Key Points
RTW Investments acquired 1,181,990 IRTC shares during Q4 2025, with an estimated position value of $210 million based on the 13F reported at quarter-end.
The position represents 2.1% of RTW’s 13F reportable AUM.
The new stake makes IRTC the fund's eleventh-largest holding (out of 91 total positions).
What happened
According to an SEC filing dated Feb. 17, 2026, RTW Investments disclosed a new position in iRhythm Holdings(NASDAQ:IRTC) after acquiring 1,181,990 shares during the fourth quarter. The fund’s quarter-end position in IRTC was valued at $210 million.
What else to know
- This is a new position for RTW Investments, representing 2.1% of its $9.98 billion 13F reportable assets under management as of Dec. 31, 2025.
- Top five holdings after the filing:
- NASDAQ:MDGL: $1.2 billion (11.6% of AUM)
- NASDAQ:INSM: $842.9 million (8.4% of AUM)
- NASDAQ:PTCT: $588.4 million (5.9% of AUM)
- NASDAQ:ARGX: $566.4 million (5.7% of AUM)
- NASDAQ:PTGX: $441.9 million (4.4% of AUM)
- As of March 19, 2026, shares of iRhythm Holdings were priced at $117.78, up 14.2% over the past year, underperforming the S&P 500 by 3.5 percentage points.
Company Overview
| Metric | Value |
|---|---|
| Revenue (TTM) | $747.1 million |
| Net Income (TTM) | -$44.6 million |
| Price (as of market close Mar. 19, 2026) | $117.78 |
| One-Year Price Change | 14.2% |
Company Snapshot
- Offers ambulatory ECG monitoring products, including the Zio XT and AT wearable patch-based biosensors, and a cloud-based data analytics platform for arrhythmia detection.
- Generates revenue primarily through sales of its Zio service, combining device sales with subscription-based monitoring and diagnostic services for healthcare providers.
- Targets healthcare institutions, physicians, and patients in the United States at risk for cardiac arrhythmias.
iRhythm Holdings, Inc. is a digital healthcare company specializing in innovative cardiac monitoring solutions. Its core offering, the Zio platform, leverages wearable biosensors and advanced analytics to improve arrhythmia detection and diagnosis.
What this transaction means for investors
RTW Investments isn't a generalist fund making a casual bet -- it's a specialized healthcare and life sciences investor with deep sector expertise, which makes this move worth a closer look. Opening a brand-new position of this size signals real conviction: at roughly $210 million, the IRTC stake becomes RTW’s eleventh-largest holding -- representing about 2.1% of the fund's total 13F-reported portfolio -- a meaningful commitment from a manager that already holds concentrated positions in names like Madrigal Pharmaceuticals(NASDAQ:MDGL) and Insmed (NASDAQ:INSM).
iRhythm Holdings sits at an interesting intersection of medical devices and digital health. Its flagship Zio patch -- a discreet, wearable cardiac monitor -- has carved out a strong niche in ambulatory ECG monitoring, a market that's likely to grow as remote patient monitoring becomes more standard in cardiology. Unlike a traditional Holter monitor, the Zio system collects continuous data over days or weeks and runs it through a cloud-based analytics platform, giving physicians a much richer picture of a patient's heart rhythm. That combination of hardware, software, and services gives iRhythm a recurring revenue model that can be stickier than a simple device sale.
For retail investors interested in the digital health space, iRhythm represents a focused play on cardiac care innovation. Those who prefer broader exposure might also consider ETFs like the Health Care Select Sector SPDR Fund(NYSEMKT:XLV) or the iShares U.S. Medical Devices ETF(NYSEMKT:IHI), which provide diversified access to companies operating across health technology and medical devices. Either way, when a specialized healthcare fund with RTW's track record makes a move this size into a new name, it's a signal worth researching.
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Andy Gould has positions in Argenx Se. The Motley Fool has positions in and recommends Argenx Se. The Motley Fool recommends Protagonist Therapeutics. The Motley Fool has a disclosure policy.
