To identify a wandering pacemaker on an ECG, one should look for:

Identifying a wandering pacemaker on an ECG involves recognizing the characteristic features of this arrhythmia. One of the key hallmarks of a wandering pacemaker is the variation in the PR interval from beat to beat. This suggests that the pacemaker activity is shifting between the atria and, sometimes, the junctional area. As a result, one can observe differences in the timing of electrical conduction through the heart. This variability in the PR interval is indicative of the changes in the primary pacemaker location, which defines the wandering pacemaker.

In contrast, a flat baseline typically indicates a lack of electrical activity or potential artifacts rather than variation in pacemaker activity. A long QT interval points to a risk of arrhythmias but does not denote a wandering pacemaker. Inverted T waves can signify various conditions, such as ischemia or other forms of arrhythmias, but they do not specifically indicate that the pacemaker is wandering. Therefore, the presence of a PR interval that varies from beat to beat is a clear and direct indicator of a wandering pacemaker on an ECG.