting Adverse Events in Patients After ST-Elevation Myocardial Infarction

Objectives

Cardiac magnetic resonance imaging (CMR) can be used for a one-step evaluation of myocardial function and pathological features after acute ST-elevation myocardial infarction (STEMI). We aimed to evaluate the value of fast microvascular occlusion (MVO) identification from contrast-enhanced steady-state free precession (CE-SSFP) combined with myocardial strain in predicting major cardiovascular adverse events (MACEs) in primary percutaneous coronary intervention (pPCI) patients with STEMI.

Methods

In total, 237 patients with STEMI who received pPCI and completed CMR scans within the following week were enrolled, MVO identification and the myocardial strain analysis were performed in CE-SSFP images without an additional method. The primary endpoint was the presence of MACE, which is defined as a composite of death, reinfarction, and congestive heart failure (HF).

Results

After 13 months of follow-up [interquartile range (IQR): 11-24], 30 patients (14%) developed MACE; the MVO (hazard ratio (HR) was 3.10; 95% CI: 1.14-8.99, p = 0.028), and the infarct size (IS) (HR: 1.03; 95% CI: 1.0-1.06, p = 0.042) and global longitudinal strain (GLS) (HR: 1.08; 95% CI: 1.01-1.17, p = 0.029) were finally associated with MACE. Receiver operating characteristic (ROC) analyses show that the area under the curve (AUC) of GLS was large (0.73 [95% CI, 0.63-0.82], p = 0.001), and the best cut-off was -11.8%, with 76.7% sensitivity and 58.9% specificity, which are greater than those of IS (0.70, 95% CI, 0.60-0.81, p < 0.001) and MVO (0.68, 95% CI, 0.58-0.78, p < 0.001). However, combining MVO and GLS resulted in a much greater finding (AUC = 0.775, 95% CI: 0.727-0.824, p < 0.001) and better sensitivity and specificity (83.3%, 66.5%).

Conclusion

Microvascular occlusion identification from contrast-enhanced cine combined with myocardial strain could be a quick and reliable option for patients with STEMI who underwent pPCI; it correlates well with the prognosis of patients with STEMI in terms of MACE.

Presence of Microvascular Dysfunction and CHA2DS2-VASc Score in Patients with ST-Segment Myocardial Infarction after Primary Percutaneous Coronary Intervention

Objective

We aimed to investigate the relation between CHA₂DS₂-VASc score and microvascular dysfunction (MVD) assessed by the index of microvascular resistance (IMR) immediately after primary percutaneous intervention (PPCI) for patients with ST-segment elevation myocardial infarction (STEMI).

Subjects and Methods

The study included 115 consecutive patients with STEMI who underwent successful PPCI. Angiographic results of reperfusion were inspected to evaluate the association of high CHA₂DS₂-VASc score and IMR. Also, we assessed echocardiographic changes with respect to CHA₂DS₂-VASc score.

Results

Subjects were stratified into 2 groups based on IMR </≥ 40 U; 72 patients (62.6) with IMR <40 U and 43 patients (37.4) with IMR ≥40 U. Patients with IMR ≥40 U had higher CHA₂DS₂-VASc score (p < 0.001). CHA₂DS₂-VASc score was significantly correlated with increased left atrial volume index, diastolic dysfunction, wall motion score index, and inversely correlated left ventricular ejection. Moreover, CHA₂DS₂-VASc score was strongly correlated with IMR (p < 0.001). At multivariate analysis, low systolic blood pressure, stent diameter, and CHA₂DS₂-VASc score were associated with MVD. Besides, CHA₂DS₂-VASc score ≥4 was the optimal value in predicting MVD (IMR ≥40) in STEMI patients.

Conclusions

The data of the current study point out that increased CHA₂DS₂-VASc score, lower systolic blood pressure <90 mm Hg, and stent diameter are associated with increased incidence of MVD (increased IMR) after PPCI of STEMI. We suggest that the CHA₂DS₂-VASc score may be a simple, inexpensive useful risk score for the prediction of MVD risk after PPCI for STEMI patients.

Clinical outcomes of nicorandil administration in patients with acute ST-segment elevation myocardial infarction undergoing primary percutaneous coronary intervention: a systematic review and meta-analysis of randomized controlled trials

BACKGROUND

Primary percutaneous coronary intervention is the treatment of choice in ST-segment elevation myocardial infarction and no-reflow phenomenon is still an unsolved problem.

