Treatment and Care of Patients with ST-Segment Elevation Myocardial Infarction-What Challenges Remain after Three Decades of Primary Percutaneous Coronary Intervention?

Primary percutaneous coronary intervention (pPCI) has revolutionized the prognosis of ST-segment elevation myocardial infarction (STEMI) and is the gold standard treatment. As a result of its success, the number of pPCI centres has expanded worldwide. Despite decades of advancements, clinical outcomes in STEMI patients have plateaued. Out-of-hospital cardiac arrest and cardiogenic shock remain a major cause of high in-hospital mortality, whilst the growing burden of heart failure in long-term STEMI survivors presents a growing problem. Many elements aiming to optimize STEMI treatment are still subject to debate or lack sufficient evidence. This review provides an overview of the most contentious current issues in pPCI in STEMI patients, with an emphasis on unresolved questions and persistent challenges.

Coronary microvascular obstruction and dysfunction in patients with acute myocardial infarction

Despite prompt epicardial recanalization in patients presenting with ST-segment elevation myocardial infarction (STEMI), coronary microvascular obstruction and dysfunction (CMVO) is still fairly common and is associated with poor prognosis. Various pharmacological and mechanical strategies to treat CMVO have been proposed, but the positive results reported in preclinical and small proof-of-concept studies have not translated into benefits in large clinical trials conducted in the modern treatment setting of patients with STEMI. Therefore, the optimal management of these patients remains a topic of debate. In this Review, we appraise the pathophysiological mechanisms of CMVO, explore the evidence and provide future perspectives on strategies to be implemented to reduce the incidence of CMVO and improve prognosis in patients with STEMI.

The Use of Thrombectomy during Primary Percutaneous Coronary Intervention: Resurrecting an Old Concept in Contemporary Practice

Optimal myocardial reperfusion during primary percutaneous coronary intervention (pPCI) is increasingly recognized to be beyond restoring epicardial coronary flow. Both invasive and non-invasive tools have highlighted the limitation of using this metric, and more efforts are focused towards achieving optimal reperfusion at the level of the microcirculation. Recent data highlighted the close relationship between thrombus burden and impaired microcirculation in patients presenting with ST-segment elevation myocardial infarction (STEMI). Moreover, distal embolization was an independent predictor of mortality in patients with STEMI. Likewise, the development of no-reflow phenomenon has been directly linked with worse clinical outcomes. Adjunctive thrombus aspiration during pPCI is intuitively intended to remove atherothrombotic material to mitigate the risk of distal embolization and the no-reflow phenomenon (NRP). However, prior trials on the use of thrombectomy during pPCI did not support its routine use, with comparable clinical endpoints to patients who underwent PCI alone. This article aims to review the existing literature highlighting the limitation on the use of thrombectomy and provide future insights into trials investigating the role of thrombectomy in contemporary pPCI.

Microvascular Obstruction in Acute Myocardial Infarction, a Potential Therapeutic Target

Microvascular obstruction (MVO) is a recognised phenomenon following mechanical reperfusion in patients presenting with ST-segment elevation myocardial infarction (STEMI). Invasive and non-invasive modalities to detect and measure the extent of MVO vary in their accuracy, suggesting that this phenomenon may reflect a spectrum of pathophysiological changes at the level of coronary microcirculation. The importance of detecting MVO lies in the observation that its presence adds incremental risk to patients following STEMI treatment. This increased risk is associated with adverse cardiac remodelling seen on cardiac imaging, increased infarct size, and worse patient outcomes. This review provides an outline of the pathophysiology, clinical implications, and prognosis of MVO in STEMI. It describes historic and novel pharmacological and non-pharmacological therapies to address this phenomenon in conjunction with primary PCI.

