The Apple Watch heart lawsuits are a cluster of patent, trade secret, and antitrust cases over the watch’s heart rate, ECG, and blood oxygen features. The biggest, brought by medical device maker Masimo, produced a $634 million jury verdict against Apple in November 2025 and briefly pulled certain Apple Watches from U.S. shelves in late 2023. Separate suits by heart-monitoring company AliveCor and a New York cardiologist have been resolved in Apple’s favor.
Here is what each case means for owners and buyers, and where the fights stand now.
What Happened to Blood Oxygen on the Apple Watch
If you bought an Apple Watch Series 9, Ultra 2, or Series 10 in the United States between January 2024 and August 2025, the blood oxygen sensor was present in the hardware but switched off in software. That was Apple’s response to a U.S. International Trade Commission ruling in October 2023 that the watches infringed two Masimo pulse oximetry patents (U.S. Patent Nos. 10,912,502 and 10,945,648) and could not be imported.1U.S. International Trade Commission. Investigation No. 337-TA-1276 Final Determination
Apple paused U.S. sales of the Series 9 and Ultra 2 on December 21 and December 24, 2023.2Reuters. Apple to Halt Sales of Some Apple Watches in US A brief appeals court stay let sales resume for a few weeks, but the Federal Circuit declined to extend it on January 17, 2024. The next day Apple put the watches back on sale with blood oxygen disabled.3Time. Apple Removes Blood Oxygen Tool From Watches
Two groups of owners were unaffected: anyone who already owned a watch before the shutoff kept the feature, and watches sold outside the United States were never changed.
In August 2025, Apple brought the feature back through a redesign. Pulse oximetry data is now calculated on the paired iPhone rather than the watch itself, with readings shown in the Health app’s Respiratory section. You need iOS 18.6.1 and watchOS 11.6.1 or later to see it.4Apple Newsroom. An Update on Blood Oxygen for Apple Watch in the US U.S. Customs and Border Protection cleared the redesign on August 1, 2025, ruling that the reconfigured watches, imported without paired iPhones, do not directly infringe Masimo’s patents.5Fierce Biotech. Masimo Sues US Customs Over Apple Watch Blood Oxygen Green Light
Masimo challenged that clearance. On August 20, 2025, it sued CBP in the U.S. District Court for the District of Columbia, arguing the agency acted without notifying Masimo and calling Apple’s redesign a “superficial modification” that still infringes when the watch and iPhone work together as intended.6Bloomberg Law. Masimo Sues US Customs Over Apple Restoring Watch’s Oxygen Tool That suit is still pending.
Meanwhile, two near-simultaneous rulings in spring 2026 sorted out the ITC side. On March 19, 2026, the Federal Circuit affirmed the original import ban on the pre-redesign watches.7U.S. Court of Appeals for the Federal Circuit. Apple Inc. v. International Trade Commission, No. 2024-1285 A day earlier, an ITC administrative law judge found the redesigned watches did not infringe,8Law360. Apple Watch Redesign Gets Early OK as Patent Loss Upheld and in April 2026 the full ITC declined to review that finding, closing the investigation into the workaround. Masimo can still appeal.9Reuters. Apple Defeats Bid for New Apple Watch Import Ban at US Trade Tribunal
For now, the practical result: new U.S. Apple Watches ship with blood oxygen working through the iPhone-based measurement.
The $634 Million Masimo Verdict
On a separate track from the import fight, Masimo sued Apple for patent infringement and trade secret theft in the Central District of California in January 2020. A first trial in May 2023 ended in a mistrial after the jury could not reach a unanimous verdict.10Reuters. US Judge Declares Mistrial in Apple-Masimo Smartwatch Trade Secrets Fight
The retrial in November 2025 went the other way. After an eight-day trial, a federal jury found that Apple infringed U.S. Patent No. 10,433,776, which covers a power-saving system for light-based pulse and oxygen monitoring, and awarded Masimo $634 million.11AppleInsider. Masimo Awarded $634M in Apple Watch Patent Infringement Verdict The patent expired in June 2022, but damages ran for the period while it was active.
Apple said the verdict was “contrary to the facts” and announced an appeal.11AppleInsider. Masimo Awarded $634M in Apple Watch Patent Infringement Verdict In December 2025 Apple filed a motion to reduce or overturn the award; Masimo opposed it in January 2026.12MassDevice. Masimo Combats Apple’s Bid to Avoid Patent Payment Analysts estimate the appeals process could take up to two years, so no money changes hands in the meantime.13Healthcare Dive. Masimo Apple Watch $634M Jury Award Patent Lawsuit
The verdict has no direct impact on existing or new Apple Watch owners. It is a damages award for past infringement, not an injunction.
