Time course of coronary flow capacity impairment in ST-segment elevation myocardial infarction.

BACKGROUND: Microvascular dysfunction in the setting of ST-elevated myocardial infarction (STEMI) plays an important role in long-term poor clinical outcome. Coronary flow reserve (CFR) is a well-established physiological parameter to interrogate the coronary microcirculation. Together with hyperaemic average peak flow velocity, CFR constitutes the coronary flow capacity (CFC), a validated risk stratification tool in ischaemic heart disease with significant prognostic value. This mechanistic study aims to elucidate the time course of the microcirculation as reflected by alterations in microcirculatory physiological parameters in the acute phase and during follow-up in STEMI patients. METHODS: We assessed CFR and CFC in the culprit and non-culprit vessel in consecutive STEMI patients at baseline (n = 98) and after one-week (n = 64) and six-month follow-up (n = 65). RESULTS: A significant trend for culprit CFC in infarct size as determined by peak troponin T (p = 0.004), time to reperfusion (p = 0.038), the incidence of final Thrombolysis In Myocardial Infarction 3 flow (p = 0.019) and systolic retrograde flow (p = 0.043) was observed. Non-culprit CFC linear contrast analysis revealed a significant trend in C-reactive protein (p = 0.027), peak troponin T (p < 0.001) and heart rate (p = 0.049). CFC improved both in the culprit and the non-culprit vessel at one-week (both p < 0.001) and six-month follow-up (p = 0.0013 and p < 0.001) compared with baseline. CONCLUSION: This study demonstrates the importance of microcirculatory disturbances in the setting of STEMI, which is relevant for the interpretation of intracoronary diagnostic techniques which are influenced by both culprit and non-culprit vascular territories. Assessment of non-culprit vessel CFC in the setting of STEMI might improve risk stratification of these patients following coronary reperfusion of the culprit vessel.

Prognostic implications of microcirculatory perfusion versus macrocirculatory perfusion in cardiogenic shock: a CULPRIT-SHOCK substudy.

BACKGROUND: After early revascularisation, restoration of macrocirculatory perfusion parameters is the primary objective in the management of cardiogenic shock complicated acute myocardial infarction. Nevertheless, vital organ perfusion may be compromised at the systemic microcirculatory level, even in patients with preserved macrohaemodynamics. Microvascular perfusion was shown to have independent prognostic value for early mortality. The present study aims to compare the prognostic value of microcirculatory versus macrocirculatory perfusion parameters. METHODS: This substudy of the culprit lesion-only percutaneous coronary intervention versus multivessel percutaneous coronary intervention in cardiogenic shock (CULPRIT-SHOCK) trial examined the sublingual capillary network using videomicroscopy post-percutaneous coronary intervention to determine the proportion of perfused capillaries (<20 µm) and perfused capillary density. Thirty-day follow-up was performed to obtain the occurrence of a combined clinical endpoint of all-cause death and renal replacement therapy. RESULTS: Videomicroscopy measurements were performed in 66 patients. There was a significant adjusted association between microcirculatory perfusion parameters and the combined clinical endpoint (proportion of perfused capillaries: P=0.020; perfused capillary density: P=0.035), whereas there was no significant adjusted association between macrocirculatory perfusion parameters and the combined clinical endpoint (systolic blood pressure: P=0.205). Normotensive patients with compromised microcirculatory perfusion parameters had a higher risk of the combined clinical endpoint than normotensive patients with preserved microcirculatory perfusion parameters (proportion of perfused capillaries: Breslow P=0.014; perfused capillary density: Breslow P=0.076). CONCLUSIONS: There is a significant and independent association between microcirculatory perfusion parameters perfused capillary density and proportion of perfused capillaries and the combined clinical endpoint of all-cause death and renal replacement therapy at 30 days follow-up. In patients with loss of haemodynamic coherence between microcirculatory and macrocirculatory perfusion parameters, microcirculatory perfusion parameters confer dominant prognostic value.

Assessing the Haemodynamic Impact of Coronary Artery Stenoses: Intracoronary Flow Versus Pressure Measurements.

Fractional flow reserve (FFR)-guided percutaneous coronary intervention results in better long-term clinical outcomes compared with coronary angiography alone in intermediate stenoses in stable coronary artery disease (CAD). Coronary physiology measurements have emerged for clinical decision making in interventional cardiology, but the focus lies mainly on epicardial vessels rather than the impact of these stenoses on the myocardial microcirculation. The latter can be quantified by measuring the coronary flow reserve (CFR), a combined pressure and flow index with a strong ability to predict clinical outcomes in CAD. However, combined pressure-flow measurements show 30-40 % discordance despite similar diagnostic accuracy between FFR and CFR, which is explained by the effect of microvascular resistance on both indices. Both epicardial and microcirculatory involvement has been acknowledged in ischaemic heart disease, but clinical implementation remains difficult as it requires individual proficiency. The recent introduced pressure-only index instantaneous wave-free ratio, a resting adenosine-free stenosis assessment, led to a revival of interest in coronary physiology measurements. This review focuses on elaborating the coronary physiological parameters and potential of combined pressure-flow measurements in daily clinical practice.