The Index of Microcirculatory Resistance as a Predictor of Echocardiographic Left Ventricular Performance Recovery in Patients With ST-Elevation Acute Myocardial Infarction Undergoing Successful Primary Angioplasty

Moderately Increased Left Ventricular Filling Pressure Suggesting Early Stage of Heart Failure with Preserved Ejection Fraction in Patients with Invasively Assessed Coronary Microvascular Dysfunction

Background: With modern diagnostic tools, incidence ischemia with no obstructive coronary atherosclerosis (INOCA) and heart failure with preserved ejection fraction (HFpEF) are found to be much higher than previously believed, and-as they lead to adverse cardiovascular outcomes-their causes and development are subjects of ongoing research. There is growing evidence that coronary microvascular dysfunction might be the underlying cause of both INOCA and HFpEF. Methods: In 65 patients with effort angina but no obstructive coronary artery disease, the index of microvascular resistance and coronary flow reserve were measured invasively in the LAD. The echocardiographic parameters, including left atrial strain, left ventricular strain, and indices of left ventricular diastolic dysfunction, were compared between two groups of patients: those with normal coronary microcirculation parameters and those with impaired coronary microvascular function. Results: Patients with coronary microvascular dysfunction had higher a E/E' index than those with normal microvessel reactivity. This finding was further confirmed by ROC analysis. The groups did not differ significantly in values of other echocardiographic parameters, including the left ventricular and left atrial strain. The prevalence of classical cardiovascular risk factors was similar in both groups. Conclusions: The coexistence of impaired coronary microvascular function with moderately elevated left ventricular filling pressures might correspond to the co-development of early stages of coronary microvascular dysfunction and HFpEF.

Impact of Coronary Microvascular Dysfunction on Functional Left Ventricular Remodeling and Diastolic Dysfunction

BACKGROUND

Coronary microvascular dysfunction (CMD) is a common complication of ST-segment-elevation myocardial infarction (STEMI) and can lead to adverse cardiovascular events. Whether CMD after STEMI is associated with functional left ventricular remodeling (FLVR) and diastolic dysfunction, has not been investigated.

METHODS AND RESULTS

This is a nonrandomized, observational, prospective study of patients with STEMI with multivessel disease. Coronary flow reserve and index of microcirculatory resistance of the culprit vessel were measured at 3 months post-STEMI. CMD was defined as index of microcirculatory resistance ≥25 or coronary flow reserve <2.0 with a normal fractional flow reserve. We examined the association between CMD, LV diastolic dysfunction, FLVR, and major adverse cardiac events at 12-month follow-up. A total of 210 patients were enrolled; 59.5% were men, with a median age of 65 (interquartile range, 58-76) years. At 3-month follow-up, 57 patients (27.14%) exhibited CMD. After 12 months, when compared with patients without CMD, patients with CMD had poorer LV systolic function recovery (-10.00% versus 8.00%; P<0.001), higher prevalence of grade 2 LV diastolic dysfunction (73.08% versus 1.32%; P<0.001), higher prevalence of group 3 or 4 FLVR (11.32% versus 7.28% and 22.64% versus 1.99%, respectively; P<0.001), and higher incidence of major adverse cardiac events (50.9% versus 9.8%; P<0.001). Index of microcirculatory resistance was independently associated with LV diastolic dysfunction and adverse FLVR.

CONCLUSIONS

CMD is present in ≈1 of 4 patients with STEMI during follow-up. Patients with CMD have a higher prevalence of LV diastolic dysfunction, adverse FLVR, and major adverse cardiac events at 12 months compared with those without CMD.

REGISTRATION

URL: https://www.clinicaltrials.gov; Unique Identifier: NCT05406297.

The Coronary Angiography-Derived Index of Microcirculatory Resistance Predicts Left Ventricular Performance Recovery in Patients with ST-Segment Elevation Myocardial Infarction

Objectives

The present study is designed to investigate the impact of coronary angiography-derived index of microcirculatory resistance (caIMR) on left ventricular performance recovery.

