Feeds:
Posts
Comments

Archive for December, 2017

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.

Read Full Post »

Bernoulli principle states  that , when a high pressure jet (Air, Water, blood etc ) moves over a conduit,  the pressure exerted by the jet on its sides (Lateral wall) reduces . The velocity gain is equal to pressure drop .This is why we take velocity as a rough guide to pressure gradient and the sacred formula in doppler echocardiography 4V2 came in to vogue . (Incidentally, Bernoulli principle shares the same principle when aircrafts  lifts from runway at its peak speed as the pressure above the wings   drops to zero or negative  and the plane lifts up.)

Please note , the pressure should drop both above and below the aircraft by Bernoulli principle .But, the engine and wings are arranged in such a way , the air speed below the aircraft is slower and hence the pressure is high below and low above and the lift occurs promptly at take of velocity. Imagine , how the valve leaflets in heart is subjected to lift and drag forces every time the blood gushes with high velocity flows.This is also the reason for the Pulsus bisferiens, SAM in HOCM, Coanda effect in supra valvular stenosis, and any post stenotic dilatation.

 

In Echocardiography the Bernoulli equation is modified.

In clinical doppler echocardiography, we have liberally simplified the original Bernoulli equation by ignoring the the proximal sub valvular velocity V1 . Further , two more components in the equation is also amputated  for our convenience ! (Flow acceleration and the viscous friction) .This is the reason we tend to err many times  especially in outflow tract gradients and prosthetic valve gradients .

Pressure recovery phenomenon.

This  is another  hemodynamic lacunae in clinical echocardiography. We know, thepeak velocity of blood is attained  just distal to site of  obstruction. As the distal velocity beyond the obstruction begins to fall, the pressure tends to recover corresponding to the loss of velocity. This happens to certain distance beyond the obstruction. Since continuous wave doppler measures the pressure in its entire axis of alignment , it  is likely to pick more pressure samples  from the recovered areas and net result is, it measures more than the true difference in gradient across the valve.The phenomenon is most relevant in assessment of Aortic stenosis and results in over estimation of severity of stenosis.

How much can be the overestimation ?

It can be up to 30 % or even more.Especially in prosthetic Aortic valves.

How to recognise it and overcome it ?

  1. First of all,  recognise such a hemodynamic phenomenon  exists and the sacred 4v square can be a myth !
  2. Never go with gradient alone in diagnosing valve stenosis. Look for 2D features also.This is more vital when you suspect acute valve obstruction.
  3. Always add the proximal sub valvular velocity (V1 ) in your Bernoulli equation .It need to be subtracted.
  4. The effect of heart rate on pressure recovery has not been properly studied.(The impact of which  could be vital and hence too many false prosthetic emergencies could be avoided, as cardiologists tend to rely mostly on gradient than anatomical diagnosis of valve obstruction like visualising thrombus or struck leaflet by TEE or fluro.

Does this phenomenon happen with cath gradient ?(Generally it’s more pronounced in doppler echo )

Yes, It does happen in cath lab also , as its related to physics of flow. It can be minimised if we can use two simultaneous catheters ,one in LV  and the other Aortic catheter placed very close to the leaflets.

pressure recovery in aortic stenosis animation

Click below for an Animated version

pressure recovery phenomenon in aortic stenosis 005

Note the pressure recovers from P 2 to P3

Reference

Pressure recovery phenomenon in doppler echocardiography

pressure recovery phenomenon doppler echocardiography

Read Full Post »

Pre-op cardiac evaluation prior to non cardiac surgery is an important area for cardiology consultation . Unlike other clinical consults this one primarily involves in the delicate and tricky job of  predicting  future events  !

acc aha guidelines for perioperative evaluation noncardiac surgery riskPeri-operative  cardiac evaluation  is done for what ?

1.To evaluate and assess established CAD or other heart disease and get a proper pre-operative work up , drug adjustment and risk reduction for a possible peri-operative event.

2.To screen for any significant CAD or other heart diseases which is hiding and asymptomatic.

3.To   treat those conditions that are detected prior to surgery .(Or simply assess & mark the risk and send them for surgery)

4.Finally and most importantly it is  often done as a routine “legal point of view”  or ” perceived  anxiety “as litigation for missed cardiac condition  looms large on the surgeon !

Risk stratifying established heart disease is relatively easy task as we know what we are talking about .The term “cardiac fitness” is used in some institution which should  probably be discouraged .No patient’s  cardiovascular system is deemed to be fit or unfit at any point of time.It all goes with the nature  and  aim of surgery .An apparently  fit person can develop more complications than a potential unfit  person as cardiac events are dynamic and directly influenced by the stress of surgery .

It’s about the probability of occurring possible events , and of course one should add to this , all those  invincible  random or remote events of Heisenberg .

How do you rule out CAD ?

A  middle aged man or women with diabetes with a T wave inversion and non specific ST segment is being planned for ca-prostate or breast  surgery .Both of them couldn’t do stress test due to associated OA knee.

