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Archive for the ‘Hardware techniques tips’ Category

Preamble * This article is meant  specifically  for cardiac professionals only .There has been so many queries to me about this device Megavac from patients  and public. It is  just another tool for assisting angioplasty in very special situations . Successful angioplasty can be performed without the need for such devices 9 out of 10 times.  I request the non medical readers to skip this article and follow your cardiologist’s advice  and don’t get unduly  anxious.

Dr Venkatesan .Chennai.India

If thrombus is the chief culprit in any vascular emergency  there can be  no second thoughts as it needs immediate  arrest without warrant! (STEMI,Acute pulmonary embolism , DVT, Acute limb ischemia etc) Since pharmacological lysis of thrombus is easy and  be done immediately  it will continue to play a major role still , in many clinical situations that critically compromise organ function .

However , large  thrombus burden  (or in which medical therapy fails to do a good job )  we must  intervene mechanically  to change the course of event.Though vascular surgery is a definitive option its always better we try out catheter based thrombectomy.

Many hardwares are being developed in the recent times. Aspiration catheters, baskets etc * .This  one from vascular capture (Minnesota USA)  appear promising as its a universal capture device that can be  used anywhere coronary , pulmonary or even in deep veins .

Clinical case examples using megavac : Video

*Few  examples of Thrombectomy devices.

1.They can be mechanical rotational devices like Amplatz Thrombectomy Device (ATD) Microvena,  Straub Rotarex (Straub Medical, Wangs, Switzerland) and the Tretorotola Device ( Arrow International, USA) employ a high-velocity rotating helix or nitinol cage that macerates the  thrombus.Disadvantage is endothelial contact with moving mechanical parts.

2.The Angiojet device (Angiojet; Possis, Minneapolis, USA) uses a rheolytic mechanism with possible   less endothelial injury as there is no true contact with endothelium.

3.Ultrasound mediated lyis ( EKOS Endowave (EKOS Corporation, USA) and Omniwave (Omnisonics Medical Technologies,  USA)  fragment with high frequency ultrasonic waves.

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Interventional cardiologists in one way be labelled as intra-cardiac and intra-vascular civil engineers.Their primary  job is to create ,or close vascular tunnels and holes in various locations within the heart.How to deliver the  working hardware  to the  site of action ?. Temporary bridges ? .The vascular access is through long sheaths though which , wires, catheters, and devices , valves  are transported. It’s the key supply line to the ultimate battle field of life , right inside the beating heart.  .

So far,the sheaths  and catheters were rigid tubes with a fixed diameter.Innovative sparks come from  strange thoughts.As we struggled to take the per-cutaneous valve for  TAVR  through small caliber sheaths , some one thought why should the sheath be fixed and static .Why can’t it accommodate  liberal sized devices just by expanding its shaft like a python ,come back to its original state once the device passes by ?

Expandable sheath 164 solo path tavi tavr cathlab hardware

Thus came the expandable sheaths. Soon this concept is going to come in a big way and most complex and large device interventions will be benefited by this.

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We are aware  , modern day cardiologists literally live within the patients coronary artery and vascular system .  It ‘s not at all surprising then , man made cardio vascular accidents  are becoming more common  , where pieces of hard ware like guide wires catheters and stents  get trapped .

Knowing about the hardware and techniques of retrieval of foreign bodies within vascular system is so important .It would appear  indulging in cath lab work with out proper salvage hardware and expertise is a  near  serious offense.Apart from this , many complex procedures require intentional snaring of wires and gadgets .

How to retrieve a foreign body from  coronary artery ?

There are few snares availablew  with  single or multiple loops  and comes in various sizes .

1.Goose neck EV3 snare (Covidien /Medtronic)

2.En snare -Multiple loops (Merit Medica)

3.Micro elite snare (Vascular solutions)

 

 

ev3 microsnare covidien

The snare is constructed of Nitinol cable and a gold plated tungsten loop. The pre-formed snare loop can be introduced through catheters without risk of snare deformation because of the snare’s super-elastic construction. The snare catheter contains a platinum-iridium radio opaque marker band.

  • Nitinol Shaft for durability and kink resistance
  • Super-elastic and shape memory properties of nitinol provide kink resistance.
  • Ideal for challenging or unplanned foreign body retrieval and manipulation cases.

goose neck snare amplatz ev3
True 90° snare loop remains coaxial to the lumen

  • Snare loop forms a true 90° angle.
  • Device remains coaxial to the lumen for proper insertion and successful retrieval or manipulation of atraumatic foreign bodies.

 

Hardware specification

ev3 goose neck

2.Ensnare

 

coronary snare ensnare merit medica

 

 

Micro elite snare

micro elite coronary snare vascular solutions

 

micro elite snare

Other retrieval devices

  1. Bioptome* (Cook medical)
  2. Needle and eye snare
  3. Multi snare
  4. Welter loop catheter
  5. Expo retrieval catheter
  6. Curry snare
  7. Simple  alternate option : 2 or three wire guide wire trapping  technique.
  8. The cheapest option :To make a custom made snare with  .014 PTCA   guidewire  with a flexible loop .
biopsy forceps

Intra cardiac biopsy forceps may help to retrieve some of the foreign bodies

 

Final message

At least few of  these retrieval devices  should be  available in  every cath lab .  Attempting to do sophisticated procedures  in your cath lab without essential hardware is akin to driving a car with defective breaks  or like flying airplane with a single engine .

