KardiaMobile and AliveCor: How They Work, What the Evidence Shows

2. What It Is

KardiaMobile is a consumer-grade personal ECG device manufactured by AliveCor, Inc. It consists of a small aluminum pad containing two dry electrodes, which the user holds between both thumbs to complete a circuit and record a Lead I equivalent ECG. The device connects to a smartphone via the microphone jack (older generations) or Bluetooth (current KardiaMobile 6L) and transmits the signal to the KardiaApp for analysis.

AliveCor offers two current KardiaMobile models:

KardiaMobile (1L): Single-electrode pad. Records a standard Lead I equivalent when both thumbs contact the electrodes. Approved recordings: 30 seconds, patient-triggered. Also capable of a Lead II approximation when placed on the left knee with one thumb on the pad. Retail price approximately $89.

KardiaMobile 6L: Six-lead ECG. Records Lead I, II, III, aVR, aVL, aVF, and a precordial approximation by placing the device on the left knee with both thumbs on the pad. Six-lead recordings capture substantially more spatial information than single-lead recordings, enabling identification of inferior vs anterior rhythm abnormalities and better P-wave characterization. FDA-cleared. Retail price approximately $149.

The KardiaApp includes:

• Automated algorithm for rhythm classification (Kardia Advanced Determination): normal, AFib, bradycardia, tachycardia, wide complex tachycardia, normal with PACs, normal with PVCs, unclassified
• Physician-read option (KardiaComplete): users can pay per tracing for a board-certified cardiologist review within 24 hours
• Family sharing
• PDF export for physician review
• Prescription use module: the Kardia platform has a prescription-grade version (KardiaComplete and KardiaCare) where physicians can configure the device for specific patients and receive automated alerts

Regulatory status:

• KardiaMobile 1L: FDA 510(k) clearance (K143760) for detection of normal sinus rhythm and AF
• KardiaMobile 6L: FDA 510(k) clearance (K201519) for detection of normal sinus rhythm, AF, bradycardia, tachycardia, normal with PACs, normal with PVCs, wide complex tachycardia
• Kardia Advanced Determination algorithm: FDA clearance for specific classifications as above

This is a meaningful regulatory distinction from the Oura Ring’s evolving clearance or WHOOP’s no-clearance status. KardiaMobile is a cleared medical device.

3. The Mechanism

3.1 Single-Lead vs Six-Lead ECG: What the Spatial Difference Means

The standard 12-lead ECG views the heart’s electrical activity from 12 spatial perspectives: six limb leads (I, II, III, aVR, aVL, aVF) derived from electrodes at the limbs, and six precordial leads (V1-V6) placed on the chest wall.

KardiaMobile 1L captures Lead I (the potential difference between the left and right arms, approximated by thumb-to-thumb contact). Lead I captures lateral wall depolarization. It reliably shows:

• Atrial fibrillation (irregular P-wave absence, irregular QRS intervals)
• Gross rate abnormalities
• Wide-complex rhythms (cannot reliably localize them)
• P-wave presence or absence

KardiaMobile 6L adds five additional leads by incorporating the leg electrode (left knee placement). This enables:

• Better P-wave characterization in leads II, III (inferior leads show P-waves best)
• Differentiation between left- and right-axis deviation
• Better characterization of wide complex rhythms (right bundle branch pattern vs left bundle branch pattern)
• Detection of inferior ischemia in Lead II and III (though sensitivity for acute MI is limited without V1-V6 chest leads)

Neither device captures the precordial leads V1-V6. This remains the critical limitation: without anterior and lateral chest leads, ST-elevation MI pattern, right bundle branch block, and V1-V6-localized arrhythmias cannot be fully characterized.

3.2 The AI Classification Algorithm

AliveCor’s Kardia Advanced Determination algorithm is one of the most extensively validated consumer ECG algorithms in clinical literature. The algorithm uses deep learning trained on millions of physician-labeled ECG recordings.

