HOw feaR affects platelet aggRegability in healthy vOlunteeRs –
a randomized crossover trial

Rationale: For centuries the term ‘blood curdling’ has been used to describe frightening situations. It has been shown that cardiovascular events, such as a myocardial infarction, occur more often during stressful times. However, the relation between the coagulation system and frightening conditions is unknown. Nowadays, the complex mechanism of the coagulation cascade and the forming of thrombosis are partially unravelled, although it is unclear which factors trigger atherosclerosis to form a myocardial infarction. We hypothesize that increased platelet aggregability plays an important role in this phenomenon. Epinephrine, a hormone which is released in high amounts during fear or stress, is able to induce platelet activation. Therefore, we suggest that fear can induce blood curdling by activating blood platelets.
Objective: To explore the influence of catecholamines, induced by fear, on platelet aggregability in healthy volunteers.
Study design: In a randomized crossover study healthy subjects will be exposed to a bloody horrifying movie. As baseline measurement subjects will watch a relaxing movie before or after the horror movie, depending on their allocated group number.
Study population: Twenty-two healthy students at the VU medical center will be recruited. Subjects must be aged between 18 and 30 years old with no prior medical history. Factors that are able to alter platelet function are excluded.
Intervention: Blood will be drawn via an indwelling venous catheter from each participant’s antecubital vein. In total four measurements (2 per movie exposure) will take place, each requiring six tubes. Blood samples are drawn fifteen minutes prior to the horror movie and after 24 minutes, following a frightful moment. During the control movie, blood will be drawn fifteen minutes prior to the documentary and after 24 minutes of viewing the documentary.
Main study parameters/endpoints: Platelet activity will be determined from the blood samples, according to the PFA-200. Secondary haemostasis activity will be measured by using factor VIII levels. Epinephrine and cortisol levels, heart rate and skin conduction are used for objective determination of fear experience, whereas subjective measurement will take place via a questionnaire.
Nature and extent of the burden and risks associated with participation, benefit and group relatedness: Participation of the study will include two visits of the Clinical Research Unit, each lasting approximately one hour. In total blood will be drawn four times via an indwelling venous catheter of the cubital vein (17 ml per time point).

We hypothesize that acute fear, induced by watching a scary movie, increases platelet activability.

Prior to movie (control & intervention) and after 24 minutes of viewing time.

Healthy subjects will be exposed to a fragment of the scary movie Grave Encounters. As a control condition participants will watch an episode of The Joy of Painting with Bob Ross before or after the horror movie, depending on their allocated group number. Prior to baseline measurements and the viewing of the movies, subjects will rest in upright position for at least 15 minutes. Equipment for measurement of skin conduction and heart rate will be applied on the subject’s fingers. Each participant will watch both movies alone, so that other participants have no influence on the measurements.