How the Masimo Fight Started
Masimo makes hospital pulse oximetry equipment. The company says Apple met with it in 2013 about possibly using Masimo’s sensor technology in what became the Apple Watch, then instead hired Masimo’s Chief Medical Officer Michael O’Reilly, an executive from Masimo’s spinoff Cercacor, and several engineers.14Bloomberg Law. Apple Set for Billion Dollar Trial in Clash Over Watch Secrets Masimo alleges Apple used confidential information those employees carried over to build the blood oxygen sensor that launched with the Apple Watch Series 6 in 2020.15MobiHealthNews. Masimo Accuses Apple of Patent Infringement Apple denies using any of Masimo’s confidential information.
AliveCor’s Antitrust and Patent Cases
AliveCor made the KardiaBand, an FDA-cleared ECG band for the Apple Watch released in 2017, and a companion app called SmartRhythm that used Apple Watch heart rate data to flag possible atrial fibrillation in the background.16AliveCor. Apple Abused Market Power in Cardio Device Market, Suit Alleges
In September 2018 Apple replaced its “Heart Rate Path Optimizer” algorithm with a newer “Heart Rate Neural Network” algorithm, stopped sharing the older data with third-party developers, and eventually removed the old algorithm from the watch. SmartRhythm no longer worked accurately, and AliveCor discontinued both SmartRhythm and KardiaBand in 2019. Around the same time, Apple launched its own Irregular Rhythm Notification feature.17Metropolitan News-Enterprise. Refusal to Deal – AliveCor v. Apple
AliveCor sued Apple in the Northern District of California in May 2021, claiming Apple broke competing heart-rhythm software to monopolize the market for heart-rate analysis apps on the Apple Watch, in violation of Section 2 of the Sherman Act.16AliveCor. Apple Abused Market Power in Cardio Device Market, Suit Alleges In February 2024 U.S. District Judge Jeffrey White granted summary judgment for Apple, calling the algorithm change a lawful product improvement.18Reuters. Apple Beats AliveCor Lawsuit Over Heart Rate Apps on Apple Watch On January 8, 2026, the Ninth Circuit affirmed, treating Apple’s conduct as a “refusal to deal” with a competitor that antitrust law does not generally prohibit.19U.S. Court of Appeals for the Ninth Circuit. AliveCor Inc. v. Apple Inc., No. 24-1392
AliveCor’s parallel patent claims also collapsed. An ITC judge had found Apple infringed two AliveCor patents in June 2022,20Fierce Healthcare. Judge Finds Apple Violated AliveCor’s Patent Rights but the Patent Trial and Appeal Board separately held all three patents unpatentable, and the Federal Circuit affirmed that on March 7, 2025.21U.S. Court of Appeals for the Federal Circuit. AliveCor Inc. v. Apple Inc., No. 23-1512 Both AliveCor tracks are closed.
The NYU Cardiologist’s Patent Suit
Joseph Wiesel, a New York University cardiologist, sued Apple in December 2019 in the Eastern District of New York. Wiesel held U.S. Patent No. 7,020,514, granted in 2006, for a method of detecting atrial fibrillation, and said Apple used his technology in the Apple Watch after he contacted the company in 2017 and that Apple refused to negotiate a license in good faith.22USA Today. Apple Sued by NYU Doctor Over Patent for Heart Monitoring Tech
On August 11, 2025, Judge Joan Azrack ruled the patent ineligible for protection, finding it directed at an abstract idea without an inventive concept, and also held that Wiesel lacked standing to sue. Apple won outright.23Bloomberg Law. Apple Defeats Doctor’s Patent Suit Over Heart Monitoring Tech
Where Things Stand
The Masimo dispute is the only active piece. Apple owes $634 million under the November 2025 jury verdict, but payment is on hold through post-trial motions and the expected appeal. New U.S. Apple Watches have blood oxygen working again through the iPhone-based workaround, which the ITC cleared in April 2026. Masimo’s suit against U.S. Customs over that clearance is still pending in Washington, D.C. AliveCor’s cases and Wiesel’s suit are over, with Apple winning each.