METHODS

We searched PubMed, EmBase, and Cochrane Central Register of Controlled Trials for relevant randomized controlled trials. The primary endpoint was the incidence of major adverse cardiac events and the secondary endpoint was the incidences of no-reflow phenomenon and complete resolution of ST-segment elevation.

RESULTS

Eighteen randomized controlled trials were enrolled. Nicorandil significantly reduced the incidence of no-reflow phenomenon (OR, 0.46; 95% CI, 0.36-0.59; P < 0.001; I² = 0%) and major adverse cardiac events (OR, 0.42; 95% CI, 0.27-0.64; P < 0.001; I² = 52%). For every single outcome of major adverse cardiac events, only heart failure and ventricular arrhythmia were significantly improved with no heterogeneity (OR, 0.36; 95% CI, 0.23-0.57, P < 0.001; OR, 0.43; 95% CI, 0.31-0.60, P < 0.001 respectively). A combination of intracoronary and intravenous nicorandil administration significantly reduced the incidence of major adverse cardiac events with no heterogeneity (OR, 0.24; 95% CI, 0.13-0.43, P < 0.001; I² = 0%), while a single intravenous administration could not (OR, 0.66; 95% CI, 0.40-1.06, P = 0.09; I² = 52%).

CONCLUSIONS

Nicorandil can significantly improve no-reflow phenomenon and major adverse cardiac events in patients undergoing primary percutaneous coronary intervention. The beneficial effects on major adverse cardiac events might be driven by the improvements of heart failure and ventricular arrhythmia. A combination of intracoronary and intravenous administration might be an optimal usage of nicorandil.

Effects of Peripheral Arterial Disease Interventions on Survival: A Propensity-Score Matched Analysis Using VQI Data

BACKGROUND

Atherectomy is currently being used extensively for occlusive peripheral artery disease (PAD) interventions without proven benefits. This analysis examines the effects of atherectomy and other endovascular interventions on patient survival.

OBJECTIVES

The aim of this study is to compare overall survival for patients undergoing PAD endovascular interventions, such as plain old balloon angioplasty (POBA), stent deployment and atherectomy.

METHODS

Propensity score matched cohorts were constructed to conduct pairwise comparisons of overall survival in patients who underwent stenosis and occlusive PAD interventions between May 2011 and February 2020 using Vascular Quality Initiative (VQI) regional registry data. Inverse probability treatment weighting method was used to compare secondary outcomes of in-hospital mortality, length of stay, complications and major amputations. Comparative analysis was performed for POBA vs stenting, POBA vs atherectomy, and stenting vs atherectomy.

RESULTS

A total number of 15281 eligible cases were identified. After propensity score matching, 6094, 4032, and 3312 cases were used to compare POBA versus stent deployment, POBA versus atherectomy and stent versus atherectomy, respectively. Stent deployment had significantly better overall survival compared with POBA and atherectomy (P < 0.001). Multivariable Cox proportional hazard models suggested stenting was associated with a reduction in mortality hazard by 30% compared with POBA (HR: 0.7; 95% CI: 0.6-0.82; P < 0.001) and a 40% mortality reduction compared with atherectomy (HR: 0.6; 95% CI: 0.48-0.75; P < 0.001). No significant difference was found between POBA and atherectomy. There was no statistical difference in other secondary outcomes which were comparable among all cohorts.

CONCLUSIONS

Stent deployment was significantly superior to POBA and atherectomy in terms of overall survival with comparable complication and amputation rates. The natural history of PAD patients presenting with claudication is associated with an extremely low annual mortality risk. Therefore, further examinations of outcomes, especially in regards to mortality rates, both POBA and atherectomy on the management of PAD patients especially those presenting with claudication is warranted.

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.

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.

Adenosine stress perfusion cardiac magnetic resonance imaging in patients undergoing intracoronary bone marrow cell transfer after ST-elevation myocardial infarction: the BOOST-2 perfusion substudy

AIMS

In the placebo-controlled, double-blind BOne marrOw transfer to enhance ST-elevation infarct regeneration (BOOST) 2 trial, intracoronary autologous bone marrow cell (BMC) transfer did not improve recovery of left ventricular ejection fraction (LVEF) at 6 months in patients with ST-elevation myocardial infarction (STEMI) and moderately reduced LVEF. Regional myocardial perfusion as determined by adenosine stress perfusion cardiac magnetic resonance imaging (S-CMR) may be more sensitive than global LVEF in detecting BMC treatment effects. Here, we sought to evaluate (i) the changes of myocardial perfusion in the infarct area over time (ii) the effects of BMC therapy on infarct perfusion, and (iii) the relation of infarct perfusion to LVEF recovery at 6 months.

