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In the modern era of cardiology,  PCI has become the single therapeutic modality  that determines the survival of both cardiologists and possibly their patients! The procedure is all about launching  a metal coil inside the coronary artery of a live beating heart.

Post dilatation vs pre dilatation

Millions of diseased and (not much) diseased coronary arteries are serviced (either re/deconstructed ) world-wide on a day-to-day basis.The benefits of the modality is  directly related to the wisdom of treating cardiologist and patient’s luck than the original severity of the disease. However, with greatly improved coronary  metallurgy , well assisted by drug coating technology and antiplatelet Industry , cardiac physicians believe they have reached the zenith of this procedure.

But the truth is , PCI still has many lingering issues regarding safety , efficacy and cost effectiveness.Early hazard in the form of acute stent thrombosis and sudden death is  a  reality. Blaming it on patients and their lesions ( condition of blood , gene included) , metal behavior is easy , but, wrong selection (Ignoring the option of CABG) and technical inadequacy of the procedure in the setting of complex  vessel wall disease (Hard calcium , deep tunnels , fissures , dead spaces ) is a major cause for concern.

Some personal thoughts about Post dilatation 

Lesion preparation , pre/per-dilatation /POTS , etc by itself  a big topic (which is not discussed here) Post dilatation after direct stenting is much more vital concept that determines not only the immediate but also the , Intermediate and long-term outcome.

Is routine post dilatation harmful ? or beneficial ?

This is the most tough question to answer . The answer is both Yes and No !  While it was thought useful and mandatory by some , the oppositeis also being adviced few  (CCL 2003 POSTIT trial)

What balloon pressure one should post dilate ? At what compliance ?  What is the Inflation time ? 

It’s akin to asking a musician  how to play a piano with fingers or guitar with various strings !

The effect of balloon pressures in the long term outcome. note both low and high pressure dilatation ( blue and orange worms ) hike the risk of restenosis. Too gentle is as dangerous as too harsh making post dilatation a secret and unique art.

 

Physics of post-dilatation  . . . again more questions !

  • Is there a role for compliant balloons ?
  • Does the compliance of balloon gets altered with hard lesions?
  • Is regional compliance matters ?
  • Can balloon exert same radial pressure all 360 degrees ?

It’s very likely, the moment balloon encounters an area of resistance it tends to avoid that area and would love to drag on to the area of least resistance and this is often diagonally opposite  zone of hard lesions ( if that segment  is free from hardness).Then , it  will face more stress and likely to bear the brunt of the force risking endothelial disruption . In other words , concentric hard lesions are more amenable for dilatation than patchy hard segments. While the physical forces vary in a stented vs non stented segment , the principle of dynamic forces on static tissue masses  with Intervening metal is too complex. (Mind you , we are not discussing  entirely different  issue , ie  thrombus laded ACS lesion , where displacement and pinching of of inter-strut thrombus into distal circualtion would cause no reflow!)

Impact of newer hardware

*Ablation catheters either rotational or Orbital can help , but must be done prior to stenting .Unfortunately , the hardness of a lesion is often realised  only after stenting

Is selective high pressure inflations over a particular struts possible ?

As of now , it would be challenging ,( if not outright impossible) .

Let us realise with all our intellect, complex PCI as a whole is taking an uncalculated risk  and leave the rest to GOD and DAPT !

Reference article 

In an elegant study of more than 90000 PCIs from Sweden and  Holland (Ref : Fröbert O, PLoS ONE. 2013 ) found routine post-dilatation pushes the harm curve little more than benefit.  The was more with both low and very high pressures .

The outcome of post-dilatation  in 900,00 PCIs 

 

Estimated cumulative event rates of stent thrombosis (Panel A) Restenosis (Panel B ) Cumulative death (Panel C) in relation to post-dilatation .Note the height of coronary Irony, Post dilatation Increase stent thrombosis and restenosis but saves life too !

 

The stunning truth revealed in this study was , early deaths were more common if  post dilatation was not done ! (Panel C in above figure) 

Role of Imaging in the decision-making prior to  Post dilatation

IVUS, OCT has been extensively used in recent times to diagnose suboptimal deployment and to asses lesion morphology.Though they are expected to improve the quality of angioplasty and hence the  outcome , the real world scenario is not really confirming our expectations.

This is because , eagle-eyed HD  imaging throws  more questions than answers in many and it converts coronary artery into a confused Pandora’s box . In fact these Imaging modalities has created fresh confusions , definitions and guidelines for malapposition under and over expansion , strut fracture, plaque prolapse, internal elastic laminar stress.( Still , I am not able eo understand  whats malapposition  vs  under deployed stent from a practical , pateint point of view !)

