Invasive Assessment of the Coronary Microcirculation in Reperfused ST-Segment–Elevation Myocardial Infarction Patients

Abstract

For patients presenting with an acute ST-segment-elevation myocardial infarction, the most effective therapy for reducing myocardial infarct size and preserving left ventricular systolic function is primary percutaneous coronary intervention (PPCI). However, mortality and morbidity remain significant. This is partly attributed to the development of microvascular obstruction, which occurs in around 50% of ST-segment-elevation myocardial infarction patients post-PPCI, and it is associated with adverse left ventricular remodeling and worse clinical outcomes. Although microvascular obstruction can be detected by cardiac imaging techniques several hours post-PPCI, it may be too late to intervene at that time. Therefore, being able to predict the development of microvascular obstruction at the time of PPCI may identify high-risk patients who might benefit from further adjuvant intracoronary therapies, such as thrombolysis, vasodilators, glycoprotein IIb/IIIa inhibitors, and anti-inflammatory agents that may reduce microvascular obstruction. Recent studies have shown that invasive coronary physiology measurements performed during PPCI can be used to assess the coronary microcirculation. In this article, we provide an overview of the various invasive methods currently available to assess the coronary microcirculation in the setting of ST-segment-elevation myocardial infarction, and how they could potentially be used in the future for tailoring therapies to those most at risk.

Cardiovascular Magnetic Resonance in Acute ST-Segment–Elevation Myocardial Infarction

“…However, this was a retrospective post-hoc analysis and intramyocardial hemorrhage was identified using T2-weighted imaging instead of the more robust T2*-weighted imaging and their findings need to be confirmed in future studies. Furthermore, there are no established therapies to prevent or minimize the burden of microvascular obstruction and intramyocardial hemorrhage in the clinical setting 4 , although promising results are emerging in the preclinical setting. 65 …”

“…3 The process of reperfusion itself can paradoxically induce further myocardial injury and cardiomyocyte death, a phenomenon termed ‘myocardial reperfusion injury’. 4 There is currently no effective therapy for reducing myocardial reperfusion injury, despite a wealth of research in this field. This has been partly attributed to undertaking clinical studies despite the lack of reproducible and robust preclinical data and the design of the clinical cardioprotection studies in terms of patient selection and inappropriate timing and mode of delivery of the cardioprotective agent.…”

A Randomized Controlled Clinical Trial of Prolonged Stent Deployment Strategy in Primary Percutaneous Coronary Intervention for ST-segment Elevation Myocardial Infarction: A Pilot study

“…The indexes of angiography for evaluating coronary microvascular circulation in the cardiac catheterization laboratory are semiquantitative and can be subjective [56]. CMR is the gold standard method to assess the MVO, MI size, LV volume and LVEF, but it is expensive and not yet widely available [56]. Areas of no-reflow have been associated with MVO as seen on magnetic resonance images and correlate with a higher degree of myocardial damage [57].…”

Invasive Evaluation of the Microvasculature in Acute Myocardial Infarction: Coronary Flow Reserve versus the Index of Microcirculatory Resistance

“…The current landscape of microcirculatory assessment tools is not without limitations [78]. The calculations and equipment involved in measurements such as hyperemic microvascular resistance (HMR) and zero-flow pressure (Pzf) are cumbersome and time consuming, making them non-viable options in typical catheterization labs.…”

“…The calculations and equipment involved in measurements such as hyperemic microvascular resistance (HMR) and zero-flow pressure (Pzf) are cumbersome and time consuming, making them non-viable options in typical catheterization labs. Also, despite its superior reproducibility, IMR measurements are still subject to interobserver/institutional variability [78]. Bulluck et al propose that future prospective studies stratify patients' risk of microcirculatory dysfunction based on IMR values (with a cutoff of >40) after P-PCI, and tailor therapeutic interventions on this basis.…”