Mar 31, 2026 filings. Quarterly 13F reports arrive up to 45 days after quarter end; this register is filed through May 29, 2026.
213 institutional managers reported holding ATRC for the quarter ended Mar 31, 2026. Reported positions total over 95% of shares outstanding; the top 10 hold 54%. 28 opened new positions; 48 closed out. Complete ranked register from SEC 13F filings.
| manager | shares | % out | value (Mar 31, 2026 close) | change | held since |
|---|---|---|---|---|---|
| Vanguard Group | 5.29M | 10.78% | $150.8M | added +7.7% | ≤2013 |
| BlackRock | 4.04M | 8.24% | $115.3M | trimmed -0.6% | ≤2013 |
| Wellington Management | 3.38M | 6.90% | $96.5M | trimmed -13.7% | ≤2013 |
| AllianceBernstein | 3.26M | 6.64% | $93.0M | trimmed -8.6% | ≤2013 |
| Hood River Capital Management LLC | 3.12M | 6.36% | $88.9M | added +0.7% | 2023 Q3 |
| Nomura Asset Management International INC. | 1.80M | 3.68% | $51.5M | trimmed -11.5% | 2025 Q2 |
| Goldman Sachs | 1.67M | 3.40% | $47.6M | added +88.4% | 2015 Q1 |
| Marshall Wace | 1.47M | 2.99% | $41.9M | added +60.7% | 2021 Q4 |
| State Street | 1.30M | 2.65% | $37.2M | added +4.8% | ≤2013 |
| Geode Capital | 1.23M | 2.50% | $35.0M | added +2.9% | ≤2013 |
| Divisadero Street Capital Management, LP | 1.16M | 2.37% | $33.1M | opened | 2024 Q3 |
| BNP Paribas Financial Markets | 1.08M | 2.21% | $31.0M | added +11.4% | 2014 Q1 |
| Neuberger Berman Group LLC | 1.05M | 2.14% | $30.0M | trimmed -3.3% | 2017 Q1 |
| Dimensional Fund Advisors | 997.8k | 2.03% | $28.5M | added +8.2% | 2019 Q2 |
| Champlain Investment Partners, LLC | 971.1k | 1.98% | $27.7M | trimmed -17.3% | 2019 Q3 |
| Gw&k Investment Management, LLC | 963.4k | 1.96% | $27.5M | added +1.2% | 2018 Q3 |
| Kennedy Capital Management LLC | 834.2k | 1.70% | $23.8M | unchanged | 2020 Q1 |
| Bank OF America CORP /DE/ | 768.6k | 1.57% | $21.9M | added +13.7% | ≤2013 |
| Two Sigma | 751.0k | 1.53% | $21.4M | added +97.4% | 2022 Q2 |
| First Light Asset Management, LLC (focused) | 729.5k | 1.49% | $20.8M | trimmed -37.9% | 2013 Q4 |
| Voya Investment Management LLC | 719.6k | 1.47% | $20.5M | added +1% | ≤2013 |
| Morgan Stanley | 719.2k | 1.47% | $20.5M | added +107.8% | 2013 Q4 |
| UBS | 621.0k | 1.27% | $17.7M | trimmed -7.8% | ≤2013 |
| Dafna Capital Management LLC | 597.4k | 1.22% | $17.0M | unchanged | ≤2013 |
| MFS Investment Management | 585.4k | 1.19% | $16.7M | added +14.5% | 2025 Q3 |
| Qube Research & Technologies LTD | 454.8k | 0.93% | $13.0M | added +56.5% | 2025 Q1 |
| Northern Trust | 449.6k | 0.92% | $12.8M | added +2.6% | ≤2013 |
| Charles Schwab Investment Management | 429.8k | 0.88% | $12.3M | trimmed -1.8% | ≤2013 |
| Grandeur Peak Global Advisors, LLC | 381.9k | 0.78% | $10.9M | added +16.3% | 2025 Q3 |
| WCM Investment Management | 359.8k | 0.73% | $10.3M | trimmed -3.5% | 2019 Q1 |
| Osterweis Capital Management INC | 349.6k | 0.71% | $10.0M | added +71.8% | 2025 Q1 |
| Connor, Clark & Lunn Investment Management LTD. | 345.4k | 0.70% | $9.9M | trimmed -8.7% | 2022 Q3 |
| FMR (Fidelity) | 336.8k | 0.69% | $9.6M | added +17.9% | 2013 Q3 |
| Nuveen | 336.7k | 0.69% | $9.6M | unchanged | 2017 Q3 |
| Renaissance Technologies | 308.7k | 0.63% | $8.8M | trimmed -4.1% | 2022 Q2 |
| Arrowstreet Capital | 277.7k | 0.57% | $7.9M | opened | 2026 Q1 |
| First Eagle Investment Management | 262.1k | 0.53% | $7.5M | added +124.8% | 2025 Q4 |
| SEI Investments CO | 260.8k | 0.53% | $7.4M | added +64.7% | 2016 Q4 |
| Wasatch Advisors LP | 253.9k | 0.52% | $7.2M | trimmed -28.2% | ≤2013 |
| Panagora Asset Management INC | 227.4k | 0.46% | $6.5M | unchanged | 2020 Q1 |
| Amundi | 225.9k | 0.46% | $6.4M | trimmed -2.1% | 2022 Q3 |
| Raymond James Financial INC | 216.9k | 0.44% | $6.2M | unchanged | 2024 Q4 |
| Universal- Beteiligungs- und Servicegesellschaft mbH | 215.5k | 0.44% | $6.1M | added +11.5% | 2025 Q1 |
| Nicholas Company, INC. | 204.6k | 0.42% | $5.8M | unchanged | 2021 Q4 |
| First Trust Advisors LP | 189.3k | 0.39% | $5.4M | added +60.7% | 2025 Q2 |
| AQR Capital | 186.4k | 0.38% | $5.3M | added +86.5% | 2020 Q2 |
| Advisors Capital Management, LLC | 182.3k | 0.37% | $5.2M | unchanged | 2021 Q1 |
| Millennium Management | 179.9k | 0.37% | $5.1M | added +9.8% | 2021 Q2 |
| State OF Wisconsin Investment Board | 167.4k | 0.34% | $4.8M | added +1.9% | 2020 Q4 |
| Adage Capital Partners GP, L.l.c. | 150.0k | 0.31% | $4.3M | added +36.1% | 2024 Q2 |
Largest 50 of 213 shown; the full ranked, searchable register is at boothcheck.com/holders/ATRC. Related filers are grouped using the filings' own included-manager declarations. Historically, several managers opening new positions in the same quarter said almost nothing about the quarter that followed (59,118 cases since 2013). A filed record, not a forecast. Nothing here is investment advice.