Classification outputs and their clinical interpretation:

• Normal: Sinus rhythm with rate 50-100 bpm, no significant ectopy, regular intervals
• AFib: Irregularly irregular rhythm with absent organized P-waves
• Bradycardia: Rate below 50 bpm in sinus rhythm
• Tachycardia: Rate above 100 bpm in sinus rhythm
• Wide complex tachycardia: QRS duration prolonged, rate raised (possible VT, SVT with aberrancy)
• Normal with PACs: Sinus rhythm with premature narrow-complex beats
• Normal with PVCs: Sinus rhythm with premature wide-complex beats
• Unclassified: Technically adequate recording that does not fit above categories; physician review recommended

Unclassified is not “normal.” A tracing classified as unclassified requires physician review. It may represent an atypical arrhythmia, a borderline or unusual reading, or a technically adequate tracing with findings outside the algorithm’s trained categories.

3.3 Dry Electrode Technology

Traditional ECG electrodes require gel or paste to ensure good electrical contact with skin. KardiaMobile uses dry stainless-steel electrodes. Dry electrode recordings have higher impedance than gel-contact recordings, which introduces more baseline noise. AliveCor has addressed this with signal processing algorithms, and validation studies show that KardiaMobile recordings are interpretable for rhythm classification despite the dry electrode limitation.

The practical implication: calloused, very dry, or cold hands produce poorer signal quality. Patients should be instructed to warm their hands before recording and to hold the device with steady gentle pressure, not gripping tightly.

4. How It Is Used

4.1 Symptom-Triggered Recording

The primary clinical value of KardiaMobile: capturing a cardiac rhythm at the moment of symptoms. This is precisely what a Holter monitor does during a continuous recording period, but KardiaMobile enables this on demand, without requiring a clinical device prescription, and the recording is immediate.

Clinical scenarios where symptom-triggered KardiaMobile recording provides high value:

• Palpitations that occur unpredictably and irregularly
• Presyncope episodes with concurrent awareness
• Known AF with intermittent episodes, where timing documentation informs rate vs rhythm control decisions
• Post-cardioversion monitoring (did this patient convert to sinus rhythm? Is the rhythm still AF?)
• Medication response monitoring (did the rate come down after adding metoprolol?)

4.2 Physician-Integrated Use

The Kardia platform allows physicians to set up device-integrated monitoring for specific patients. The physician can configure automated alerts (e.g., alert if any recording classified as AF is submitted), review a patient’s recording history, and communicate with the patient through the app.

At Carle Foundation Hospital in Urbana and its affiliated clinics across central Illinois, KardiaMobile is an established part of the arrhythmia monitoring toolkit for select patients. The prescription-grade Kardia integration allows the clinic to receive AF alert transmissions within 24 hours of a patient recording. For rural patients in the Carle system who would otherwise require a 90-minute drive to access cardiology, this between-visit monitoring capability reduces care gaps.

4.3 Screening vs Diagnostic Use

Screening use (asymptomatic high-risk population): The REHEARSE-AF trial (see below) evaluated KardiaMobile as a screening tool in patients 65 and older. Screening in high-risk asymptomatic individuals detects clinically important AF. This is a legitimate and evidence-supported use.

Diagnostic use (symptomatic patient): A symptomatic patient who captures an AF recording during their symptoms has, effectively, a diagnostic ECG. This recording, reviewed by a physician, is sufficient to confirm AF for clinical decision-making. A 12-lead ECG confirming the finding at a clinical visit adds spatial detail but is not strictly necessary if the KardiaMobile recording shows unambiguous AF.

Post-treatment monitoring: KardiaMobile is widely used by patients with known paroxysmal AF to monitor for recurrence after cardioversion or ablation. The patient records daily and submits tracings for review.

4.4 What a Cardiologist Does With the Recording

When I receive a KardiaMobile tracing from a patient:

1. Verify technical quality: Is the baseline stable? Is there adequate R-wave amplitude? Are there major artifacts?

2. Override or confirm the algorithm classification: The algorithm is accurate but not infallible. Unclassified tracings often have interpretable findings when a cardiologist applies clinical context.

