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Archive for the ‘cath lab tips and tricks’ Category

Improper or technically deficient stent deployment is a major factor for post stent events .Few terminologies are used in assessing stent deployment.

Under expanded stent (UES) 

A stent is not fully  expanded to the desired or to its specified diameter.

This is often due to inadequate balloon pressure during inflation .

Many times its technical and It requires post dilatation.

Under-deployed stent is  often  due to a struts hitting a  hard surface or calcium .

What is mal-apposed stent  ? (MPS)

It’s a fine gap between the vessel wall and the stent.

It can be observed immediate or late. Immediate is usually due undersizing of stent.

Intermediate or late malapposition  can be due to many  reasons

  1. Due to dissolution of thrombus in the  vessel stent interface
  2. Positive vessel remodelling creating new gap between vessel wall  and stent remodeling
  3. Vessel wall regaining vasomotion and  ? ( Is it the culprit with bio vascular scaffold)
  4. Stent rejection hypersensitivity and inflammatory reaction is a rare possibility.

What is the acceptable mal-apposition ?

No stent deployment is perfect . Mal-apposition can be focal confined to one or two struts or can be diffuse . (Branch vessel are naturally malapposed)Doing a routine OCT /IVUS is inviting trouble as no cardiologist can sleep in  comfort even after a reasonably good procedure.So we have created a safe  dead space with a width of 200 micron as an acceptable mal-apposition  (As if , the 7 micron RBCs and 2 micron  platelets can’t  get trapped in this dead space)

Is routine post-dilatation the  answer for all  mal-appostion?

Not really , still It is most logical step. Liberal post-dilatation  can be a problem as it may increase plaque prolapse and may re-release or dislodge  the  thrombus trapped during the initial expansion and triggering a no- reflow.

Undersizing vs underexpanded stent

Selecting a smaller stent for a given vessel diameter is another common error that result in MPS. This again can be tackled(Though not ideal)  by high pressure inflations.

under-expanded-stent-vs-malapposition-post-dilatationstent-malapposition-vs-underexpansion-mal-apposition-under-expansion-ivus-oct
under-expanded-stent-vs-malapposition-post-dilatation-200-microns

under-expanded-stent-vs-malapposition

Is self expanding stent best option for preventing mal-apposition ?

May be.It has more radial strength, and it is expected to take care of the current and possible  future gaps of created by positive remodeling.

Other stent related issues 

  • Plaque prolapse
  • Stent edge dissection
  • Longitudinal miss
  • Stent fatigue and fracture

Final message 

UES and MPS , though discussed separately by cardiologists , from the patient point of view , the difference is  camouflaged in technical semantics since both carry risk significant risk of recurrent ACS or restenosis .It has become fashionable to believe one needs to  be worried more about visible UES than invisible MPS.

Reference

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Bifurcation  angioplasty is a  newly conquered(Or not yet !)  target  for Interventional cardiologists.We have come a long way  in planning  interventions  for left main  with state of the art  hardware, expertise and  image assistance .However , every  classification , approach, strategy  for BFL talks about tackling the main and  side branches meticulously.

Still . . . one question  is not answered clearly is  . . .

A mini MCQ.

Answer: Open for contribution.

My inference

*It all depends upon the Indication and Individual arterial ischemic burden. In ACS, if  LAD territory is infarcted and beyond 24 hours.LAD becomes a  side kick to the vital LCX which supplies  the remaining life sustaining myocardium which includes the critical basal segments.

Final message 

Since , the risks involved in the interventions of  left main and its bifurcation is inherently linked  with , what exactly we mean (and do ! ) to the side branch .Its mandatory we spare few intellectual moments before our hands invade the coronary battle zone.

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There is something to understand in the movement of dissection flaps with reference to incoming coronary blood flow.Why some dissections dangerously escalate and totally occlude within moments while some others seal spontaneously ? Though uncommon ,  retrograde dissections has some unique hemo–anatomical property .

dissection flaps antegrade vs retrograde

 

 

 

benign dissection no flow limiting self sealing

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Cardiologists do magic inside the human coronary artery , that too in a  live beating heart , unlike the surgeons.Blocks are removed , holes are closed, valves are inserted ,  scars are burnt, new electrical connections  are laid .They do this with relative blind vision with good degree of success. Still, as we aim for more precise interventions we require excellent imaging  modalities to assist us.

