What is a likely outcome when the heart’s primary pacemaker fails and alternate pacemakers develop in the atria?

When the heart's primary pacemaker, located in the sinoatrial (SA) node, fails, it can lead to the development of alternate pacemakers in the atria. This often results in atrial fibrillation. In this condition, multiple ectopic foci within the atria create chaotic electrical activity. As a result, instead of a single, coordinated contraction facilitated by the SA node, the atria contract in a rapid and disorganized manner. This irregular electrical activity can lead to the ineffective pumping of blood and an increased risk of thrombosis, which can further complicate patient outcomes.

Atrial fibrillation is characterized by an erratic rhythm and can be identified on an electrocardiogram (ECG) by the absence of distinct P waves, replaced instead by irregularly shaped waves or oscillations. Understanding this mechanism is critical for recognizing the importance of the SA node's role in maintaining a normal heart rhythm.