METHODS AND RESULTS

In 51 patients from BOOST-2 (placebo, n = 10; BMC, n = 41), S-CMR was performed 5.1 ± 2.9 days after PCI (before placebo/BMC treatment) and after 6 months. Infarct perfusion improved from baseline to 6 months in the overall patient cohort as reflected by the semi-quantitative parameters, perfusion defect-infarct size ratio (change from 0.54 ± 0.20 to 0.43 ± 0.22; P = 0.006) and perfusion defect-upslope ratio (0.54 ± 0.23 to 0.68 ± 0.22; P < 0.001), irrespective of randomised treatment. Perfusion defect-upslope ratio at baseline correlated with LVEF recovery (r = 0.62; P < 0.001) after 6 months, with a threshold of 0.54 providing the best sensitivity (79%) and specificity (74%) (area under the curve, 0.79; 95% confidence interval, 0.67-0.92).

CONCLUSION

Infarct perfusion improves from baseline to 6 months and predicts LVEF recovery in STEMI patients undergoing early PCI. Intracoronary BMC therapy did not enhance infarct perfusion in the BOOST-2 trial.

Index of Microcirculatory Resistance at the Time of Primary Percutaneous Coronary Intervention Predicts Early Cardiac Complications: Insights From the OxAMI (Oxford Study in Acute Myocardial Infarction) Cohort

Background

Early risk stratification after primary percutaneous coronary intervention (PPCI) for ST‐segment–elevation myocardial infarction is currently challenging. Identification of a low‐risk group may improve triage of patients to alternative clinical pathways and support early hospital discharge. Our aim was to assess whether the index of microcirculatory resistance (IMR) at the time of PPCI can identify patients at low risk of early major cardiac complications and to compare its performance against guideline‐recommended risk scores.

Methods and Results

IMR was measured using a pressure–temperature sensor wire. Cardiac complications were defined as the composite of cardiac death, cardiogenic shock, pulmonary edema, malignant arrhythmias, cardiac rupture, and presence of left ventricular thrombus either before hospital discharge or within 30‐day follow‐up. In total, 261 patients undergoing PPCI who were eligible for coronary physiology assessment were prospectively enrolled. Twenty‐two major cardiac complications were reported. Receiver operating characteristic curve analysis confirmed the utility of IMR in predicting complications and showed significantly better performance than coronary flow reserve, the Primary Angioplasty in Myocardial Infarction II (PAMI‐II), and Zwolle score (P≤0.006). Low microvascular resistance (IMR ≤40) was measured in 159 patients (61%) of the study population and identified all patients who were free of major cardiac complications (sensitivity: 100%; 95% CI, 80.5–100%).

Conclusions

IMR immediately at the end of PPCI for ST‐segment–elevation myocardial infarction reliably predicts early major cardiac complications and performed significantly better than recommended risk scores. These novel data have implications for early risk stratification after PPCI.

Cardiac MR Imaging in Acute Coronary Syndrome: Application and Image Interpretation

Acute coronary syndrome (ACS) is a frequent cause of hospitalization and coronary interventions. Cardiac magnetic resonance (MR) imaging is an increasingly used technique for initial work-up of chest pain and early post-reperfusion and follow-up evaluation of ACS to identify patients at high risk of further cardiac events. Cardiac MR imaging can evaluate with accuracy a variety of prognostic indicators of myocardial damage, including regional myocardial dysfunction, infarct distribution, infarct size, myocardium at risk, microvascular obstruction, and intramyocardial hemorrhage in both acute setting and later follow-up examinations. In addition, MR imaging is useful to rule out other causes of acute chest pain in patients admitted to the emergency department. In this article, a brief explanation of the pathophysiology, classification, and treatment options for patients with ACS will be introduced. Indications of cardiac MR imaging in ACS patients will be reviewed and specific cardiac MR protocol, image interpretation, and potential diagnostic pitfalls will be discussed. ^© RSNA, 2017 Online supplemental material is available for this article.