Is the Self expanding  stent is the answer ?

The conundrum of post dilatation might be cracked if the built-in radial force of self expanding stents is optimally utilised .This could be useful in some  tricky lesions when the vessel goes for progressive Glagovian  remodeling post PCI. The self expanding stent because of the stored potential energy keep hugging the vessel wall as it expands centrifugally.

Final Message

Post dilatation is neither a mandatory nor a sacred  protocol in cath lab. However , it would seem bulk of PCI’s still will require it . Its done judiciously with reference to   clinical setting, (ACS vs CCS) , type and location of lesion , stent characteristics etc .Most Importantly , the experience of the cardiologists counts ,and he or she will decide when, where, how much of post dilatation is required (or not required) .

Please remember , PCI as a whole (more so the Pre/ Post dilatation !)  is an art by itself. It’s never learnt in text books or even  watching  live work shops. Every young Cardiologists are enouraged to master the art of PCI ,  with a huge caveat . Always ensure  patient’s  Interest are placed first in every step forward. If you are not clear in comphrehending  “What is meant by true  patient’s Interest ? never Indulge in the procedure or call your mentor , if you have one !

Reference

1.Brodie BR1, Cooper C, Jones MCatheter Cardiovasc Interv. 2003 Jun;59(2):184-92. Is adjunctive balloon postdilatation necessary after coronary stent deployment? Final results from the POSTIT trial. Postdilatation Clinical Compartative Study (POSTIT) Investigators.

2.Fröbert O, Sarno G, James SK, Saleh N, Lagerqvist B. Effect of Stent Inflation Pressure and Post-Dilatation on the Outcome of Coronary Artery Intervention. A Report of More than 90 000 Stent Implantations. Agostoni P, ed. PLoS ONE. 2013;8(2):e56348. doi:10.1371/journal.pone.005634

3.Zhang Z-J, Marroquin OC, Stone RA, et al. Differential effects of post-dilation after stent deployment in patients presenting with and without acute myocardial infarction. American heart journal. 2010;160(5):979-986.e1. doi:10.1016/j.ahj.2010.07.007.

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Cardiologists at confused cross roads !

Perils of  limited Intellect & Infinite greed  

When not so appropriately trained cardiologists  do Inappropriate things “use becomes misuse” . . . then, it won’t take much time for science to become total abuse. That’s what happened with the murky world of coronary stents .No surprise, it’s time to firefight the healers instead of the disease !

Now ,Comes the ORBITA study . Yes , it looks like a God sent path breaking trial that spits some harsh truths not only in cardiology, but also in behavioral ethics .Let us not work over time and hunt for any non-existing loop holes in ORBITA. Even if it has few, it can be condoned for sure as we have essentially lived out of flawed science  for too long  Injuring many Innocent hearts !

ORBITA pci vs medical mangement drsvenkatesan courage bari2d ethics in stenting auc criteria inappropriate coronary stenting placebo effect of stenting acc aha esc guidelines chronic st

Yes , its enforced premature funeral  times for a wonderful technology !

GIF Image courtesy http://www.tenor.com

Meanwhile, let us pray for a selective resurrection of  stenting in chronic coronary syndromes  and stop behaving like lesser professionals !

Postample

Extremely  sorry . . . to  all those discerning academic folks , who are looking for a true scientific review of ORBITA , please look elsewhere !

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hole in heart asd vsd hole in raod potholes

https://timesofindia.indiatimes.com/india/potholes-claimed-6-lives-a-day-in-india-in-2016/articleshow/61283355.cms

(more…)

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How often you assess the success of Primary PCI with degree of  ST segment regression or resolution ?

I posed this query to a  freshly hatched , Intelligent and energetic cardiologist in an upscale dedicated heart care center.

He said, “No, we don’t .We always go with TIMI flow in IRA .TIMI 3 flow with less than 30% narrowing of IRA is success, that’s it ! He continued ,very often ,we don’t even Insist to take serial ECGs after the procedure .  . . forget about analysing ST segment  !  His body language seemed to suggest,  he didn’t expect such a question (Silly !)  from me , talking about ECG  in this era of hyper Interventionism where we literally live within the coronary artery !

What a grave error in coronary cognition ?  . . . thats commited  day in day out of cath lab  all over the globe !

TIMI flows across IRA lesion tell  more about epicardial patency while the humble ECG  reveals the true myocardial reperfusion.

So ,which will you use for assessment for successful reperfusion ? Ideally both , right !

