What is the fine-grained topic of the following text: Abstract Introduction Because of the unusual anatomy of an anomalous origin of the right coronary artery from the left sinus of Valsalva, selective cannulation of the guiding catheter in percutaneous coronary intervention for these cases is always challenging. Only return the topic.
Percutaneous coronary intervention for cases with anomalous origin of the right coronary artery from the left sinus of Valsalva.