Heart failure (HF) is a multifactorial chronic syndrome with an enormous public health impact.1 Its incidence is also increasing, as are the morbidity and mortality rates, despite the latest therapeutic innovations.

For this reason, it is perfectly permissible to speculate about the unsuitable way we are monitoring HF in the patient's home. In fact, perhaps we have not been monitoring it properly so far, predicting it in a timely or sensitive enough manner, or even treating the correct decompensating factors.

We performed an exhaustive literature search on this topic and found that increases in heart rate,2 low heart rate variability, a rise in ventricular filling pressures, atrial and ventricular arrhythmias, high respiratory rate and pulmonary congestion are the main parameters believed to predict precipitating HF decompensations.3,4

HF home monitoring has been shown to improve HF management and ambulatory follow-up of HF patients has proven to be cost-effective.5,6

As we have discussed in part I of this series of articles, in which we presented the theoretical rationale for the development of MONITORIA, home monitoring of HF should be by means of a device as this is the only way we can obtain continuous objective data on patient status, apart from the healthcare provider visits and self-monitoring.7

Telemonitoring without implantable devices is perhaps the best option for elderly advanced patients, and improved technology and effective predictive models would anticipate sudden decompensation events. Accordingly, we designed a non-invasive device that we believe will revolutionize outpatient follow-up, management of HF and its outcomes.

This device (designated from now on as MONITORIA) will provide non-invasive remote monitoring of HF patients, by capturing vital and electrophysiological signs (heart rate, and heart rate variability, T wave variability, electric conduction abnormalities, atrial and ventricular arrhythmias, respiratory rate and peripheral oxygen saturation), hemodynamic signs (systemic arterial blood pressure, right and left atrial pressures), transthoracic bioimpedance), chemical signs (skin sodium content), and physical activity levels.

The MONITORIA device (MOnitoring NonInvasively To Overcome mortality Rates of heart Insufficiency on Ambulatory), currently under development and being tested, is a state-of-the-art multimodal array of sensors that will provide real-time monitoring of several physiologic, hemodynamic and chemical variables in HF patients, allowing health professionals to have a timely multifaceted perspective of HF.

By providing these data, it will be possible to detect more promptly early signs of decompensation, act on them and stabilize patients at home, avoiding hospitalizations. Furthermore, any time the patient needs a medical emergency team (MET) at home (such as in the event of an effective or impending cardiac arrest or suspicion of a myocardial infarction) to overcome possible waste of time (sometimes the MET can take upwards of 30 min to reach the patient), MONITORIA is designed with a cardioverter-defibrillator function. This way, in certain cases of cardiac arrest (including the presence of ventricular fibrillation or sustained ventricular tachycardia), the device will send a shock trying to defibrillate the patient, while waiting for the emergency team to arrive.

The objective of our researchis to develop the most appropriate device for home monitoring of chronic HF. This device is MONITORIA and for simplicity we chose to separate our MONITORIA research into three articles. This is part II, and the purpose is to describe the technical specifications of the device's design. Part I gave theoretical basis and rationale surrounding MONITORIA's development. Part III will present the MONITORIA prototype and the validation tests.

Taking into account the rationale presented in the previous section, supported by evidence in the literature, MONITORIA is being designed with the set of sensors/electrodes shown in Figure 1, which are described in detail below.

Figure 1.

MONITORIA multisensor array.

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MONITORIA is a home monitoring device, designed for the follow-up of HF patients, and consists of the following main components:

MONITORIA's electronic sensors and circuitry are embedded in a thoracic vest designed to fit both sexes, and adjustable to different body shapes by means of VelcroTM buckles on the back. This thoracic vest is made of a breathable elastic material which has to be washable and user-friendly. It has two main parts: the thoracic vest itself (washable part) and a flexible platform to be placed inside the thoracic vest, containing all the circuitry components.

The part with the electronic components is a flexible printed circuit board covered in mechanically flexible polyethylene terephthalate (PET) substrate, where the tips of the electrodes, the sensors’ surface and the rechargeable battery are located externally. This part must be fixed to the textile enclosure to avoid relative motion between them.