But , as of 2017 ST segment regression is not considered worthy to  define success of pPCI  by the all powerful world scientific cardiology community .This is unfortunate (Or Intentional ?) we have  ignored  this Inspite periodic research papers showing the importance of the same.  (Link to this land mark Brodie BR AJC 2005)

Do you know , none of the  trials that celebrated the superiority of primary PCI in the last two decades used  ST segment criteria. But then ,we realised much later even TIMI 3 flow can have near zero myocardial perfusion. So ,can we now say all these trials are invalid ?

We also never bothered to include no reflow as a liability during pPCI. We have enough data to say even restored No reflow during pPCI has worrying long-term outcome  as reocclusion and tissue level perfusion is dismal .(Can we call it a pPCI failure equivalent ?) This is because the Cocktail  of anti no-reflow drug  we administer often give us a momentary satisfaction with transient myocardial blushes ! (Only to occlude minutes later as the patient is wheeled out of cath lab .We will never ever know how often this happens  !) This is because , microvascular bed integrity is notoriously unpredictable and defies the conventional salvage time window . We have seen patients with ultrafast pPCI ending up with severe LV dysfunction.

to-succeed-in-life-you-need-two-things-ignorance-and-confidence-quote-1

Final message

If you apply the ST regression criteria by 90* minutes after  pPCI (as we do for lysis ) the true success rate of pPCI will emerge .My prediction would be , if you do that routinely  the hype of perceived superiority of pPCI might go down the drain (At Least in all low risk STEMI ! ) Let us do a large-scale trial comparing ST regression with TIMI flows, blushes ,frame counts etc and rediscover the true face of our beleaguered coronary microcirculatory sense !

*In fact ST regression should occur much early with pPCI than lysis (May be 10 minutes after restoring IRA patency ! )

Post-ample and a Quiz !

If coronary thrombus laden IRA  is the chief culprit in STEMI battle field , Why is that Immediate , routine aspiration of thrombus in the ground zero is counter productive ?

That’s what the sophisticated mega trials of coronary thrombus  TASTE, TOTAL revealed.  I’m looking for an answer !

Reference

 

Counter point (and adding more confusion !)

Surprisingly , a Danish(DANAMI)  study showed  ST regression may not be Important in pPCI .This appears curious , especially when it suggests , ST segment regression didn’t occur because of more complete revascularisation by PCI !

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Technology is a great equalizer.Never in my dreams, I would  have thought as I drive through the dense Nilgiris forest , a satellite  located 36000 Km up in the sky would guide  me through  every turn and bend most accurately.

The curvy roads are coded with  live traffic  flow in Red ,orange & green . That’s “Google map”  for you. (By the way, proud to note Google runs with an Indian CEO who hails from my city Chennai !)

Now , coming to academics , . .Some one thought,  if the traffic in the entire globe can be monitored with few clicks,  How about  adding live traffic data to the otherwise  dumb anatomical coronary angiogram images we get in a non Invasive  CT scan ?  We can even color code the different segments of coronary artery based on the velocity profile and pressure drop. That is CT- FFR . Now technology is  available to get online live FFR as well. (Siemens )

Live coronary traffic blood flow 

Fractional_Flow_Reserve_Coronary_CTA (1)

Heart flow the newest technology in coronary Imaging and  non invasive Quantitative assessment is possible .It provides direct information about how to navigate the coronaries and intervene only the reddish areas  leaving the greens untouched.

Principle

Its called computational fluid dynamics .A super computer calculates live FFR for the entire segment by measuring the drop in  CT density data in Hounsfield units and translates into pressure equivalents and hence non invasive FFR.This modality has been approved by FDA.The heart -flow and Siemens has come out with onsite CT FFR.

Reality check :Have we conquered the coronary physiology ?

Trying to  understand coronary flow with a engineering mind-set is Insulting the complexities of biology. Be reminded , Invasive FFR is assumed as a gold standard, Inspite of the fact that , its blessed with flaws in concept , techniques ,(Hyperemia vs no hyperimia) and lesional variation . Now ,what is the big deal , a non invasive CT -FFR  is compared Impure gold standard  and claiming a breakthrough ?

Of course,logic would suggest,if both FFRs are flawed why not use  a less invasive one that is CT -FFR. It can atleast save time, cost, and potential procedure related issues.May be ideal in ACS situations were catheter FFR can destabilise the patient.Further, it can provide  continuous live information in a hybrid lab , hence post procedure FFR is readily assessed . (Converting Red coronary into Green ones  would become cardiologists new moto!)

