Final answer:
To distinguish first-degree heart block from other types of dysrhythmias, look for an abnormally long PR interval on an ECG. Other types of dysrhythmias may have different patterns on an ECG, such as incomplete blocks or no correlation between atrial and ventricular activity.
Step-by-step explanation:
In order to distinguish first-degree heart block from other types of dysrhythmias, it is important to look at the characteristics of each condition. First-degree heart block is characterized by a delay in conduction between the SA and AV nodes, which results in an abnormally long PR interval on an ECG. On the other hand, other types of dysrhythmias may have different patterns on an ECG, such as incomplete blocks where some impulses are not followed by a QRS complex, or complete blocks where there is no correlation between atrial and ventricular activity.