Background A growing volume of data suggests that simple manual thrombus aspiration followed by direct stenting improves myocardial reperfusion and clinical outcome compared with conventional primary PCI, but there is still limited data comparing the in vivo performance among different devices. This study aimed to compare the efficacy and operability of thrombus aspiration by the Diver CE (Invatec, Brescia, Italy) and ZEEK (Zeon Medical Inc., Tokyo, Japan) aspiration catheters in ST-segment elevation myocardial infarction (STEMI) and their impact on 3-month outcome.Methods From September 2004 to June 2008, 298 consecutive patients with STEMI who received manual thrombus aspiration were involved in a single center retrospective analysis. Of them, 229 and 69 were treated with Diver CE and ZEEK aspiration catheters, respectively. Primary endpoints were myocardial blush grade (MBG), thrombolysis in myocardial infarction (TIMI) flow grade, ST-segment elevation resolution (STR), device pushability and trackability as judged by the frequency of usage of dual guide wires and aspiration efficacy as indicated by size distribution of aspirated thrombi. Secondary endpoints were 3-month outcome including left ventricular end diastolic diameter (LVEDD), left ventricular ejection fraction (LVEF), as well as cardiac death, target lesion revascularization (TLR), re-infarction and their combination as major adverse cardiac events (MACE).Results Baseline characteristics were not different between the two groups expect for a higher frequency of temporary cardiac pacing in the ZEEK group (ZEEK) than in the Diver CE group (Diver CE) (0.44% vs 5.8%, P=0.002). Visible retrieved thrombi were achieved in 65.9% of the Diver CE and 68.1% of the ZEEK (P=0.74). Aspirated thrombi were categorized as small thrombi (<3.5 mm), moderate thrombi (3.5-7.0 mm) and large thrombi (>7.0 mm). Small thrombi were more frequently seen in the Diver CE (61.6% vs 42.6%), whereas moderate and larger thrombi were more frequently found in the ZEEK (38.4% vs 57.4%) (P=0.021). Rates of dual wire utilization were 1.7% of the Diver CE and 7.2% of the ZEEK (P=0.052). There were no differences in MBG, STR and TIMI flow grade between the two groups. No differences were found in cardiac death, TLR, re-infarction, MACE, LVEDD and LVEF between the Diver CE and the ZEEK during 3-month follow-up.Conclusions Both Diver CE and ZEEK manual aspiration catheters are effective for thrombectomy in STEMI. In clinical practice, ZEEK presents a stronger aspiration capacity for moderate to large thrombi compared with Diver CE, but Diver CE displays a trend towards better pushability and trackability than ZEEK. Differences in aspiration capacity and operability between Diver CE and ZEEK in this setting do not influence myocardial reperfusion and 3-month outcome.