William Blair & Company
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William Blair & Company’s iRhythm Holdings IRTC Stock Holding History

William Blair & Company’s Portfolio IRTC Stock Details IRTC Fund Activity
Bought
Maintained
Sold
Quarter Market Value Status Shares Change in
Stake 		Trade Value Portfolio Weight Portfolio Position
2026
Q2 		$62.4M Sell
524,690
-103,695
-17% -$12.1M 0.16% 125
2026
Q1 		$74.2M Sell
628,385
-90,412
-13% -$13M 0.21% 107
2025
Q4 		$128M Sell
718,797
-21,924
-3% -$3.89M 0.34% 69
2025
Q3 		$127M Buy
740,721
+1,390
+0.2% +$221K 0.34% 72
2025
Q2 		$114M Sell
739,331
-50,668
-6% -$6.55M 0.32% 76
2025
Q1 		$82.7M Buy
789,999
+185,262
+31% +$19.6M 0.25% 91
2024
Q4 		$54.5M Sell
604,737
-39,704
-6% -$3.12M 0.16% 126
2024
Q3 		$47.8M Sell
644,441
-154,639
-19% -$12.3M 0.14% 128
2024
Q2 		$86M Sell
799,080
-33,854
-4% -$3.46M 0.27% 87
2024
Q1 		$96.6M Buy
832,934
+27,842
+3% +$3.13M 0.3% 79
2023
Q4 		$86.2M Sell
805,092
-306,325
-28% -$26.7M 0.29% 81
2023
Q3 		$105M Buy
1,111,417
+68,983
+7% +$7.01M 0.4% 65
2023
Q2 		$109M Buy
1,042,434
+33,745
+3% +$4.05M 0.4% 61
2023
Q1 		$125M Buy
1,008,689
+95,737
+10% +$10.4M 0.5% 49
2022
Q4 		$85.5M Buy
912,952
+89,871
+11% +$9.78M 0.37% 68
2022
Q3 		$103M Buy
823,081
+144,685
+21% +$20.9M 0.47% 49
2022
Q2 		$73.3M Sell
678,396
-12,767
-2% -$1.69M 0.33% 76
2022
Q1 		$109M Sell
691,163
-63,892
-8% -$8.2M 0.38% 63
2021
Q4 		$88.9M Buy
755,055
+64,831
+9% +$5.95M 0.28% 86
2021
Q3 		$40.4M Buy
690,224
+55,540
+9% +$2.94M 0.14% 147
2021
Q2 		$42.1M Buy
634,684
+136,521
+27% +$10.8M 0.15% 148
2021
Q1 		$69.2M Buy
498,163
+285,555
+134% +$51.2M 0.26% 88
2020
Q4 		$50.4M Buy
212,608
+44,898
+27% +$10.2M 0.18% 123
2020
Q3 		$39.9M Sell
167,710
-17,620
-10% -$3.12M 0.17% 121
2020
Q2 		$21.5M Buy
185,330
+156,974
+554% +$17.3M 0.1% 171
2020
Q1 		$2.31M Buy
28,356
+23,814
+524% +$1.97M 0.01% 485
2019
Q4 		$309K Buy
+4,542
New +$308K ﹤0.01% 1163

Other funds holding IRTC

BlackRock
BlackRock New York $6.73T AUM 46.02% 1-Year Est. Return
RI
RTW Investments New York $11.7B AUM 174.13% 1-Year Est. Return
Vanguard Portfolio Management
Vanguard Portfolio Management Malvern, Pennsylvania $2.22T AUM
Artisan Partners
Artisan Partners Milwaukee, Wisconsin $63.1B AUM 35.51% 1-Year Est. Return
Vanguard Capital Management
Vanguard Capital Management Malvern, Pennsylvania $4.68T AUM
Millennium Management
Millennium Management New York $276B AUM 44.8% 1-Year Est. Return
Fidelity Investments
Fidelity Investments Boston, Massachusetts $2.3T AUM 54.33% 1-Year Est. Return
UBS AM
UBS AM Chicago, Illinois $550B AUM 43.33% 1-Year Est. Return
Geode Capital Management
Geode Capital Management Boston, Massachusetts $1.88T AUM 44.46% 1-Year Est. Return
EAM
Eventide Asset Management Boston, Massachusetts $7.48B AUM 104.76% 1-Year Est. Return

William Blair & Company's IRTC Position: Q2 2026 in Review

William Blair & Company reduced its iRhythm Holdings (IRTC) stake by 17% in Q2 2026, selling an estimated $12.1M and leaving 524,690 shares worth $62.4M. The position accounts for 0.16% of the portfolio, ranked #125.

William Blair & Company first reported a position in IRTC in Q4 2019 and has held it in 27 quarters since. The position peaked at $128M in Q4 2025. 304 funds tracked by Wall St. Rank hold IRTC as of Q2 2026.

  • William Blair & Company held 524,690 shares of iRhythm Holdings worth $62.4M as of Q2 2026.
  • William Blair & Company sold 103,695 iRhythm Holdings shares in Q2 2026, an estimated $12.1M.
  • iRhythm Holdings made up 0.16% of William Blair & Company's portfolio in Q2 2026, its #125 holding.
  • William Blair & Company first reported a position in iRhythm Holdings in Q4 2019 and has held it in 27 quarters since.
  • William Blair & Company's iRhythm Holdings position peaked at $128M in Q4 2025.
  • 304 funds tracked by Wall St. Rank held iRhythm Holdings as of Q2 2026.

Based on William Blair & Company's 13F filing for Q2 2026, filed 11 Aug 2026.