Prospects for Precision Medicine in Acute Myocardial Infarction: Patient-Level Insights into Myocardial Injury and Repair

The past decade has seen a marked expansion in the understanding of the pathobiology of acute myocardial infarction and the systemic inflammatory response that it elicits. At the same time, a portfolio of tools has emerged to characterise some of these processes in vivo. However, in clinical practice, key decision making still largely relies on assessment built around the timing of the onset of chest pain, features on electrocardiograms and measurements of plasma troponin. Better understanding the heterogeneity of myocardial injury and patient-level responses should provide new opportunities for diagnostic stratification to enable the delivery of more rational therapies. Characterisation of the myocardium using emerging imaging techniques such as the T1, T2 and T2* mapping techniques can provide enhanced assessments of myocardial statuses. Physiological measures, which include microcirculatory resistance and coronary flow reserve, have been shown to predict outcomes in AMI and can be used to inform treatment selection. Functionally informative blood biomarkers, including cellular transcriptomics; microRNAs; extracellular vesicle analyses and soluble markers, all give insights into the nature and timing of the innate immune response and its regulation in acute MI. The integration of these and other emerging tools will be key to developing a fuller understanding of the patient-level processes of myocardial injury and repair and should fuel new possibilities for rational therapeutic intervention.

Prognostic Role of Residual Thrombus Burden Following Thrombectomy: Insights From the TOTAL Trial

BACKGROUND

It is unclear whether more effective forms of thrombus removal than current aspiration catheters would lead to improved outcomes. We sought to evaluate the prognostic role of residual thrombus burden (rTB), after manual thrombectomy, in patients undergoing primary percutaneous coronary intervention with routine manual thrombectomy in the TOTAL trial (Thrombectomy Versus PCI Alone).

METHODS

This is a single-arm analysis of patients from the TOTAL trial who underwent routine manual aspiration thrombectomy. The rTB was quantified by an angiographic core laboratory using the Thrombolysis in Myocardial Infarction criteria and validated using existing optical coherent tomography data. Large rTB was defined as grade ≥3. The primary outcome was death from cardiovascular causes, recurrent myocardial infarction, cardiogenic shock, or new or worsening heart failure within 180 days.

RESULTS

Of 5033 patients randomized to routine thrombectomy, 2869 patients had quantifiable rTB (1014 [35%] had large rTB). Patients with large rTB were more likely to have hypertension, previous percutaneous coronary intervention, myocardial infarction, or Killip class III on presentation but less likely to have Killip class I. The primary outcome occurred more frequently in patients with large rTB, even after adjustment for known risk predictors (8.6% versus 4.6%; adjusted hazard ratio, 1.83 [95% CI, 1.34-2.48]). These patients also had a higher risk of cardiovascular death (adjusted hazard ratio, 1.83 [95% CI, 1.13-2.95]), cardiogenic shock (adjusted hazard ratio, 2.02 [95% CI, 1.08-3.76]), and heart failure (adjusted hazard ratio, 1.74 [95% CI, 1.02-2.96]) but not myocardial infarction or stroke.

CONCLUSIONS

Large rTB is a common finding in primary percutaneous coronary intervention and is associated with increased risk of adverse cardiovascular outcomes, including cardiovascular death. Future technologies offering better thrombus removal than current devices may decrease or even eliminate the risk associated with rTB. This, potentially, can turn into a strategic option to be studied in clinical trials.

REGISTRATION

URL: https://www.

CLINICALTRIALS

gov; Unique identifier: NCT01149044.

Pressure-controlled intermittent coronary sinus occlusion improves the vasodilatory microvascular capacity and reduces myocardial injury in patients with STEMI

BACKGROUND

Preliminary data suggest that pressure-controlled intermittent coronary sinus occlusion (PICSO) might reduce the infarct size (IS) in patients with anterior ST-elevation myocardial infarction (STEMI). However, the applicability of this therapy to patients with inferior STEMI and its exact mechanism of action is uncertain.

METHODS AND RESULTS

Thirty-six patients (27 anterior and 9 inferior) with STEMI underwent PICSO-assisted-primary percutaneous intervention (PPCI) and were compared with matched controls who underwent standard PCI (n = 72). Median age was 63 (55-70) years and 82% were male. Coronary microvascular status was assessed using thermodilution-derived index of microcirculatory resistance (IMR) and the vasodilatory capacity was assessed using the resistive reserve ratio (RRR). IS and microvascular obstruction (MVO) were assessed using cardiovascular magnetic resonance imaging (CMR) within 48 h and 6 months of follow-up. At completion of PPCI, IMR improved significantly in PICSO-treated patients compared with controls in patients with either anterior (63.7 [49.8-74.6] vs. 35.9 [27.9-47.6], p < 0.001) or inferior STEMI (60.0 [47.6-67.1] vs. 22.7 [18.4-35.0], p < 0.001). RRR significantly improved after PICSO treatment for anterior (1.21 [1.01-1.42] vs. 1.73 [1.51-2.16], p = 0.002) or inferior STEMI (1.39 [1.05-1.90] vs. 2.87 [2.17-3.78], p = 0.001), whereas it did not change in controls compared with baseline. Patients treated with PICSO presented significantly less frequently with MVO (66.6% vs. 86.1%, p = 0.024) and smaller 6-month IS compared with controls (26% [17%-30%] vs. 30% [21%-37%], p = 0.045).

