Atrial tachycardia is often initiated by which of the following?

Atrial tachycardia is often initiated by a premature atrial contraction (PAC). PACs are early beats that occur in the atria and can lead to a reentrant circuit in the atrial tissue, which promotes an increased heart rate. When a PAC occurs, it can trigger an abnormal electrical pathway that causes the atria to beat faster than normal, resulting in atrial tachycardia. This mechanism is notable because PACs can introduce ectopic signals that disrupt the normal rhythm, leading to sustained episodes of tachycardia.

Other conditions like premature ventricular contractions (PVCs), atrial fibrillation, or ventricular flutter typically do not initiate atrial tachycardia due to their different origins and the nature of their electrical activity in the heart. Understanding this mechanism helps in recognizing the triggers of atrial tachycardia and is critical for effective diagnosis and management in patients experiencing this condition.