Background

IMR has been established as a gold standard for coronary microvascular assessment and a predictor of left ventricular recovery after ST-segment elevation myocardial infarction (STEMI). CaIMR is a novel and accurate alternative of IMR.

Methods

The present study retrospectively included 80 patients with STEMI who underwent primary percutaneous coronary intervention (PCI). We offline performed the post-PCI caIMR analysis of the culprit vessel. Echocardiography was performed within the first 24 hours and at 3 months after the index procedure. Left ventricular recovery was defined as the change in left ventricular ejection fraction (LVEF) more than zero.

Results

The mean age of the patients was 58.0 years with 80.0% male. The average post-PCI caIMR was 43.2. Overall left ventricular recovery was seen in 41 patients. Post-PCI caIMR (OR: 0.948, 95% CI: 0.916–0.981, p = 0.002), left anterior descending as the culprit vessel (OR: 3.605, 95% CI: 1.23–10.567, p = 0.019), and male (OR: 0.254, 95% CI: 0.066–0.979, p = 0.047) were independent predictors of left ventricular recovery at 3 months follow-up. A predictive model was established with the best cutoff value for the prediction of left ventricular recovery 2.33 (sensitivity 0.610, specificity 0.897, and area under the curve 0.765). In patients with a predictive model score less than 2.33, the LVEF increased significantly at 3 months.

Conclusions

The post-PCI caIMR can accurately predict left ventricular functional recovery at 3 months follow-up in patients with STEMI treated by primary PCI, supporting its use in clinical practice.

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.

An early echocardiographic prediction for functional myocardial recovery after ST elevation myocardial infarction

Goals Discrimination of the time course of functional recovery in early period following ST elevation myocardial infarction (STEMI) has prognostic importance. This study aims to establish the ability of the combined systolic-diastolic index (E / (Ea x Sa), for differentiating recoverable myocardium or persistent non-viability in subjects with STEMI.Material and methods 77 patients with first acute STEMI were enrolled to the study. Serial transthoracic echocardiography (TTE) examinations were performed at the time of the admission (immediately after reperfusion), hospital discharge (5±1 days) and control examination (30±2 days). To assess the association between E / (Ea×Sa) index and myocardial recovery, two categories (Transient stunning and persistent non-viability) were defined on basis of improvement of left ventricle ejection fraction (LV EF) (Improvement was defined as an increase more than 10 % in LV EF at day 30 compared to baseline).Results 55 patients (71.4 %) had improvement of LV EF and 24 patients (28.6 %) had no recovery of systolic function (30 days LV EF 48.78±6.1 vs. 39.31±8.1 %, p=0.01). The E / (Ea×Sa) index were significantly higher in the "non-viability" than in stunning group on predischarge and 1 month (1.61±0.64 vs 1.25±0.43, p=0.01 and 1.33±0.25 vs 1.14±0.21, p=0.01, respectively). The change in the E / (Ea×Sa) index in early period (within 5±1 days) was higher in the stunning group (26 %) compared to non-viability group (15 %) (p=0.033). E / (Ea×Sa) index was found to be a significant predictor of myocardial recovery in multivariable logistic regression (OR 0.91, 95 % CI 0.83-0.98, p=0.001). Roc curve showed that the cutoff value of E / (Ea×Sa) index is 1.29 with 73 % of sensitivity and 61 % of specificity (AUC: 0.71, p=0.01, CI: 0.54-0.89).Conclusions Our findings suggest that E / (Ea×Sa) index is a strong predictor of functional recovery; the odds of recovery decreases as E / (Ea×Sa) index value increases.