CONCLUSION

PICSO therapy may improve microvascular function and vasodilatory capacity, which contributes to reducing IS in patients with STEMI undergoing PPCI.

The Role of Coronary Physiology in Contemporary Percutaneous Coronary Interventions

Invasive assessment of coronary physiology has radically changed the paradigm of myocardial revascularization in patients with coronary artery disease. Despite the prognostic improvement associated with ischemia-driven revascularization strategy, functional assessment of angiographic intermediate epicardial stenosis remains largely underused in clinical practice. Multiple tools have been developed or are under development in order to reduce the invasiveness, cost, and extra procedural time associated with the invasive assessment of coronary physiology. Besides epicardial stenosis, a growing body of evidence highlights the role of coronary microcirculation in regulating coronary flow with consequent pathophysiological and clinical and prognostic implications. Adequate assessment of coronary microcirculation function and integrity has then become another component of the decision-making algorithm for optimal diagnosis and treatment of coronary syndromes. This review aims at providing a comprehensive description of tools and techniques currently available in the catheterization laboratory to obtain a thorough and complete functional assessment of the entire coronary tree (both for the epicardial and microvascular compartments).

Novel Applications for Invasive and Non-invasive Tools in the Era of Contemporary Percutaneous Coronary Revascularisation

Percutaneous coronary intervention (PCI) is an expanding treatment option for patients with coronary artery disease (CAD). It is considered the default strategy for the unstable presentation of CAD. PCI techniques have evolved over the last 4 decades with significant improvements in stent design, an increase in functional assessment of coronary lesions, and the use of intra-vascular imaging. Nonetheless, the morbidity and mortality related to CAD remain significant. Advances in technology have allowed a better understanding of the nature and progression of CAD. New tools are now available that reflect the pathophysiological changes at the level of the myocardium and coronary atherosclerotic plaque. Certain changes within the plaque would render it more prone to rupture leading to acute vascular events. These changes are potentially detected using novel tools invasively, such as near infra-red spectroscopy, or non-invasively using T2 mapping cardiovascular magnetic resonance imaging (CMR) and ¹⁸F-Sodium Fluoride positron emission tomography/ computed tomography. Similarly, changes at the level of the injured myocardium are feasibly assessed invasively using index microcirculatory resistance or non-invasively using T1 mapping CMR. Importantly, these changes could be detected immediately with the opportunity to tailor treatment to those considered at high risk. Concurrently, novel therapeutic options have demonstrated promising results in reducing future cardiovascular risks in patients with CAD. This Review article will discuss the role of these novel tools and their applicability in employing a mechanical and pharmacological treatment to mitigate cardiovascular risk in patients with CAD.

Pre-procedural ATI score (age-thrombus burden-index of microcirculatory resistance) predicts long-term clinical outcomes in patients with ST elevation myocardial infarction treated with primary percutaneous coronary intervention

BACKGROUND

The ATI (Age-Thrombus burden-Index of Microvascular Resistance [IMR]) score was developed to predict suboptimal myocardial reperfusion in patients with ST-Elevation Myocardial Infarction (STEMI). When applied in the early phases of revascularization (e.g. before stent insertion), it predicts which patients are most likely to have a larger infarct size. In this study, we assessed the score's utility in determining which STEMI patients are at highest risk of clinical events during follow-up.

METHODS

The ATI-score was calculated prospectively in 254 STEMI patients using age (>50 years = 1 point), pre-stenting IMR (>40 U and < 100 U = 1 point; ≥100 U = 2 points) and angiographic thrombus score (4 = 1 point, 5 = 3 points); the cohort was stratified in high vs. low-intermediate ATI-score strata (≥4 vs. < 4, respectively).

