ICD/CRT-D: Inappropriate shocks

  • by BarbD
  • 2018-10-02 17:35:20
  • ICDs

Does anyone know the real statistics on how many people get inappropriate shocks from their ICD/CRT-D?   I’ve been reading a LOT of stories on here where people are getting multiple inappropriate shocks and the idea of that is just terrifying to me.  Is there anything I can do or should ask about in order to minimize this risk?  I’ve read something about SmartShock Technology – does anyone have any experience with this? Do all CRT-D devices have this technology or do you have to ask for it?

I have been getting short runs of VTach as well as frequent PVCs.   Does the CRT-D just send out little pulses to stop the VT and PVCs?   I assume I would not feel those?   Or by pacing the 2 ventricles does the CRT-D eliminate the possibility of getting runs of VT and PVCs?   How do they program it to deliver an actual shock – when your heartrate gets above a certain number?



by Grateful Heart - 2018-10-02 21:56:55

Less than 1% have problems with their device, but that is TOTAL, not just inappropriate shocks.  So for most of us who find this site....we are definitely in the minority.

There are so many parameters to these devices.  The CRT-D will pace you faster than the VT in order to pace you out of VT or VF then drop back to normal pacing.  I feel it but I am told most do not feel it.  It is not painful, just feels like your heart is beating very fast (which it is).  This is also programmed according to what your heart needs.  

One of the leads for a CRT-D (the right ventricle lead) is the shocking lead as well as a pacing lead for the RV.  Your EP will program that lead and the other 2 for what is optimal for you and your condition.

Here's what I want to tell you:  I have had my device for 10 years.  I just had my 1st replacement 2 months ago.  I have never been shocked in those 10 years.  I have read your recent posts concerning all of this and I understand.  I did not know about this site 10 years ago, I wish I had.  I was on my own trying to figure this out.  I sought a 2nd opinion because I thought they must be wrong....they weren't, the 2nd EP confirmed it. 

The best advice is to find a doc that you trust.  Ask questions when you don't understand.  Learn all you can about your device and condition and then you can educate your family and friends and ease their mind as well.  It's a process and it takes time.

None of us have a crystal ball so we don't know if we will ever be shocked.  But find some solace if your were shocked....your CRT-D saved your life.

Feel free to private message me if you want....or ask your other questions here.  We've all been there.

Grateful Heart

Inappropriate shocks

by Sheela2288 - 2018-10-03 03:27:54

My doctor told me less than two percent, when it happened to me, I found the internet les than one percent. I was also told it was my fault because I passed out after returning home the day after placement, even though the Boston Scientific rep said it wasn’t right when I left. Took me three tries for my pacer. Hope this helps, I’m looking for answers myself. 

Inappropriate shocks

by Sheela2288 - 2018-10-03 03:31:23

My doctor told me less than two percent, when it happened to me, I found the internet less than one percent. I was also told it was my fault because I passed out after returning home the day after placement, even though the Boston Scientific rep said it wasn’t right when I left. Took me three tries for my pacer. Hope this helps, I’m looking for answers myself. 

Rates of ICD Shocks

by Heart-Rhythm-Center.com - 2018-10-03 10:00:00


Anywhere from 2-7% of patients receive "appropriate" shocks from their device within several years of implant. "Appropriate" means that the device delivered a therapy for a life threatening arrhythmia like ventricular tachycardia or ventricular fibrillation. Unfortunately, approximately 10-30% of shocks patients receive (depends on the study) may be "inappropriate"; that is, shocks delivered for arrrhythmias other than VT/VF such as atrial fibrillation. These inappropriate shocks do not mean your device is malfunctioning rather, these devices err on the side of caution if the automatic algorithms cannot tell what type of rhythm is causing your bottom chambers to be so fast. Your doctor can program your device to minimize these inappropriate therapies but there is no way to guarantee these programming changes will be completely effective. The most important thing to discuss with your doctor after a therapy is if the device is working properly. 

Hope that helps.

Huge Difference

by BarbD - 2018-10-03 13:09:40

Heart Rythm Center - are you saying 10-30% of people with ICDs receive inappropriate shocks??   That's a big difference from what the others have said. 

inappropriate shocks

by AgentX86 - 2018-10-03 14:08:25

No, the number was 2-7% of ICD patients received shocks but of that group, perhaps 10-30% were inappropriate. Using those statistics, the number of ICD patients receiving inappropriate shocks is between 0.2% and 2%. I'd be surprised if it were 2% but that's only a guess on my part.

