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Archive for the ‘Cardiology -Technology’ Category

It is just past midnight: This is a gloomy conversation between a patient’s son and a cardiologist in the silent waiting room, just outside the dim-lit ICU of a popular 4-star hospital in Chennai.

“I am sorry to say, Mr. B., your father didn’t make it. Has succumbed to the heart attack. We have been trying to resuscitate him for the past one hour. We have done everything. We have managed to open up IRA, and 2 more critical blocks still it couldn’t help. It was a massive one. Sorry again.

“Doctor, I feel very bad. What went wrong, I want to know. Doc, did you try ECMO ?,” the elder son queried

“No, we didn’t”

Do you have it in your hospital doctor?

“No,we don’t have it”

The son in distress couldn’t take it lightly. “How can you say that doctor? such a big hospital doesn’t have ECMO, “What a mistake we have done, we should have gone elsewhere” he quipped 

The visibly exhausted cardiologist was taken aback and struggled to retain his composure. He took some time and tried to explain the bereaved family with a semi-scientific explanation.

Please understand the reality. Do you know, how likely an emergency ECMO will resuscitate a patient with cardiogenic shock and arrest” 

  • ECMO is not a magic machine  that will bring back your heart to life
  • It is a temporary circulatory support device ideally used prophylactically in high-risk situations
  • It takes a minimum of 20 to 30 mts (If it’s in ready mode) to insert the AV ECMO , Further, there must be some cardiac activity till the ECMO takes over.
  • It is almost impossible to resuscitate with ECMO after cardiac arrest and circulatory standstill.
  • In fact, prolonged CPR with an absent pulse is a contraindication for ECMO.
  •  

“Let me go little deeper into the hemodynamics of ECMO, even if it is inserted on time, ECMO doesn’t support coronary circulation much, (the one that matters most in the failing heart) ECMO circuit that brings oxygenated blood from below upwards in descending aorta. This stream may not reach the aortic root as it has to competes with ventricular contractions however feeble it may be” (Ref 1)

“Don’t mistake me, In my opinion, all these macines like ECMO Is more like a fancy customary add on machine in a high profile patients”.  

“So, you are saying, my dad is destined to die, that’s not at all fair doctor”.

“I can’t say that openly, it could be the fact. A series of miracles could have saved your dad’s life. A tandem heart as a bridge to an emergency heart transplant is a dream thought. Of course, for a heart transplant to happen someone else should have lost their lives in time, just to save your father’s life. That’s in God’s domain”.

The son gradually got back to his quieter sense. “Sorry doctor, I misunderstood  ECMO I was told it was like a lifeboat that will bring back life from a dying heart. Thanks for all your efforts doctor. “No worries, even, many of us haven’t come to real terms with this ECMO stuff. Thanks to misplaced mainstream media coverage concerning celebrity lives”

The much-relieved cardiologist left for home in peace of mind.

Reference

1.Junji Kato, Takahiko Seo ,Hisami Ando et al  Coronary arterial perfusion during venoarterial extracorporeal membrane oxygenation,  The Journal of Thoracic  and Cardiovascular Surgery, Volume 111, Issue 3, 1996, Pages 630-636,

 

Postamble

Final message

We must realize ECMO is not a new breakthrough technology. It’s  a 50-year old concept, that was used primarily in infants with respiratory failure. (VV ECMO) In the complex high-risk interventional cardiology field, it has a different purpose. It gives the aggressive players a little more time to try their luck of reperusing a failing heart. 

All these circulatory assist devices Like ECMO, Impella, IABP help to support the heart before a cardiac standstill. Ideally, we may use them prophylactically ( in situ and ready to fire)  It has helped save  lives especially in pre and post-transplant hearts However, it’s too complex a procedure to be relied upon after unanticipated Ischemic cardiac arrest. We can expect, It might get miniaturized and user friendly soon.

 

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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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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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Artificial pacemaker is one of the major discoveries in cardiology that has given new lease of life to patients suffering from serious bradycardia and heart blocks . Now, the technology has grown beyond pacing , for delivering shock ,defibrillate , resynchronise failing heart etc. For accomplishing  all these tasks we need electrical power . . . non stop on board !