3. Extract clinical measurements: P-wave presence/absence, PR interval, QRS duration (if widened), QT estimation (rough from Lead I), rate, regularity.

4. Apply clinical context: A 72-year-old with hypertension and diabetes who submits a “Normal with PACs” tracing during palpitations is different from a 28-year-old athlete with the same classification.

5. Determine next step: Confirm in clinic? Proceed to treatment based on recording? Order additional monitoring (14-day patch for paroxysmal events not yet captured)?

5. The Evidence

5.1 REHEARSE-AF Trial (Halcox 2017, JACC)

This is the key randomized controlled trial for KardiaMobile-based AF screening.

Design: 1,001 participants age 65 and older without known AF, randomized to twice-daily KardiaMobile screening for 12 months vs standard care (usual care, no scheduled ECG monitoring).

Primary outcome: AF diagnosed by physician over 12 months.

Results: New AF diagnosed in 3.8% of the KardiaMobile group vs 1.9% of the standard care group (HR 1.96, 95% CI 1.01-3.79). Patients in the KardiaMobile group diagnosed with AF were significantly more likely to have anticoagulation initiated.

Key findings: Twice-daily recording protocol was the most effective; once-daily recording also outperformed standard care. The number needed to screen for 12 months to detect one additional case of AF: approximately 53 patients.

5.2 mSToPS Trial (Turakhia 2019, JAMA)

This trial compared immediate vs delayed continuous ambulatory monitoring in 2,659 high-risk adults identified through claims data. While mSToPS used the iRhythm Zio patch rather than KardiaMobile, it established the principle that mobile ECG monitoring in at-risk populations detects more AF and leads to more anticoagulation initiation, with follow-up data suggesting this translates to a reduction in stroke and thromboembolism events.

5.3 STROKESTOP Trial (Svennberg 2021, Lancet)

Design: Swedish population-level screening study. 28,768 individuals age 75-76 randomized to invitation for AF screening (twice-daily KardiaMobile recording for 2 weeks) or standard care.

Results: AF detected in 3.0% of the screening group vs 2.1% in the control group (OR 1.45, 95% CI 1.20-1.75). Stroke or systemic embolism at 6.9 years follow-up: 5.45 per 100 person-years in the screening group vs 5.68 in control (HR 0.96, 95% CI 0.88-1.04). This difference was not statistically significant at p=0.45.

Interpretation: Population-level KardiaMobile AF screening at age 75-76 detected more AF and led to more anticoagulation, but did not produce a statistically significant reduction in stroke or embolism at the population level. Individual patient benefit from anticoagulation is established; population-level screening benefit via KardiaMobile requires a more targeted approach focused on higher-risk individuals.

5 / Solid 01637-8)

5.4 Algorithm Accuracy Studies

Lau 2013 (J Arrhythmia): Early KardiaMobile algorithm validation. Sensitivity for AF 96%, specificity 94% vs physician-read ECG. 4 / Promising

Galloway 2019 (npj Digital Medicine): Validation of AliveCor deep-learning algorithm in 9,773 ECGs from a diverse population. F1 score 0.90 for AF detection. 4 / Promising

Hannun 2019 (Nature Medicine): AliveCor’s deep-learning cardiologist-level arrhythmia detection. 12-lead ECG from Holter, not KardiaMobile specifically, but established the platform’s algorithmic capability. 4 / Promising

5.5 AF Screening Debate: SCREEN-AF Trial (Gladstone 2021)

Design: 856 patients age 75 and older with hypertension, randomized to 2 weeks of KardiaMobile monitoring vs standard care.

Results: New AF detected in 5.6% of screening group vs 2.9% of standard care group (OR 2.01). 97% of detected cases received anticoagulation. No long-term stroke outcome data from this trial.

Current guideline position: The 2023 ACC/AHA AF guidelines acknowledge that screening for AF in high-risk older adults is reasonable (Class IIb recommendation) but note that evidence of stroke reduction from screening programs is not yet definitive. The STROKESTOP result contributes to this uncertainty. Screening with KardiaMobile in patients 65 and older with additional risk factors (hypertension, diabetes, heart failure) is supported as clinically reasonable.

