Functional angiography-derived index of microcirculatory resistance validated with microvascular obstruction in cardiac magnetic resonance after STEMI.

The index of microcirculatory resistance (IMR) measured after primary percutaneous coronary intervention (PCI) for ST-segment elevation myocardial infarction (STEMI) is associated with microvascular obstruction (MVO) and adverse clinical events. To evaluate MVO after successful primary PCI for STEMI without pressure wires or hyperemic agents, we investigated the feasibility and usefulness of functional angiography-derived IMR (angio-IMR). The current study included a total of 285 STEMI patients who underwent primary PCI and cardiac magnetic resonance (CMR). Angio-IMR of the culprit vessel after successful primary PCI was calculated using commercial software. MVO, infarct size, and myocardial salvage index were assessed using CMR, which was obtained a median of 3.0 days [interquartile range, 3.0-5.0] after primary PCI. Among the total population, 154 patients (54.0%) showed elevated angio-IMR (> 40 U) in the culprit vessel. MVO was significantly more prevalent in patients with angio-IMR> 40 U than in those with angio-IMR ≤ 40 U (88.3% vs 32.1%, P <.001). Infarct size, extent of MVO, and area at risk were significantly larger in patients with angio-IMR> 40 U than in those with angio-IMR ≤ 40 U (P <.001 for all). Angio-IMR showed a significantly higher discriminatory ability for the presence of MVO than thrombolysis in myocardial infarction flow grade or myocardial blush grade (area under the curve: 0.821, 0.504, and 0.496, respectively, P <.001). Angio-IMR was significantly associated with CMR-derived infarct size, extent of MVO, and area at risk. An elevated angio-IMR (> 40 U) after primary PCI for STEMI was highly predictive of the presence of MVO in CMR. This trial was registered at ClnicalTrialsgov (Identifier: NCT04828681).

Shin D ，Kim J ，Choi KH ，Dai N ，Li Y ，Lee SH ，Joh HS ，Kim HK ，Kim SM ，Ha SJ ，Jang MJ ，Park TK ，Yang JH ，Song YB ，Hahn JY ，Choi SH ，Choe YH ，Gwon HC ，Lee JM ... -  《-》

Angiography-versus wire-based microvascular resistance index to detect coronary microvascular obstruction associated with ST-segment elevation myocardial infarction.

Microvascular obstruction (MVO) measured by cardiac magnetic resonance (CMR) after ST-segment elevation myocardial infarction (STEMI) has important prognostic implications. While invasive index of microvascular resistance (IMR) have been shown to predict the occurrence and extent of MVO, the role of the angiography-based microvascular resistance (Angio-IMR) for this purpose remains unknown. The present study aims to perform a head-to-head comparison of wire-based and angiography-derived microcirculatory resistance (IMR and Angio-IMR, respectively) for the detection of MVO. Patients with a first STEMI and multivessel disease underwent CMR for detection of MVO, and angio-IMR and IMR measurements during PPCI and at 30 day follow up, both in STEMI culprit and non-culprit vessels. 58 patients were included (mean age 60.7 ± 9.9 years, 82% male). At the time of PPCI, angio-IMR and IMR exhibited significant correlation (r = 0.70, P < 0.001), and agreement (coefficient of agreement 0.58). Both indices showed good predictive value of MVO [Angio IMR: AUC 0.79 (95% CI: 0.667-0.928); IMR: AUC 0.70 (95% CI: 0.539-0.853); p = 0.15]. Angio-IMR 40 U and IMR 34 U were identified as best cut-offs for prediction of MVO. In non-culprit vessels, angio-IMR and IMR also correlated well (rho = 0.59, p < 0.001), with overall lower mean values compared to culprit vessels (Angio-IMR: 36 vs. 23; IMR: 39 vs. 22, p < 0.001 for both comparisons). Angio-IMR constitutes a valid alternative to wire-based IMR in predicting MVO in STEMI. Angio-IMR and IMR show a good correlation in the acute and subacute STEMI phases, both in culprit and non-culprit vessels.

Wang L ，Travieso A ，van der Hoeven N ，Lombardi M ，van Leeuwen MAH ，Janssens G ，Shabbir A ，Mejía-Rentería H ，Milasinovic D ，Gonzalo N ，Nijveldt R ，van Royen N ，Escaned J ... -  《-》

Coronary angiography-derived index of microcirculatory resistance and evolution of infarct pathology after ST-segment-elevation myocardial infarction.

This study sought to evaluate the association of coronary angiography-derived index of microcirculatory resistance (angio-IMR) measured after primary percutaneous coronary intervention (PPCI) with the evolution of infarct pathology during 3-month follow-up after ST-segment-elevation myocardial infarction (STEMI). Patients with STEMI undergoing PPCI were prospectively enrolled between October 2019 and August 2021. Angio-IMR was calculated using computational flow and pressure simulation immediately after PPCI. Cardiac magnetic resonance (CMR) imaging was performed at a median of 3.6 days and 3 months. A total of 286 STEMI patients (mean age 57.8 years, 84.3% men) with both angio-IMR and CMR at baseline were included. High angio-IMR (>40 U) occurred in 84 patients (29.4%) patients. Patients with angio-IMR >40 U had a higher prevalence and extent of MVO. An angio-IMR >40 U was a multivariable predictor of infarct size with a three-fold higher risk of final infarct size >25% (adjusted OR 3.00, 95% CI 1.23-7.32, P = 0.016). Post-procedure angio-IMR >40 U significantly predicted presence (adjusted OR 5.52, 95% CI 1.65-18.51, P = 0.006) and extent (beta coefficient 0.27, 95% CI 0.01-0.53, P = 0.041) of myocardial iron at follow-up. Compared with patients with angio-IMR ≤40 U, those with angio-IMR >40 U had less regression of infarct size and less resolution of myocardial iron at follow-up. Angio-IMR immediately post-PPCI showed a significant association with the extent and evolution of infarct pathology. An angio-IMR >40 U indicated extensive microvascular damage with less regression of infarct size and more persistent iron at follow-up.

