On propranolol for wolff parkinson white syndrome. last night my pulse was 39 while laying down. b/p was normal & it's normal now. should i worry?

No exact answer: The beta-blocker is obviously causing bradycardia (heart rate<60). At 19 you should have plenty of physiological reserve to stay hemodynamically stable even with HR = 39, so you had no symptoms. However, let your doctor know. (S)he may want to lower your dose of propranolol because possible side effects of beta-blockers are depression and impotence.