The Potential Use of the Index of Microcirculatory Resistance to Guide Stratification of Patients for Adjunctive Therapy in Acute Myocardial Infarction

The goal of reperfusion therapies in ST-segment elevation myocardial infarction has evolved to include effective reperfusion of the microcirculation subtended by the culprit epicardial coronary artery. The index of microcirculatory resistance is measured using a pressure- and temperature-sensing coronary guidewire and quantifies microvascular dysfunction. The index of microcirculatory resistance is an independent predictor of microvascular obstruction, infarct size, and adverse clinical outcomes. It has the advantage of being immediately measurable in the catheterization laboratory, before the results of blood biomarkers or noninvasive imaging become available. This provides an opportunity for additional intervention that may alter outcomes. In this review, the authors provide a critical appraisal of the published research on the emerging role of the index of microcirculatory resistance as a tool to guide the stratification of patients for adjunctive therapeutic strategies in acute ST-segment elevation myocardial infarction.

Mechanical and Pharmacological Revascularization Strategies for Prevention of Microvascular Dysfunction in ST-Segment Elevation Myocardial Infarction: Analysis from Index of Microcirculatory Resistance Registry Data

Objectives

We aimed to identify mechanical and pharmacological revascularization strategies correlated with the index of microcirculatory resistance (IMR) in ST-elevation myocardial infarction (STEMI) patients.

Background

Microvascular dysfunction (MVD) after STEMI is correlated with infarct size and poor long-term prognosis, and the IMR is a useful analytical method for the quantitative assessment of MVD. However, therapeutic strategies that can reliably reduce MVD remain uncertain.

Methods

Patients with STEMI who underwent primary percutaneous coronary intervention (PCI) were enrolled. The IMR was measured with a pressure sensor/thermistor-tipped guidewire immediately after primary PCI. High IMR was defined as values ≥66^th percentile of IMR in enrolled patients (IMR > 30.9 IU).

Results

A total of 160 STEMI patients were analyzed (high IMR = 54 patients). Clinical factors for Killip class (P=0.006), delayed hospitalization from symptom onset (P=0.004), peak troponin-I level (P=0.042), and multivessel disease (P=0.003) were associated with high IMR. Achieving final thrombolysis in myocardial infarction myocardial perfusion grade 3 tended to be associated with low IMR (P=0.119), whereas the presence of distal embolization was significantly associated with high IMR (P=0.034). In terms of therapeutic strategies that involved adjusting clinical and angiographic factors associated with IMR, preloading of third-generation P2Y12 inhibitors correlated with reducing IMR value (β = −10.30, P < 0.001). Mechanical therapeutic strategies including stent diameter/length, preballoon dilatation, direct stenting, and thrombectomy were not associated with low IMR value (all P > 0.05), and postballoon dilatation was associated with high IMR (β = 8.30, P=0.020).

Conclusions

In our study, mechanical strategies were suboptimal in achieving myocardial salvage. Preloading of third-generation P2Y12 inhibitors revealed decreased IMR value, indicative of MVD prevention.

Lancaster G, W. Zarich S. Invasive Evaluation of the Microvasculature in Acute Myocardial Infarction: Coronary Flow Reserve versus the Index of Microcirculatory Resistance

Acute myocardial infarction (AMI) is one of the most common causes of death in both the developed and developing world. It has high associated morbidity despite prompt institution of recommended therapy. The focus over the last few decades in ST-segment elevation AMI has been on timely reperfusion of the epicardial vessel. However, microvascular consequences after reperfusion, such as microvascular obstruction (MVO), are equally reliable predictors of outcome. The attention on the microcirculation has meant that traditional angiographic/anatomic methods are insufficient. We searched PubMed and the Cochrane database for English-language studies published between January 2000 and November 2019 that investigated the use of invasive physiologic tools in AMI. Based on these results, we provide a comprehensive review regarding the role for the invasive evaluation of the microcirculation in AMI, with specific emphasis on coronary flow reserve (CFR) and the index of microcirculatory resistance (IMR).