Final message

The point of contention for the modern day  cardiologist is ,they have realized (Not all ofcourse !) in a harsh way that , they must use a physiological confirmation of a lesion severity before indulging on fixing it with a metal. Whether CT-FFR will increase the number of angioplasties  or reduce will remain a mystery . Whatever it does , it should do it for appropriate reasons . We know any technology has a shelf life and If MRI can provide the MRI-FFR (Journal of Cardiovascular Magnetic Resonance January 2014, 16:O55)  , CT will be pushed back for obvious reasons (Prohibitive radiation hazard)

Reference

Status of MRI based FFR 

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True patients* present with symptoms , please , don’t ever think all your patients  bring their coronary artery for general servicing !

Ofcourse , we are the service provider to our patients . Though  heart is a mechanical pump it can never be considered equivalent to automobile engine .

For a Heart service station equipped with 24/7 lab,  the benefits may be  more if you treat the angiogram rather than the  patient.

Let us not misunderstand the word service , please show restraint, your patients will thank you forever.

* Silent significant CAD are indeed a problem in minority that requires selective wisdom.However, we can’t be aggressive hunters for CAD in population, as there is huge cost for human hunting !

Reference

Recent article which debates the issue of PCI in CTO
http://circ.ahajournals.org/content/135/15/1382?etoc=#sec-1

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Coronary artery lumen has unique character . Its well-known  LAD diameter is not constant , it tapers in its distal course.(Unlike RCA which is more tubular ) It is estimated LAD looses 15 % of its diameter for every 30mm length.Fortunately LCX has no such long course to make tapering a visible threat. (Though it may still be an Issue !)

Is there a hemodyanmic purpose for this tapering in LAD ?

Should be, God never designs anatomy without a physiological purpose.We have to find it  out.(Can it be meant for  flow acceleration as the flow is entriely diastolic in LAD while in RCA its both in systole and diastole ?_

What is the relationship between tapering angle and final distal diameter?

Schematic of an artery with a tapered angle of 0:16 .Ref XIANG SHEN Journal of Mechanics in Medicine and Biology Vol. 16, No. 8 (2016)

So, if you have a long lesion in proximal LAD and planning to stent with a 40 mm or long  stent the distal end is hyperinflated by atleast 1.5mm, if we use a non tapered stent. Though , gain of extra  diameter  in distal segments might appear attractive, this may not work to our advantage , since it defies and distorts  the natural hemodynamic flow pattern. Further , when you have tapering vessel, proximal optimisation becomes more important.

How about a tapering coronary stent ?

It should be a welcome addition to our already overflowing coronary hardware in fixing long lesions . Its still a surprise why only very few are making this type of stent.

Meril has developed a  tapered stent up to 60 mm long  (Biomime morph).It should be useful in specific lesions sub types.Its worthwhile to note  tapering stents are used more often in carotid artery .

Advantages of long tapering stent over two stents of different sizes.

  • It avoid the vulnerable overlapping zone with double metallic load.
  • Possibly cause less restenosis
  • Low risk for stent fracture
  • It reduces procedure time and of course the cost of stent by 50 %

Why the concept of Tapered stent is not that popular ?

I can only guess, probably lack of free availability and  to a certian extent ignorance as well !  However ,current status about tapering stents is expected to evolve, though many cardiologist still  feel it’s not clinicaly important issue to use a tubular stent in tapering vessel.

Alternative  interventions in tapered vessel.

  • Wall stent and other self expendable stents
  • Tapered balloon Angioplasty (Laird Am Journal of card 1996)

Experts  in this modality are  welcome to share their experience.

Reference 

1.Zubaid MC, Buller C, Mancini GB. “Normal angiographic tapering of the coronary arteries”. Can J Cardiol 2002; 18: 973-980

2.Timmins LH, Meyer CA, Moreno MR, Moore JE Jr. “Mechanical modeling of stents deployed in tapered arteries”. Ann Biomed Eng 2008; 36: 2042-2050

3.Javier SP, Mintz GS, Popma JJ, Pichard AD, Kent KM, Satler LF, Leon MB. “Intravascular ultrasound assessment of the magnitude and mechanism of coronary artery and lumen tapering”. Am J Cardiol 1995; 75: 177-180

4.Laird JR, Popma JJ, Knopf WD, Yakubov S, Satler L, White H, Bergelson B, Hennecken J, Lewis S, Parks JM, Holmes DR. “Angiographic and procedural outcome after coronary angioplasty in high-risk subsets using a decremental diameter (tapered) balloon catheter. Tapered Balloon Registry Investigators”. Am J Cardiol 1996; 77: 561-568

5. YONG-QUAN DENG, ZHONG-MIN XIE and SONG  ASSESSMENT OF CORONARY STENT DEPLOYMENT IN TAPERED ARTERIES: IMPACT OF ARTERIAL TAPERING XIANG SHEN*, Journal of Mechanics in Medicine and Biology Vol. 16, No. 8 (2016) 1640015 

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