Journal of Clinical and Preventive Cardiology

: 2019  |  Volume : 8  |  Issue : 4  |  Page : 173--182

Wellysis S-PAtch Cardio versus Conventional Holter Ambulatory Electrocardiographic Monitoring (The PACER Trial): Preliminary Results

Satyanarayana Upadhyayula1, Ravi R Kasliwal2,  
1 Department of Cardiology, Medanta - Mediclinic, New Delhi, India
2 Division of Clinical and Preventive Cardiology, Department of Cardiology, Medanta Heart Institute, Gurgaon, Haryana, India

Correspondence Address:
Dr. Satyanarayana Upadhyayula
MD, FEM, FIMSA MIAE, Department of Cardiology, Medanta . Mediclinic, New Delhi


Aims and Objectives: The Wellysis S-PAtch Cardio versus Conventional Holter Ambulatory Electrocardiographic Monitoring (PACER) trial consists of multiple arms. First arm is a prospective, interventional, nonrandomized, single group assignment, diagnostic substudy with intention to treat. This head-to-head trial aims to compare the diagnostic yield, or ability to detect arrhythmias – especially paroxysmal atrial fibrillation (PAF) – of the conventional Ambulatory Holter monitoring device with the Wellysis S-Patch Cardio, a novel, low-profile device consisting of a single positive bipolar lead corresponding to the standard limb lead II (n = 10). Second arm is a validation substudy of the Wellysis S-Patch Cardio device in terms of overall performance (n = 86). Background: It is widely recognized that technology can improve the health of populations in countries around the world. Smartphone technology is at the forefront of innovation in low-, middle-, and high-income countries. The smartphone technology has already improved the doctor–patient interaction, reducing costs and improving care for patients. Methodology: In the comparator arm, patients who satisfied the eligibility criteria as well as referred for ambulatory ECG monitoring were consented and enrolled prospectively to have the Holter monitor and the Wellysis S-Patch Cardio device placed simultaneously (n = 10) for 24–48 h and the incidence of clinically significant arrhythmias were compared. A feedback questionnaire was given to patients/paramedics and clinicians after completion of the study. The overall performance (patient, paramedic and clinician feedback and questionnaire derived subjective composite index of comfort, usability, interference with daily activities, adverse events, adaptability, robustness, repeatability, durability, clinical analysis, clarity of recorded signals, efficiency, accuracy, and cost-effectiveness) of Wellysis S-Patch Cardio device was compared with multi lead Holter Monitor in this head to head trial (n = 10). In the validation arm patients who satisfied the eligibility were consented and enrolled prospectively to have the Wellysis S-Patch Cardio device placed (n = 86) for 24–48 h and the incidence of clinically significant arrhythmias noted. Results: Preliminary results from the comparator arm (n = 10), Mc Nemars analysis, revealed odds ratio 1.000, 95% confidence interval 0.072–13.796, χ2 = 0.250, DF = 1, P < 0.6171; supporting the null hypothesis-Wellysis S-Patch Cardio is comparable to Holter in terms of Overall Performance (comfort, usability, interference with daily activities, adverse events, adaptability, robustness, repeatability, durability, clinical analysis, clarity of recorded signals, efficiency, accuracy, and cost-effectiveness). Conclusion: Multi lead ambulatory Holter monitoring remains the gold standard for arrhythmia detection. However, Wellysis S-Patch Cardio device has a definite complementary role in the detection of PAF in cryptogenic stroke patients.

