Digitalis does not increase which parameter of heart-
Ans. is 'c' i.e., Myocardial oxygen demand Effect of digitalis on hearto Main mechanism of action of digitalis is to increase in force of contraction of heart - a positive inotropic action.o Amongst given options, option d is the best choice - heart rate is decreased by digitalis and there is increase myocardial contractility without a propartionate increase in O2 consumption.How does digitalis decrease heart rate?# Heart rate is decreased by digitalis mainly in patients with CHF.# In CHF there is sympathetic overactivity and i vagal tone because of | CO2# Digitalis increases myocardial contractility (major action) - | CO and better emptying of ventricle - improvement in circulation - restoration of diminished vagal tone and abolish sympathetic overactivity - | Heart rate. Beside above main mechanism digitalis slows the heart rate by -A) Increased vagal tonei) Reflexly through nodosa ganglion.ii) Direct stimulation of vagal centre.iii) Sensitization of SA nodes to Ach.B) Extravagal - Direct depressant action on SA and AV nodes."The vagal action manifests early and can be blocked by atropine, whereas extravagal action becomes prominent later and cannot be reversed by atropine
Force of contraction
Myocordial contractility
Myocardial oxygen demand
Cardiac output
Digitalis