An inverted P wave is a characteristic finding on an electrocardiogram (ECG) that indicates a specific type of abnormal heart rhythm. It is called "inverted" because the P wave, which normally represents the electrical activity of the atria during atrial depolarization, appears upside down. This inversion occurs when the atrial depolarization happens in a retrograde fashion, meaning it travels in the opposite direction to the normal sequence. In the context of nonparoxysmal junctional tachycardia, the atria are activated from below (from the atrioventricular junction) rather than from above (the sinus node), which results in the P wave being inverted. Here's the translation: 在心电图（ECG）上，倒置的P波是指示特定类型心律失常的特征性发现。之所以称之为“倒置”，是因为P波（通常代表心房去极化期间的心电活动）出现了上下颠倒的情况。当心房去极化以逆行方式发生时，即与正常顺序相反的方向传播，就会发生这种倒置。在非阵发性交界性心动过速的背景下，心房是从下方（房室交界区）而不是从上方（窦房结）被激活的，这导致P波倒置。 read more >>

Rationale: Nonparoxysmal (gradual-onset) junctional tachycardia is a supraventricular rhythm with narrow QRS complexes and a regular rate, usually between 60�C140 bpm. The distinguishing feature of this ECG is retrograde conduction of the atrium causing an inverted P wave, best observed in lead II.read more >>