Effects of digitalis glycosides on the heart:

1 Increased myocardial contractility 2 Increased myocardial contractility which causes an increase in MVO2 (myocardial volume O2) 3 Electrophysiologic activity- it indirectly incease the vagal tone of the heart 4 Heart rate. In CHF patients, digitalis slows the HR (a (-) chronotropic effect) due to a combination of vagal and sinoatrial (S-A ) nodes. Tachycardia is seen with excessive doses of digitalis (a (+) chronotropic effect). It has little effects on the heart rate of normal individuals.