Financial Data and Key Metrics Changes - The company achieved a year-over-year revenue growth of 54%, reaching $47.2 million in Q1 2019 [9][37] - Gross margins increased by 3.4 percentage points to 75.2% compared to the prior year [9][42] - The net loss for Q1 2019 was $8 million, or a loss of $0.33 per share, compared to a net loss of $11.1 million, or a loss of $0.47 per share for the same period last year [44] Business Line Data and Key Metrics Changes - The company continues to see strong adoption of its Zio platform, with significant growth in both existing and new accounts [10][13] - Salesforce productivity levels have risen, with new reps achieving higher productivity earlier than expected [41] - Zio AT, a newer component of the platform, is expanding the addressable market and has shown positive early impacts [13][17] Market Data and Key Metrics Changes - Medicare accounted for approximately 27% of total sales in Q1 2019 [23] - The payer landscape remains challenging, with many health plans having restrictive coverage policies [14][22] - The company is targeting a previously unaddressed segment of the market with Zio AT, which is expected to enhance market penetration [10][18] Company Strategy and Development Direction - The company is focused on expanding its sales team and improving productivity, aiming to increase the total sales rep headcount to 130-140 [12] - The strategy includes increasing market penetration with the single Zio platform and expanding into new indications [10][11] - The company is working closely with the American College of Cardiology to convert its CPT code from temporary to permanent status, which is crucial for reimbursement [25][28] Management's Comments on Operating Environment and Future Outlook - Management expressed confidence in the company's competitive positioning and the clinical superiority of the Zio service [36] - The company raised its revenue guidance for 2019 to $206 million to $211 million, reflecting continued confidence in growth [50] - Management noted that the market for undiagnosed atrial fibrillation patients is significant, with over 10 million potential patients [18][75] Other Important Information - The company reported a mix shift away from non-contracted and legacy client billing claims, now both in the single digits [37] - The operating expenses for Q1 2019 were $43.5 million, an increase of 33% year-over-year, but the lowest growth rate experienced in nearly three years [42][43] - The company is confident that there will not be substantial changes to its Medicare reimbursement rate during the code conversion process [32] Q&A Session Summary Question: Why not expand the commercial organization more in the back half of the year? - Management indicated that the market is expanding and productivity expectations are increasing, suggesting that further expansion of the salesforce is a possibility [56][58] Question: Expectations for AT in the back half of the year? - Management confirmed that expectations for AT revenue are already factored into the guidance provided [66] Question: Current competitive landscape and share loss? - Management stated that they do not see significant success from competitors and believe Zio continues to take share from the status quo [70][72] Question: Insights from the Apple Heart Study? - Management believes that longer-term continuous monitoring, like Zio, is more effective than shorter-term monitoring methods [78] Question: Trends in same-store versus new-store revenue mix? - Management expressed hope to maintain a 60-40 split, indicating strong penetration in existing accounts [84] Question: Impact of AT on gross margins? - Management expects some initial absorption costs with the launch of AT, but guidance for gross margins remains at 75% to 76% for the year [95]

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-K (Mark One) ☒ ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the fiscal year ended December 31, 2018 OR ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 FOR THE TRANSITION PERIOD FROM TO Commission File Number 001-37918 iRhythm Technologies, Inc. (Exact name of Registrant as specified in its Charter) Delaware 20-8149544 (State or other jurisdict ...