Reperfusion ventricular arrhythmia bursts identify larger infarct size in spite of optimal epicardial and microvascular reperfusion using cardiac magnetic resonance imaging

AIMS

Ventricular arrhythmia (VA) bursts following recanalisation in acute ST-elevation myocardial infarction (STEMI) are related to larger infarct size (IS). Inadequate microvascular reperfusion, as determined by microvascular obstruction (MVO) using cardiac magnetic resonance imaging (CMR), is also known to be associated with larger IS. This study aimed to test the hypothesis that VA bursts identify larger infarct size in spite of optimal microvascular reperfusion.

METHODS

All 65 STEMI patients from the Maastricht ST elevation (MAST) study with brisk epicardial flow (TIMI 3), complete ST recovery post-percutaneous coronary intervention and early CMR were included. Using 24-hour Holter registrations from the time of admission, VA bursts were identified against subject-specific Holter background VA rates using a statistical outlier method. MVO and final IS were determined using delayed enhancement CMR.

RESULTS

MVO was present in 37/65 (57%) of patients. IS was significantly smaller in the group without MVO (median 9.4% vs. 20.5%; p < 0.001). IS in the group with MVO did not differ depending on VA burst ( n = 28/37; median 20.8% vs. 19.7%; p = 0.64). However, in the group without MVO, VA burst was associated with significantly larger IS ( n = 17/28; median 10.5% vs. 4.1%; p = 0.037). In multivariable analyses, VA burst as well as anterior infarct location remained independent predictors of larger infarct size.

CONCLUSION

In the presence of suboptimal reperfusion with MVO by CMR, VA burst does not further define MI size. However, with optimal TIMI 3 reperfusion and optimal microvascular perfusion (i.e. no MVO), VA burst is associated with larger IS, indicating that VA burst is a marker of additional cell death.

Cardiovascular magnetic resonance imaging assessment of outcomes in acute myocardial infarction

Cardiovascular magnetic resonance (CMR) imaging uniquely characterizes myocardial and microvascular injury in acute myocardial infarction (AMI), providing powerful surrogate markers of outcomes. The last 10 years have seen an exponential increase in AMI studies utilizing CMR based endpoints. This article provides a contemporary, comprehensive review of the powerful role of CMR imaging in the assessment of outcomes in AMI. The theory, assessment techniques, chronology, importance in predicting left ventricular function and remodelling, and prognostic value of each CMR surrogate marker is described in detail. Major studies illustrating the importance of the markers are summarized, providing an up to date review of the literature base in CMR imaging in AMI.

Proximal culprit lesion and coronary artery occlusion independently predict the risk of microvascular obstruction in acute myocardial infarction

Microvascular obstruction (MO) and coronary flow have been independently described to have a high prognostic impact after acute myocardial infarction (AMI). Their interdependence has not been precisely elucidated, so far. Aim of this study was to investigate the impact of coronary flow on the occurrence of MO in patients with AMI. 336 patients with revascularized AMI were examined by cardiac magnetic resonance imaging. Patients were categorised into two groups based on the presence of MO. Procedural characteristics and marker of infarct size were analyzed. MO was present in 110 (33 %) and absent in 226 (67 %) patients. Both groups differed significantly regarding pre- and post-interventional thrombolysis in myocardial infarction (TIMI) flow. After multivariable regression analysis pre-interventional TIMI-flow 0, proximal culprit lesion, post-interventional TIMI-flow <III and creatine-kinase-myocardial band (CK-MB) remained strong independent predictors for MO. Odds ratios for pre-interventional TIMI-flow 0 were 2.31 (95 % CI 1.04-5.11, P = 0.034); for proximal culprit lesion 11.94 (95 % CI 5.70-25.01, P < 0.001); for post-interventional TIMI-flow III 0.28 (95 % CI 0.10-0.74, P = 0.010) and for CK-MB 1.50 (95 % CI 1.24-1.82, P < 0.001). Pre-interventional proximal coronary artery occlusion (TIMI 0) and insufficient post-interventional coronary reperfusion (TIMI-flow  <III) have a high impact on the occurrence of MO in AMI.

Ventricular arrhythmia burst is an independent indicator of larger infarct size even in optimal reperfusion in STEMI

OBJECTIVE

We hypothesized that ventricular arrhythmia (VA) bursts during reperfusion phase are a marker of larger infarct size despite optimal epicardial and microvascular perfusion.

