Help on CRT-D report comment

I see my EP every 3 months and my appt was last week.  They did some adjusting, but no ventricular arrhythmias.

They uploaded my report to my portal....a first!  They mentioned I am have tachycardia and pvcs, which I'm aware of between symptoms and my Apple watch.  

I have an Abbott CRT-D.  There is an alert saying "V Sense Amplitude below 4.0 mV.  

Can anybody explain the alert to me?  It actually says 2 alerts on the report but it only states the above.  At says to see highlighted areas but nothing is highlight on the portal copy.  Thanks!



by Lavender - 2023-12-04 08:26:47

I looked on your manufacturer's website. It says:

Customer Service For Patients And Caregivers

These materials are not intended to replace your doctor’s advice or information. For any questions or concerns you may have regarding the medical procedures, devices and/or your personal health, please discuss these with your physician.

Cardiac Rhythm Management Products (Pacemakers, ICDs, ICMs, CRT-Ds, CRT-Ps)

Product Support

Email us at

Call us at (800) 722-3774

So, ask your pacemaker team first and then if they can't help, call or email ABBOTT. 

I have called my pacemaker manufacturer before and received answers but I would start with the team who put that report into your portal. 💕

Nice to hear from you

by Gemita - 2023-12-05 04:58:16

Hello Islandgirl, I had an eye clinic appointment yesterday, but saw your message.  How are you?  Have you received any answers from your cardiac team about the alert?

It is difficult to know how to answer your question because we do not know what parameters have been set up in your ICD to keep you safe from dangerous ventricular arrhythmias like VT or VF.  No doubt this is the reason for your 4 mV alert. 

There doesn’t appear to be any current guideline-based recommendation of a minimum R wave amplitude at implant for patients receiving an ICD or CRT-D.  However, it would appear that the safe R wave amplitude setting  in patients with ICDs is more than 5-7 mV. With an R wave amplitude of less than 2.5 mV for example, there could be a significant risk of under sensing during Ventricular Fibrillation which clearly would be life threatening for you.  Undersensing VF however, is extremely rare when intrinsic R waves are more than 5 mV in sinus rhythm (see link).

The best thing is to ask your doctors what the significance of this drop means for you personally and what might be causing it although I note you received some settings adjustments, so this has probably been fixed?

Sensing is clearly complex and not something that I fully understand, but I suspect the answer is that while 4 mV is clearly not ideal, it is perhaps not critical at this stage and they will be watching you very closely from now on to see whether the R wave amplitude remains in a safe range for you.  

The R wave represents the electrical stimulus as it passes through the main portion of the ventricular walls. The wall of the ventricles are very thick due to the amount of work they have to do and, consequently, more voltage is required.

Hope otherwise you are doing better?

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