Though , the energy required for sustaining an electric pacemaker is miniscule (About 40 micro watts) still, the lithium ion battery can last only around  10 years with the available technology.Various alternate sources for power* are being  explored. One great innovation is on the horizon .A new “scientific spark”  came from a totally unexpected  quarter.

 If Automatic Swiss watch can run without a battery  life long ?  Why not a cardiac  pacemaker  ?

 How about harvesting mechanical energy from the heart itself  ? (The ultimate biological bundle of energy ! ) .

The concept was  originally suggested by University of Berne Switzerland , researchers from Stanford has successfully used the cardiac  muscle activity as a dynamo to generate and store minute amount of electricity that can sustain heartbeats in an electro  mechanical coil loop model.

heart-powered-pacemaker

A person’s heartbeat  moves a magnet and generate electricity for a pacemaker

enerharvpromo-1

Trials done on pig’s heart are promising .(Reference 1)

Final message 

The idea may look dramatic , but it works.Hope  it becomes reality in our patients in near future.

Further reading

* Creating gene modified  biological pacemaker cell is .

Sharing this  article from  Via: New Scientist

By Lisa Zyga
Science Blogger
InventorSpot.com

  At first glance, this idea seems somewhat impossible, like using the movement of an engine’s pistons to power a car. However, researchers David Tran and his colleagues from Stanford University explain in a recent patent that the idea is very plausible. For one thing, a heart-powered pacemaker can generate and store more electricity than required to operate, and use the stored energy when needed. Also, a battery could be included in the pacemaker, and power from the heart would extend the life of the battery.

Overall, the researchers hope that the invention could at least double the lifetime of today’s pacemakers. Currently, the batteries in pacemakers can last up to ten years, although they typically last only four to five years. (Originally, batteries lasted for as little as a year.)

The invention also has the potential to reduce the size of the pacemaker by one-half or more. For example, a typical commercial pacemaker with a volume of 16 milliliters may be reduced in overall size to as small as 1-8 milliliters.

An embedded generator could continuously produce power in several ways, such as through electromagnetic induction or the piezoelectric effect (electric energy generated via mechanical stress).

In the Stanford team’s design, the generator is implanted near the heart wall, such as attached to the myocardium or pericardium, which would subject the generator to regular pulsating movements produced by the beating heart.

The generator itself consists of a magnet, a conductor (both micro- or even nano-sized), and electrical leads hooked up to the medical device. Contraction of the heart muscle causes relative motion between the magnet and the conductor (such as a coil of wire). This relative motion between the magnetic and coil induces an electric current in the wire, which is transmitted through the leads to the implanted pacemaker.

Movements produced by the beating heart would have a frequency of between about 0.5 Hz and 2 Hz, which could generate between 40 microwatts and 200 microwatts of power. The pacemaker would only require about 40 microwatts, so the excess power could be stored and used for later use, such as when the heart stops beating.

Besides using the movement generated by the muscular contractions of the heart, other versions of the pacemaker could generate power from heat differentials, physiological pressures, and flows and movements, such as blood flow. And in addition to pacemakers, the researchers suggest that similar systems could be used to power defibrillators, ventricular assist devices, muscle , neurological stimulators, cochlear implants, monitoring devices, and drug pumps.

Reference

http://powerelectronics.com/energy-harvesting/energy-harvesting-poised-eliminate-pacemaker-battery

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In this wireless networked world nothing is personal, not even your heart beat.Modern pacemakers and ICDs have wireless connectivity with the manufacturers.This is value added service for regular monitoring and solving  any technical issues.

assets_174815Hacking  a device like pacemaker and ICD  and instant deactivation or triggering a new event   is a distinct possibility .It was shown in a fictional TV series “Home land” that prompted the  ex American wise president Dick Cheny to switch off all wireless function in his ICD. Now ,the US homeland security  cyber emergency  response team has decided to probe the issue .

pacemaker hacking icd

Perils of technology is taking us to new uncharted territories , while your  SA   AV node are at risk of being  remote controlled !

Meanwhile Medtronic has clarified they have increased the security features and pacemaker /ICD hacking is not an issue to be worried . But the threat is genuine !

Reference

1. Frenger P Hacking medical devices a review – Biomed Sci Instrum.  biomed 2013.2013;49:40-7

3.Fox news

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