METHODS

126 STEMI patients were studied with 24h continuous, 12-lead Holter monitoring. Myocardial blush grade (MBG) was determined and VA bursts were identified against subject-specific background VA rates in core laboratories. Delayed-enhancement cardiovascular magnetic resonance imaging was used to determine infarct size.

RESULTS

In the group with MBG 3 no significant differences were found for baseline characteristics between burst versus no burst (102 vs. 24). In those with optimal epicardial and microvascular reperfusion (TIMI 3, stable ST-recovery, and MBG 3), VA burst was associated with larger infarct size (N=102/126; median 11.0 vs. 5.1%; p=0.004).

CONCLUSION

In the event of MBG 3, VA bursts were associated with significantly larger infarct size even if optimal epicardial and microvascular reperfusion was present.

Microvascular Obstruction Evaluation Using Cardiovascular Magnetic Resonance (CMR) in ST-Elevated Myocardial Infarction (STEMI) Patients

BACKROUND

Restoration of blood flow in epicardial coronary artery in patients with acute myocardial infarction can, but does not have to restore efficient blood flow in coronary circulation. The aim of the study was a direct comparison of microvascular obstruction (MVO) detected by rest and stress perfusion imaging and gadolinium enhancement obtained 2 min. (early MVO) and 15 min. (delayed MVO) post contrast.

MATERIAL/METHODS

106 patients with first anterior myocardial infarction were studied. Cardiovascular magnetic resonance (CMR) was performed 5±2 days after primary percutaneous coronary intervention (pPCI). Stress and rest perfusion imaging was performed as well as early and delayed gadolinium enhancement and systolic function assessment. Scoring of segmental function, perfusion defect, MVO and scar transmurality was performed in 16 segment left ventricular model.

RESULTS

The prevalence of MVO varies significantly between imaging techniques ranging from 48.8% for delayed MVO to 94% with stress perfusion. Median sum of scores was significantly different for each technique: stress perfusion 13 (7; 18), rest perfusion 3 (0.5; 6), early MVO 3 (0; 8), delayed MVO 0 (0; 4); p<0.05. Infarct size, stress and rest perfusion defects were independent predictors of LV EF at discharge from hospital.

CONCLUSIONS

Imaging protocol has a significant impact on MVO results. The study is the first to describe a stress-induced MVO in STEMI patients. Further research is needed to evaluate its impact on a long term prognosis.

Temporal course of microvascular obstruction after myocardial infarction assessed by MRI

PURPOSE

We aimed to analyze the extent of microvascular obstruction (MO) after the index event compared with the follow-up at a median of three months.

METHODS

We identified 31 patients with MO after primary percutaneous coronary intervention of acute myocardial infarction by cardiac magnetic resonance imaging. The initial examination was performed after the index event, and 27 patients had the follow-up exam after a median of three months (interquartile range, 2-4 months). In addition, we examined 10 patients without MO after transmural myocardial infarction, as a control group.

RESULTS

MO disappeared in 23 of 27 patients (85%) in the follow-up and transformed into transmural late gadolinium enhancement. In patients with persistent MO, mean MO size decreased from 2.25% to 1.25%. In patients with MO, mean infarct size decreased significantly from 20.8% to 14.7% (P < 0.001). In the control group, mean infarct size decreased from 12.7% to 10.5% in the follow-up scan (P = 0.137).

CONCLUSION

MO is significantly reduced during the follow-up after acute myocardial infarction.

Frame counting improves the assessment of post-reperfusion microvascular patency by TIMI myocardial perfusion grade: Evidence from cardiac magnetic resonance imaging

BACKGROUND

Quantitative modification of TIMI myocardial perfusion grade (TMPG) by the method of frame counting may improve its sensitivity and the false negative rate for post-reperfusion microvascular dysfunction (MVD) in ST segment-elevated myocardial infarction (STEMI) patients.

METHODS

The durations of contrast-washout from infarction area of 139 patients were measured by counting the cine-frame numbers between the appearance and disappearance of myocardial blush. The achieved new index, TMP Frame Counting (TMP-FC) was referenced by cardiac magnetic resonance, by which MVD was defined as microvascular obstruction on gadolinium late-enhancement imaging.

