Effects of Digitalis Drugs

Digitalis drugs primarily enhance myocardial contractility directly, thereby increasing stroke volume and reducing end-systolic residual volume and end-diastolic pressure.

These effects help alleviate organ congestion, increase urine output, and slow heart rate.

The mechanism underlying digitalis-induced enhancement of myocardial contractility involves inhibition of the sodium-potassium-ATPase pump in the cell membrane. This inhibition leads to increased intracellular sodium concentration, which subsequently promotes calcium influx—thereby augmenting myocardial contractility.

Although enhanced myocardial contractility increases myocardial oxygen consumption, the accompanying reduction in ventricular cavity size decreases ventricular wall tension, resulting in an overall reduction in myocardial oxygen demand. Consequently, digitalis preparations improve myocardial work efficiency without increasing myocardial oxygen consumption.