Sky Labs has reported new clinical findings supporting the use of its CART ring-type blood pressure monitor in two cardiovascular populations where reliable ambulatory measurement can be challenging: atrial fibrillation and severe heart failure. At ESC Congress 2026, investigators presented a 24-hour monitoring study in patients with atrial fibrillation that achieved an analyzable data rate of approximately 80%, while a separate study in heart failure patients with a mean ejection fraction of 29% found high agreement between CART measurements and conventional 24-hour ambulatory blood pressure monitoring within European Society of Hypertension error-margin criteria.
The announcement is notable because cuffless blood pressure devices are moving from consumer-wearable novelty toward a more demanding clinical question: whether they can produce information reliable enough to guide treatment in patients whose cardiovascular physiology is already abnormal. CART BP pro has been approved as a medical device in South Korea since 2023, is reimbursed there using an existing 24-hour ambulatory blood pressure monitoring code and is now used across more than 2,000 Korean medical institutions, according to Sky Labs. The company reports more than 300,000 cumulative prescriptions and says ring-type cuffless monitoring has been incorporated into the 2026 Korean Society of Hypertension guideline framework.
Why can atrial fibrillation make blood pressure monitoring more difficult?
Most conventional automated blood pressure monitors depend on oscillometric analysis of pressure fluctuations in an inflatable cuff. The device assumes a sufficiently regular sequence of arterial pulses to estimate systolic and diastolic pressure from those oscillations.
Atrial fibrillation disrupts that regularity. Beat-to-beat filling of the ventricles varies because the rhythm is irregular, producing differences in stroke volume and pulse amplitude from one beat to the next. A single cuff measurement can consequently be more variable, and repeated measurements may be required before clinicians are comfortable with the result.
A wearable using photoplethysmography approaches the problem differently. CART BP pro collects optical pulse-wave signals at the finger and applies algorithms to derive blood pressure information repeatedly over time. Rather than depending entirely on occasional arm-cuff inflation, the system can collect many measurements across ordinary activity and sleep.
That does not automatically make PPG superior. Irregular rhythm can also complicate optical signals, while motion, peripheral perfusion and sensor contact create their own sources of error. The approximately 80% analyzable-data rate reported in the AF study therefore matters because it addresses the practical question of whether useful data can be recovered despite rhythm irregularity.
What exactly did the new atrial fibrillation study show?
Ki-Hong Lee of Chonnam National University Hospital presented the AF findings at ESC 2026. According to Sky Labs, approximately 80% of the collected 24-hour data were analyzable, allowing investigators to evaluate blood pressure behavior across the day and observe nocturnal dipping patterns.
Nocturnal dipping refers to the normal tendency for blood pressure to fall during sleep. Absent, reduced or reversed dipping can be associated with cardiovascular risk and can be missed completely by office measurements performed during daytime clinic visits.
This illustrates why 24-hour monitoring can provide more information than repeatedly checking blood pressure at a desk. It can reveal nighttime hypertension, morning surges and variability associated with medication timing or daily activity.
However, Sky Labs’ release does not provide the AF study’s sample size, detailed bias statistics or complete distribution of systolic and diastolic errors. That limits how far the new presentation can be interpreted independently. Full peer-reviewed data will be necessary to determine whether the approximately 20% of non-analyzable measurements occurred randomly or were concentrated among particular patients or clinical situations.
Why is the severe heart failure analysis particularly interesting?
The second ESC presentation involved patients with severe heart failure whose mean ejection fraction was only 29%. Ejection fraction estimates how much blood the left ventricle ejects with each contraction, and a mean near 29% indicates a population with markedly impaired systolic function.
According to investigator In-Cheol Kim of Keimyung University Dongsan Hospital, simultaneous CART and conventional 24-hour ABPM measurements showed high agreement and met European Society of Hypertension error-margin criteria.
Blood pressure management can be unusually important in heart failure because several disease-modifying medicines lower pressure while also improving longer-term outcomes. Clinicians may need to distinguish between a patient whose pressure is genuinely too low and one whose office measurement does not reflect the rest of the day.
Continuous or frequent wearable measurements could potentially help physicians understand whether dizziness occurs during actual hypotension, whether nighttime pressure becomes excessive, or whether medication changes alter blood pressure outside the clinic.
The current presentation does not prove that using CART to guide heart-failure therapy improves hospitalization or mortality. It establishes a measurement question rather than an outcomes question.
How does CART BP pro measure blood pressure without inflating a cuff?
The ring uses photoplethysmography, or PPG, which shines light into tissue and detects changes associated with pulsatile blood flow. Sky Labs states that its system applies deep-learning algorithms to those signals to estimate blood pressure. Its published product specifications describe measurements across a systolic range of 70–180 mmHg and diastolic range of 40–120 mmHg.
The appeal is obvious from a user perspective. Conventional ambulatory blood pressure monitors repeatedly inflate an arm cuff, including during sleep, which can be uncomfortable and sometimes wakes the patient. A ring can potentially collect measurements with much less disturbance.
