Exhibit 99 Form 3 Joint Filer Information Name: New Leaf Venture Associates II, L.P. Address: c/o New Leaf Venture Partners, 7 Times Square, Suite 3502 New York, NY 10036 Designated Filer: New Leaf Ventures II, L.P. Issuer & Ticker Symbol: iRhythm Technologies, Inc. (IRTC) Date of Event Requiring Statement: October 25, 2016 Signature: /s/ Craig L. Slutzkin, attorney-in-fact, New Leaf Venture Associates II, L.P., as general partner of New Leaf Ventures II, L.P. Name: New Leaf Venture Management II, L.L. C. Address: c/o New Leaf Venture Partners, 7 Times Square, Suite 3502 New York, NY 10036 Designated Filer: New Leaf Ventures II, L.P. Issuer & Ticker Symbol: iRhythm Technologies, Inc. (IRTC) Date of Event Requiring Statement: October 25, 2016 Signature: /s/ Craig L. Slutzkin, attorney-in-fact, New Leaf Venture Management II, L.L.C, as general partner of New Leaf Venture Associates II, L.P Name: Philippe O. Chambon Address: c/o New Leaf Venture Partners, 7 Times Square, Suite 3502 New York, NY 10036 Designated Filer: New Leaf Ventures II, L.P. Issuer & Ticker Symbol: iRhythm Technologies, Inc. (IRTC) Date of Event Requiring Statement: October 25, 2016 Signature: /s/ Craig L. Slutzkin, attorney-in-fact on behalf of Philippe O. Chambon, as Member of New Leaf Venture Management II, L.L.C Name: Jeani Delagardelle Address: c/o New Leaf Venture Partners, 1200 Park Place, Suite 300 San Mateo, CA 94403 Designated Filer: New Leaf Ventures II, L.P. Issuer & Ticker Symbol: iRhythm Technologies, Inc. (IRTC) Date of Event Requiring Statement: October 25, 2016 Signature: /s/ Craig L. Slutzkin, attorney-in-fact on behalf of Jeani Delagardelle, as Member of New Leaf Venture Management II, L.L.C Name: Ronald M. Hunt Address: c/o New Leaf Venture Partners, 7 Times Square, Suite 3502 New York, NY 10036 Designated Filer: New Leaf Ventures II, L.P. Issuer & Ticker Symbol: iRhythm Technologies, Inc. (IRTC) Date of Event Requiring Statement: October 25, 2016 Signature: /s/ Craig L. Slutzkin, attorney-in-fact on behalf of Ronald M. Hunt, as Member of New Leaf Venture Management II, L.L.C Name: Liam Ratcliffe Address: c/o New Leaf Venture Partners, 7 Times Square, Suite 3502 New York, NY 10036 Designated Filer: New Leaf Ventures II, L.P. Issuer & Ticker Symbol: iRhythm Technologies, Inc. (IRTC) Date of Event Requiring Statement: October 25, 2016 Signature: /s/ Craig L. Slutzkin, attorney-in-fact on behalf of Liam Ratcliffe, as Member of New Leaf Venture Management II, L.L.C