5.6 6L vs 1L: Does Six Leads Change Clinical Outcomes?

The 6L device provides additional diagnostic information. In comparative studies, the 6L more accurately characterizes flutter, identifies inferior vs anterior arrhythmia burden, and reduces the “unclassified” rate compared to the 1L by providing more leads for the algorithm to analyze. However, no published randomized clinical trial has demonstrated that 6L recording changes downstream clinical outcomes compared to 1L recording for the primary indication of AF detection.

For a patient whose primary concern is AF detection, the 1L is sufficient. For a patient with more complex arrhythmia history or with a cardiologist who wants more spatial information, the 6L is preferable. 4 / Promising

5.7 Evidence Summary Table

6. The Patient Experience

6.1 Using the Device

The KardiaMobile device is the size of a business card. It fits in a wallet or pocket. Recording takes 30 seconds. The user places both thumbs on the electrodes, opens the KardiaApp (free download), taps “Record,” and holds still. The app displays the tracing in real time and classifies it within seconds of recording completion.

The learning curve is minimal. Most patients achieve acceptable recording quality within one or two attempts. Common errors: holding too tightly (muscle artifact), recording while in motion, not using both thumbs (producing a single-electrode artifact tracing).

For older patients with arthritis or tremor: the 6L device, placed on the knee, may produce better recordings than the 1L held with trembling hands. Patients should record during rest, not during activity, for arrhythmia characterization purposes (though recording during activity may be clinically relevant for capturing exercise-induced arrhythmia).

6.2 The “Unclassified” Reading

Approximately 9-17% of KardiaMobile recordings are classified as “unclassified” in real-world studies. This category causes significant patient anxiety. Patients interpret “unclassified” as alarming; it is not inherently alarming. It means:

• The recording is technically adequate but does not meet criteria for any specific classification
• OR the recording contains findings outside the algorithm’s specific classification categories
• OR the algorithm lacks confidence in a specific classification

Patients should be explicitly told: “Unclassified means the algorithm cannot categorize it, not that something dangerous is happening. Bring it to your doctor’s attention.”

6.3 Cost and Access

KardiaMobile retails for $89-$149. No subscription is required for basic use. The KardiaComplete physician review service costs additional per-tracing fees. KardiaCare subscription (approximately $9.99/month) includes unlimited physician reviews and other features.

Medicare Part B and many commercial insurance plans cover ambulatory cardiac monitoring. KardiaMobile used in a physician-supervised protocol may be reimbursable under specific CPT codes, but this depends on how the device is deployed within a clinical workflow. Patients purchasing KardiaMobile as a consumer product pay out-of-pocket.

For patients in rural Illinois who cannot readily access a cardiology clinic, KardiaMobile provides a meaningful bridge: the patient can record an arrhythmia during a symptom episode at home and share it with a cardiologist via telemedicine within the same day.

7. Decisions and Trade-Offs

7.1 When KardiaMobile is the Right Tool

• Patient with palpitations seeking symptom-rhythm correlation
• Patient with known paroxysmal AF monitoring for episode frequency and rate
• Patient 65 and older with AF risk factors in a clinical screening program
• Post-cardioversion or post-ablation monitoring for recurrence
• Patient whose primary care physician wants remote rhythm surveillance without prescribing a formal ambulatory monitor

7.2 When KardiaMobile is Not the Right Tool

• Patient with syncope or presyncope: KardiaMobile records only when the patient activates it. A patient who loses consciousness cannot operate the device. An event monitor with auto-trigger capability or an implantable loop recorder is needed.
• Patient with very infrequent episodes (occurring less than once per week): the probability of capturing a rare arrhythmia with a hand-held device requiring patient activation is low. Extended monitoring (30-day event monitor, 14-day patch, or ILR) is more appropriate.
• Patient who needs assessment of ST changes, QT interval, or axis: a 12-lead ECG in a clinical setting is required.
• Patient who cannot operate the device (cognitive impairment, bilateral hand tremor, paralysis): alternative monitoring strategies are needed.

