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Routine intracoronary thrombus aspiration before primary percutaneous coronary intervention (PCI) in STEMI patients does not seem to reduce mortality but may reduce stent thrombosis and reinfarction. The aim of this observational study was to evaluate the impact of thrombus aspiration on mortality and stent thrombosis using all available data from the national all-inclusive Swedish Coronary Angiography and Angioplasty Registry (SCAAR).
We included all consecutive patients registered in SCAAR between January 2005 and September 2014 undergoing PCI for STEMI. We used instrumental variable analysis (for hidden selection bias) with propensity score to evaluate the effect of thrombus aspiration on stent thrombosis and mortality at thirty-days and one-year. Administrative region was employed as treatment-preference instrumental variable using two-stage least squares regression. The variables used to calculate the propensity score were: age; sex; hypertension; hyperlipidemia; smoking status; diabetes; arterial access site; severity of coronary artery disease; completeness of revascularization; prior MI, coronary by-pass surgery and/or PCI; use of drug-eluting stents; cardiogenic shock and procedural success. In a substudy (n=155), we evaluated the effect of thrombus aspiration on coronary flow reserve at one week and at four months after primary PCI. Coronary flow reserve was evaluated by measuring coronary flow velocity in the left anterior descending artery with transthoracic color Doppler echocardiography before and during adenosine infusion (140 microgram/kg/min). We modelled predictive value of thrombus aspiration on coronary flow reserve by means of propensity score adjusted linear regression.
In total, 42,645 patients were included in the study of whom 10,653 (25%) were treated with thrombus aspiration. There were 2659 (6.2%) deaths at thirty-days and 3745 (8.7%) at one-year and 255 (0.5%) cases of stent thrombosis at thirty-days and 409 (0.9%) at one-year. Mortality was not different between the groups at thirty-days (b -0.019; 95% CI -0.063 to 0.024; P=0.56) or at one-year (b -0.017; 95% CI -0.073 to 0.039; P=0.38). Thrombus aspiration was associated with a lower risk of stent thrombosis both at thirty-days (b -0.031; 95% CI -0.045 to -0.016; P<0.001) and at one-year (b -0.033; 95% CI -0.051 to -0.015; P<0.001). However, a landmark analysis after thirty-days showed no effect of thrombus aspiration on stent thrombosis at one-year (b -0.0027; 95% CI -0.014 to 0.0081; P=0.63). Thrombus aspiration was not associated with improved coronary flow reserve at one week (b -0.008; 95% CI -0.091 to -0.075; P=0.84) or at four months (b -0.054; 95% CI -0.137 to 0.029; P=0.21). The number of in-hospital neurological complications were 122 (0.3%) of which 90 occurred in the PCI-only group (0.3%) and 32 in the thrombus aspiration group (0.3%). Unadjusted and adjusted analyses have shown no differences in risk of stroke between the groups.
Thrombus aspiration before primary PCI was associated with decreased risk of stent thrombosis but not with improved coronary flow reserve. Mortality was not different between the groups.