I would say that the Zoll LifeVest is a Class III device due to the fact that it has a high amount of risk. If the device fails there is the possibility of sudden cardiac death. I would think that the most difficult part of getting approval would be the vest incorrectly measuring heart rate and giving a shock or vest malfunction and not being able to give the shock a patient needs. It seems as though there are enough safety precautions and backups on the vest to prevent an unwanted treatment, such as the alarm and button to shut it off.

Being that this post started about a year ago I found that patients have started using this device. The FDA game Premarket Approval and works with Zoll to address the concerns of possible failure. There was one death due to failure of the vest in November of 2017, however it was after the device displayed a service code which they tell users to contact Zoll immediately for service and a replacement if needed.

I do believe that this is a marketable device as long as the amount of people that are not candidates for/refuse the implantable cardioverter-defibrillators is substantial. Someone mentioned the HeartStart FR3 as a competitor to the Zoll LifeVest. While they do achieve the same goal I think are different because the LifeVest is automatic, after it senses the problem the alarm goes off and it delivers the treatment. The HeartStart FR3 is more of a portable defibrillator. It needs to be placed and set off to deliver the shock. This device can be used by anyone but is suggested to be put in ambulances and used by professionals when the LifeVest is to be worn and used anytime and anywhere.

References
https://www.fda.gov/safety/medwatch/safetyinformation/safetyalertsforhumanmedicalproducts/ucm592710.htm

https://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfpma/pma.cfm?id=P010030S056

http://www.heart.org/idc/groups/heart-public/@wcm/@hcm/documents/downloadable/ucm_300340.pdf