Effects of Timolol on Platelets in Coronary Sinus Blood and on Myocardial Ischemia during Pacing-induced Angina

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Abstract
The effect of timolol on blood platelet function was studied in coronary sinus and caval vein blood at rest and during pacing-induced angina in 20 patients with coronary heart disease. During pacing-induced angina, lactate measurements confirmed that coronary sinus blood was sampled from ischemic regions in 13 men. The ischemia did not influence platelet function. In blood from non-ischemic myocardium, platelet activation was found during pacing: the ADP-induced aggregation, platelet retention and plasma .beta.-thromboglobulin levels increased moderately but significantly. Timolol administration prevented this platelet activation, possibly by inhibiting catecholamine release from the myocardium, and reduced the ischemic response during pacing as judged from lactate measurements and ST depressions. Timolol reduced platelet activation induced in non-ischemic regions of the heart during tachycardia stress as well as myocardial ischemia.