RESULTS

After 3 years of follow-up, patients with high ATI-score presented a higher rate of Major Adverse Cardiac Events (MACE) defined as the composite of all-cause mortality, resuscitated cardiac arrest and new heart failure diagnosis (Hazard Ratio [HR]: 3.07; 95% Confidence Interval [CI]: 1.19-7.93; p = 0.02). The ATI-score showed a moderate discriminative power (c-stat: 0.69), not significantly different from that of other risk scores used in the STEMI setting. A high ATI-score was an independent predictor of MACE (HR: 3.24; 95% CI: 1.22-8.58; p = 0.018).

CONCLUSIONS

The ATI-score can discriminate patients at higher risk of long-term adverse events. The score allows predication of subsequent events even before coronary stenting, and consequently it may allow the option of individualized therapy in the early stages of the clinical care-pathway.

The Comparison between Two Risk Scores as for the Prediction of Coronary Microvascular Obstruction during Primary Percutaneous Intervention

Fundamento:

Para pacientes com infarto do miocárdio com elevação do segmento ST (IAMCST) que sofrem de obstrução coronariana microvascular funcional e estrutural (OCM) subsequente, nenhuma abordagem terapêutica específica e definitiva de atenuação foi comprovada como válida em testes de larga escala atuais, o que destaca a necessidade de abordar seu reconhecimento precoce.

Objetivos:

Este estudo teve como objetivo comparar o desempenho de dois escores de risco clínico com uma medida objetiva de OCM durante intervenção coronária percutânea (ICP) em casos de IAMCST

Métodos:

A medição do índice de resistência microcirculatória (IRM) foi realizada e os parâmetros clínicos e angiográficos basais também foram registrados. Os pacientes foram divididos em entre os grupos OM (obstrução microvascular) e NOM (não-obstrução microvascular), de acordo com o valor de IRM pós-procedimento. O risco de OCM foi avaliado para todos os participantes pelos escores preditivos SAK e ATI, respectivamente. Cada sistema foi calculado somando-se as pontuações de todas as variáveis. As curvas de características do operador receptor (ROC) e a área sob a curva (AUC) de dois modelos de risco foram utilizadas para avaliar o desempenho discriminatório. Um ecocardiograma foi realizado sete dias após o procedimento para avaliar a fração de ejeção do ventrículo esquerdo (FEVE). Um valor P bicaudal de <0,05 foi considerado estatisticamente significativo.

Resultados:

Entre os 65 pacientes elegíveis com IAMCST, 48 foram alocados no grupo NOM e 17 no grupo OM, com uma incidência de OCM de 26,15%. Não houve diferença significativa na AUC entre os dois escores. A FEVE avaliada para o grupo NOM foi maior do que para o grupo OM.

Conclusão:

Os escores SAK e ATI tiveram bom desempenho para estimar o risco de OCM após ICP primário para pacientes com IAMCST.

Pressure-bounded coronary flow reserve to assess the extent of microvascular dysfunction in patients with ST-elevation acute myocardial infarction

AIMS

Assessment of microvascular function in patients with ST-elevation acute myocardial infarction (STEMI) may be useful to determine treatment strategy. The possible role of pressure-bounded coronary flow reserve (pb-CFR) in this setting has not been determined. In this study we aimed to compare pb-CFR with thermodilution-derived physiology including the index of microcirculatory resistance (IMR) and CFRthermo in a consecutive series of patients enrolled in the OxAMI study. Moreover, we aimed to assess the presence of microvascular obstruction (MVO) and myocardial injury on cardiovascular magnetic resonance (CMR) imaging performed at 48 hours and six months in STEMI patients stratified according to pb-CFR.

METHODS AND RESULTS

Thermodilution-pressure-wire assessment of the infarct-related artery was performed in 148 STEMI patients before stenting and/or at completion of primary percutaneous coronary intervention (PPCI). The extent of the myocardial injury was assessed with CMR imaging at 48 hours and six months after STEMI. Post-PPCI pb-CFR was impaired (<2) and normal (>2) in 69.9% and 9.0% of the cases, respectively. In the remaining 21.1% of the patients, pb-CFR was "indeterminate". In this cohort, pb-CFR correlated poorly with thermodilution-derived coronary flow reserve (k=0.03, p=0.39). The IMR was significantly different across the pb-CFR subgroups. Similarly, significant differences were observed in MVO, myocardium area at risk and 48-hour infarct size (IS). A trend towards lower six-month IS was observed in patients with high (>2) post-PPCI pb-CFR. Nevertheless, pb-CFR was inferior to IMR in predicting MVO and the extent of IS.

