Where does paroxysmal junctional tachycardia (PJT) originate?

Where does paroxysmal junctional tachycardia (PJT) originate?

• A. An irritable atrial focus
• B. An irritable ventricular focus
• C. An irritable AV junction automaticity focus
• D. An ectopic foci in the heart

Answer: (C)

Paroxysmal junctional tachycardia (PJT) originates from an irritable automaticity focus located in the atrioventricular (AV) junction. This area includes the tissue surrounding the AV node and can take over pacing when the normal conduction pathways are disrupted or when there's increased automaticity in this region.

In PJT, the ectopic focus in the AV junction fires abnormally, leading to rapid heart rates that can vary in duration. The characteristic feature of PJT is that the heart rhythm is junctional, meaning that it typically lacks or shows inverted P waves, depending on the relationship between atrial and ventricular contractions.

The other options refer to different potential sources of arrhythmias but do not accurately capture the origin of PJT. An irritable atrial focus would lead to atrial tachycardias, whereas an irritable ventricular focus typically produces ventricular tachycardia. An ectopic foci in the heart could refer to various locations that generate abnormal rhythms but does not specifically pinpoint the AV junction, which is key for understanding PJT.