To ensure water protection in the circuitry region, the textile vest that covers it must be hydrophobic on the inner surface – in contact with the PET substrate containing the circuit – and hydrophilic on the outside – in contact with the skin. Gore-Tex19 is an example of this kind of material, as it is breathable, stretchable and has a double layered membrane with hydrophobic and hydrophilic surfaces. To improve the patient's comfort, the remaining area of the vest, which does not contain any circuitry inside, has to be made from a washable and stretchy type of cotton.20 The hydrophilic side (in contact with the skin) must have holes with the shape and size of the electrodes and sensor's surface (to allow direct contact between the sensors with the skin), and the area surrounding these holes should be made of a silicone gel, in order to improve the steadiness of the electrodes/sensors in contact with the skin.

Finally, to guarantee that the thoracic vest is worn properly and adjusted to the patient's thorax we decided to include a tight-switch sensor in the vest.

Figure 2 shows the MONITORIA thoracic vest.

Figure 2.

The thoracic vest in which the MONITORIA is embedded.

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  Patient mobile phone application:

All the data given by the sensors are recorded transiently in the patient's mobile phone, before being sent to the cloud server. The patient's mobile phone will have an application, specifically developed for MONITORIA, which instructs the patients whenever appropriate. This will inform them of the most suitable time for meals (ensuring the correct measurement of skin sodium content) and giving them the feedback regarding their physical activity, informing them if they have already reached the average physical activity required for each, or advising them to walk a little more. This patient feedback will be displayed on the phone screen in written form, but sound commands will also be issued ensuring that those who are unable to read or write and/or visually impaired patients can also understand the instructions provided.

Moreover, as part of their daily hygiene, patients must remove the thoracic vest when they bathe, but this period should never exceed 30 minutes. Whenever this happens the phone app will emit an alarm informing the patients that they have to put the thoracic vest back on again.

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  Medical application:

The patient's mobile phone application uploads the data to the cloud-based server every 24h to make this information available to the attending physician.

Then, according to a pre-specified protocol, the physician will access a passworded medical application on their personal computer, specifically developed for MONITORIA, retrieving all the data recorded in the cloud.

Once the application is open, the default page gives an overview of all the patients connected to the system. Then the physician can choose which patient to analyze in more detail. The individual patient's page shows, by default, the summary statistics of each parameter for the last 24 h, 7 days or 30 days (detailed statistics visualized by clicking on each icon). There is also the possibility of changing this view to a raw format data, assessing all data without any statistical processing.

The medical application also provides an alarm menu which displays all the alarms emitted in the last 30 days, specifying their nature, the professional contacted (if it was only the attending physician or also the national emergency system) and the success of the actions taken.

The MONITORIA sensors will be activated when the healthcare provider dresses the patient, for the first time, in the thoracic vest. At this time the physician will, also, determine if the system needs the cardioverter-defibrillator function as well (with an upgraded version, see below).

The MONITORIA performs continuous real time capture, analysis and transmission of all data on a daily basis. Significant alterations in a patient's variables (see alarms below) alert the attending physician immediately via a text message. This message includes the name of the patient, their telephone number and address, and information concerning the alarm (mainly nature and duration of the event).

Whenever the physician receives an alert, they immediately make a phone call to the patient to gauge their clinical status, and depending on the nature of the alarm and the information directly provided by the patient or their relatives, the physician will instruct the patient on what to do next. This action plan may include alteration in therapeutics (adding/stopping medication, altering dose) or scheduling an urgent appointment at a day hospital/outpatient clinic. Figure 3 presents an overview of MONITORIA's remote monitoring system.

Figure 3.

Generic representation of MONITORIA's remote monitoring system.

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Whenever there is a potentially life-threatening or lethal situation (imminent or consummate cardiac arrest, potential myocardial infarction…), the system will also send an alert to the national emergency medical system and a medical emergency team will be sent immediately to the patient's home. In order to improve the specificity and sensitivity of this function the basal ECG of each patient must be acquired and registered previously and only new abnormalities considered. This personalized methodology is necessary to avoid pitfalls in diagnosis.