7.3 KardiaMobile vs Apple Watch for a Symptomatic Patient

The choice between a symptom-triggered KardiaMobile recording and an Apple Watch notification is not always obvious. Consider:

• KardiaMobile advantage: Patient-controlled, high-quality signal, 30-second deliberate recording, 6L option for more spatial information. Better for patients with recognizable palpitation symptoms who can activate the device during an episode.

• Apple Watch advantage: Passive monitoring catches arrhythmias the patient does not notice. AFib detected during sleep or during activities where a patient cannot operate a handheld device.

For a patient with recognizable palpitations: KardiaMobile. For a patient with no symptoms but raised risk: Apple Watch passive monitoring. For a patient who has had a stroke with no identified cause: neither is sufficient; an ILR or extended ambulatory monitor is indicated.

7.4 The Prescription vs Consumer Boundary

KardiaMobile occupies an unusual regulatory space: it is FDA-cleared as a medical device but sold consumer-direct without a prescription. A cardiologist who reviews a KardiaMobile tracing and makes a clinical decision based on it is practicing standard cardiology with electronic patient-submitted data, a workflow that is equivalent to reviewing a patient-submitted blood pressure log.

The device is not a toy. Its classification algorithm is validated. A cardiologist’s review of a KardiaMobile tracing followed by a clinical decision is not lesser medicine than reviewing a monitor tracing generated by a hospital-prescribed device.

8. The SDE Synthesis

Tom’s case illustrates the time-sensitivity of AF detection. Every day in AF without anticoagulation in a CHA2DS2-VASc 4 patient is a day of unprotected thromboembolic risk. The gap between symptom onset and formal clinical monitoring can be weeks. A KardiaMobile in the hands of a patient with a suspicious symptom history closes that gap to days.

The Stop Dying Early framework emphasizes that the preventable deaths in cardiology are most often deaths in the gap between a clinically present condition and the clinical recognition of that condition. AF is silent in a meaningful fraction of patients; when it is symptomatic, the symptoms are often attributed to anxiety, deconditioning, or caffeine. The interval between first AF symptoms and first clinical recognition is, on average, more than a year in population studies.

KardiaMobile is a direct attack on that interval. It puts a validated medical device in the patient’s hands. When the symptom occurs, the recording occurs. The interpretation is immediate. The care gap collapses.

The SDE Audit includes a review of any prior arrhythmia monitoring data. A KardiaMobile recording library, if the patient has been tracking, provides a temporal record of rhythm that informs the clinical assessment: How frequent are episodes? What is the rate during AF? Has there been spontaneous cardioversion documented?

For patients in the SDE Cohort with known paroxysmal AF, KardiaMobile serves as the between-visit monitoring tool of choice for daily rhythm self-assessment. It supplements but does not replace quarterly ambulatory monitoring patch recordings or clinic visits.

SDE Offer Routing:

• SDE Audit (Tier 1): KardiaMobile recording library reviewed as part of initial arrhythmia assessment
• SDE Cohort (Tier 2): KardiaMobile as between-visit AF monitoring tool for patients with known paroxysmal AF
• SDE Snapshot (rapid evaluation): For patients presenting with recent KardiaMobile AF recording seeking urgent cardiology confirmation

Sex Differences in ECG Screening, AFib Incidence, and Kardia Use

9.1 AFib Screening in Women: The Evidence for Under-Diagnosis

Atrial fibrillation has historically been framed as a disease predominantly affecting older men. The epidemiology is more nuanced. The lifetime risk of developing AF is approximately 1 in 4 for both men and women over 40 5 / Solid . However, women present later in the disease course, often with more advanced remodeling and higher symptom burden at the time of first diagnosis. The AFFIRM trial and subsequent registries have documented that women with AF have higher rates of stroke, heart failure, and hospitalization than men with AF, even after adjusting for age and comorbidities 5 / Solid .

