Detection of reversible platelet aggregates in the blood of smokers and ex-smokers with peripheral vascular disease.

OBJECTIVE: To demonstrate that smoking increases platelet aggregation in vivo, that smoking cessation reverses platelet aggregation and that this explains, in part, why smoking perpetuates the development of peripheral vascular disease. DESIGN: Prospective case-control study involving three groups of patients: smokers with peripheral vascular disease, ex-smokers with peripheral vascular disease and smokers with peripheral vascular disease who quit smoking during the study. SETTING/PARTICIPANTS: Fourteen smokers and seven ex-smokers, new patients with confirmed peripheral vascular disease, attending the vascular clinic at Fremantle Hospital between February and November, 1988. INTERVENTIONS: Blood samples taken weekly from all subjects for five weeks. Week 1 was taken as the baseline before smoking cessation in the six smokers who were assigned to stop smoking during the study. MAIN OUTCOME CRITERIA: Platelet aggregate ratio, an indicator of in-vivo platelet aggregability where an increase in platelet aggregate ratio suggests a decrease in platelet function. RESULTS: Only three of six smokers stopped smoking for the duration of the study. Median platelet aggregate ratios were: smokers = 0.85 (range, 0.79-0.92) v. non-smokers = 0.93 (range, 0.91-1.00). The difference was statistically significant P less than 0.0002. The difference in platelet aggregate ratios between smokers and quitters was not statistically significant. CONCLUSIONS: This study demonstrated an increase in platelet aggregability in smokers compared to ex-smokers but there was no clear evidence that platelet function was fully reversed after only four weeks cessation of smoking. The data suggested that platelet function of the ex-smokers had fully reversed to normal over a longer period. This could explain the decreased incidence of complications of peripheral vascular disease in ex-smokers. The small number of patients able to quit smoking impeded this study.