Virtual assessment of microvascular resistance in young women with ST-Elevation Myocardial Infarction: a sub-analysis of the WAMIF registry

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Abstract Background Coronary microvascular dysfunction (CMD) is a frequent yet under-recognized contributor to adverse outcomes in young women with ST-elevation myocardial infarction (STEMI). The angiography-derived index of microcirculatory resistance (IMR), particularly the quantitative flow ratio-based methods (A-IMR and NH-IMR angio), may offer insights into microvascular health without the need for invasive instrumentation. Purpose This study aimed to evaluate CMD using angiography-derived IMR in young women with STEMI from the WAMIF registry and to assess its clinical, biological, and prognostic correlates. Methods Among the 314 women enrolled in WAMIF, 102 out of the 191 STEMI cases with either atherothrombosis or spontaneous coronary artery dissection and suitable post-PCI imaging were included. A-IMR and NH-IMR angio were retrospectively calculated. Clinical, biochemical, procedural, and imaging data were analyzed according to IMR threshold of 40 U, and its prognostic value was evaluated at one-year follow-up. Results Median age was 44 years; 78.4 % were smokers, 24.5 % obese. No significant differences in A-IMR or NH-IMR angio were found across major coronary arteries or between infarct-related and non-culprit vessels. A-IMR ≥40 U was observed in 56.9 % and NH-IMR angio ≥40 U in 54.9 %. Elevated IMR values correlated positively with blood pressure, QFR, BMI, and ischemic time, and negatively with antithrombin activity. Multivariate analysis identified antithrombin activity and platelet count as independent predictors of high IMR. Elevated IMR was associated with reduced post-PCI TIMI flow and longer delays to reperfusion. Despite limited statistical power, higher A-IMR was predictive of recurrent MI (AUC 0.720, p < 0.001). A-IMR and NH-IMR angio demonstrated excellent concordance (R² = 0.995, ICC = 0.998). Conclusions Angiography-derived IMR is elevated in more than one half of young women with STEMI and is associated in particular with longer delays and reduced post-PCI TIMI flow. A-IMR and NH-IMR angio provide interchangeable assessments of CMD, with potential prognostic implications. These findings underscore CMD as a relevant pathophysiological and therapeutic target in this population.IMR distribution across coronary arterisFor image description, please refer to the figure legend and surrounding text. ROC curve for predicting MI recurrenceFor image description, please refer to the figure legend and surrounding text.

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