In  PCI of CTO(Chronic total occlusion)   the critical element to know  is  the morphology of the  tissue plane , what  exactly  we burrow ?  as we navigate  through complex, often hard shapeless tortuous tissue tunnels  . Our patients will be  surprised to know we are currently doing this with our eyes shut. If only we have a camera guide in the tip of the wire it give us tremendous advantage .

CTO pathology

The CTO morphology .Image source : Kenichi Sakakura ,Eur Heart J. 2014 Jul 1;35(25):1683-93.

The exiting IVUS technology can only look sideways . Now a new vision is added by annular array of transducer at tip with CMOS sensor .The technology is just coming out it would be  use for us in the near future .

Anatomy of the forward looking ultrasonic eye

ivus forward loooking cto intervention

Reference

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A patient with near 90% LAD disease who had a significant TMT/EST positivity with no clinical angina  was  subjected to FFR by a scientific  cardiac physician. Since FFR was recorded as  .9 , he was adviced against a stent and sent home with drugs.

Now , in the  physiological assessment of a coronary lesion ,  which one you are going to trust , TMT positivity or FFR ?

FFR  measures trans-lesional pressure drop  by creating a artificial exercise physiology  in a particular coronary bed by injecting just one of coronary vasodilators  namely Adenosine. FFR assessment can never be considered truely  physiological .There has been huge discrepancy in the amount , rate and route of administration and the hyperemic response to Adenosine.

Final message

In a single vessel disease population , if TMT is positive the lesion is to be taken as significant, irrespective of FFR.(Provided Anemia and other systemic factors are excluded )

*Read this and get ready to get  confused further , single vessel disease with TMT positivity  doesn’t mean medical management is never an option .OMT ,(optimal medical therapy ) even though a battered concept is not yet dead for SVD !

 

 

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Every one talks about  coronary excesses ! It happens  both  in acute and chronic  fashion , not withstanding the inappropriately  understood  . . .   appropriately  released  guidelines  on inappropriateness ! The  burden  of coronary syndromes of the humanity, I am afraid would  include these man made excess as well !

I stumbled upon two  small  “gems ” in this other wise wild dark  cardiology literature  .One from Kamaer , Netherlands and other from  Escaned from Spain.

Both  talk about a  simple and logical modality in the management of STEMI . If bulk of the STEMI events are due to coronary thrombosis just tackle it  . No more  . . . no less” Stent only , if there is tight residual lesion.

1. From Amsterdam , Holland.

krammer thrombus aspiration alone priamry poba for stemi no stent

2.This one is from Spain.These studies I am sure , only a fraction of the interventional community would have read .Reason ? We are always hijacked by the moments of glamor ! I am just sharing them .hope few are benefited

primary POBA thrombus aspiration alone for stemi no stent stemithrombus aspiration alone for stemi no stent priamry pobaThese two studies with total number of 44 patients has a potential to redefine  the entire practice pattern of acute interventional coronary care.(Of course , if only , we are ready to make sense out of it !)

But , the concept will be heavily banished by strong visible and invisible forces   for the simple reason it suggests a true possibility  of knocking  out the role of  stent from acute STEMI arena.

When I discussed with my colleagues  for a large scale study  on isolated thrombus aspiration in STEMI , they told it  is not possible for ethical reasons !

I was amused , denying such a study is biggest ethical blow to the field interventional  cardiology !

Final message

Proof of concept does not require numbers .A study with less than 50 subjects  can be far superior than multi-centre ,multi-blinded , self steered ,peer reviewed largesse ! The truth of the study lies in the core consciousness  of people who do it , not in the numbers and exotic statistical methods !.

After all , one of the greatest medical study  was  done by James Lind  (Father of RCT) who discovered vitamin c as an antidote for scurvy,  with a hand full of sailors  while they crossed the Atlantic many centuries ago !

After thought

You say , thrombus aspiration is great , Why the hell , TAPAS , INFUSE AMI, and TASTE studies  confuse us regarding thrombus aspiration  ?

Don’t blame it on thrombus aspiration .We do it perfectly . It is because of what  we do after that ! We decorate the coronary lumen finally with a piece of metal cherry  undoing all the goodness of a great pudding !

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Interventional cardiologist extraordinary  cath lab tips invasive great

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