In the future, MONITORIA will be able to send shocks or function as a pacemaker to treat certain arrhythmias (ventricular fibrillation [>30 sec and HR≥200 bpm] or sustained ventricular tachycardia [>30 sec] with HR of ≥150 bpm) or blockade/pause >3 sec, as suitable. We are now studying the best specifications to avoid inappropriate shocks as this is associated with high mortality and morbidity.

The decision to activate the cardioverter defibrillator function would be taken by the physician the very first time the patient utilizes the device. If the patient has ischemic heart disease or a cardiomyopathy with reduced left ventricular ejection fraction (special caution is required when ≤35%), the cardioverter defibrillator function should be activated. This is because Röger et al.21 found that patients with LVEF>35% did not benefit from cardioverter defibrillator. In MONITORIA the first shock will be 150 J. If the arrhythmia occurs at separate episodes, with ≥3 min in between, then the system will consider them separate arrhythmias and will fire separate shocks.

MONITORIA generates alarms in the following situations:

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  New onset of atrial fibrillation, atrial fibrillation with rapid ventricular rate, sustained ventricular tachycardia, ventricular fibrillation;

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  Electric conduction pauses ≥2 secs or complete atrioventricular block. De novo right bundle branch block;

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  A 2 mm rise in ST segment in two out of three leads in each group (limb or precordial leads) generating high suspicion of myocardial ischemia;

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  Heart rate ≤40bpm or ≥120bpm, lasting more than 5 min, and no (or minimal) physical activity detected;

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  Peripheral oxygen saturation ≤89%, lasting more than 5 min;

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  Instantaneous lung impedance ≤100 Ω, in three consecutive measurements, or ΔLIR<18%;

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  Systolic blood pressure ≤70 mmHg or ≥200 mmHg; and/or diastolic blood pressure ≤35 mmHg or ≥100 mmHg, lasting at least 5 min;

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  Right atrial pressure ≥8 mmHg in three consecutive measurements;

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  Left atrial pressure ≥12 mmHg in three consecutive measurements.

At present, despite technological and pharmacological innovations, HF continues to cause a huge public health impact and is a major economic and social burden.

In this paper we present MONITORIA, a promising device that we believe will change the paradigm of ambulatory follow-up of patients with HF, essentially because it is part of a follow-up program (the GENICA project) that takes into account a multi-perspective feature of HF development. It is based on real world patients, adapting innovations not to the disease but rather to patients.

In the near future, predictive analysis will be built upon this technology by establishing algorithms for preventing clinical events such as impending HF decompensation before it occurs in the outpatient setting.

As soon as the MONITORIA's development and prototype testing phase is concluded, an article (part III of this series of three articles) will be published reporting the results of validation tests.

MONITORIA and its follow-up strategy will provide optimization of HF patient care, reducing significantly their exacerbations, hospital admissions (hospitalizations) and mortality, thus reducing costs. Consequently, HF-associated burden will also be attacked at the source.

MONITORIA has some limitations, mainly related to the strict schedule; it has to be used continuously so the measurements are taken properly, the patient has to rest during the night so certain measurements are taken accurately and the batteries must be changed every 24h (some patients may not remember this, so for ease we added an alarm as a reminder for patients). This whole system may be complex in patients’ daily lives. However, these limitations may be overcome by the beneficial effect that the accurate monitoring of such a deadly disease can have on patients

A home monitoring programme using MONITORIA may be useful (feasible) after validation for particular subsets of HF patients, especially those with severe forms of HF at higher risk of decompensation and (re)hospitalization, with no cognitive dysfunction or depression, and additionally, those at ease with new technologies or who live with a caregiver who is.

We are now studying the best specifications to avoid inappropriate shocks as this is associated with high mortality and morbidity. This is why this function should only be activated by the responsible physician who is able decide on its use according to patient need to avoid lethal consequences.

The authors declare that no funding was provided conducting this study or preparation of this manuscript.

The authors have no conflicts of interest to declare.