## 4 Biosensors in the Field of Healthcare
### Smart Implants for Cardiovascular Disease  
In recent years, healthcare providers and researchers have shown increasing interest in telemedicine to monitor heart rhythms and mitigate adverse reactions associated with CVD and PVD therapies. For example, observing abnormal heart rhythms and monitoring ISR post-treatment. They believe that the coronavirus pandemic (COVID-19) has strongly encouraged a shift from providing \"in-office\" health service to remote monitoring. They assume that remote monitoring is a key to improving healthcare systems by increasing the accessibility of more people to health services and offering personalised treatment [110]. The innovation and development of smart implantable devices for CVD is not an entirelynew endeavour; as, some devices have already been commercialised with, others in development. For example, CardioMEMS(tm) is a small implantable device (15 \(\times\) 3.4 \(\times\) 2 mm), see Table 3, developed by the Abbott company used to remotely monitor the pulmonary artery pressure of patients with HF [111]. CardioMEMS(tm) consists of three main components: (1) inductor, (2) pressure-sensitive capacitor, and (3) two nitinol loops. The capacitor is made of two conductive layers separated by a space medium. When pressure is applied, these conductive layers move towards each other, decreasing the space between them and altering the capacitance of the circuit. This change causes a shift in the resonant frequency of the circuit, which is directly correlated to the force exerted on the sensor's surface. Both inductor and capacitor are encapsulated within medical-grade biocompatible silicone. Indeed, biocompatibility and adherence of ISO standard 10993:2018 are an essential element of the regulatory process (See [[https://www.fda.gov/](https://www.fda.gov/)]([https://www.fda.gov/](https://www.fda.gov/)), accessed on 9 September 2024). CardioMEMS(tm) relies on wireless electromagnetic coupling technology to share data with  
Figure 5: Applications of implantable biomedical devices. Source: [109]. cardiologists from the patient's home. Such technology enables HF management, reduces frequent inpatient admissions, and potentially reduces the cost [112; 113]. In addition, an implantable loop recorder, such as the Medtronic's Reveal LINQTM (Table 3), is a heart rhythm monitor. This device can be implanted under the skin in the chest for up to 3 years, where it records any abnormal activity of the heart's electrical rhythm [114]. The size of this device is 7 \(\times\) 45 \(\times\) 4 mm, and it is equipped with wireless telemetry to transmit data (recorded ECG) to the clinic, wirelessly [115]. For security and privacy, Reveal LINQTM transmits data daily to an external unit, called MyCareLinkTM, monitoring within a range of up to 6 feet. Then, MyCareLinkTM requires a 3G network connection for wireless data transmission [116]. The treatment of abnormal heart rhythms started in the 20 th century when [PERSON], a Canadian biomedical scientist, designed and built the first non-implantable pacemaker (Figure 6A). His pioneering work led to the development of the first implantable pacemaker by [PERSON] (Figure 6B). In 1958, the first implantable pacemaker was entirely inserted in a patient in Stockholm, Sweden, by cardiologist [PERSON] [117; 118]. In early 1970, Dr. [PERSON] introduced the idea of producing leadless pacemakers to encounter the challenges of traditional pacemakers such as lead dislodgment and short battery life [119; 120]. After a few decades, St. Jude Medical Inc. (now known as Abbott) developed NanostimTM, the first leadless pacemaker that was completely implanted in the right ventricle of a human's heart. NanostimTM received the CE mark in 2013 and become the first intracardiac pacemaker to be launched across Europe. Similarly, Medtronic developed their first generation of a leadless pacemaker, called MicraTM (Figure 6C), which is 93% smaller than their conventional pacemaker. Their breakthrough pacemaker received FDA approval by 2016.