<prompt> Myocardial contractility is increased by:AtropineDecreased end diastolic volumeIncreased heart rate from 70 to 150 beatsminReduced arterial pH to 7.3  <response>: 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. 