Overview

Thirty ambulatory patients were subject to 24-hour cardiac rhythm monitoring with the YouCare device and a 3-lead Holter monitor, simultaneously. During the study, the patients performed activities of daily living. All subjects who met the inclusion/exclusion criteria (Table 1) were equipped with the YouCare device, its associated smartphone, and a Holter monitor for 24 h.

Table 1 Eligibility criteria

The protocol and overall study were approved by an ethics committee (Internal code: 156/2022/Disp/AOUBo by the Comitato Etico Area Vasta Emilia Centro - CE-AVEC – Bologna, Italy), registered on the Italian Ministry of Health website, and on clinicaltrials.gov (Identifier NCT05771142). The study was conducted in accordance with the Declaration of Helsinki, and each participant provided written informed consent.

YouCare System

The YouCare device (AccYouRate Group S.p.A.; L’Aquila, Italy; Fig. 1) is a crop top garment made of cotton and ceramic with integrated polymer-based electrodes and an acquisition module for data recording and processing. The garment contains 3 polymer-based electrodes that, when in contact with the skin, allow the acquisition of a single-lead ECG. Two of the electrodes are located close to the diaphragm just below the major pectoral muscles (Fig. 1F). A third electrode is positioned on the back of the chest belt, and it has the function of the right leg lead used to reduce the noise and artifacts present on the other two electrodes. The control unit, anchored to the garment via four metal snap fasteners (Fig. 1D-E), has an ECG sampling rate of 246 Hz and collects and sends the data to a smartphone via Bluetooth for storage.

In addition to the one-lead ECG, the garment is paired with a control unit (Fig. 1C) that has an accelerometer, a gyroscope, and body temperature sensor. A respiration waveform is derived from the ECG. YouCare garments are offered in varied sizes and custom fit for women and men (Fig. 1A, B). Garment size is important to ensure continuous sensor contact with the skin, leading to the best signal quality.

Fig. 1

The YouCare device is a garment with polymer-based sensors directly integrated in the garment fabric. When in direct contact with the skin, the device can record a single-lead ECG through sensors in the belt around and below the chest. There are two versions, one for men (A) and one for women (B) with different sizes. The garment is connected to the control unit, that works as an acquisition and transmission module, (C, D) through four snaps (E). Polymer-based sensors provide contact with the skin (F)

ECG Holter Monitor

The Holter recording system (SEER 1000 GE Healthcare, Chicago, Illinois) features three leads with an ECG sampling rate of 256 Hz, 0.05–70 Hz response, and 12-bit resolution. The system uses standard disposable silver/silver chloride (Ag/AgCl)–gelled electrodes. The electrode-skin connection was reinforced with medical tape to ensure stable contact.

Assessment and Validation of Signal Quality

ECG signal qualities from both devices were evaluated according to two independent approaches:

1)

Qualitative Assessment: ECG signal quality was evaluated by a team of three expert cardiologists and classified according to three categories: “Good” (all major ECG features - P, QRS, and T - are visible for diagnostic purposes), “Acceptable” (the QRS is visible), and “Not Readable” (mostly noise with no ECG waveforms clearly visible).

2)

Quantitative Validation: R-R interval comparison between the YouCare device and the Holter monitor were performed after extracting 30 consecutive minutes of data where the quality was at least “Acceptable”. The time distances between corresponding R waves of each device were classified as either within the measurement error (of 8 milliseconds, as determined from error propagation rules [9]), or over the measurement error. The R-R interval comparison was not performed for two patients (#’s 2 and 25) because thirty consecutive minutes of stable signals were not available. Only the longest, uninterrupted recordings were analyzed, and the corresponding segments of the Holter ECG were isolated for comparison. The analysis was performed with Python and its libraries (i.e.: Numpy v.1.17.3, Pandas v1.3.4, Neurokit2 v0.1.7 [10]) in conjunction with ANScovery (SparkBio S.r.l., San Lazzaro di Savena, Bologna, Italy) [11].

Patient Surveys

A survey of the patients in the study was performed via follow-up phone interview in which patients were asked to rate both the YouCare and Holter devices on a scale of four levels of comfort: very comfortable, comfortable, uncomfortable, very uncomfortable. Four patients were unreachable via the telephone and three did not participate due to a language barrier.