CONCLUSIONS

Pb-CFR can identify microvascular dysfunction in patients after STEMI. It provided superior diagnostic performance compared to thermodilution-derived CFR in predicting MVO. However, IMR was superior to both pb-CFR and thermodilution-derived CFR and, consequently, IMR was the most accurate in predicting all of the studied CMR endpoints of myocardial injury after PPCI.

No-reflow phenomenon in ST-segment elevation myocardial infarction: still the Achilles' heel of the interventionalist

Improvements in systems, technology and pharmacotherapy have significantly changed the prognosis over recent decades in patients presenting with ST-segment elevation myocardial infarction. These clinical achievements have, however, begun to plateau and it is becoming increasingly necessary to consider novel strategies to further improve outcomes. Approximately a third of patients treated by primary percutaneous coronary intervention for ST-segment elevation myocardial infarction will suffer from coronary no-reflow (NR), a condition characterized by poor myocardial perfusion despite patent epicardial arteries. The presence of NR impacts significantly on clinical outcomes including left ventricular dysfunction, heart failure and death, yet conventional management algorithms neither assess the risk of NR nor treat NR. This review will provide a contemporary overview on the pathogenesis, diagnosis and treatment of NR.

Angiography-derived index of microcirculatory resistance as a novel, pressure-wire-free tool to assess coronary microcirculation in ST elevation myocardial infarction

Immediate assessment of coronary microcirculation during treatment of ST elevation myocardial infarction (STEMI) may facilitate patient stratification for targeted treatment algorithms. Use of pressure-wire to measure the index of microcirculatory resistance (IMR) is possible but has inevitable practical restrictions. We aimed to develop and validate angiography-derived index of microcirculatory resistance (IMR_angio) as a novel and pressure-wire-free index to facilitate assessment of the coronary microcirculation. 45 STEMI patients treated with primary percutaneous coronary intervention (pPCI) were enrolled. Immediately before stenting and at completion of pPCI, IMR was measured within the infarct related artery (IRA). At the same time points, 2 angiographic views were acquired during hyperaemia to measure quantitative flow ratio (QFR) from which IMR_angio was derived. In a subset of 15 patients both IMR and IMR_angio were also measured in the non-IRA. Patients underwent cardiovascular magnetic resonance imaging (CMR) at 48 h for assessment of microvascular obstruction (MVO). IMR_angio and IMR were significantly correlated (ρ: 0.85, p < 0.001). Both IMR and IMR_angio were higher in the IRA rather than in the non-IRA (p = 0.01 and p = 0.006, respectively) and were higher in patients with evidence of clinically significant MVO (> 1.55% of left ventricular mass) (p = 0.03 and p = 0.005, respectively). Post-pPCI IMR_angio presented and area under the curve (AUC) of 0.96 (CI95% 0.92–1.00, p < 0.001) for prediction of post-pPCI IMR > 40U and of 0.81 (CI95% 0.65–0.97, p < 0.001) for MVO > 1.55%. IMR_angio is a promising tool for the assessment of coronary microcirculation. Assessment of IMR without the use of a pressure-wire may enable more rapid, convenient and cost-effective assessment of coronary microvascular function.

Reflectance spectral analysis for novel characterization and clinical assessment of aspirated coronary thrombi in patients with ST elevation myocardial infarction

OBJECTIVE

The visual appearance of coronary thrombi may be clinically informative in ST elevation myocardial infarction (STEMI) patients undergoing primary percutaneous coronary intervention (pPCI). However, subjective assessment is poorly reproducible and cannot provide an objective basis for treatment decisions or patient stratification. We have assessed the feasibility of a novel reflectance spectroscopy technique to systematically characterize coronary artery thrombi retrieved by aspiration during pPCI in patients with STEMI, and the clinical utility for predicting distal microvascular obstruction.

APPROACH

Patients with STEMI treated with pPCI and thrombus aspiration (n = 288) were recruited from the Oxford Acute Myocardial Infarction (OxAMI) Study. Of these, 158 patients underwent cardiac magnetic resonance imaging within 48 h for assessment of microvascular obstruction (MVO). Coronary thrombi were imaged by reflectance spectroscopy across wavelengths 500-800 nm.

