Which rhythm is described as very dangerous in acute myocardial infarction or heart disease and is commonly caused by digoxin toxicity, presenting with a rapid, regular pulse and signs of decreased cardiac output?

Which rhythm is described as very dangerous in acute myocardial infarction or heart disease and is commonly caused by digoxin toxicity, presenting with a rapid, regular pulse and signs of decreased cardiac output?

• A. Atrial Tachycardia
• B. Atrial Flutter
• C. Atrial Fibrillation
• D. Junctional Tachycardia

Answer: (A)

This rhythm is most characteristic of atrial tachycardia caused by digoxin toxicity, especially in the setting of acute myocardial infarction or structural heart disease. Digoxin toxicity can provoke a rapid, regular atrial rhythm by increasing automaticity in atrial tissue. When the AV node conducts normally or with only modest block, the ventricles follow that rapid atrial rate, producing a fast, regular pulse. In a patient with ischemic heart disease, this rapid, regular rhythm reduces diastolic filling time, lowering cardiac output and worsening signs of heart failure or shock.

Other patterns each have distinguishing clues. Atrial flutter has a sawtooth atrial pattern and, depending on conduction, can produce a rapid but typically more organized ventricular response; it’s not the classic digoxin-associated arrhythmia. Atrial fibrillation creates an irregularly irregular rhythm with no distinct P waves, which shifts the hemodynamic picture and is common in heart disease but not the hallmark digoxin-toxicity presentation described here. Junctional tachycardia arises from the AV junction and usually shows different P-wave patterns and a different clinical context, making it less tied to digoxin toxicity.