Archive for March, 2023

The main reason for all those jitters, we cardiologists, get every time we puncture the IAS is not due to a lack of expertise and experience perse. There are two more reasons. First and foremost, it is still largely a blind* procedure. (Even in this era, where drones with HD vision shoot one-meter targets from a 1000 KM range )  *TEE and ICE are there, but they rarely give enough confidence. 

The second reason is more important and is rectifiable. It is the perception error in our anatomical cognition, that is fed to us from first-year medical school. We are made to believe (at least to people like me ) The right atrium is aligned like a perfect box on the right side, sharing a wall called IAS, and the left atrium is obediently placed left of the right atrium. Please realize the heart is such a complex twisted single tubular organ, the venous end, in a stunning backward loop brings the LA  most superior and posterior to the right atrium overriding the left-right relationship.) 

The right atrial terrain and IAS with multiple bumps and holes. Note the true IAS constitutes only 20% . This is where our punctures need to be.

Development of IAS 

IAS development and the number of layers it sandwiches, the tortuous tracts of PFOs, the fossas, and its variable limbus is a big topic. Further, It is worth recalling, the true IAS hardly forms 20 % of the area of the interatrial contact surface.

(the differential regression of sinus venous,  along with infolding of the roof and along with curious septum spurium , the ubiquitous septum secundum make the texture, area & shape of IAS, a fascinating creation, though troublesome for the cardiologists ! ) Whoever named that part of vanishing  IAS  as spurious, (I think it is Henrry Grey ) has much fore-vision.


Forget about all this. Tell me how to cross this difficult terrain 

Coming to the real world of interventions,  we need to do targeted punctures in different spots of IAS in various interventions.(Mitra clips, LAA device, PTMC, PV abaltions, Mitral paravalvular leaks , TMVR etc) This has made this task even more tricky. Experts are always there to help us out. Like swimming, it can never be learned in books.

This 19-minute clip from. Seoul, South Korea is an excellent resource. Thanks to  Dr. Sang Weon Park 


Along with sound anatomical knowledge, improved hardware, and imaging like deflectable sheaths, TEEs, and ICE (intracardiac echo ), let us hope, it will soon become an easier task for everyone.

Final message

 Understanding “attitudinal cardiac anatomy” with fluoroscopic overlay is the key. Again, it needs to be stressed, “Right is not right, and left is not left” when it comes to true atrial geo position. LA is equally posterior, superior, and of course to the left of RA. Some of my colleagues are blessed with a special 3-dimensional skillset  (Inherited ?) I failed miserably to understand this, till very late. I am sure, Dr. Park’s video will help all our youngsters to cross the difficult gateway to the left side of the heart. 


One more good read

B. O’Brien et al. / International Journal of Cardiology 233 (2017) 12–22


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Fibrillation is a continuous, chaotic muscular activity. In AF, atrial muscle is expected to lose all coordinated contractions with fibrillatory waves replacing P waves. Have you ever spotted a suspicious  P wave in a strip of otherwise explicit AF?  If not, this write-up is not for you.

An evolving rare theme in Atrial fibrillation 

Have a look at this ECG 

Here is an ECG, that was reported as AF, multiple APDs, or Possible AF, Pre AF. I suggested the term AF in transition. While few agreed, many said it is a straightforward SR with APDs, making it appear irregular RR. 

But, the fact of the matter is, ECGs are insensitive to pick all fibrillatory wavelets. It can selectively pick a few coarse F waves and make them appear as P. I think, in this era, we should not diagnose AF by proxy, ie absent P waves. Rather, we need to look actively for fibrillatory wavelets. (Imagine all sinus arrests will qualify for f fine AF with a slow ventricular rate  is it not ?)

The semantics of AF nomenclature is long. Intermittent AF, and paroxysmal AF, are well-known entities. It is now clear, AF can occur for a few seconds and vanish too. It seems we need to play some more linguistics with the most common cardiac arrhythmia. (Non-sustained AF,  evanescent AF, etc )

Some thoughts on this hide &  seek P waves 

  • Apart from the conventional list of absent P waves, one more example is repetitive APD can stun the atrial muscle for a few moments or minutes.
  • Then, we always have the issue( eluded to earlier) of sinus node paralysis, with irregular junctional escape mimicking AF.
  • Amiodarone can reduce fibrillatory rate, and (AF cycle length ?) Coarse F waves slow and stabilize it to mimic an organized P wave
  • P on Ta waves (Like R on T ) can trigger a nonsustained AF for a few moments in a functional manner without real pathology in atria.


A funny memory  brings back an EP truth 

During our student days, my Professor used to trap us with this question, Which atria would fibrillate in mitral stenosis?  Many of us blinked, and few had no hesitation to say, it is the LA that fibrillates. Now, after 50 years we realize, how fascinating the secrets AF has unfolded. Some organized activities are often in the right atrium, even as LA begins the process of AF. It is possible it may take variable time for the left atrial chaos to spill over to RA*. During these electrical uncertain times, some of the right atrial P wave activity refuses to die down.  Even more dramatic one Atrium alone can permanently fibrillate and others completely insulated by blocking the signal in the Interatrial pathways. (Ref 1 ) Ndrepepa’s paper in the JCE 2000)

Final message.

True scientists rarely bother about questioning a dictum. The concept of non-uniform AF was first thought of by (Schrmp et al Ref 2) 100 years ago in 1920, and Zipes(Ref 3) hypothesized this in 1973. now, in the Year 2000, Ndrepepa confirmed it with EP studies. The spotting of occasional  P waves is not forbidden in AF if the contralateral atria decide to block the incoming AF signals and keep generating their own P waves 

Young EP guys, now that you are equipped with the sophisticated intracardiac GPS,  please pursue this provocation in AF. One more piece of evidence we observed in the echo lab. Try to look at Tricuspid doppler A velocity waves in full-blown AF patients. You can see the surprise for yourself. This is very good research work to do. This is one of the ideas I gave to my fellows at MMC. Now, it is free for all to pursue whoever wants to do this. The clinical implication* will follow.

* A lingering query, how common is RAA clot in mitral stenosis with AF and the possible threat of pulmonary embolism?


1,Ndrepepa G, Zrenner B, Schreieck J, Karch MR, Schneider MA, Schömig A, Schmitt C. Left atrial fibrillation with regular right atrial activation and a single left-to-right electrical interatrial connection: multisite mapping of dissimilar atrial rhythms. J Cardiovasc Electrophysiol. 2000 May;11(5):587-92

2.Zipes DP. DeJoseph RL: Dissimilar atrial rhythms in man and dog. AmJCardioi I973;32:6l8-628.

3.Schrumpf P: De 1’interference de deux rythmes sinusaux. Preuve  du dualisme du nodule de Keilh. Arch Mai Qwur 1920;l3:168-173


The snapshot from Ref 1 . The term Isolated AF confined to one atrium could be a rare event, but, no one can deny we have plenty to learn from them


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