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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; hyperlipidaemia; 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 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 (risk reduction -1.9; 95% CI -6.3 to 2.4; P=0.56) or at one-year (risk reduction -1.7; 95% CI -7.3 to 3. 9; P=0.38). Thrombus aspiration was associated with a lower risk of stent thrombosis both at thirty-days (risk reduction -3.1; 95% CI -4.5 to -1.6; P<0.001) and at one-year (risk reduction -3.3; 95% CI -5.1 to -1.5; P<0.001). However, a landmark analysis after thirty-days showed no effect of thrombus aspiration on stent thrombosis at one-year (risk reduction -0.27; 95% CI -1.4 to 0. 81; P=0.63).
Mortality was not different between the groups. Thrombus aspiration before primary PCI was associated with decreased risk of stent thrombosis. While our study provides important evidence for external validity of the two largest RCTs with thrombus aspiration regarding mortality, future studies should determine whether this treatment may be cost-effective for prevention of stent thrombosis even in the absence of mortality benefit.