PF4 and endothelial dysfunction: Some of the proposed mechanisms are as follows:high sympathetic tone; increased cortisol and catecholamine; endothelial dysfunction;abnormal platelet activation, including enhanced platelet reactivity and release ofplatelet products (such as platelet factor 4 and b-thromboglobulin); augmented releaseof inflammatory markers; decreased heart rate variability; accelerated atherogenesis;and poor adherence10,11.