Case 3 — Electrocardiogram (ECG)

Simultaneous recordings of the six limb leads, three leads at a time. Calibration signal 1 cm = 1 mV; paper speed 50 mm/second. Sinus rhythm at approximately 125 beats per minute. The QRS complexes are small and show an abnormal terminal vector directed cranially (toward the head), evidenced by an S wave in leads II, III, and aVF with lead I at baseline during the same interval, suggesting a terminal right or left axis deviation.
Simultaneous recordings of the six limb leads, three leads at a time. Calibration signal 1 cm = 1 mV; paper speed 50 mm/second.

Quiz

1. What is the rhythm?

2. What is the heart rate?

3. The terminal (i.e., last) portion of the QRS complex is isoelectric in lead I and negative in leads II, III, and aVF. This means the terminal vector is directed toward:

↑