How to cite this article:
Upadhyayula S, Kasliwal RR. Wellysis S-PAtch Cardio versus Conventional Holter Ambulatory Electrocardiographic Monitoring (The PACER Trial): Preliminary Results.J Clin Prev Cardiol 2019;8:173-182

How to cite this URL:
Upadhyayula S, Kasliwal RR. Wellysis S-PAtch Cardio versus Conventional Holter Ambulatory Electrocardiographic Monitoring (The PACER Trial): Preliminary Results. J Clin Prev Cardiol [serial online] 2019 [cited 2022 Aug 18 ];8:173-182
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Full Text

Atrial fibrillation (AF) is the most common cardiac arrhythmia leading to risk of thromboembolic events. The associated risk of AF for stroke is 1.5% for those aged 50–59 years and 23.5% for those aged 80–90 years. AF can often be difficult to detect due to its asymptomatic and paroxysmal nature. Associated delay in the initiation of therapy can lead to an increased risk of ischemic stroke. Patients are traditionally monitored for AF with continuous inpatient ward telemetry, continuous inpatient/outpatient Holter monitoring which often proved to be ineffective in the detection of AF. As a result, patients are not anticoagulated leading to an increased risk of recurrence of stroke. Recent advances in technology have allowed for the development of a novel wireless device called the Wellysis S-Patch Cardio [Figure 1] that can collect and store ECG data to be interpreted by a Cardiologist anytime, anywhere online in real time.[1],[2]

AF is often asymptomatic yet associated with critical adverse outcomes. The global economic burden of AF is humongous. The management expense of AF is a staggering $26 billion annually in the United States alone. The Holter Ambulatory electrocardiographic monitoring, first introduced in the late 1940s, is the most commonly used method to detect cardiac arrhythmias in the outpatient ambulatory setting. Holter monitoring has low diagnostic yield of 15%–39%, because majority of PAF episodes are asymptomatic, as a result of which most of the patients are unable to activate their event recorder. However, the standard multi-lead, 24-h Holter monitor remains the gold standard for arrhythmia detection.[3],[4],[5]{Figure 1}


The highest diagnostic yield for arrhythmia detection is usually the first 7 days of ambulatory ECG monitoring. Multi-lead recordings also allow for improved detection of aberrant/broader QRS complexes where a single lead recording may not detect the altered QRS complex width because the leading edge or trailing edge of the QRS complex may be relatively isoelectric to the single lead recording vector. Holter is superior in broad complex tachyarrhythmia detection rather than narrow complex arrhythmia detection.

Historical vignette

Norman Jefferis (“Jeff”) Holter, member editorial board of the Journal of Nuclear Medicine, was a distinguished physicist who had served with the University of California Institute of Oceanography. He realized that the newer trends in cardiologic practice would require ambulatory ECG documentation. The original unwieldy apparatus [Figure 1] and [Figure 2] consisting of a bulky ECG radio transmitter and heavy batteries (together weighing 85 pounds) looked cumbersome and impractical (like Willem Einthovens Electrocardiograph) even in those days. Holter planned a practical miniature tape recording and data reduction system to document evanescent arrhythmias, including conduction defects, an important advancement to facilitate a clinically important and accurate diagnosis and prognosis for the patient at high risk of imminent sudden cardiac death.[6]{Figure 1}{Figure 2}

Wellysis S-Patch Cardio

Wellysis S-Patch Cardio is a bipolar single lead device consisting of two electrodes. The negative electrode with the contained bio-processor represents the right upper arm (RA) lead and is placed close to the sternum in the region of conventional V1-V2 precordial leads. The positive electrode with the contained battery represents the conventional left lower limb (LL) lead and is placed in the vicinity of the V3-V4 precordial leads. The word “Lead” refers to an imaginary line between two ECG electrodes. The two electrodes of Wellysis S-Patch Cardio are placed over the precordium. However unlike the precordial unipolar leads in the conventional EKG which measure electrical activity that is moving in a front-back direction (coronal) and/or a right–left direction (sagittal), the bipolar single lead Wellysis S-Patch Cardio measures electrical signals in the up–down (frontal) direction between its two electrodes and outputs them as the Standard limb lead II EKG (II = LL-RA). Out of the 12 leads in the conventional EKG, standard limb lead II represents the best lead for detecting arrhythmias.

The importance of technology in healthcare is becoming increasingly evident. The smartphone can play an important role in making it a reality and is becoming more accessible for millions around the world by streamlining clinical workflows and enhancing patient's experience.

