The ECG tracing shows an atrial rate of 80/min and a ventricular rate of 32/min with an undetermined PR interval and a widened QRS complex. This best describes which condition?

The condition described in the question is characterized by an atrial rate of 80 beats per minute and a ventricular rate of only 32 beats per minute, along with an undetermined PR interval and a widened QRS complex. This pattern is indicative of a complete dissociation between the atria and the ventricles, which is characteristic of third-degree AV block (complete heart block).

In third-degree AV block, the atria and ventricles are electrically independent. The atria can still beat at their intrinsic rate, and in this case, that rate is 80 beats per minute. However, the ventricles are unable to conduct impulses from the atria due to a complete blockage at the AV node or below, leading to a much slower ventricular rate. This blocks the normal conduction pathway, causing the ventricular rate to drop significantly, as seen with a rate of 32 beats per minute.

The widened QRS complex suggests that the ventricular depolarization is taking longer than normal, which can occur because the escape rhythm from the ventricles is arising from a lower region of the conduction system (such as the bundle of His or the Purkinje fibers), rather than through the typical conduction system.

While first-degree AV block, second-degree AV block,