The Kardia device is particularly well-suited to the female clinical presentation for one reason: symptoms. Women with paroxysmal AF are more likely than men to report palpitations and are more likely to seek evaluation for them 4 / Promising . The 6L KardiaMobile, with its ability to capture a 6-lead ECG at the moment of symptoms, addresses the primary diagnostic challenge in women with paroxysmal AF: the symptom is present but by the time the patient reaches a clinic, the rhythm has converted.

9.2 The Special Case of Women with SVT

Supraventricular tachycardia (SVT), including atrioventricular nodal reentrant tachycardia (AVNRT) and atrioventricular reentrant tachycardia (AVRT), is more common in women than in men. The female-to-male ratio for AVNRT is approximately 2:1 5 / Solid 90019-1). AVNRT characteristically presents as abrupt-onset rapid regular palpitations (typically 150-250 bpm) that terminate abruptly. The symptoms are often attributed to anxiety, especially in young women, creating a diagnostic delay.

The KardiaMobile ECG recorded during a symptomatic episode of SVT shows a regular narrow-complex tachycardia with a short PR interval or no visible P-waves (pseudo-S waves in inferior leads, pseudo-R waves in V1). A patient who can record a 30-second Kardia strip during an episode provides the cardiologist with diagnostic evidence that would otherwise require ambulatory monitoring or an emergency department visit. This is one of the highest-yield use cases for the KardiaMobile in clinical practice: the woman in her 30s or 40s with episodic palpitations that last 10-30 minutes and have been attributed to anxiety.

9.3 Gender-Related Access Considerations

The KardiaMobile has a lower upfront cost than most ECG-capable wearables ($99 for the 6L model as of 2024). This makes it more accessible to patients who cannot afford a new Apple Watch. For women in rural Illinois who have had episodic palpitations for years without a diagnosis because they could not reproduce the rhythm during a clinic visit, the KardiaMobile represents a clinically decisive diagnostic tool. The cardiologist at OSF HealthCare in Peoria, the nurse practitioner at an SIU Medicine clinic in Springfield, or the primary care physician at a Carle rural clinic in Champaign can provide a KardiaMobile prescription that the patient uses at home for weeks or months until the arrhythmia occurs.

Technical Notes — What the Kardia Algorithm Does and What It Cannot

10.1 Lead Configuration and What Each Lead Offers

The KardiaMobile 1L records a modified Lead I (right hand to left hand) and provides rhythm analysis. The 6L records Leads I, II, III, aVR, aVL, aVF by using finger electrodes (Leads I, II, III) and a single thigh pad electrode (for the augmented limb leads) or alternative electrode configurations. This is not a 12-lead ECG; the precordial leads (V1-V6) are absent. What the 6L can detect that the 1L cannot:

• Inferior ST changes (Leads II, III, aVF)
• Lateral ST changes (Lead I, aVL)
• Left axis deviation (relevant for left anterior fascicular block)
• Right axis deviation (right heart strain, right bundle branch block pattern)
• Some P-wave morphology improvements over single-lead recording

What neither the 1L nor the 6L can provide: anterior ST changes (V1-V4) or posterior changes (V7-V9). A patient with a proximal LAD occlusion causing anterior STEMI may have minimal or no changes on a 6L Kardia if the 6L leads do not adequately sample the anterior wall. This is a fundamental limitation that patients who use Kardia during chest pain symptoms must understand. Kardia is not a substitute for emergency evaluation with a full 12-lead ECG.