MAIN RESULTS

Spectral data were analysed using function fitting and multivariate models. The coefficient 'c _red' determined from the fitting procedure correlated with the visually-assessed colour of thrombi ('red' or 'white') and with MVO. When applied to a reduced data set, consisting of spectra from 20 patients with the largest MVO and from 20 propensity-score-matched patients with no MVO, three multivariate analysis methods were able to discriminate spectra of thrombi from patients without MVO and with the largest MVO.

SIGNIFICANCE

Reflectance spectral analysis of coronary thrombus provides new insights into the pathology of STEMI, with potential clinical implications for emergency patient care. Further studies are warranted for validation as a point-of-care stratification tool in predicting the degree of microvascular injury and clinical outcomes in STEMI.

The predictive value of stress hyperglycemia on thrombus burden in nondiabetic patients with ST-segment elevation myocardial infarction

: It is established that hyperglycemia directly effects the platelet functions and fibrin structure. In this study, we aimed to investigate the predictive value of hyperglycemia on thrombus burden in nondiabetic patients with ST-segment elevation myocardial infarction (STEMI) who underwent to primer percutaneous coronary intervention (PPCI). We enrolled 619 nondiabetic patients with STEMI who received PPCI. Patients were divided two groups according to thrombus burden. Stress hyperglycemia was determined as blood glucose concentration more than 180 mg/dl and angiographic coronary thrombus burden was scored based on thrombolysis in myocardial infarction thrombus grades. Patients with thrombus grades 4 were defined as large thrombus burden (LTB), patients with thrombus burden less than thrombus grades 4 were defined as small thrombus burden. A total of 68 (11.0%) STEMI patients had stress hyperglycemia, while 223 (36.0%) patients had LTB. Sex, the prevalence of hypertension, smoking, and dyslipidemia were not different between the thrombus burden groups (P > 0.05 for all parameters). Compared with the patients with small thrombus burden, the patients with LTB were had significantly higher admission blood glucose concentrations (135 ± 39.1 mg/dl vs. 145.9 ± 43.1, P = 0.002, respectively). The multivariate logistic regression analysis demonstrated that stress hyperglycemia is an independent predictor of LTB (odds ratio: 3.025, confidence interval 1.200-7.622, P = 0.019). Admission hyperglycemia is associated with the LTB which cause adverse cardiac outcomes. Hyperglycemia may play a role on thrombus development.

Hyper-acute cardiovascular magnetic resonance T1 mapping predicts infarct characteristics in patients with ST elevation myocardial infarction

BACKGROUND

Myocardial recovery after primary percutaneous coronary intervention in acute myocardial infarction is variable and the extent and severity of injury are difficult to predict. We sought to investigate the role of cardiovascular magnetic resonance T1 mapping in the determination of myocardial injury very early after treatment of ST-segment elevation myocardial infarction (STEMI).

METHODS

STEMI patients underwent 3 T cardiovascular magnetic resonance (CMR), within 3 h of primary percutaneous intervention (PPCI). T1 mapping determined the extent (area-at-risk as %left ventricle, AAR) and severity (average T1 values of AAR) of acute myocardial injury, and related these to late gadolinium enhancement (LGE), and microvascular obstruction (MVO). The characteristics of myocardial injury within 3 h was compared with changes at 24-h to predict final infarct size.

RESULTS

Forty patients were included in this study. Patients with average T1 values of AAR ≥1400 ms within 3 h of PPCI had larger LGE at 24-h (33% ±14 vs. 18% ±10, P = 0.003) and at 6-months (27% ±9 vs. 12% ±9; P < 0.001), higher incidence and larger extent of MVO (85% vs. 40%, P = 0.016) & [4.0 (0.5-9.5)% vs. 0 (0-3.0)%, P = 0.025]. The average T1 value was an independent predictor of acute LGE (β 0.61, 95%CI 0.13 to 1.09; P = 0.015), extent of MVO (β 0.22, 95%CI 0.03 to 0.41, P = 0.028) and final infarct size (β 0.63, 95%CI 0.21 to 1.05; P = 0.005). Receiver-operating-characteristic analysis showed that T1 value of AAR obtained within 3-h, but not at 24-h, predicted large infarct size (LGE > 9.5%) with 100% positive predictive value at the optimal cut-off of 1400 ms (area-under-the-curve, AUC 0.88, P = 0.006).

