 Wearable electrocardiograph patch maker IRhythm Technologies Incs NASDAQ: IRTC lowered its revenue guidance for 2021 due to unforeseen impacts related to the COVID-19 Delta variant, customer staffing challenges, and delayed account launches and expansion. It expects sales of 317 million - 319 million consensus 323.46 million dropped from a previous estimate of 320 million - 325 million. 