• Digitalis
• Therapeutic Window of Digoxin
• ECG and Digoxin

Digitalis

• Foxglove (Digitalis)
• It is a genus of plants with about 35 species
• The plants contain glycosides, which are used to make the drug digoxin
• Digoxin is used:
• To control heart rate in atrial fibrillation
• For the treatment of heart failure
• Effects of digoxin:
• Positive inotropic - increases myocardial contractility
• Negative dromotropic - slows impulse conduction through the conduction system
• Negative chronotropic - slows heart rate

ECG and Digoxin

• ECG changes occur at therapeutic levels of digoxin
• The patient is not digitally toxic
  
  
• Changes are mainly in leads with high R waves (I, V5, V6)
• Digoxin affects repolarization (ST segment and T wave)
  
  
• Main ECG features
• Boat-shaped ST depression
• Flat, Negative, Bifasic T waves
  
  
• Secondary ECG features
• Prolonged PQ interval
• Shortened QT interval
• U wave

Digoxin and Atrial Fibrillation

• Atrial Fibrillation
• The heart rhythm is irregularly irregular
• No P waves are visible
• Boat-shaped ST depressions (II, III, aVF, V5, V6)
• The patient is not digoxin toxic

Digoxin and Atrial Fibrillation

• Atrial Fibrillation
• The heart rhythm is irregularly irregular
• P waves are not visible
• It is not atrial flutter
• In V1, sawtooth-like waves are present, but the heart rhythm is irregularly irregular
• Boat-shaped ST depressions (V6, II)
• The patient is not digoxin toxic

Digoxin and Sinus Rhythm

• Sinus Rhythm
• The P wave is before the QRS complex (V1)
• Boat-shaped ST depressions (I, II, III, aVF, V5-V6)
• Ventricular Extrasystoles
• These may indicate digoxin toxicity
• The patient may be digoxin-toxic