RESULTS

Median TMP-FC differed significantly between patients with and without MVD (126 frames, IQR 105-160 vs. 86 frames, IQR 75-100, p<0.001). By receiver-operating characteristic analysis, the cutoff of TMP-FC at ≥ 95.5 frames represented an independent predictor of MVD (OR=11.61, p<0.001). TMP-FC had similar specificity (75%) and positive predictive value (88%), but significantly improved sensitivity (85.3%) and negative predictive value (70.2%) for MVD compared with TMPG (88.6%, 86.5%, 33.7% and 38.2%, respectively) and other traditional angiographic assessments, leading to a better overall accuracy (area under the curve: 0.801 compared with 0.612 from TMPG, p<0.001) for the evaluation of microvascular patency. TMP-FC was positively correlated with MVD extent (r=0.5, p<0.001). Abnormal TMP-FC was associated with larger infarction size (28.67 ± 13.72% vs. 16.51 ± 10.68% of left ventricular mass, p<0.001) and lower LVEF (49.37 ± 11.06% vs. 56.84 ± 9.72%, p<0.001).

CONCLUSION

Frame counting can improve the accuracy of TMPG for MVD. Moreover, TMP-FC is correlated with the degree of MVD and cardiac detriments, which is useful for risk stratification.

Effect of microvascular obstruction and intramyocardial hemorrhage by CMR on LV remodeling and outcomes after myocardial infarction: a systematic review and meta-analysis

The goal of this systematic analysis is to provide a comprehensive review of the current cardiac magnetic resonance data on microvascular obstruction (MVO) and intramyocardial hemorrhage (IMH). Data related to the association of MVO and IMH in patients with acute myocardial infarction (MI) with left ventricular (LV) function, volumes, adverse LV remodeling, and major adverse cardiac events (MACE) were critically analyzed. MVO is associated with a lower ejection fraction, increased ventricular volumes and infarct size, and a greater risk of MACE. Late MVO is shown to be a stronger prognostic marker for MACE and cardiac death, recurrent MI, congestive heart failure/heart failure hospitalization, and follow-up LV end-systolic volumes than early MVO. IMH is associated with LV remodeling and MACE on pooled analysis, but because of limited data and heterogeneity in study methodology, the effects of IMH on remodeling require further investigation.

Cyclosporine A reduces microvascular obstruction and preserves left ventricular function deterioration following myocardial ischemia and reperfusion

Postconditioning and cyclosporine A prevent mitochondrial permeability transition pore opening providing cardioprotection during ischemia/reperfusion. Whether microvascular obstruction is affected by these interventions is largely unknown. Pigs subjected to coronary occlusion for 1 h followed by 3 h of reperfusion were assigned to control (n = 8), postconditioning (n = 9) or cyclosporine A intravenous infusion 10–15 min before the end of ischemia (n = 8). Postconditioning was induced by 8 cycles of repeated 30-s balloon inflation and deflation. After 3 h of reperfusion magnetic resonance imaging, triphenyltetrazolium chloride/Evans blue staining and histopathology were performed. Microvascular obstruction (MVO, percentage of gadolinium-hyperenhanced area) was measured early (3 min) and late (12 min) after contrast injection. Infarct size with double staining was smaller in cyclosporine (46.2 ± 3.1 %, P = 0.016) and postconditioning pigs (47.6 ± 3.9 %, P = 0.008) versus controls (53.8 ± 4.1 %). Late MVO was significantly reduced by cyclosporine (13.9 ± 9.6 %, P = 0.047) but not postconditioning (23.6 ± 11.7 %, P = 0.66) when compared with controls (32.0 ± 16.9 %). Myocardial blood flow in the late MVO was improved with cyclosporine versus controls (0.30 ± 0.06 vs 0.21 ± 0.03 ml/g/min, P = 0.002) and was inversely correlated with late-MVO extent (R² = 0.93, P < 0.0001). Deterioration of left ventricular ejection fraction (LVEF) between baseline and 3 h of reperfusion was smaller with cyclosporine (−7.9 ± 2.4 %, P = 0.008) but not postconditioning (−12.0 ± 5.5 %, P = 0.22) when compared with controls (−16.4 ± 5.5 %). In the three groups, infarct size (β = −0.69, P < 0.001) and late MVO (β = −0.33, P = 0.02) were independent predictors of LVEF deterioration following ischemia/reperfusion (R² = 0.73, P < 0.001). Despite both cyclosporine A and postconditioning reduce infarct size, only cyclosporine A infusion had a beneficial effect on microvascular damage and was associated with better preserved LV function when compared with controls.