It provides a real time continuous 24 × 7 wearable technology to monitor and manage cardiovascular conditions. At 11 g, it is much lighter than the traditional Holter monitor and makes it very comfortable for the patient to use and easier for the doctor to manage their patients. The solution provides continuous monitoring from 24 h up to 7 days test duration which makes it a bespoke innovative offering. It further provides an access to the artificial intelligence analytics service on cloud environment along with the mobile application for diagnosis of rhythm disorders of the heart [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7], [Figure 8], [Figure 9], [Figure 10].{Figure 3}{Figure 4}{Figure 5}{Figure 6}{Figure 7}{Figure 8}{Figure 9}{Figure 10}

Study description

Paroxysmal AF (PAF) is often undetected because of its short duration, episodic, and frequently asymptomatic nature, leading to suboptimal secondary prevention. However, systematic review suggests conventional 24-h Holter monitoring will identify AF in only an additional 4.6% of patients. The optimal investigation strategy, including modality, efficacy, cost-effectiveness, duration of investigation, and patient subgroup, remains undefined. The objective of this project is to conduct a pragmatic multicenter Wellysis S-Patch Cardio versus Conventional 24 h Holter monitoring to detect PAF. The study design, the study protocol, and the overall performance questionnaire are summarized below [Table 1], [Table 2], [Table 3], [Table 4].{Table 1}{Table 2}{Table 3}{Table 4}

Eligibility criteria

The inclusion and exclusion criteria are as follows:

Inclusion criteria

Clinical diagnosis of acute ischemic strokeCerebral ischemia defined as stroke (sudden focal neurologic deficit lasting >24 h consistent with the territory of a major cerebral artery and categorized as ischemic) and/or a corresponding lesion on brain imagingCryptogenic transient ischemic attack/minor stroke syncope of uncertain etiologyPresyncope of uncertain etiologyPalpitations of uncertain etiologySuspected arrhythmia-related signs and symptoms, as judged by the investigatorsPatients intend to wear ECG monitorsAre capable of giving informed consentAble to comply with long-term continuous monitoring with Wellysis S-PatchCardioSinus rhythm on the surface ECG.

Exclusion criteria

Have known skin allergies, conditions, or sensitivities (e.g. allergy to adhesives and psoriasis)Any abnormal or friable skin over the anterior thorax and upper abdomenAny dermatitis or infected skinA sternal or thoracic incision that extends under the patch within 3 months from the date of enrolmentPatients with chest injuriesIntracerebral hemorrhage in medical historyEnd-stage renal diseasePregnant womenCurrently participating in another trial or who participated in a previous clinical trialAre anticipated to be exposed to high frequency surgical equipment during the monitoring periodInfective endocarditisStroke induced by trauma, infection or surgery procedureDementia or suspected noncomplianceKnown cancer except cancer prostate with normal prostate specific antigen, or basal cell carcinoma.


Patients (n = 86) were instructed to wear both devices demographic data including date of birth, age, gender, weight, height, chest circumference, body surface area, indication for ambulatory ECG monitoring, prior congenital heart disease, prior cardiac surgery, and prior Holter or Wellysis S-Patch Cardio device use was collected. Wellysis S-Patch Cardio is a light weight (device 8 g + battery 3 g = 11 g) device containing a bioprocessor which continuously collects ECG data for up to 60 h and transmits it in real time via a bluetooth connection to an android smartphone application. The initial coupling is made via an internet connection that pairs the device with precreated patient profile. The actual device is easily applied with only two standard ECG electrodes placed typically in V2-V4 position. Patients keep the phone within 3 m of them throughout the test period. Wellysis S-Patch Cardio sends data to phone via bluetooth at all times and does not require an internet connection [Figure 3], [Figure 4], [Figure 5]. The cardio application allows the patient to be able to add symptoms/activities either by using a precreated list or by entering their own information. At the end of the test the recorded information is uploaded to a Cloud-based database via an internet connection. Arrhythmia events were defined as supraventricular tachycardia (>4 beats), AF (>4 beats), pause >3 s, atrioventricular block (Mobitz type II or third-degree atrioventricular block), ventricular tachycardia (>4 beats), or polymorphic ventricular tachycardia/ventricular fibrillation.

