Saving myocardium: the protective role of filter devices during culprit overexpansion in STEMI

Background The slow flow phenomenon during primary percutaneous coronary intervention (PCI) in ST-elevation myocardial infarction (STEMI) is associated with adverse outcomes and impaired myocardial salvage. Excessive expansion of the culprit lesion may increase distal embolization and lead to slow flow phenomenon, thereby limiting myocardial salvage. Although filter devices are designed to prevent embolization during stent deployment, their impact on myocardial salvage remains uncertain. Purpose We investigated whether culprit lesion expansion volume (CEV) assessed by intravascular imaging is associated with myocardial salvage and whether distal filter device use modifies this relationship in STEMI patients. Methods Consecutive STEMI patients who underwent primary PCI with intravascular imaging (IVUS, OCT, or OFDI) and cardiac magnetic resonance (CMR) at approximately 4 days and 6 months between 2017 and 2025 were included. Culprit expansion volume (CEV) was calculated as the difference between pre- and post-stent lumen volumes, approximated as two combined conical frustums. Myocardial salvage index was derived from acute phase area-at-risk (T2-weighted imaging) and chronic phase infarct size (late gadolinium enhancement). Correlation analyses were performed according to filter device use. Multivariable linear regression analysis was conducted to identify independent determinants of myocardial salvage index. Results A total of 64 patients were analyzed (median age 69 years [IQR 62–75], 86% male). In patients without filter device use, CEV was significantly negatively correlated with salvage index (r=0.58, p=0.02). In contrast, no significant association was observed in patients using filter devices (r=－0.05, p=0.75), suggesting attenuation of the adverse effect of excessive expansion. In multivariable regression analysis (R²=0.20), chronic kidney disease was negatively associated with salvage index (β=−0.17, 95% CI −0.31 to −0.03, p=0.02), whereas filter device use (β=0.15, 95% CI 0.003 to 0.33, p=0.04) and final myocardial blush grade 3 (β=0.17, 95% CI 0.03 to 0.30, p=0.02) were independently associated with higher salvage index. CEV itself was not independently associated with salvage index after adjustment. Conclusions Excessive culprit lesion expansion is associated with impaired myocardial salvage in STEMI when distal protection is not used. Distal filter device use and achievement of myocardial blush grade 3 are independently associated with improved myocardial salvage. These findings suggest that distal embolic protection may mitigate microvascular injury during aggressive stent expansion and support selective use of filter devices in cases requiring large stent deployment.picture1