What rhythm is characterized by a varying P wave shape?

• A. Wandering pacemaker
• B. Ventricular fibrillation
• C. Atrial flutter
• D. Normal sinus rhythm

Answer: (A)

The rhythm characterized by a varying P wave shape is the wandering pacemaker. This arrhythmia occurs primarily due to changes in the location of the electrical impulse's origin within the atria. In a wandering pacemaker, the P waves appear with different shapes and sizes because they originate from multiple ectopic atrial foci. Each focus may have slightly different properties, leading to the variation in the P wave morphology seen on the EKG tracing.

In contrast, the other options present different characteristics. For instance, atrial flutter typically shows a regular "sawtooth" pattern of P waves (F-waves), not varying shapes. Normal sinus rhythm has uniform P waves that originate from the sinoatrial node, thus lacking the variability seen in a wandering pacemaker. Ventricular fibrillation is a chaotic rhythm without distinct P waves, making it not applicable in this context. Understanding these distinctions clarifies why the wandering pacemaker is identified by the varying appearance of P waves.