Demographic variables

The demographic clinical characteristics and arrhythmias detected in our cohort of 86 patients are summarized in [Table 5]. We performed subgroup analyses for key demographic factors such as age, sex, race, and ethnicity in the PACER trial. We intend to make for underenrolling certain patient types (e.g. women and ethnic minorities) so that the enrolled study population represents the Indian population as a whole. We have data to assess whether age, race, or ethnicity is associated with clinically meaningful differences in outcomes. Efforts are being made to promote subgroup enrollment with minimum enrollment targets for age, race, and ethnicity subgroups. We have prespecified subgroup analyses in the statistical analysis plan for the comparator and the validation arms. Also shown are the graphical representation of the subgroup analyses results pertaining to age, sex, race and ethnicity in the PACER trial [Figure 11], [Figure 12], [Figure 13], [Figure 14], [Figure 15], [Figure 16], [Figure 17].{Table 5}{Figure 11}{Figure 12}{Figure 13}{Figure 14}{Figure 15}{Figure 16}{Figure 17}


The PACER trial was conducted under the supervision of Cardiology team at Medanta, and reports were interpreted with relevant findings which were analyzed by the cardiologist. With 82% of patients finding the Wellysis S-Patch Cardio comfortable to wear and 80% indicating they would prefer it over the Holter monitor, it is clearly a less obtrusive and more patient-friendly monitoring platform. The results – clinical metrics, operational metrics, and statistical analysis are summarized in [Table 6] and [Table 7].{Table 6}{Table 7}

Study limitations

The PACER trial is ongoing and the results presented are preliminary (comparator arm). The patients enrolled included all those referred for ambulatory ECG monitoring rather than for determination of a previously undocumented arrhythmia. The PACER trial is open labeled, and both the comparator as well as the validation arm is uncontrolled. In addition, the Wellysis S-Patch Cardio device could not be validated in complex arrhythmia due to small sample size.[7],[8],[9]


Multilead ambulatory Holter monitoring remains the gold standard for arrhythmia detection. Wellysis S-Patch Cardio device has a definite complementary role in the detection of PAF in patients with cryptogenic stroke.

Wellysis S-Patch Cardio provided clinical rate and rhythm data comparable to Holter monitoring with acceptable technical utility. Heart rate and ectopy were well measured. AF was recorded, and correlation between Holter and Wellysis S-Patch Cardio was excellent. The Wellysis S-Patch Cardio appeals as a screening tool for patients with suspected paroxysmal/silent AF.

Wellysis S-Patch Cardio ECG data analytics enables faster diagnosis of patient's cardiac status. Real-time ECG monitoring drastically reduced workload of clinical staff, improved workflow efficiency as well as wait time for patients who are in need of treatment.

Enhanced user experience and comfort was noted with Wellysis S-Patch Cardio device as it was light weight (8 g device + 3 g battery = 11 g) and water resistant. When it comes to overall performance (patient, paramedic and clinician feedback and questionnaire derived subjective composite index of comfort, usability, interference with daily activities, adverse events, adaptability, robustness, repeatability, durability, clinical analysis, clarity of recorded signals, efficiency, accuracy, and cost-effectiveness), the Wellysis S-Patch Cardio device was found to be comparable to conventional Holter in a subset of patients.

Over the total wear time of both devices, the Wellysis S-Patch Cardio detects arrhythmia events comparable to Holter monitor. Multi lead Holter monitoring is indicated during the 1st week immediate post event. However, Wellysis S-Patch Cardio device may be used for prolonged monitoring of postdischarge (after 1 week postevent) patients for the detection of PAF.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.


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