10.2 The Kardia AI Classification Algorithm

AliveCor’s AI classification algorithm for the 1L and 6L devices was validated against physician-adjudicated ECG recordings from the mSToPS study, the AliveCor proprietary dataset, and subsequent published validation studies. The algorithm classifies each recording into one of several categories:

• Normal: Regular rhythm consistent with sinus rhythm, no QRS widening, no ST changes within algorithm sensitivity
• AFib: Irregular RR interval with absence of distinct P waves
• Bradycardia: Heart rate below 50 bpm
• Tachycardia: Heart rate above 100 bpm
• Wide QRS: QRS duration above a threshold consistent with bundle branch block or ventricular rhythm
• Unclassified: Insufficient signal quality, excessive artifact, or a rhythm that does not fit other categories
• Possible AFib: Rhythm with features suggestive but not diagnostic of AFib (equivocal)

The sensitivity and specificity for AFib detection in the 1L device are well validated: sensitivity 93-98%, specificity 97-99% in controlled studies comparing to cardiologist-adjudicated 12-lead ECG 5 / Solid . However, PPV in community screening depends on the pre-test probability of AF. In a 75-year-old with known paroxysmal AF recording during palpitations, the PPV is high. In a 28-year-old with no risk factors recording out of curiosity, a single “Possible AFib” reading has a much lower probability of representing true AFib.

10.3 Limitations in Specific Arrhythmias

Atrial flutter: The KardiaMobile algorithm may classify atrial flutter with 2:1 block (regular rhythm at approximately 150 bpm) as “Normal” or “Tachycardia” rather than correctly identifying the flutter mechanism. Flutter at 2:1 block creates a regular narrow complex tachycardia at a rate that looks, to an algorithm, like sinus tachycardia. The flutter waves (sawtooth pattern in inferior leads) may be visible on the 6L tracing to a trained reader, but the algorithm does not always flag them. A patient who records a Kardia strip during an episode of atrial flutter at 2:1 block may receive a “Tachycardia” classification rather than a more specific one.

Preexcitation (WPW): The KardiaMobile 1L can demonstrate the short PR interval and delta wave of Wolff-Parkinson-White syndrome in some cases. However, the algorithm does not classify preexcitation patterns specifically. A patient with WPW who records a strip in sinus rhythm with a delta wave may receive a “Normal” or “Unclassified” classification depending on the magnitude of the delta wave. The 6L provides better sensitivity for WPW pattern recognition because the delta wave is typically best seen in precordial leads, and the inferior and lateral limb leads of the 6L may show characteristic changes.

Ventricular tachycardia: The KardiaMobile “Wide QRS” classification captures any broad complex rhythm. This includes bundle branch block with sinus tachycardia, aberrant conduction during SVT, and ventricular tachycardia. Distinguishing VT from SVT with aberrancy using a 6L recording is possible in some cases but is not reliable enough for clinical decision-making without cardiologist review. A patient who records a Kardia strip during a symptomatic broad complex tachycardia should seek emergency evaluation without waiting for the AI classification.

The Screening Debate — Mass Population Screening vs Clinically Triggered Monitoring

11.1 REHEARSE-AF and the Argument for Community Screening

The REHEARSE-AF trial (Halcox J, et al., JACC 2017; DOI: 10.1016/j.jacc.2017.08.034) randomized 1,001 patients aged 65 and older with no history of AF to twice-weekly ECG monitoring with KardiaMobile plus usual care versus usual care alone. At 12 months, the KardiaMobile group had a significantly higher rate of AF diagnosis (3.8% vs 1.0%, p=0.007). Newly detected AF led to initiation of anticoagulation in 10 of the 19 newly diagnosed patients in the KardiaMobile group 5 / Solid .

What REHEARSE-AF did not show: whether those anticoagulation initiations led to fewer strokes. The trial was not powered for clinical outcomes. The AF that was detected may have included very short runs of AF (less than 30 seconds on monitoring, now categorized as “subclinical AF” or AHRE (atrial high rate episodes) whose clinical significance and stroke risk remain uncertain. The LOOP study (Svendsen JH, et al., Lancet 2021; DOI: 10.1016/S0140-6736(21)01698-6) used implantable loop recorders for AF screening in 6,004 patients with stroke risk factors and found that while AF detection rate was 3-fold higher in the ILR group, stroke and systemic embolism rates were similar at 65 months (9.4% vs 8.9%, HR 1.05, p = 0.5764). This result has important implications for the Kardia screening debate: detecting more AF does not automatically translate into preventing more strokes.

