A 52-year-old man has recurrent symptomatic atrial flutter with 2:1 conduction at 150 bpm despite rate-control therapy. Catheter ablation is planned. Which structure is the target that provides permanent cure in the common variety?
- A Pulmonary vein ostia
- B Cavotricuspid isthmus ✓
- C AV node slow pathway
- D Left atrial posterior wall
Correct answer: B. Cavotricuspid isthmus
Explanation
Typical atrial flutter is a macro-reentrant circuit confined to the right atrium, circulating counterclockwise around the tricuspid annulus. The critical slow-conduction zone is the cavotricuspid isthmus between the inferior vena cava and the tricuspid valve. Creating a linear lesion across this isthmus with demonstrated bidirectional block cures typical flutter in over 90 percent of patients. Pulmonary vein isolation targets atrial fibrillation, not flutter, which kills that distractor.
Reference: Braunwald's Heart Disease: A Textbook of Cardiovascular Medicine, 12th ed.
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Written and medically reviewed by the StethoPrep medical team.