CONCLUSION

Hyper-acute T1 values of the AAR (within 3 h post PPCI, but not 24 h) predict a larger extent of MVO and infarct size at both 24 h and 6 months follow-up. Delayed CMR scanning for 24 h could not substitute the significant value of hyper-acute average T1 in determining infarct characteristics.

Index of Microcirculatory Resistance as a Tool to Characterize Microvascular Obstruction and to Predict Infarct Size Regression in Patients With STEMI Undergoing Primary PCI

OBJECTIVES

This study aimed to compare the value of the index of microcirculatory resistance (IMR) and microvascular obstruction (MVO) measured by cardiac magnetic resonance (CMR) in patients treated for and recovering from ST-segment elevation myocardial infarction.

BACKGROUND

IMR can identify patients with microvascular dysfunction acutely after primary percutaneous coronary intervention (pPCI), and a threshold of >40 has been shown to be associated with an adverse clinical outcome. Similarly, MVO is recognized as an adverse feature in patients with ST-segment elevation myocardial infarction. Even though both IMR and MVO reflect coronary microvascular status, the interaction between these 2 parameters is uncertain.

METHODS

A total of 110 patients treated with pPCI were included, and IMR was measured immediately at completion of pPCI. Infarct size (IS) as a percentage of left ventricular mass was quantified at 48 h (38.4 ± 12.0 h) and 6 months (194.0 ± 20.0 days) using CMR. MVO was identified and quantified at 48 h by CMR.

RESULTS

Overall, a discordance between IMR and MVO was observed in 36.7% of cases, with 31 patients having MVO and IMR ≤40. Compared with patients with MVO and IMR ≤40, patients with both MVO and IMR >40 had an 11.9-fold increased risk of final IS >25% at 6 months (p = 0.001). Patients with MVO and IMR ≤40 had a significantly smaller IS at 6 months (p = 0.001), with significant regression in IS over time (34.4% [interquartile range (IQR): 27.3% to 41.0%] vs. 22.3% [IQR: 16.0% to 30.0%]; p = 0.001).

CONCLUSIONS

Discordant prognostic information was obtained from IMR and MVO in nearly one-third of cases; however, IMR can be helpful in grading the degree and severity of MVO.

Can Thrombus Burden Predict Contrast-Induced Nephropathy in Patients With ST-Segment Elevation Myocardial Infarction?

The incidence of contrast-induced nephropathy (CIN) increases in the range from patients with unstable angina to ST-segment elevation myocardial infarction (STEMI). Platelet activation has been associated with pathophysiology of nephropathy and thrombus burden in the infarct-related arteries. We investigated the impact of thrombus burden on CIN in patients with STEMI. We enrolled 883 patients with STEMI who received primary percutaneous coronary intervention. Patients were divided into groups according to thrombus burden and CIN development. Thrombus burden was scored based on thrombolysis in myocardial infarction thrombus grades (TGs). Thrombus grade 4 was defined as large thrombus burden (LTB), while thrombus burden <TG 4 was defined as small thrombus burden. A total of 126 (14.2%) patients with STEMI had CIN, while 313 (35.4%) patients had LTB. Compared to CIN (-) patients, CIN (+) patients were older, had lower hemoglobin levels, lower ejection fraction, and higher contrast media volume administration. Multivariate logistic regression analysis demonstrated that LTB, age, hypertension, and admission glomerular filtration rate were independent predictors of CIN (P = .016, P < .001, P = .028, P < .001, respectively). Thrombus burden, which is measurable during angiography, may be helpful in the determination of CIN risk in patients with STEMI.

Assessing and managing coronary microcirculation dysfunction in acute ST-segment elevation myocardial infarction

INTRODUCTION

Microvascular dysfunction in the setting of acute ST-segment elevation myocardial infarction (STEMI) is an indicator of poor long-term prognosis. Prompt assessment and pharmacological or procedural therapy (prophylactic or post onset of dysfunction) may improve outcomes in STEMI post-primary percutaneous intervention. Areas covered: The aim of this review is to provide a comprehensive analysis of the evidence available about the assessment and management of coronary microcirculatory injury/dysfunction in STEMI. We also aim to elucidate the possible strategies that could be applied in clinical practice to support the application of already available or novel therapeutic strategies for the prevention and management of microvascular impairment. Expert commentary: There are multiple established methods in assessing microvascular dysfunction, both non-invasively and invasively. Invasive physiological measurements allow real-time assessment of microvascular dysfunction and have prognostic cut-off values. Multiple therapeutic modalities exist for both preventing and treating microvascular dysfunction. These can be either pharmacological or mechanical, and there is no algorithm to guide if, how and when to apply them. Future research into both procedural and pharmacological therapy guided by physiological measurements is needed, with the aim of recognizing high-risk patients who would benefit from therapy.

