Wearable cardioverter defibrillator

Wearable cardioverter defibrillator

A wearable cardioverter defibrillator (WCD) is a device worn by patients who are at risk for sudden cardiac arrest (SCA). A WCD allows physicians time to assess for their patient's arrhythmic risk and make appropriate plans.

A WCD is lightweight and easy to wear. The WCD is non-invasive and consists of two main components – a garment and a monitor. The garment, worn under the clothing, detects arrhythmias and delivers treatment shocks. The monitor is worn around the waist or from a shoulder strap and records the arrhythmias. The WCD continuously monitors the patient’s heart and, if a life-threatening heart rhythm is detected, it can deliver a treatment shock to restore normal heart rhythm. The entire event, from detecting a life-threatening arrhythmia to automatically delivering a treatment shock, usually occurs in less than a minute. Timely defibrillation is the single most important factor in saving an SCA victim’s life. A treatment shock must be delivered within a few minutes after an event to be effective; with each passing minute, a patient’s chances of survival drops 10 percent. The WCD does not require bystander intervention and has a 98 percent first treatment shock success rate for resuscitating patients from SCA.

The WCD may be prescribed for patients at high risk of SCA following a heart attack, before or after bypass surgery or stent placement, as well as for those with cardiomyopathy or congestive heart failure that places them at particular risk.

The WCD is a therapeutic option, listed along with implantable cardioverter defibrillators (ICDs), in the ACC/AHA/ESC Guidelines for the Management of Patients with Ventricular Arrhythmias and the Prevention of Sudden Cardiac Death. It is also a Class I recommendation in the International Society for Heart and Lung Transplantation Guidelines for the Care of Cardiac Transplant Candidates.

History

In 1986, M. Stephen Heilman and Larry Bowling founded Lifecor and along with a team of former Intec employees who developed the first implantable cardioverter defibrillator (ICD) began development of the WCD. The WCD was extensively tested for three years in 17 major medical centers across the United States and Europe. The clinical data collected from those trials allowed Lifecor to obtain FDA approval for use of the WCD in the United States.

In 2001, the FDA approved the LifeVest wearable cardioverter defibrillator. The Lifecor business was acquired by ZOLL Medical Corporation in 2006 and Asahi Kasei in 2012. The LifeVest is currently marketed in the United States, Europe, and Israel.

According to ZOLL, the company that manufactures the LifeVest, the LifeVest has been prescribed to more than 100,000 patients.

Insurance coverage in the United States

The WCD is covered by most health plans in the United States, including commercial, state, and federal plans as Durable Medical Equipment (DME) for those patients at high risk of cardiac arrest, including:

• Primary prevention [Ejection fraction (EF) ≤35% and Myocardial Infarction (MI), Non Ischemic Cardiomyopathy (NICM), or other Dilated Cardiomyopathy (DCM)] including:
  • After recent MI (Coverage during the 40-day ICD waiting period)
  • Before and immediately after CABG or PTCA (Coverage during the 90-day ICD waiting period)
  • Listed for cardiac transplant
  • Recently diagnosed NICM (Coverage during the three-to-nine month ICD waiting period)
  • New York Heart Association (NYHA) Class IV heart failure
  • Terminal disease with life expectancy of less than one year
• ICD indications when patient condition delays or prohibits ICD implantation
• ICD explantation

Assessment of usefulness

The wearable cardioverter defibrillator is an option for patients who are at risk for sudden cardiac arrest (SCA) and are not candidates for or who refuse an implantable defibrillator. Numerous protocols have been published for the management of patients that are at risk for SCA. The Heart Rhythm Society (HRS) SCD Primary Prevention Protocol is independent medical education developed by physicians from HRS to serve as a tool for Cardiologists (general and specialty) and other Healthcare professionals regarding identification of patients that should be screened for SCD risk, recommended patient treatment options and considerations, and timing for referral to an Electrophysiologist. The HRS SCD Screening Protocol includes a recommendation for consideration of a wearable cardioverter defibrillator as part of the treatment path for patients at risk of SCD.

Controversy

Not all cardiologists agree that a wearable cardioverter defibrillator is medically beneficial or necessary, compared to standard medical treatment for patients at risk for SCA^[1]. There have been reports of the WCD delivering unwanted and/or inappropriate treatment shocks (sometimes attributed to user error on the part of the patient)^[2]. In January 2018, the FDA issued a Safety Alert^[3] related to a known malfunction in some units which could prevent the WCD from delivering a treatment shock. Zoll had previously issued (in September 2017) a recall of the WCD in an attempt to address the issue^[4], instructing users to return the device for replacement if the device displayed a specific error message indicating the malfunction. Copies of the alert were included in all subsequent shipments of the device.

The results of a randomized controlled trial were presented at the American College of Cardiology’s 67th Annual Scientific Session (in the spring of 2018). The study results apparently did not show sufficient evidence to show the WCD reduced sudden cardiac arrest in post-heart attack patients. In the group that wore the WCD, 1.6% died from sudden cardiac arrest, and in the group that didn’t wear the WCD, 2.4% died, which is arguably not a statistically significant difference.^[5][6]

References

• Reek et al., “Clinical Efficacy of the Wearable Defibrillator in Acutely Terminating Episodes of Ventricular Fibrillation Using Biphasic Shocks,” PACE, 2002, 25 (4, part II):577.
• Wase, “Wearable Defibrillators: A New Tool in the Management of Ventricular Tachycardia/Ventricular Fibrillation,” EP Lab Digest, 2005; 12:22–24
• Feldman et al., “Use of a Wearable Defibrillator in Terminating Tachyarrhythmias in Patients at High Risk for Sudden Death: Results of WEARIT/BIROAD”, PACE, 2004, 27:4 l–9.
• Reek et al., “Clinical Efficacy of the Wearable Defibrillator in Acutely Terminating Episodes of Ventricular Fibrillation Using Biphasic Shocks,” PACE, 2002, 25(4, part II):577.
• Keller et al., “Using the LifeVest as a Bridge to ICD implantation: One Urban Community Hospital’s Experience,” EP Lab Digest, 2008; Vol. 8, Issue 8.
• Elrod, “Measuring the Effectiveness of Wearable Defibrillators and Implantable Devices: EP Lab Digest Speaks with Jeffrey Olgin, MD about the VEST/PREDICTS study,” EP Lab Digest, 2008; Vol. 8, Issue 7.

Specific

External links

• The Zoll LifeVest
• Heart Rhythm Society (HRS) SCD Primary Prevention Protocol