Subcutaneously Insertable Cardiac Monitor for Atrial Fibrillation and HF Using ECG and Phonocardiography as Biomarkers

Abstract

Heart failure (HF) affects more than 6 million patients in the United States, with more than 1 million hospitalizations, at a staggering annual cost of $40B. Current standard and criteria for managing HF is largely based on clinician assessment of symptoms and physical examination, which suffer from low sensitivity and specificity. In addition, these modalities are not helpful at home, where patients are most vulnerable. Furthermore, long-term patient compliance has been a persistent weakest link in the chain resulting in poor utilization and poor outcomes. Implantable pulmonary artery pressure monitoring (ie, CardioMEMS, Abbott Cardiovascular) is the gold standard when it comes to remote HF monitoring. However, this approach is expensive, complex, and suffers from low adoption, as it requires cardiac catheterization laboratory implantation and a suite of support staff. Wearable monitors, on the other hand, bring convenience and temporary solution; however, they are not suited for a long-term monitoring, as the wearables have not been able to address long-term compliance issues. To address these limitations, Future Cardia is developing a long-term monitoring solution that improves patient compliance and outcomes with actionable data while reducing workloads for clinicians and—most importantly—improving patient compliance by reducing at-home regimens. Future Cardia uses 2 main sensors to monitor electrical and mechanical activities of the heart, single-lead electrocardiography (ECG) to monitor cardiac arrythmias, and 3 axis accelerometer (piezoelectric) sensors for heart sounds and activity. The third sensor is in development. The office-based subcutaneous insertion approach is a common procedure that allows simple and effective device deployment and use for the clinician and patients for the purpose of long-term monitoring. Future Cardia’s sensing and detection algorithm assesses each heartbeat and automatically records ECGs based on beat-to-beat instability in addition to routine recordings throughout the day as a baseline. The subcutaneous approach with 2-year battery longevity allows Future Cardia to deliver actionable data to clinicians who treat patients with HF with convenience and ease. Our goal with the trending data is to develop a simple but effective titrating algorithm, similar to what we have seen for the patient population with diabetes: that is, for patients to make predetermined medication adjustments under clinician supervision. Recorded data are securely sent to the smartphone via Bluetooth Low Energy, which is then pushed to cloud-based computing for the clinician to review via secured web portal, similar to what the clinicians are already doing with current atrial fibrillation insertable cardiac monitors in the market. Future Cardia has elected to keep the alerts and notifications inactive for the time being until its utility is proved effective for patients and clinicians (Figure 1). Figure 1 An Acute HF Induction Recording Using Future Cardia Device at Duke University As heart failure (HF) progresses, we can observe changes in QRS, which will allow us to measure changes in electromechanical activation time (EMAT) and left ventricular systolic time (LVST). In addition, we can also observe S1, S2, S3, and S4 in real time. (A) Pre-HF induction. (B) Post-HF induction. Limitation of heart sound auscultation is time, location, and user dependent. For example, auscultation of pathologic heart sound (S3) in HF is time consuming and not always present. Furthermore, some physicians simply miss it because of its infrequent nature. Future Cardia mitigates this limitation by recording ECG and heart sounds throughout the day for 2 years. This method allows Future Cardia to count the number of S3 episodes and compare it daily, weekly, and monthly for the duration of the device. The advantage of the subcutaneous approach is that it eliminates user variabilities and ensures precise and continuous acquisition of data. Future Cardia uses a traditional signal processing to extract amplitude and frequency changes in ECG and heart sounds (S1, S2, S3, S4). And because we acquire stable and consistent ECG and heart-sound data from 1 exact location, we can calculate changes in electromechanical activation time (EMAT), left ventricular systolic time, cardiac output, contractility, and activity-posture over a long period of time. After 2 years of intensive research and development, we have built a multisensor subcutaneous insertable cardiac monitor with superior wireless technology for better connectivity and longer vector for clearer ECG to reduce oversensing and undersensing problems. Our first-in-men implant will start in Q3/Q4 2023 to observe patients with atrial fibrillation and HF. And we will leverage predicate devices (Medtronic LINQ II, Boston Scientific LUX DX) in the 510K space, with existing reimbursement to enter the U.S. market for 2024.