A recent peer-reviewed awake-versus-asleep validation study compared CART BP pro with conventional ABPM over roughly 24 hours. Investigators found meaningful agreement in changes between awake and asleep pressure, although the authors cautioned that this represented only one component of the broader ESH validation framework and did not by itself establish that the ring could replace conventional ABPM.
That caution is important. Cuffless monitoring is attractive precisely because it is easier, but easier cannot mean less accurate when clinicians may alter antihypertensive therapy based on the result.
Why does nighttime blood pressure matter so much?
Clinic readings provide a narrow snapshot. A patient can have normal blood pressure during an appointment yet experience elevated pressure during sleep, while another can appear hypertensive in the clinic because of anxiety but have much lower values during ordinary life.
Twenty-four-hour ABPM helps separate those patterns. It is used to identify white-coat hypertension, masked hypertension, nocturnal hypertension and abnormal dipping, all of which can change how clinicians interpret cardiovascular risk.
A ring could potentially make this type of monitoring easier to repeat. Instead of tolerating an inflating cuff for one uncomfortable night, a patient could theoretically wear a ring over longer periods and generate a richer longitudinal picture.
Longer observation also introduces new analytical challenges. Hundreds or thousands of measurements can overwhelm clinicians unless software converts them into interpretable summaries without concealing important exceptions.
Cuffless monitoring therefore represents both a sensing problem and a clinical-information problem. The hardware needs to measure pressure accurately, and the software needs to present that information in a way that improves decisions rather than simply generating more data.
How established is CART BP pro in actual clinical practice?
Sky Labs says CART BP pro is used in more than 2,000 Korean medical institutions and has exceeded 300,000 cumulative prescriptions. The product received Korean medical-device approval in 2023 and subsequently obtained reimbursement under the existing E6547 24-hour ambulatory blood pressure monitoring code.
The 2026 Korean hypertension guidelines also opened the door to validated cuffless technologies as tools for out-of-office blood pressure assessment. Sky Labs has promoted CART BP pro as the first ring-type product incorporated into such a national guideline environment.
That makes the company’s development pathway unusual compared with consumer wearables that first accumulate millions of users and only later attempt to prove clinical utility. CART has been built around prescription use and reimbursement in its home market.
International expansion will be a different challenge. Regulatory requirements, validation standards and reimbursement systems vary by country, and Korean approval does not constitute U.S. FDA authorization.
Is CART BP pro FDA cleared in the United States?
No U.S. FDA clearance is identified for CART BP pro in the current announcement. Sky Labs describes it as a prescription-only medical device, and its current established regulatory and reimbursement claims relate primarily to South Korea.
That distinction is essential because the global market for cuffless blood pressure devices is attracting technology companies, wearable manufacturers and specialist medical-device developers. A product used clinically in Korea should not automatically be described as an FDA-cleared blood pressure ring.
The company has been building validation evidence that could support broader regulatory expansion, and ClinicalTrials.gov lists studies evaluating CART BP technology as a wearable cuffless monitor and as part of blood-pressure-guided management.
Future U.S. regulatory submissions would need to define the precise intended use, patient population, calibration requirements and circumstances under which clinicians may rely on the measurements.
What could cuffless monitoring change in heart failure and atrial fibrillation care?
The largest opportunity may not be simply replacing one blood-pressure device with another. A wearable can potentially change measurement from an occasional event into a longitudinal physiological stream.
For an atrial-fibrillation patient, blood pressure data could be interpreted alongside heart-rate and rhythm information. For heart-failure patients, clinicians could potentially see how blood pressure changes after medication titration, during worsening congestion or across sleep.
But clinical usefulness requires prospective evidence. A monitor can agree with a reference device yet still fail to improve treatment because physicians do not know what to do with the additional information.
The next generation of studies therefore needs to move from validation toward management. Researchers should ask whether ring-guided therapy improves blood-pressure control, medication optimization, patient comfort, adherence or cardiovascular outcomes compared with ordinary monitoring.
Sky Labs’ recruiting CART-BP randomized trial in uncontrolled hypertension is one example of that transition, evaluating management guided by the wearable rather than simply technical agreement.
What should clinicians watch next?
First, the full AF and heart-failure datasets need publication with patient counts and detailed accuracy statistics. The headline results are encouraging, but physicians evaluating a measurement device need more than conference quotations.
Second, broader ESH-style validation across different circumstances matters. A cuffless device should remain reliable during sleep, activity, position changes and across clinically important blood pressure ranges.
Third, global regulation will determine how far CART travels outside South Korea. The product already has unusually large real-world exposure in its domestic market, but international adoption requires authorities to be convinced that its convenience does not compromise clinical accuracy.
The concept has obvious appeal: replace an arm cuff that repeatedly wakes patients with a ring capable of recording cardiovascular information throughout ordinary life. The ESC 2026 findings suggest that this may remain feasible even in atrial fibrillation and severe heart failure. The remaining question is whether sufficiently rigorous validation and outcomes evidence can turn a convenient wearable into a globally accepted clinical blood-pressure instrument.