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Athar Sadiq matharsadiq@gmail.com — 10/15/2026
— “What is unusual here?” —
Dear Respected Prof. Grauer. I hope you are doing well.
I would greatly appreciate your expert opinion on the attached ECG, particularly regarding the underlying rhythm.
The patient has diabetes mellitus, hypertension, and known coronary artery disease, with previous PCI involving three drug-eluting stents in 2022 and 2024. LV systolic function is preserved, with Grade II diastolic dysfunction. The patient is clinically stable without heart failure symptoms but has limited mobility. The referral to me was for preoperative cardiac assessment before knee replacement and radiofrequency ablation for knee pain.
ECG showed right axis deviation consistent with left posterior fascicular block (LPFB), associated with poor R-wave progression.
My main concern is the rhythm, which is difficult to interpret, and the underlying conduction pattern is unclear.
I would be grateful for your interpretation, particularly regarding the atrioventricular conduction pattern.
Please feel free to discuss this ECG on your ECG blog if you find it interesting.
Thank you very much for your time and expertise.
Kind regards — M Athar Sadiq
Consultant Interventional Cardiologist
MY THOUGHTS and REPLY to M Athar Sadiq:
This is a very challenging tracing — that I definitely want to use as a case for my ECG Blog. I will probably publish it in about a month. I’ll be happy to acknowledge you — as M Athar Sadiq (from Muscat, Oman) if you like — or the case can be anonymous. JUST LET ME KNOW. In any case — I’ll let you know when I publish it!
I’ll add that I shared this tracing with Dr. Willy Frick — who is a cardiologist who also often writes for Dr. Smith’s ECG Blog (as I do). I believe he shares my opinion of this tracing — which I describe below.
I agree with your interpretation of the 12-lead in this patient with known coronary disease, as well as evidence of impaired conduction with the LPHB. I see no acute ST-T wave changes.
What is so interesting about this case — is the total variability and unpredictability of PR and R-R intervals! I have seen cases of “vagotonic block” (See my ECG Blog #61) — in which because of intense vagal tone (from vomiting, pain, exertion) — there can be surprising variability in PR, R-R intervals, as well as variable forms of AV block. But as I understand — this was a preop ECG in a patient not under any specific stressors.
https://www.ekgblog.com/2013/02/ecg-interpretation-review-61-av-block.html
I see NO repetition of PR intervals on your patient’s ECG! This is unusual. Almost always with simple AV Wenckebach — the 1st beat in most groups is preceded by a constant PR interval. But as you can see from the measurement figure that I have attached — ALL PR intervals are different! And all R-R intervals are different — which is NOT what I’d expect if there were junctional escape beats (typically — the preceding R-R interval of junctional escape beats is constant! (but it is totally variable here).
The most logical way for me to explain this — is that there is autonomic influence occurring throughout the tracing despite no obvious vasovagal stimulus! Although impossible to know for certain (because of the complete variability in PR and R-R intervals) — I think it most logical to postulate that there is AV Wenckebach (as I show on my attached laddergram) — with the variation in PR and R-R intervals being caused by alteration of underlying autonomic tone. Given this patient’s known history of significant coronary disease and conduction defect ( = the LPHB) — and perhaps older age? (How OLD is this patient?) — these factors may predispose to variation (instability) of underlying vasovagal tone. That said — I cannot recall seeing any other case showing this much unpredictable variability in intervals.
Bottom Line — I believe the reason there are more “on time” P waves than QRS complexes — is that there is 2nd-degree AV block of the AV Wenckebach (Mobitz I) type plus underlying coronary and conduction system disease producing the variation in autonomic tone. That said — there seems to be NO higher-grade AV block, so it should be fine to go ahead with the surgery.
I hope the above is helpful to you! — : ) Ken
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MY QUESTIONS TO WILLY FRICK
Hi Willy. I’ve just spent the past hour-plus “playing” with your ECG Toolkit. I’ve saved 2 tracings on a VERY interesting case (that I’ll also pick your brain on) — sent to me from an interventional cardiologist from Oman. I was going to use this as a case on my ECG Blog.
Here is the history: The patient has diabetes mellitus, hypertension, and known coronary artery disease, with previous PCI involving three drug-eluting stents in 2022 and 2024. LV systolic function is preserved, with Grade II diastolic dysfunction. The patient is clinically stable without heart failure symptoms but has limited mobility. The referral to me was for preoperative cardiac assessment before knee replacement. ECG showed right axis deviation consistent with left posterior fascicular block (LPFB), associated with poor R-wave progression. My main concern is the rhythm, which is difficult to interpret, and the underlying conduction pattern is unclear.
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My “Take” (as per the attached laddergram) — is that this is some kind of 2nd-degree Mobitz I ( = AV Wenckebach) tracing, as the P wave rhythm is fairly (not completely) regular — and there are more QRS complexes than P waves ==> 2nd-degree AV block. The fascinating part is that ALL of the PR intervals and all of the R-R intervals vary! (sometimes not by much — but I believe the variability phenomenon is real! The only way I can explain this is that there must be variation in autonomic tone! The patient presumably is an older adult (age not given) — with a history of coronary disease and assuming no RVH … what looks like LPHB on his 12-lead (therefore conduction baseline conduction system abnormalities).
There are of course a bunch of other potential laddergram explanations for this … (ie, Could be some form of dual level AV block — there could be junctional escape beats — although against this as a sole explanation is the fact that those P waves with a real long interval that look like they are not conducting are NOT associated with a constant R-R interval as is usually seen with junctional escape. And the reason I really think all QRS complexes are more likely to be conducted — is that despite “on time” P waves — R-R intervals are occurring “earlier-than-expected. What do you think? (I will write you now my feedback on using your EKG Toolkit for this case —
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