Wang X ，Guo Q ，Guo R ，Guo Y ，Yan Y ，Gong W ，Zheng W ，Wang H ，Ai H ，Que B ，Xu L ，Huo Y ，Fearon WF ，Nie S ... -  《-》

Combination of the Thermodilution-Derived Index of Microcirculatory Resistance and Coronary Flow Reserve Is Highly Predictive of Microvascular Obstruction on Cardiac Magnetic Resonance Imaging After ST-Segment Elevation Myocardial Infarction.

The aim of this study was to investigate the predictive accuracy of invasive coronary microvascular indexes for identifying microvascular obstruction (MVO) on cardiac magnetic resonance imaging (CMR) in patients treated with primary percutaneous coronary intervention (PCI) for ST-segment elevation myocardial infarction (STEMI). We hypothesized that a combination of the index of microcirculatory resistance (IMR) and the thermodilution-derived coronary flow reserve (CFRthermo) will enhance the predictive accuracy of detecting MVO compared with either index alone. The IMR and CFRthermo were measured using a single pressure sensor/thermistor-tipped guidewire in 40 STEMI patients immediately after PCI and related to MVO assessed by CMR day 7. The primary endpoint was the predictive accuracy of the IMR for detecting MVO. Patients with an IMR >36 (upper tertile) had a higher rate of MVO compared with those with an IMR ≤36 (93% vs. 39%; p = 0.001). MVO occurred in all patients with an IMR >36 and a CFRthermo ≤1.7 and in no patients with an IMR ≤36 and a CFRthermo >1.7. The IMR remained an independent predictor of MVO (odds ratio: 1.212, 95% confidence interval [CI]: 1.004 to 1.464; p = 0.045) after adjustment for age, creatine kinase-myocardial band, myocardial blush grade, thrombus burden, and CFRthermo. Both the IMR (area under the curve, 0.868, 95% CI: 0.719 to 0.956; p = 0.001) and the CFRthermo (area under the curve, 0.706, 95% CI: 0.536 to 0.842; p = 0.03) were predictive of MVO. Combined IMR and CFRthermo increased the area under the curve for MVO to 0.941. In patients who underwent primary PCI for STEMI, an increased IMR has an independent predictive value for MVO detection, and combined high IMR and low CFRthermo are highly predictive of MVO. These indexes could be used to further risk-stratify patients and guide regional and systemic therapies.

Ahn SG ，Hung OY ，Lee JW ，Lee JH ，Youn YJ ，Ahn MS ，Kim JY ，Yoo BS ，Lee SH ，Yoon J ，Kwon W ，Samady H ... -  《-》

Index of Microcirculatory Resistance as a Tool to Characterize Microvascular Obstruction and to Predict Infarct Size Regression in Patients With STEMI Undergoing Primary PCI.

This study aimed to compare the value of the index of microcirculatory resistance (IMR) and microvascular obstruction (MVO) measured by cardiac magnetic resonance (CMR) in patients treated for and recovering from ST-segment elevation myocardial infarction. IMR can identify patients with microvascular dysfunction acutely after primary percutaneous coronary intervention (pPCI), and a threshold of >40 has been shown to be associated with an adverse clinical outcome. Similarly, MVO is recognized as an adverse feature in patients with ST-segment elevation myocardial infarction. Even though both IMR and MVO reflect coronary microvascular status, the interaction between these 2 parameters is uncertain. A total of 110 patients treated with pPCI were included, and IMR was measured immediately at completion of pPCI. Infarct size (IS) as a percentage of left ventricular mass was quantified at 48 h (38.4 ± 12.0 h) and 6 months (194.0 ± 20.0 days) using CMR. MVO was identified and quantified at 48 h by CMR. Overall, a discordance between IMR and MVO was observed in 36.7% of cases, with 31 patients having MVO and IMR ≤40. Compared with patients with MVO and IMR ≤40, patients with both MVO and IMR >40 had an 11.9-fold increased risk of final IS >25% at 6 months (p = 0.001). Patients with MVO and IMR ≤40 had a significantly smaller IS at 6 months (p = 0.001), with significant regression in IS over time (34.4% [interquartile range (IQR): 27.3% to 41.0%] vs. 22.3% [IQR: 16.0% to 30.0%]; p = 0.001). Discordant prognostic information was obtained from IMR and MVO in nearly one-third of cases; however, IMR can be helpful in grading the degree and severity of MVO.

De Maria GL ，Alkhalil M ，Wolfrum M ，Fahrni G ，Borlotti A ，Gaughran L ，Dawkins S ，Langrish JP ，Lucking AJ ，Choudhury RP ，Porto I ，Crea F ，Dall'Armellina E ，Channon KM ，Kharbanda RK ，Banning AP ... -  《-》