They all say appropriate.....

by BOBTHOM - 2018-10-04 09:22:32

They are always appropriate shocks unless your leads have failed or you were involved in a major accident that damaged your device.  It's always about symantics.  Just like they are always "Successful", in reality that just means it successfully delivered the therapy, not that it actually resolved the event.

All the newer ICD/PaceMakers have similar technoligies the "SmartShock" may be a manufacturers specific implementation.

I have a basic ICD, it fired the first time 1 year and 1 week after implant, then 3 weeks after that, and then 7 months after that it fired 5 times within 15 minutes.  I feel all of the therapies, even those they tell me are not happening and are in my head.  But again, it's all in the symantics.

Asked my EP doc

by BarbD - 2018-10-04 14:08:56

I went ahead and asked my EP doc since there was such a variation in answers, and he said 8-10% of people with ICDs are shocked inappropriately.  I was really surprised and upset by that number.  If there are  roughly 800K people with ICDs in the US, that means up to 80,000 people may get inappropriate shocks?  That's a really scary number.

Even scarier...

by BOBTHOM - 2018-10-05 00:10:45

An even scarier number was when I saw that each time it fires it increases your risk for it firing again or death by 4X.  They have not been able to determine if that is because your heart function has weakened so much naturally or if their was damage caused by the shocks that reduced the function.  Either way, the less it goes off the better off you are!   But don't let that keep you up all night, it's there to do it's job and it's all we've got!

Another thing to worry about

by BarbD - 2018-10-05 14:53:23

BOBTHOM - the more I read the more anxious I get about getting a CRT-D.  So now we have to worry about getting inappropriate shocks, and then an increased risk of death if we do get 1 or more of these shocks.  I guess I'm just a big coward because I don't know how I would function if I was worried about this all the time.

And the alternative is......

by BOBTHOM - 2018-10-13 22:48:25

Nothing to worry about.  It sucks, it hurts, but, what's the alternative?   And remember, the majority of patients do NOT get inapproprate shocks.   And I believe the number of times an individual gets an inapproprate shock is low unless there is a lead issue.

It sucks, but it's a reality, part of life.

Here's an article with more details...

by BOBTHOM - 2018-10-22 21:43:28

Here's an article which can be found at:


ICD Shocks: What every physician needs to know.

Multiple clinical trials support the use of implantable cardioverter-defibrillators (ICDs) for prevention of sudden cardiac death in patients with heart failure (HF). Of the patients who have an ICD implanted for primary prevention, approximately 20% to 35% will experience an appropriate shock within 1 to 3 years of the implant. Another one third of patients will experience an inappropriate shock, defined as a shock delivered through the device for a non–life-threatening problem over the same time period.

Implantable cardioverter-defibrillators are implanted for both primary prevention of ventricular arrhythmic (VA) death in patient populations known to be at high risk for VA death or as secondary prevention for those who have already survived a VA event. Shocks delivered through these implanted devices to cardiovert ventricular tachycardia or to defibrillate ventricular fibrillation are, although lifesaving, painful, often poorly tolerated, and not without at least transient detrimental effect to the heart in terms of myocardial dysfunction.

Patients with significant left ventricular dysfunction at baseline (the vast majority of ICD patients) appear to be most at risk for developing acute myocardial dysfunction following shock. Repetitive shocks are associated with recurrent hospitalizations, anxiety, depression, and even posttraumatic stress disorder. Whether appropriate or inappropriate, an ICD shock is associated with a 2- to 5-fold increase in mortality, with the most common cause being progressive HF.


by BarbD - 2018-10-23 13:25:05

The statistics in this article are even worse than I thought - 1/3 of patients get an inappropriate shock within 1 to 3 years of implant??   The more I read the more scared I get.  Why are there so many variations in how often shocks occur?  Some people say 1%, my EP 8-10 % , now 33% !  How does a patient know whats true and what isn't so we can make an informed decision?  If the shock rate is so high and can cause physical as well as emotional damage and increased mortality, why aren't these devices fixed so they do not shock inappropriately at such a high rate??

You know you're wired when...

You take technology to heart.

Member Quotes

I am 100% pacemaker dependant and have been all my life. I try not to think about how a little metal box keeps me alive - it would drive me crazy. So I lead a very active life.