Why, When and How Should Clinicians Use Physiology in Patients with Acute Coronary Syndromes?

Determinants and Prognoses of Visual-Functional Mismatches After Mechanical Reperfusion in ST-Elevation Myocardial Infarction

Background

Discordance between the anatomy and physiology of the coronary has important implications for managing patients with stable coronary disease, but its significance in ST-elevation myocardial infarction has not been fully elucidated.

Methods

The retrospective study involved patients diagnosed with ST-elevation myocardial infarction (STEMI) who underwent percutaneous coronary intervention (PCI), along with quantitative coronary angiography (QCA) and quantitative flow ratio (QFR) assessments. Patients were stratified into four groups regarding the severity of the culprit vessel, both visually and functionally: concordantly negative (QCA-diameter stenosis [DS] ≤ 50% and QFR > 0.80), mismatch (QCA-DS > 50% and QFR > 0.80), reverse mismatch (QCA-DS ≤ 50% and QFR ≤ 0.80), and concordantly positive (QCA-DS > 50% and QFR ≤ 0.80). Multivariable logistic regression analyses were conducted to identify the clinical factors linked to visual-functional mismatches. Kaplan‒Meier analysis was conducted to estimate the 18-month adverse cardiovascular events (MACE)-free survival between the four groups.

Results

The study involved 310 patients, with 68 presenting visual-functional mismatch, and 51 exhibiting reverse mismatch. The mismatch was associated with higher angiography-derived microcirculatory resistance (AMR) (adjusted odds ratio [aOR]=1.016, 95% CI: 1.010-1.022, P<0.001). Reverse mismatch was associated with larger area stenosis (aOR=1.044, 95% CI: 1.004-1.086, P=0.032), lower coronary flow velocity (aOR=0.690, 95% CI: 0.567-0.970, P<0.001) and lower AMR (aOR=0.947, 95% CI: 0.924-0.970, P<0.001). Additionally, the mismatch group showed the worst 18-month MACE-free survival among the four groups (Log rank test p = 0.013).

Conclusion

AMR plays a significant role in the occurrence of visual-functional mismatches between QCA-DS and QFR, and the mismatch group showed the worst prognosis.

Role of Intracoronary Imaging in Acute Coronary Syndromes

Intravascular imaging with optical coherence tomography (OCT) and intravascular ultrasound provides superior visualization of the culprit plaques for acute coronary syndromes (ACS) compared with coronary angiography. Combined with angiography, intravascular imaging can be used to instigate ‘precision therapy’ for ACS. Post-mortem histopathology identified atherothrombosis at the exposed surface of a ruptured fibrous cap as the main cause of ACS. Further histopathological studies identified intact fibrous caps and calcified nodules as other culprit lesions for ACS. These plaque types were subsequently also identified on intravascular imaging, particularly with the high-resolution OCT. The less-common non-atherothrombotic causes of ACS are coronary artery spasm, coronary artery dissection, and coronary embolism. In this review, the authors provide an overview of clinical studies using intravascular imaging with OCT in the diagnosis and management of ACS.

A clinical trial comparing complete revascularization at the time of primary percutaneous coronary intervention versus during the index hospital admission in patients with multi-vessel coronary artery disease and STEMI uncomplicated by cardiogenic shock

OBJECTIVE

In this study, we aimed to compare major adverse cardiac and cerebrovascular events (MACCE), defined as a composite of death, stroke, myocardial infarction and symptom-induced revascularization, and mortality within one year of randomization between two strategies; complete revascularization including non-culprit lesions percutaneous coronary intervention (PCI) during primary PCI (PPCI) versus complete revascularization during the same hospital admission in patients with multi-vascular coronary artery disease (MVD) presenting with ST-elevation myocardial infarction (STEMI) uncomplicated by cardiogenic shock.

METHODS

We randomized in a 1: 1 manner 100 patients with MVD and STEMI uncomplicated by cardiogenic shock who had undergone successful culprit-lesion PCI to either a strategy of complete revascularization with PCI of angiographically significant non-culprit lesions in the index PPCI procedure or to a strategy of complete revascularization during a second procedure that took place during the same hospital admission.

RESULTS

The first primary outcome was death within a timeframe of one year and the second a composite of MACCE within a year following complete revascularization. Of the total number of patients monitored, 4% in each of the two groups was associated with the first primary outcome (p=0.984) and the second primary outcome in 6% (p=0.970). There was no statistical difference between outcomes in the two groups.

CONCLUSION

Among patients with MVD and STEMI uncomplicated by cardiogenic shock, there was no difference regarding outcomes when using a strategy of complete revascularization of non-culprit lesions during PPCI or the same hospital admission.

Association of quantitative flow ratio-derived microcirculatory indices with anatomical-functional discordance in intermediate coronary lesions

Discrepancy between coronary lesion severity and functional significance has always been a relevant issue in the management of patients undergoing coronary angiography and/or revascularization. We sought to investigate the relationship between quantitative flow ratio (QFR)-derived microcirculatory indices and anatomical-functional mismatch/reverse mismatch in intermediate coronary lesions. Intravascular ultrasound (IVUS) imaging and QFR were analyzed in 117 de novo intermediate coronary lesions. Lesions with QFR ≤ 0.8 were considered hemodynamically significant. Anatomical significance of the lesions was defined according to the best cutoff value of combined IVUS parameters for predicting QFR ≤ 0.8. QFR-derived microcirculatory indices including contrast-flow QFR minus fixed-flow QFR (cQFR-fQFR), hyperemic flow velocity and angiography-derived index of microcirculatory resistance (IMR_angio) were calculated. The best cutoff values of IVUS parameters for predicting QFR ≤ 0.8 were minimum lumen area (MLA) 3.1mm² and plaque burden (PB) 70%, with area under the curve of 0.635 and 0.703, respectively. The total discordance rate of lesion functional significance between IVUS and QFR assessments was 26.5%, with 21 lesions (17.9%) being classified as mismatch (MLA ≤ 3.1mm² and PB ≥ 70% and QFR > 0.8) and 10 lesions (8.5%) as reverse-mismatch (MLA > 3.1 mm² or PB < 70% and QFR ≤ 0.8). At multivariate analysis, IMR_angio was identified as an independent predictor of mismatch (OR1.675, 95%CI:1.176-2.386, P = 0.004), whereas hyperemic flow velocity was identified as an independent predictor of reverse-mismatch (OR 1.233, 95%CI:1.073-1.416, P = 0.003). In intermediate coronary lesions, although MLA 3.1mm² and PB 70% determined by IVUS are predictive of QFR-defined functional significance, the discordance rate remains substantial. QFR-derived microcirculatory indices are independently associated with anatomical-functional discordance between IVUS and QFR assessments.