Sir,—I read with great interest the article on the effect of atrioventricular asynchrony on platelet activation by Lau,et al.1 The authors conclude that “loss of atrioventricular synchrony related to single chamber ventricular pacing is a major cause of increased platelet activation.”

However, the tables and text indicate that in both modes of DDD pacing, platelet activation is increased by approximately 160–200% compared with the control group. Twelve of their patients had a permanent pacemaker implanted because of sick sinus syndrome—most probably a defect in impulse generation with or without accompanying tachyarrhythmias. In those patients, an attempt at AAI pacing could have proven effective, perhaps with concentrations of both platelet …