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Archive for the ‘Cardiology -Technology’ Category

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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