Final answer:
A PR interval of six small boxes on an ECG indicates a first-degree AV block, which is an abnormality that shows a delay in conduction from the SA node to the ventricular cells and is not a normal finding.
Step-by-step explanation:
When a patient's PR interval is six small boxes on the ECG graph, this indicates a delay in conduction between the SA and AV nodes, known as a first-degree AV block. The standard PR interval duration should be between three to five small squares on the ECG, which corresponds to 0.12 to 0.20 seconds. Six small boxes equate to 0.24 seconds, which is longer than normal. Therefore, the nurse determines that this ECG finding is an indicator of a problem with conduction from the SA node to the ventricular cells. It is important to note that while a first-degree AV block indicates a delay, it does not typically result in the dropping of beats; this is more characteristic of higher degree AV blocks.
In summary, a PR interval comprising six small boxes is an abnormal finding that suggests a first-degree AV block, also known as a partial block. This is not a normal finding; rather, it's a disturbance in the electrical conduction system of the heart, specifically between the atria and ventricles.