Acknowledgement

Image source , content and courtesy respective manufacture web site

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Complex coronary lesions require  not only  expertise it needs better hardware .A key  factor is the support from  guide catheter.Innovations are hall mark  Interventional cardiology community.Every few years a hard ware breakthrough is expected.

Boston scientific has an answer for improving frequent guide catheter destabilisation in complex anatomy and lesions .A dramatic new concept for guide catheter support .They have named it  in a hollywood fashion “Guidezilla”

Major advantage : Extending the tip of the guide with an anchor to  facilitate smooth balloon approach to the  lesion which  i avoids repeated disengagement of guide catheter.

Watch this animation . It comes with a music stunning too !

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  1. The concept of  FFR is based on pressure gradient  alone.In any hydraulic model (Both biological and non biological systems ) pressure difference  is the least   important parameter  that determines flow.
  2. FFR  is unphysiological  as hyperemia   is  artificially induced one .(Adenosine  is not the only parameter that determines it !)
  3. Serial obstructions and branch point hemodynamics are  conveniently ignored.
  4. Reproducibility  remains a big question mark .
  5. On safety  issues  FFR  is a suspect.( Often times , it  requires expertise comparable to  that of a  complex  PCI !) .Beware , the FFR unit has stiff catheter system and is an additional health hazard .  I have witnessed   atleast two cases  where  insignificant lesions were  made significant by  FFR related Injury .
  6. And  now the  knock out punch ,  ! Probably the most vital  issue for which FFR should be banished * , it is not taking into account of vulnerabilty of a plaque .( An FFR > .9 with a hanging , eccentric , mid LAD lesion was left alone by one of the  academically up to date ,  evidence  based interventional cardiologist!  )
           (*If perfomed  in isolation without IVUS/OCT  )
I am still wondering how this concept came into cardiologist domain and into the cath lab .It should have  never been let out of theoretical physics labs !
Final message
The best way to assess physiological significance of an anatomical obstruction is  to  do  exercise  stress test .
If  the lesion is  able to sustain good exercise capacity , it  can be deemed physiological unimportant.
While , this is an explicit  proof  in single vessel disease  ,  even  in   multivessel  CAD ,   EST  is   a  collective  measure of  coronary  reserve flow .( Something like instantaneous equivalent of virtual  multivessel  FFR  )
Moderated After thought
FFR is a highly specialized theoretical  tool , that has very limited role in cath lab .
The two major practical (Non academic)  use of FFR   is to shun away  those   internet fed ,  annoying, pseudo  intellectual patients ,  who constantly ask for  angioplasty  for  obliviously insignificant lesions !
FFR comes very handy  to  bail out  cardiologists at  times of distress   ! (To escape  from the wrath of our patients   after a sub optimal &  technically inferior   PCIs   and   in  the  long term confabulations  in   restenosis  after stenting !  )

//

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The link between brain and the  hand  starts right from fetus .  It is a well known fact  vertebral artery   competes with hand blood flow  . In the right side , there  is one more  vascular issue !  .Bracho cephalic  artery  arises  directly  from aorta and supplies the  right  hand and  right half of brain.

It remains a mystery  why left brain  is   blessed with a  separate  origin ,  while right has to share it with blood meant for hand  .It is beyond science  . . . isn’t

It is possible the left hemisphere  of brain   has more   purpose   to be alive  ,  with bulk of the cognition work to do . Hence   God created a  separate  supply to it !  Of course , he  would   have never  thought ,  the  possibility of  his ” mean” creations   adventuring  within the   arterial tree  !

Click over the Image for animation

right radial artery coronary angiogram  pci  risk of stroke 002

Please remember  whenever  we   play with   catheters and wires  through   radial route , we  are  hugging  and scraping   the artery meant  for cerebral circulation !

Final message

Femoral Interventions  enjoys a proven  track record. Currently ,  radial route has virtually taken over with  few  advantages . However , the  overall stroke risk in the two approaches  remain  low but genuine (.4 %) .It may be true , arch manipulation is more  with  femoral but  the threat to  vertebral and brachiocephalic circulation  is more with radial .  When the available evidence are  not conclusive  and  new ones are not forth coming  . . . it is wiser to rely on common sense !

Reference

I think  this 2011  study  from the  prestigious stroke journal  has convincingly answered the issue

cholesterol and ateromatous emboli following coroanry intervention 2

cholesterol and ateromatous emboli following coroanry intervention  radial vs  femoral 2

It concludes , the right radial approach  is indeed risky  to develop cerebral  micro embolism   when compared to right femoral

A Review article in  Circulation

cholesterol and ateromatous emboli following coroanry intervention 2  radial vs  femoral 2

Other references

1.http://stroke.ahajournals.org/content/38/7/2176.full.pdf+html

2.Transient Cortical Blindness after Coronary Angiography Journal of International Medical Research. 2009;37:12461251,

3. Stroke and Cardiac Catheterization Circulation. 2008;118:678683,

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Interventional   cardiology has  grown leaps and bound in the last few decades  .We are able to clip the wings of mitral valve  without surgery when it prolapses

We  can deliver a huge aortic valve and fix it with wires .

But  . . . we have no proper  preformed   guiding catheter  that can  sit into RCA ostium directly   and snugly  for a long time to enable complex RCA angioplasties !

An now try this one .

 

Here is  a  pending patent for  a preformed RCA catheter

preformed rca catheter

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