European Journal of Cardiovascular Medicine

Epicardial coronary artery patency and thrombolysis in myocardial infarction (TIMI) flow are not dependable indicators of myocardial tissue perfusion during reperfusion treatment. Notwithstanding good coronary patency, tissue perfusion may be compromised or nonexistent.^[1,2] The myocardial blush grade (MBG) is a proven angiographic method for evaluating myocardial perfusion in individuals with ST-elevation acute myocardial infarction (STEMI).^[3,4] It is closely associated with prognosis in patients receiving primary coronary intervention (PCI) for STEMI.^[5,6]

The management of ST segment elevation acute myocardial infarction (STEMI) has concentrated on revascularizing the coronary artery.^[7-9] However, the patency of the artery does not ensure sufficient tissue perfusion; indeed, up to 30% of patients exhibiting normal epicardial flow (Thrombolysis In Myocardial Infarction [TIMI] grade 3) have insufficient tissue perfusion due to damage to the microcirculation.^[10-12]

While angiography is very successful in detecting instances of significantly impaired microcirculation (TIMI<3), its efficacy in individuals with TIMI 3 flow remains contentious. Myocardial blush is an angiographic metric designed to evaluate myocardial perfusion, while its measurement reliability and variability remain questionable.^[13]

Consequently, it is unsurprising that microvascular dysfunction, indicated by the grade, is less in patients with preserved ejection fraction and was determined to be independent of epicardial artery variables in another investigation.^[12] Moreover, the extent of fibrosis due to malperfusion was more likely to elevate the stiffness index of the heart, leading to a reduction in ejection fraction and negative consequences such as arrhythmia and heart failure.

Although it may be presumed that outcomes for individuals with decreased ejection fraction are poorer, the degree to which MBG can accurately represent the anticipated clinical characteristics has not been extensively examined.

This observational research was undertaken at our institute. Approval was obtained from the ethics committee. The sample size was determined with computerized software. Considering an average of 5 patients hospitalized for intervention, we projected an anticipated population of 134 individuals for the research within one month. The sample size was determined to be 100 patients, utilizing an expected frequency of 0.5, a confidence interval of 95%, and a design effect of 1.0.

Criteria for Inclusion and Exclusion

Patients with ST-elevation myocardial infarction, aged over 18 years, who arrived at the emergency room within 12 hours of chest discomfort following initial percutaneous coronary intervention. Myocardial infarction is characterized by an ST-elevation of at least 2mm in two contiguous leads for males over 40 years and 2.5mm for males under 40 years. In females, it was characterized by a ST elevation of 1.5 mm. Patients with established chronic renal disease, bundle branch block anomalies, atrioventricular blocks, shock, pregnancy, and ischemic cardiomyopathy were excluded.

Research Methodology

Before the intervention, the left ventricular ejection fraction was determined using the modified Simpson’s approach. All patients received a loading dose of 300 mg of aspirin and 600 mg of clopidogrel prior to primary angioplasty. An echocardiographic examination was conducted using a Philips CX50-DS and 3.5 MHz transducers by a single sonographer to reduce bias. The Philips Azurion 2017 angiographic system was employed for the intervention.

All patients received 70 to 100 IU/kg of heparin prior to the commencement of the surgery. All patients received coronary stenting, and the last angiographic run displayed the venous phase of the contrast injection.

All patients had pre-procedure echocardiography and were evaluated within 24 hours following PPCI.

Data Acquisition

The myocardial blush grade was assessed immediately post-PPCI by the primary operator and validated by the secondary lab operator monitoring the operation. The grading system consisted of 0, 1, 2, and 3, indicating no myocardial blush, little myocardial blush, myocardial blush with impaired clearance, and normal myocardial blush, respectively. The 5 TIMI score was assessed immediately following the surgery. The patients were thereafter monitored for three months. The LVEF was re-evaluated with the same methodology at three months. The patients' negative outcomes, including arrhythmia, heart failure, and cardiogenic shock, were also examined at the 3-month follow-up period. The characteristics including age, gender, concomitant diseases, culprit artery, vascular disease, TIMI score, MBG, ejection fraction prior to and during the surgery, and results were documented on a proforma.

The mean age of the study population was observed to be 59.5 ± 12.71 years. In the present study, 75% of the study participants were males.

The mean age of the females was observed to be higher, however, the difference was no significant difference. The most common indication was anterior wall MI, followed by inferior wall MI.

85% of the study population had T2DM, while 91% if them had hypertension.

The most common angiographic finding was SVD (41%), followed by DVD in 32%.

The most common vessel involved, and for which PTCA was performed, was observed to be LAD.

Myocardial blush grade was assessed after primary angioplasty, as previously described: 5 grade 0/1: no myocardial blush or minimal myocardial blush or contrast density; grade 2: moderate myocardial blush or contrast density but less than that obtained during angiography of a contralateral or ipsilateral non-infarct-related coronary artery; grade 3: normal myocardial blush or contrast density, comparable with that obtained during angiography of a contralateral or ipsilateral non-infarct-related coronary artery.

In the present study, we observed that MBG grade 2 was noted in half the population.

When we correlated the MBG with TIMI, we noted that there was a significant association.

There was no difference in the pre- and post-PTCA echocardiography.

When we observed the complications overall and by MBG grade, there was no difference.

When we correlated MBG with age, gender, co-morbidities and complications, there was no difference noted between the three grades.

Our investigation indicated that elevated MBG levels were seen in elderly individuals and those with diabetes mellitus. This contrasts with a 2018 study and others that indicated older age and diabetes were more indicative of severe microvascular blockage, possibly resulting in a poor blush grade.^[13,14,15]

In the current investigation, there was no variation in the EF among the different grades of MBG. The likely explanation for this is that the blush grade may remain elevated even in patients exhibiting superior ejection fractions, as cardiac remodeling in these instances is probably influenced by inflammation rather than obstruction, leading to a depletion of cardiomyocytes that contributes to remodeling in the low-grade, low-ejection cohort.^[16] Multi-vessel disease was also observed to correlate with a lower grade, consistent with findings from a comparable research.^[17] The underlying explanation may be that an increased number of arteries associated with disease load elevates the likelihood of microembolization from infarct material, leading to blockage.

Enhancements in MBG markedly reduced negative effects. A research indirectly assessed the effects of inadequate reperfusion indicated by a low blush grade by electrocardiography. QRS prolongation was substantially correlated with an increased risk of arrhythmia and cardiac failure. The extended ischemia causes damage to the Purkinje system, ultimately leading to severe consequences. Ten Our investigation revealed no variation in the incidence of arrhythmia, heart failure, and cardiogenic shock among the various MBG grades. This contrasted with the findings of Rehman et al., where lower grades were predominantly indicative of a heightened risk of heart failure (32.00; 95% CI-5.95–172.24; p=0.00) and cardiogenic shock (66.00; 95% CI-9.99–436.06; p=0.00).

In the present study, we observed a significant association between MBG and TIMI. Rasoul and team^[14] previously indicated that MBG correlates with TIMI flow in the epicardial artery. Nonetheless, over one-third of individuals exhibiting TIMI 3 flow demonstrate MBG 0/1, signifying inadequate tissue perfusion. This compromised myocardial perfusion correlates with more widespread necrosis and hence serves as a predictor of suboptimal regional and global contractile function, possessing predictive capability that exceeds TIMI flow.^[5,8,16]

In the present study, we found a significant association between MBG and TIMI, suggesting that MBG can predict adverse events after thrombolysis/PTCA in those with ACS. However, we found no association between age, gender, co-morbidities or EF.

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