My 8yo son has cardiac svt. he had an ablation last year, but it was unsuccessful because his problem area lies in the av node. can ablation solve this without installing a pacemaker?

Very possibly: My understanding is AV nodal reentrant tachycardia is the most common cause of supraventricular tachycardia. Ablation may be the preferred treatment, especially in a child, who would experience years of freedom from symptoms. Catheter ablation carries a 90% success rate, which means 10% may need further treatment. Repeat ablation can be done with a similarly high success rate. I hope he does well.