Dynamic changes in injured myocardium, very early after acute myocardial infarction, quantified using T1 mapping cardiovascular magnetic resonance

BACKGROUND

It has recently been suggested that myocardial oedema follows a bimodal pattern early post ST-segment elevation myocardial infarction (STEMI). Yet, water content, quantified using tissue desiccation, did not return to normal values unlike oedema quantified by cardiovascular magnetic resonance (CMR) imaging. We studied the temporal changes in the extent and intensity of injured myocardium using T1-mapping technique within the first week after STEMI.

METHODS

A first group (n = 31) underwent 3 acute 3 T CMR scans (time-point (TP) < 3 h, 24 h and 6 days), including cine, native shortened modified look-locker inversion recovery T1 mapping, T2* mapping and late gadolinium enhancement (LGE). A second group (n = 17) had a single scan at 24 h with an additional T2-weighted sequence to assess the difference in the extent of area-at-risk (AAR) compared to T1-mapping.

RESULTS

The mean T1 relaxation time value within the AAR of the first group was reduced after 24 h (P < 0.001 for TP1 vs.TP2) and subsequently increased at 6 days (P = 0.041 for TP2 vs.TP3). However, the extent of AAR quantified using T1-mapping did not follow the same course, and no change was detected between TP1&TP2 (P = 1.0) but was between TP2 &TP3 (P = 0.019). In the second group, the extent of AAR was significantly larger on T1-mapping compared to T2-weighted (42 ± 15% vs. 39 ± 15%, P = 0.025). No change in LGE was detected while microvascular obstruction and intra-myocardial haemorrhage peaked at different time points within the first week of reperfusion.

CONCLUSION

The intensity of oedema post-STEMI followed a bimodal pattern; while the extent of AAR did not track the same course. This discrepancy has implications for use of CMR in this context and may explain the previously reported disagreement between oedema quantified by imaging and tissue desiccation.

Index of microcirculatory resistance-guided therapy with pressure-controlled intermittent coronary sinus occlusion improves coronary microvascular function and reduces infarct size in patients with ST-elevation myocardial infarction: the Oxford Acute Myocardial Infarction - Pressure-controlled Intermittent Coronary Sinus Occlusion study (OxAMI-PICSO study)

AIMS

The Oxford Acute Myocardial Infarction PICSO (OxAMI-PICSO) study aimed to assess the efficacy of index of microcirculatory resistance (IMR)-guided therapy with pressure-controlled intermittent coronary sinus occlusion (PICSO) in anterior ST-elevation myocardial infarction (STEMI).

METHODS AND RESULTS

Patients with anterior STEMI treated with primary percutaneous coronary intervention (pPCI) were enrolled. Pre-stenting IMR was measured and PICSO treatment delivered if pre-stenting IMR was >40. No PICSO treatment was considered in patients with a pre-stenting IMR ≤40. The control group was derived from a historical cohort of STEMI patients with pre-stenting IMR >40 enrolled in the observational OxAMI study. IMR was measured after completion of pPCI in all patients and within 48 hours in PICSO patients and controls. Cardiac magnetic resonance imaging was performed per protocol for infarct size (IS) assessment within 48 hours after pPCI and at six months. A total of 105 patients were enrolled (25 PICSO, 50 controls with pre-stenting IMR >40, 30 with pre-stenting IMR ≤40). Compared to controls, patients treated with PICSO had a lower IMR at 24-48 hours (24.8 [18.5-35.9] vs. 45.0 [32.0-51.3], p<0.001) and lower IS at six months (26.0% [20.2-30.0] vs. 33.0% [28.0-37.0], p=0.006).

CONCLUSIONS

An IMR-guided treatment with PICSO in anterior STEMI is feasible and may be associated with reduced IS and improved microvascular function.