If coronary atherosclerosis is defined as CAD , there is no way you can rule out CAD.In fact near 100% of elderly population will have evidence for CAD ( at least some degree)  in the walls of the coronary .All that is required is  just few minutes  of  heightened adrenergic drive or prolonged fall in blood pressure to trigger  acute coronary syndrome in any person who may have shown even a  normal coronary angiogram. How does it happen ?  We have sufficient technological jargons to use in such situations endothelial dysfunction, plaque erosion  erosion ,micro or macro vascular spasm  coronary auto circulation failure etc ..

Is exercise stress test , Doubtamine stress , or CAG must for all persons suspected to harbor CAD ?

This could be the key question that makes most  cardiologist tentative in their office .suspicion is relative and subjective term .So we have the guidelines .Guidelines are simply guidelines. It may give you comfort if you follow that either academically or legally .

Iam not convinced .Iam new gen cardiologist. Iam unable to rule out CAD without CAG , my cardiology training over a decade has never taught me to r/o CAD clinically

I will go ahead with a screening coronary angiogram in all persons in whom I suspect CAD strongly  .If the patient is not willing for CAG I will do a doubtamine stress echo.

What if  you detect a positive Doubtamine  test or a significant multi-vessel CAD in an other asymptomatic person ?

Now you are stuck again !

  • Are you going to postpone the surgery pending further evaluation possible revascularization
  • Are you going to clear the patient with added risk frightening every one from surgeon to anesthetist, pateitn and their  family.

How guilty are we ?  If we fail to predict a cardiac event during non cardiac surgery ?

We need not feel guilty at all as long as you have done the basic tests and given your learnt opinion.I would think no court of law can plead guilty for that. (But your local reputation may be at stake !)

Final message

It is very important to realise , pre-op screening should not be a “hunting ground for CAD”.What we refer to as cardiac fitness is actually is  a  logical guess  considering all risk factors and comorbid conditions and make a learnt decision depending upon the  aim of surgery and the urgency of surgery .(Read at least once the meticulously prepared ACC guidelines of 2014)

Forbidden thoughts

In real world , it  appears the task of  risk stratification and pre-op evaluation is mainly driven by the fear of litigation rather than true concern about  the impact of surgery on the ultimate outcome.In this  gentle world of noble professionals  one can’t question the true Indication of a surgery however dubious it may appear  as it considered serious violation of Hippocrates oath* (Not respecting or suspecting  your colleagues’s  credentials !) But , I earnestly believe a genuine review of decision about surgery or procedure is to me made.

In my humble opinion , if surgery can be postponed or( if could be altogether avoided in few !)  till complete cardiac stability is achieved is the  most desirable option in high risk patients .

* Am I misquoting Hippocrates ?

Consider this true story . Recently a elderly women  came for cardiac clearance for  laproscopic  Cholecystectomy . As I was doing echocardiogram the patient  asked me  with real concern , “Is the surgery really necessary doctor ? my doctor says its urgent “ . I casually told her since its a incidentally detected small gall stone , if its not troubling  you surgery may be not be urgent , rather may be avoided. Few days went past. I don’t know whatever happened to that women , she opted out of the  scheduled surgery .

Next week,  , there was  huge uproar from the surgeon , who  called my associate and censured my behavior.He went on to add , as a cardiologist I have no business to comment about the gall bladder condition. Even if what I uttered could be truth , as a doctor you don’t have  a right to breach  other doctors opinion.

After few days of self deliberation , I agreed with  him and realised in harsh way ,  freedom of expression can never be taken as granted especially in dealing with others patients  !

My colleagues ridiculed my Ignorance  , aren’t you aware every patient is a registered property of some doctor ? An Anesthetist friend of mine working in a corporate hospital, said If I start scrutinising the indication of surgeries I assist, I cant win my bread for my family beyond few days !

I simply couldn’t comprehend .” A patient is a patient “ What is the demarcation between my and your patient. She asked me a question I answered it to my conscience , that’s it. Should I behave like a deaf mute ?after 30 years in to medical practice !

I was still restless over the week .Finally, I decided to  get the answer from Horse’s mouth and  mailed  the query direct to father of medicine,

To  query@hippocrates.heaven

Dear Mr Hippocrates ,

Here  is a story of  “Fit gall bladder and an unfit surgeon” . Did I really err on that day or was my behavior unprofessional in any way as others thought ?

Yours greatly

S.Venkatesan.Physician,Chennai .India

I got a surprisingly shocking reply ,

From query@hippocrates.heaven to drvenkatesans@yahoo.co.in

Dear Dr.Venkatesan

I could feel your inner fight about the things happen in medical profession . However genuine your thoughts are, I am sorry , I say this with pain , you are largely unfit to practice medicine in the planet earth. Please try to change yourself or try changing the planet !

Learn to take things easy in life !

With regards.

Hippocrates. (Digitally signed )

 

Read Full Post »