Microvascular dysfunction determines infarct characteristics in patients with reperfused ST-segment elevation myocardial infarction: The MICROcirculation in Acute Myocardial Infarction (MICRO-AMI) study

BACKGROUND

In patients with reperfused ST-elevation myocardial infarction (STEMI) both invasive and non-invasive assessments of microvascular dysfunction, the index of microcirculatory resistance (IMR), and microvascular obstruction (MVO) by cardiovascular magnetic resonance (CMR), independently predict poor long-term outcomes.

AIMS

The aims of this study were to investigate whether an invasive parameter (IMR), assessed at the time of primary percutaneous intervention (PPCI), could predict the extent of MVO in proportion to infarct size (MVO index).

METHODS

50 patients presenting with STEMI and TIMI flow ≤ I in the infarct related artery were prospectively recruited to the study, before undergoing PPCI. All patients underwent invasive IMR assessment at maximal hyperaemia using adenosine, and following stent insertion. CMR was performed on day 2 following STEMI, MVO was assessed both on first-pass rest perfusion (early MVO) and in the late gadolinium enhancement (LGE) images (late MVO) along with infarct size. The MVO index was calculated as the ratio of late MVO/infarct size. Differences between IMR quartiles and the MVO index were investigated.

RESULTS

The median IMR was 38.5 (range 9 to 202). The median size of late MVO was 1.9% LV (range 0 to 21.0% LV). IMR predicted late MVO (p<0.01) and as IMR increased, the MVO index increased (r = 0.70, [95% CI 0.53, 0.82], p<0.001). An IMR cut-off of 40 significantly predicted the presence of late MVO on CMR (p<0.001).

CONCLUSION

IMR measured at the time of PPCI in acutely reperfused STEMI is associated with the presence and severity of infarct damage as measured by the MVO index.

TRIAL REGISTRATION

The Microcirculation in Acute Myocardial Infarction (MICRO-AMI). Clinicaltrials.gov NCT01552564. Registered 9th March 2012.

Early peripheral endothelial dysfunction predicts myocardial infarct extension and microvascular obstruction in patients with ST-elevation myocardial infarction

INTRODUCTION AND OBJECTIVES

The role of endothelial dysfunction (ED) in patients with ST-elevation myocardial infarction (STEMI) is poorly understood. Peripheral arterial tonometry (PAT) allows non-invasive evaluation of ED, but has never been used for this purpose early after primary percutaneous coronary intervention (P-PCI). Our purpose was to analyze the relation between ED assessed by PAT and both the presence of microvascular obstruction (MVO) and infarct extension in STEMI patients.

METHODS

ED was assessed by the reactive hyperemia index (RHI), measured by PAT and defined as RHI <1.67. Infarct extension was assessed by troponin I (TnI) release and contrast-enhanced cardiac magnetic resonance (ceCMR). MVO was assessed by ceCMR and by indirect angiographic and ECG indicators. An echocardiogram was also performed in the first 12 h.

RESULTS

We included 38 patients (mean age 60.0±13.7 years, 29 male). Mean RHI was 1.87±0.60 and 16 patients (42.1%) had ED. Peak TnI (median 118 mg/dl, IQR 186 vs. 67/81, p=0.024) and AUC of TnI (median 2305, IQR 2486 vs. 1076/1042, p=0.012) were significantly higher in patients with ED, who also showed a trend for more transmural infarcts (63.6% vs. 22.2%, p=0.06) and larger infarct mass on ceCMR (median 17.5%, IQR 15.4 vs. 10.1/10.3, p=0.08). Left ventricular ejection fraction (LVEF) was lower and wall motion score index (WMSI) was higher on both echocardiogram and ceCMR in patients with ED. On ceCMR, MVO was more frequent in patients with RHI <1.67 (54.5% vs. 11.1%, p=0.03). ECG and angiographic indicators of MVO all showed a trend toward worse results in these patients.

CONCLUSIONS

The presence of ED assessed by PAT 24 h after P-PCI in patients with STEMI is associated with larger infarcts, lower LVEF, higher WMSI and higher prevalence of MVO.