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Can Smart Wearables Detect Heart Conditions Such As Atrial Fibrillation (AF)?

  • 12 Aug 2022
  • 3 mins

There is an increased use of wearables for cardiovascular monitoring outside the classic clinical settings. Our cardiologist Dr. Kelvin Wong talks about the medical use of wearables for arrhythmia detection and discusses if they will take over conventional screening tools used in clinics.


Silent AF

AF is characterized by rapid and irregular heart rhythm. It is the most common heart rhythm disorder in the population. Patients with AF may have an increased risk of stroke, heart failure and mortality1.

“AF is an aging disease and is projected to become an epidemic in the near future. Recent screening programs are picking up increased incidence of AF in the ageing population,” Dr. Wong said.

AF tends to be a progressive disease. It may start as paroxysmal AF which affects patient now and again, gradually increasing in frequency and duration until it becomes persistent AF. “It may be silent in up to 30% of patients, i.e. patients are unaware of the AF episodes. By the time they are diagnosed and see us (specialists), they tend to be at the later stages and the treatment options may be limited.


Screening for AF

Hence, it is important for screening to be done for early detection of AF. Early detection and treatment of AF has the potential to improve long term outcomes for patients. ”

“There is opportunistic screening, whereby patients, especially over 65 years old, attending the clinic for consultation for any issues are screened for AF, such as pulse taking or using other screening tools (see later). Systematic screening is also recommended for those who are age 75 years and above. These people can have 12 lead ECG or even more prolonged ECG monitoring to try and detect AF.” he advised.

There are increased number of devices/tools used to diagnose and monitor AF. Designs and functionality have also evolved in recent years.

“The conventional Holter monitor involves several electrodes and electrical leads attached to the body. Patients are advised not to shower during the period of monitoring. Now, there are more convenient devices which are attached to patient by a single patch without wires. Patients are able to shower and potentially can be monitored for up to two weeks.”

In addition to medical grade ECG monitor patch/devices, Dr. Wong shared that there are also various smart phone applications and devices for mass market consumers that can detect AF


Design Principles Behind Wearables for Medical Use

Today, consumer-grade smart watches and wristbands have high processing power and numerous sophisticated sensors that record physical activity and can be used to monitor our heart health anytime, anywhere. In fact, many specialists are recommending the use of these smart wearables as an adjunct to monitor and even diagnose patients with heart rhythm disorders.

These wearables abide by the following basic principles to support their applications in cardiovascular disease detection, prevention, and management, according to Dr. Wong.

“The basic principle is that physical activity and high heart rates are often inversely correlated to adverse cardiovascular outcomes,” he said. This is based on previous studies showing that people with higher level of physical activity is often associated with fewer cardiovascular disease (CVD) events. A high resting heart rate may potentially be a marker of risk in pulmonary exercise testing (PET).

“In general, the wearables incorporate a triaxial accelerometer, which measures the linear acceleration along three different planes. Often, there is also a gyroscope that measures angular motion, the global positioning system (GPS) and barometers, allowing for more accurate assessment of physical activity and positioning,” he explained.

Next is the heart rate and heart rhythm sensors.

“Another principle is that high heart rate during recovery after exercise also correlates to the risk of adverse cardiovascular events in both healthy individuals and those with heart failure. This can be easily measured through wearables such as smart watches,” he added.

These wearables use the analysis of photoplethysmography (PPG) that measures changes in microvascular blood volume that translates into pulse waves. “The analysis of the pulse wave will show if there’s arrhythmia or normal heart rhythm. In addition, several of these wearables are also able to generate a single lead ECG which can really help with the diagnosis of cardiac arrhythmias.”

“Nowadays, there are several devices which is FDA approved for the detection of AF. The Apple Watch, Samsung watch, Huawei watch and Fitbit Sense can perform heart rate monitoring and record single lead ECG.”


Clinical Decision Making Using Wearable Device Recording

In an Apple funded study2 where almost half a million people participated in over an 8-month period, 0.5 per cent of the participants received a notification of an irregular pulse. Among those notified, three per cent were over sixty-five years old. However, only 450 returned the ECG patches and of these, AF was identified in 153 (34 per cent of participants).

The overall yield of 34 per cent among those who were notified was clinically relevant and the study concluded that wearable devices can indeed detect irregular pulses.

Fuelled by the hype of trendy consumer-driven smart health devices, consumers are rapidly adopting wearables to assist in the monitoring and screening their own health. As sensors and processing technologies continue to evolve, wearables could gain complex functions and be integrated into cardiovascular practice.

“Physicians are now more comfortable diagnosing AF based on a single-lead ECG, and this is likely to evolve over time as more physicians get accustomed to using wearables for screening and detection,” he concluded


Proactive Management for early detected AF

“AF may be managed according to the “ABC algorithm” as proposed by the European Society of Cardiology.” said Dr. Wong.

“’A’ stands for Anticoagulation to prevent a stroke, ‘B’ stands for Better symptom control and ‘C’, is for managing Cardiovascular risk factors, such as hypertension, Diabetes Mellitus, etc.

With such a simple and structured management for AF, patients who are diagnosed early can then be proactively managed to avoid complications such as stroke and heart failure, leading to improved morbidity and mortality in the long term.
 



Reference
1Martinez C, Katholing A, Freedman SB. Adverse prognosis of incidentally detected ambulatory atrial fibrillation. A cohort study. Thromb Haemost. 2014 Aug;112(2):276-86. doi: 10.1160/TH4-04-0383. Epub 2014 Jun 18. PMID: 24953051; PMCID: PMC6374983.


2https://www.nejm.org/doi/full/10.1056/nejmoa1901183#article_citing_articles
Contributed by

Dr. Kelvin Wong
Cardiologist
Farrer Park Hospital