iRhythm Technologies said it closed a $16 million Series D round for its Zio wearable heart monitor, saying it plans to use the proceeds to further its commercial footprint and research & development efforts.

Led by Norwest Venture Partners, which added partner Casper de Clercq to iRhythm’s board, the latest financing including contributions from existing backers New Leaf Ventures, Synergy Life Science Partners and Kaiser Permanente Ventures.