Characterizing the inflammatory tissue response to acute myocardial infarction by clinical multimodality noninvasive imaging

BACKGROUND

Myocardial infarction (MI) triggers a systemic inflammatory response which determines subsequent healing. Experimentally, cardiac positron emission tomography and magnetic resonance imaging have been used successfully to obtain mechanistic insights. We explored the translational potential in patients early after MI.

METHODS AND RESULTS

Positron emission tomography/computed tomography and cardiac magnetic resonance were performed in 15 patients <7 days after first MI. Cardiac magnetic resonance showed regional transmural late gadolinium enhancement and edema exceeding the area of late gadolinium enhancement. Using F-18 deoxyglucose with heparin pretreatment, metabolic rate of glucose (MRGlc) was significantly increased in infarct versus remote myocardium (median, 2.0 versus 0.4 mg/min per 100 mL; P=0.0001). MRGlc in infarct correlated with remote myocardium (ρ=0.64; P=0.01), spleen (ρ=0.82; P=0.0002), and bone marrow(ρ=0.57; P=0.03), but not with muscle or liver. Regionally, F-18 deoxyglucose score was highest in segments with late gadolinium enhancement versus edema only and remote (median, 2.0 versus 1.8 versus 0.4; P<0.0001). Patients requiring repeat intervention during preliminary follow-up of 11±5 months tended to have higher early post-MI MRGlc. Five patients with chronic, stable MI served as controls. Opposite to acute MI, MRGlc was lower in infarct (median infarct/remote ratio, 0.6 versus 3.2 for acute MI; P=0.001), and there was no correlation with bone marrow or spleen MRGlc.

CONCLUSIONS

Increased glucose utilization after heparin-induced suppression of myocyte uptake appears to mostly reflect inflammatory activity in damaged myocardium early after MI. Consistent with prior preclinical observations, and in contrast to chronic MI, this is associated with activity in spleen and bone marrow as sources of inflammatory cells. Positron emission tomography and cardiac magnetic resonance multimodality characterization of the acutely infarcted, inflamed myocardium may provide multiparametric end points for clinical studies aiming at support of infarct healing.

Magnetic resonance-derived circumferential strain provides a superior and incremental assessment of improvement in contractile function in patients early after ST-segment elevation myocardial infarction

BACKGROUND

We evaluate whether circumferential strain derived from grid-tagged CMR is a better method for assessing improvement in segmental contractile function after STEMI compared to late gadolinium enhancement (LGE).

METHODS

STEMI patients post primary PCI underwent baseline CMR (day 3) and follow-up (day 90). Cine, grid-tagged and LGE images were acquired. Baseline LGE infarct hyperenhancement was categorised as ≤25 %, 26-50 %, 51-75 % and >75 % hyperenhancement. The segmental baseline circumferential strain (CS) and circumferential strain rate (CSR) were calculated from grid-tagged images. Segments demonstrating an improvement in wall motion of ≥1 grade compared to baseline were regarded as having improved segmental contractile-function.

RESULTS

Forty-five patients (aged 58 ± 12 years) and 179 infarct segments were analysed. A baseline CS cutoff of -5 % had sensitivity of 89 % and specificity of 70 % for detection of improvement in segmental-contractile-function. On receiver-operating characteristic analysis for predicting improvement in contractile function, AUC for baseline CS (0.82) compared favourably to LGE hyperenhancement (0.68), MVO (0.67) and baseline-CSR (0.74). On comparison of AUCs, baseline CS was superior to LGE hyperenhancement and MVO in predicting improvement in contractile function (P < 0.001). On multivariate-analysis, baseline CS was the independent predictor of improvement in segmental contractile function (P < 0.001).

CONCLUSION

Grid-tagged CMR-derived baseline CS is a superior predictor of improvement in segmental contractile function, providing incremental value when added to LGE hyperenhancement and MVO following STEMI.

KEY POINTS

Baseline CS predicts contractile function recovery better than LGE and MVO following STEMI. Baseline CS predicts contractile function recovery better than baseline CSR following STEMI. Baseline CS provides incremental value to LGE and MVO following STEMI.