11.2 The STROKESTOP Study

STROKESTOP (Svennberg E, et al., Lancet 2021; DOI: 10.1016/S0140-6736(21)01671-8) randomized 28,768 75-76-year-olds in Sweden to invitation for ECG screening with a handheld single-lead ECG device (equivalent to KardiaMobile 1L) twice daily for two weeks versus no screening. The primary outcome was stroke, systemic embolism, bleeding, or death at 6.9 years. The screening group had a modestly lower composite event rate (31.9% vs 33.4% per 1,000 person-years; rate ratio 0.96, 95% CI 0.92-1.00, p = 0.045), driven primarily by AF detection and subsequent anticoagulation initiation 4 / Promising . The absolute benefit was small: the number needed to screen to prevent one composite event was approximately 235 at 6.9 years.

The STROKESTOP result is the strongest evidence to date that population-level AF screening with a handheld ECG device reduces adverse clinical events in older adults. The effect is modest and the number needed to screen is high, but the downstream harm of screening (false positives, anticoagulation in patients who do not need it, anxiety) appears manageable in the STROKESTOP population.

11.3 Current Guideline Stance

The 2023 ACC/AHA/HRS AFib guideline gave opportunistic ECG screening in patients over 65 a Class IIa recommendation (reasonable to consider) while stopping short of recommending systematic population-level screening (DOI: 10.1016/j.jacc.2023.08.017). The distinction is meaningful: opportunistic screening (checking rhythm during a clinic visit) has a Class IIa designation; systematic screening of all older adults (the STROKESTOP model) has not been given a Class I recommendation because the absolute outcome benefit remains modest. The KardiaMobile is a tool for both opportunistic and systematic screening. How aggressively to apply it depends on the specific patient’s risk profile, preferences, and access to follow-up anticoagulation management.

Illinois-Specific Access and Practical Use Patterns

12.1 Rural AF Diagnosis in Central Illinois

Paroxysmal AFib is among the most frequently missed diagnoses in rural Illinois cardiology practice. A patient in Decatur, Mattoon, or Danville who has intermittent palpitations lasting minutes to hours faces a fundamental diagnostic problem: primary care visits are 20-40 minutes, rhythm strips are rarely obtained during symptomatic episodes, and wait times for cardiology consultation at regional referral centers (Carle Foundation Hospital in Urbana, OSF HealthCare in Peoria, BroMenn Medical Center in Bloomington) can stretch to 4-8 weeks.

The KardiaMobile changes this equation without requiring geographic relocation. A primary care physician in Mattoon can hand a $99 KardiaMobile to a patient, instruct them to record a strip at the onset of the next episode, and email the PDF to the cardiologist. This triage model is particularly valuable for patients who cannot take time off work to travel to a specialty center for an ambulatory monitor fitting. It is also valuable for patients who have already had a Holter monitor with no findings; the KardiaMobile’s on-demand recording nature is better suited to episodic arrhythmias than the continuous-recording Holter.

12.2 SDE Program Integration

In the SDE Audit protocol, patients presenting with palpitations, presyncope, or unexplained dyspnea receive a 30-day KardiaMobile loan as part of the initial evaluation. Recordings are transmitted via the AliveCor platform, reviewed by the SDE clinical team, and flagged recordings are escalated for immediate cardiologist review. The Carle Foundation Hospital system has integrated AliveCor transmission into its ambulatory telemedicine framework, allowing rural patients in the Carle network to have their Kardia ECGs reviewed by cardiologists at the main Urbana campus without driving.

For patients in the SDE Executive program (employed adults in leadership roles who require rapid arrhythmia evaluation), the KardiaMobile 6L is standard issue in the onboarding kit. The 6L provides enough diagnostic information for a cardiologist to distinguish most common arrhythmias from artifact without requiring an additional clinic visit. The goal is not to replace the cardiologist but to reduce the time-to-diagnosis for arrhythmias that occur outside office hours and outside clinical settings.