When Heartmender dies, its persist ability triggers, returning it from your graveyard to the battlefield without a -1/-1 counter on it due to Vizier of Remedies.
Resolve the Viscera Seer ability
Repeat.
This classic loop transforms the dreary drawback of persist into an engine of endless rebirth, relying entirely on Vizier of Remedies to quietly rewrite the rules of counter placement so that Heartmender returns from the graveyard completely pristine every single time. With that infinite recursion secured, Viscera Seer turns each sacrifice into a scry to dig through your deck while churning out endless creature leaves-the-battlefield, enters-the-battlefield, and death triggers.