Ablation Frontiers, a Carlsbad, Calif., developer of devices for treating irregular heartbeats known as cardiac arrythmias, raised $21.8 million in a third funding round. The Novartis Venture Fund led the round, joined by Affinity Ventures, Hexagon Investments, Trellis Health Ventures, Versant Ventures, Aberdare Ventures, and Pequot Ventures.

Ablation Frontiers apparently aims to use radio energy, directed by a catheter, to burn away malfunctioning heart tissue that contributes to arrythmia. The company’s Catheter Ablation System has been approved in Europe, but is still undergoing trials in the U.S.