Explained: The Power of a Wearable Cardioverter Defibrillator

Defibrillation is the only therapy to treat someone in cardiac arrest. Every minute that a person in Sudden Cardiac Arrest (SCA) does not receive defibrillation, their chances of survival drop by 7-10%, making rapid defibrillation imperative for survival and one of the key steps in saving a life from SCA. Wearable Cardioverter Defibrillators (WCDs), a wearable defibrillator, are a newer type of medical device that help ensure that people at high risk of experiencing SCA have an essential layer of protection against a deadly event.

What is a Wearable Defibrillator? 

Wearable cardioverter defibrillators (WCD) are battery-powered wearable devices that have defibrillators built into them. WCDs are worn by someone at risk of sudden cardiac death (SCD). They automatically detect certain irregular and life-threatening heartbeats, known as arrhythmias. Then, they can automatically deliver a treatment shock to correct the arrhythmia and restore a normal rhythm to the heart. 

WCDs consist of:

• A garment (vest), worn directly against the skin under clothing
• Two defibrillator pads that are placed vertically across the wearer’s back 
• An electrode belt, which goes across the wearer’s rib cage and both detects life-threatening heart rhythms, and delivers any needed lifesaving shock
• A monitor, which can be worn around the waist or with a shoulder strap, and continuously records the person’s heart rate. 

The devices perform similar actions to treat ventricular tachycardia (VT) or ventricular fibrillation (VF) as an automated external defibrillator (AED). However, this device is different from an AED. Although AEDs are automatic, they do need a willing bystander to perform certain functions, such as powering them on, placing pads on the patient’s chest, delivering a shock (if it is a semi-automatic device), and making sure it is safe to deliver a shock to the patient.  

Learn more about How to Use an AED

A WCD does not require assistance from a bystander. The device continuously monitors the patient’s heart rate and delivers a treatment shock if needed, typically within one minute. The device is designed to work 24 hours a day, even when the person is alone or asleep. 

How does a WCD Work?

WCDs are designed to be worn at all times, other than while bathing or swimming, and can be concealed beneath clothes. When in use, WCDs are worn directly against the patient’s skin. Heart rate and rhythm data are sent to the monitor, which can automatically detect a life-threatening change. If this occurs, an alert will sound or the vest will vibrate to determine if the patient is conscious. If the person is conscious, a SCA has not occurred and a shock is not needed, so the patient can turn off the alarm and a shock will not be delivered.  

If the patient is not conscious and unresponsive, gel will be released over the electrodes contained within the vest and a treatment shock will be delivered. The entire process, from the beginning of the SCA event, to the delivery of the first shock, usually takes around one minute. If the first shock does not restore a normal heartbeat, the WCD will deliver another one. This process will repeat for up to five shocks in total.

Benefits of a Wearable Defibrillator

The greatest benefit of a WCD is that it constantly monitors the heart’s rhythm and can intercede with a corrective shock nearly immediately, without bystander assistance. It’s quite common that people don’t feel any signs or symptoms of a rhythm disorder at all. Without a WCD, the patient might not even know they are experiencing an arrhythmia until it’s too late. Without any physical warnings, a patient’s condition could worsen, and they could go unconscious before being able to call for help.

With a WCD, the patient doesn’t need to wait for rescuers to arrive with an AED to receive a lifesaving shock. The device is constantly ready to deploy a corrective shock, so there’s no time wasted waiting for the delivery of an AED.

Patients may be prescribed a WCD due to a variety of circumstances, including:

• people with reduced heart function after a heart attack or people who are recovering their strength after a debilitating cardiac injury
• before or after someone has a cardiac stent placed
• people who are unable to have an implantable cardio-defibrillator (ICD) surgically placed, or are waiting to have one installed
• people with a history of cardiomyopathy or heart failure
• people with high risk of near term cardiac death
• children with ventricular heart rhythm disorders that put them at risk for sudden cardiac death
• people currently discussing more long-term options with their care team who need a safeguard in place in the meantime

Drawbacks of a Wearable Defibrillator

The American Heart Association put out a science advisory on WCDs in 2016, stating,

“Providers need to keep many factors in mind and to continuously weigh the individual risks and benefits of ICD placement and WCDs in their patients. Furthermore, discussion of patient preferences is an integral part of patient care and WCD therapy. Further research, including randomized trials, is needed to better inform the optimal use of WCD therapy.”

Some of those important factors to keep in mind include:

• A high price point. Even with insurance coverage, WCDs may be expensive.
• Possible mishaps. Like any medical device, WCDs have the potential to malfunction, which could be life-threatening.
• Discomfort. Some patients have reported that they can feel bulky and uncomfortable to wear. Irritations like skin rashes, itchiness, and sleep disruption can occur. And some patients have reported difficulty getting a WCD to fit properly.
• Causing stress. Immediate attention is needed if and when the various device alarms become activated, which can feel burdensome or provoke anxiety.

Conclusion

For some patients, an ICD will be the right long-term remedy for a high risk of SCD. But, not for all. Patients with other medical issues, heart conditions, inadequate insurance, or infection may not be eligible for an ICD. WCDs can be a non-invasive alternative option for the short or long term.

Researchers have been studying WCDs in recent years and there are currently some trials ongoing. But so far, the only WCDs approved by the FDA for use in the United States are the Zoll LifeVest and the ASSURE System. As researchers and engineers continue refining WCDs, we are hopeful these devices will only save more and more lives.

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