Final answer:
Arrhythmogenic foci in the left atrium can be accessed with a catheter using a procedure called catheter ablation.
Step-by-step explanation:
Arrhythmogenic foci in the left atrium are areas in the heart that initiate abnormal electrical impulses, leading to arrhythmias. If a catheter is required to access these foci, a procedure called catheter ablation may be performed. During this procedure, a catheter is inserted into the heart through a blood vessel and guided to the left atrium. Once in position, the catheter delivers energy (such as radiofrequency or cryotherapy) to destroy or modify the abnormal tissue causing the arrhythmia.