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What is Myocardial  contractility  is  increased by: and explain in detail?
Option A: Atropine is a muscarinic receptor antagonist that is used to inhibit the effects of excessive vagal activation on the heart, which is manifested as sinus bradycardia and AV nodal block. Effect on contractility is negligible. 
Option B: Decrease EDV decreases contractility by Frank Starling law.
Option  D:  Acidosis, hypercapnoea and hypoxia inhibit myocardium contractility.
Option C: This effect is known as Bowditch Effect (Myocardial tension increases with an increase in heart rate).