Aspiration thrombectomy is used in primary percutaneous coronary interventions, but the importance of thrombus constituency has been scarcely investigated. The objective of this study was to evaluate thrombus constituency and its association with clinical, laboratory, and angiographic findings in patients with ST-segment elevation myocardial infarction.

From April 2010 to May 2011, 562 patients with ST-segment elevation myocardial infarction undergoing primary percutaneous coronary interventions were considered for inclusion, and information on thrombi characteristics was available for 113 patients. Thrombus material were obtained and classified as white or red based on its constituency. Samples were analyzed by 3 independent pathologists blinded to clinical characteristics.

The mean age of patients was 58.6 ± 12.7 years, and 69% were men. White thrombi were present in 31% of cases, and red thrombi, in 69%. Patients with white thrombi had smaller vessels and lower ischemic times. All other clinical, angiographic, and laboratory characteristics did not differ. White thrombi were smaller and associated with fibrin infiltration, whereas red thrombi were associated with red blood cell infiltration. Thirty-day death rates were lower in patients with white thrombi than red (0% vs 10.1%, respectively; P = .05), as were 30-day major adverse cardiac event rates (4.2% vs 13.9%; P = .10). Total ischemic time was well correlated with fibrin infiltration (R = −0.30; P < .01), red blood cell infiltration (R = 0.27; P < .01), and thrombus volume (R = 0.22; P = .02).

White thrombi were present in one-third of cases and were associated with lower ischemic times, higher fibrin infiltration, smaller thrombus volume, and lower mortality. These findings suggest that thrombus constituency may be a useful prognostic tool in this setting.