The importance of antiplatelet failure due to antiplatelet resistance may differ between those receiving mono antiplatelet and dual antiplatelet treatment (DAPT). Smoking is a well-known factor which influences the resistance of clopidogrel. Here, we compared antiplatelet resistance between those who receive mono and dual antiplatelet treatment and between smokers and non-smokers.

We have consecutively enrolled patients who experienced ischemic stroke under antiplatelet treatment. First, patients were divided into three groups according to the antiplatelet treatment at the time of stroke; aspirin, clopidogrel and DAPT. Demographics, conventional risk factor and aspirin (ARU) and P2Y12 reaction unit (PRU) measured by VerifyNow was compared between the three groups. Among those who received DAPT, patients were dichotomized to smokers and non-smokers. ARU and PRU were compared between the two groups.

Among 783 patients, 485 patients were under aspirin, 133 patients under clopidogrel and 165 patients under DAPT. There was no significant difference in demographics and risk factor among three groups. However, ARU was higher in those under aspirin than DAPT (482.00±73.12 vs. 453.02±82.94; p=0.001), and PRU was higher in those under clopidogrel than DAPT (257.79±92.82 vs. 225.71±87.71; p=0.013). Among those under DAPT, 88 patient were non-smokers and 76 patients were smokers. Smokers were younger, more male, but had less hypertension. The ARU was similar between the two groups, PRU was significantly lower in the smoker group (195.95±80.66 vs. 245.98±85.31; p=0.004).

Antiplatelet resistance may be more important in those receiving mono antiplatelet than in those receiving DAPT. Therefore, selecting antiplatelet agent may be more critical in those receiving mono antiplatelet. Smokers’ paradox was also confirmed in stroke population and can be considered in determining antiplatelet treatment strategy.