Imaging the myocardial microcirculation post-myocardial infarction

The myocardial microcirculation provides the vital pressure control and metabolic homeostasis for normal muscle function. Microvascular dysfunction is implicated in chronic cardiac disease and can signify higher risk, but its effect in acute myocardial infarction (AMI) can be profound. Modern management of AMI is focussed entirely on timely epicardial coronary patency, but as a result can leave microcirculatory devastation in its wake. The 'no-reflow' phenomenon occurs in up to 40 % of those successfully reperfused following an ST-elevation AMI (STEMI), and reflects significant microvessel injury that at its most severe involves both microvascular obstruction (MVO) and intramyocardial haemorrhage. Myocardial contrast echocardiography and cardiac magnetic resonance imaging have both led the field in establishing MVO as the prime determinant of adverse left ventricular (LV) remodeling, LV dysfunction, heart failure and increased mortality. These imaging techniques will be essential to support future research endeavours and shift focus to the maintenance of microvascular flow in AMI.

Utility of Thrombectomy in Primary Percutaneous Coronary Intervention

Thrombectomy in the setting of primary percutaneous coronary intervention allows for improved macrovascular and microvascular perfusion, possible limitation of infarct size, and the preservation of left ventricular function and myocardial viability. The beneficial tissue level effects of thrombectomy have translated into an improvement in cardiovascular mortality. A variety of thrombectomy devices are currently available, including aspiration thrombectomy catheters and rheolytic catheters. A review of the various types of thrombectomy devices available, clinical evidence for their use, clinical pearls for use, and device troubleshooting are presented.

CMR of microvascular obstruction and hemorrhage in myocardial infarction

Microvascular obstruction (MO) or no-reflow phenomenon is an established complication of coronary reperfusion therapy for acute myocardial infarction. It is increasingly recognized as a poor prognostic indicator and marker of subsequent adverse LV remodeling. Although MO can be assessed using various imaging modalities including electrocardiography, myocardial contrast echocardiography, nuclear scintigraphy, and coronary angiography, evaluation by cardiovascular magnetic resonance (CMR) is particularly useful in enhancing its detection, diagnosis, and quantification, as well as following its subsequent effects on infarct evolution and healing. MO assessment has become a routine component of the CMR evaluation of acute myocardial infarction and will increasingly play a role in clinical trials of adjunctive reperfusion agents and strategies. This review will summarize the pathophysiology of MO, current CMR approaches to diagnosis, clinical implications, and future directions needed for improving our understanding of this common clinical problem.

Infarct tissue characterization in implantable cardioverter-defibrillator recipients for primary versus secondary prevention following myocardial infarction: a study with contrast-enhancement cardiovascular magnetic resonance imaging

Knowledge about potential differences in infarct tissue characteristics between patients with prior life-threatening ventricular arrhythmia versus patients receiving prophylactic implantable cardioverter-defibrillator (ICD) might help to improve the current risk stratification in myocardial infarction (MI) patients who are considered for ICD implantation. In a consecutive series of (ICD) recipients for primary and secondary prevention following MI, we used contrast-enhanced (CE) cardiovascular magnetic resonance (CMR) imaging to evaluate differences in infarct tissue characteristics. Cine-CMR measurements included left ventricular end-diastolic and end-systolic volumes (EDV, ESV), left ventricular ejection fraction (LVEF), wall motion score index (WMSI), and mass. CE-CMR images were analyzed for core, peri, and total infarct size, infarct localization (according to coronary artery territory), and transmural extent. In this study, 95 ICD recipients were included. In the primary prevention group (n = 66), LVEF was lower (23 ± 9 % vs. 31 ± 14 %; P < 0.01), ESV and WMSI were higher (223 ± 75 ml vs. 184 ± 97 ml, P = 0.04, and 1.89 ± 0.52 vs. 1.47 ± 0.68; P < 0.01), and anterior infarct localization was more frequent (P = 0.02) than in the secondary prevention group (n = 29). There were no differences in infarct tissue characteristics between patients treated for primary versus secondary prevention (P > 0.6 for all). During 21 ± 9 months of follow-up, 3 (5 %) patients in the primary prevention group and 9 (31 %) in the secondary prevention group experienced appropriate ICD therapy for treatment of ventricular arrhythmia (P < 0.01). There was no difference in infarct tissue characteristics between recipients of ICD for primary versus secondary prevention, while the secondary prevention group showed a higher frequency of applied ICD therapy for ventricular arrhythmia.