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Archive for February, 2015

We have two options to manage AF.Rate or rhythm control .(Of course , in the strict sense , rhythm control also confers  rate control that is built in-situ with SR ) .There was an initial confusion which strategy would fare better .For a decade or so rhythm control was thought to be supreme. That’s logical to expect as we restore physiology in the later .” We know, medical science  often disrespects logic , and  scientists reinvent this harsh fact in regular fashion” Now , we have clear, consistent data that proved  rate control is a better strategy in most situations of AF .(AFFIRM, RACE 1 and 2 studies). The aim of treatment of AF are the following .

  1. Improve symptoms of palpitation
  2. Improve hemodynamics
  3. Reduce MVO2 and hence avoid ischemia
  4. Prevent tachycardic cardiomyopathy in the long-term
  5. Avoid stroke .

Unfortunately or fortunately rate control strategy was able to fulfill all these aims with fair degree of success. There are at-leaset  3 reasons why rhythm control fared poorly .

  1. Rhythm control is actually a myth. Only about 35 % patients  remained in SR at any time in rhythm control .Runs of transient AF can occur at  any given day* and make a mockery of the much hyped rhythm control !(*Due to heightened adrenergic tone or adverse biochemistry/ hypoxia)
  2. The drugs used to maintain SR are far more toxic . The complex EP procedures to convert to SR has not helped either.
  3. Most importantly , rate control with anticoagulants were able to achieve better  stroke reduction than rhythm control group.The reason being stroke risk was unabated even if rhythm is back to sinus,  as risk of ischemic stroke continue to emanate  from as many  sites like aorta, aortic arch and carotid. Hence, in a stroke prone population with AF  , it is the meticulous anticoagulant that’s is going to prevent strokes  rather than rhythm control .Since the rhythm  control patients would  need  to  continue anticoagulants , they lose  a  presumed logical therapeutic advantage.

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A short systolic murmur over pulmonary area (ie Left second inter coastal space ) is listed among 6 other auscultatory  feature  of pulmonary arterial hypertension.Though it is an accepted sign  many would question  the existence of such a murmur or its relevance in PHT.

Why does it occur  ?

Acoustics  principle  tells us whenever  velocity of blood  flow exceeds a critical point(Raynolds number*) in a specific anatomical territory , a  turbulent zone is created  and  a murmur could be generated .This is why many physiological situations like pregnancy, anemia, and some benign outflow murmurs occur.

 

In pulmonary hypertension , three things are thought to contribute for the murmur generation

  1. Dilated pulmonary artery  promotes Raynauld turbulence
  2. Increased flow velocity (This is correlated with pulmonary artery acceleration time in Doppler)
  3. RV contractility  (A normally functioning   RV is required to generate the murmur .Once RV dysfunction sets the  murmur of pulmonary hypertension usually disappear , of course a TR murmur may appear and confuse the picture )

Reference

* Reynolds number is a way to predict under ideal conditions when turbulence will occur. The equation for Reynolds number is:

Reynolds number(Where v = mean velocity, D = vessel diameter, ρ = blood density, and η = blood viscosity )

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Originally used in early 1990s,  self expanding coronary stents (Wall stent from Boston scientific )  subsequently lost interest because of delivery related issues. Many feel , it makes cardiologist judgment tentative and delivery system prevail over our hand skills. It is possible stents can longitudinally jump with high radial force making a geographical miss more likely.While it could be true with any technique till we master it, one should recall ,most endo-vascular work other than coronary still involve self expandable techniques.

Balloon expandable  stent is ruling the PCI field  for more than 2 decades. There has been recent surge of interest in the self expanding  technique and it could make a great difference in the PCI arena provided we take the proper cues.

Self expanding stents have some unique advantage

  • It has  high radial force.
  • Approximation with lesion is best
  • It tends to take the shape of the vessel than any other stent
  • Since the mal-opposition and gap between stent and vessel wall is minimal stent thrombosis is theoretically is  lower.

Where is self expanding stent useful ?

  • Ectatic and very irregular lesions
  • Bifurcation lesions where multi dimensional vessels with different shaped ostia converge.
  • Eccentric lesions (Non calcified) may be benefited by self expanding stents
  • Self expanding covered self (Is it available >)  may be the best bet for perforations and for thrombus  to be plastied against the wall.
  • In some small vessels PCI
  • Finally it may have a  role in primary PCI (APPOSITION 1 to 5 )

What are the self expanding stents available ?

  1.  Devax system   ( 2003)
  2.  Stentys
  3.  Radius (Boston scientific)
  4. Capella Sideguard.
  5. Cardiomind Sparrow
  6. vProtect luminal shield.

Final message

For some reason , self expanding stents were not tested widely  and  large scale data is not available. However ,  they are unique modalities in metal delivery and must be mastered and many patient subsets will be benefited by it. They are not obsolete yet, APPOSITION 5 study will answer some of the issues.

Reference

1. Agostoni P, Verheye S. Novel self-expanding stent system for enhanced provisional bifurcation stenting: examination by StentBoost and intravascular ultrasound. Catheter Cardiovasc Interv 2009;73:481
2.Jsselmuiden A, Verheye S. First report on the use of a novel self-expandable stent for treatment of ST elevation myocardial infarction. Catheter Cardiovasc Interv 2009;74:850
3.Verheye S1, Grube E, Ramcharitar S, Schofer JJ,.First-in-man (FIM) study of the Stentys bifurcation stent–30 days results.

EuroIntervention. 2009 Mar;4(5):566-71
4. van Geuns  R.-J., Tamburino  C., Fajadet  J.,  Self-expanding versus balloon-expandable stents in acute myocardial infarction: results from the APPOSITION II study: Self-expanding stents in ST-segment elevatation myocardial infarctiion. J Am Coll Cardiol Intv. 2012;5:1209-1219.

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Heart by development  originates from near  the same spot , where the brain develop (Neuralcrest) .Hence there is no surprise  to note,  heart being a primary  vascular organ still retain many neural connections with brain .Eyeballs with it’s  extensive neural inputs  can be considered as adirect extension of brain.

Oculo cardiac reflex .

When the eyeballs or the ocular muscles are manipulated or massaged slowing of heart rate can occur .This is due to  a reflex called  Oculo cardiac reflex mediated by  vagal stimulation .This phenomenon is also referred to as  Aschner phenomenon

The circuit

  • Afferent _Trigeminal branch of opthalmic nerve
  • Center- Medulla : Trigeminal  neural signal  spill over signals  to Vagal nucleus
  • Efferent- Vagus -SA node

Biochemical mediator -Acetyl choline

Prevention

  • Adequate local anesthesia
  • Retro bulbar block of ciliary ganglion
  • Prompt Atropine injection
oculo cardiac reflex

Courtesy :Indian journal of Ophthalmology

 

Clinical scenarios

  1. Opthalmic surgery : Serious bradycardia  even  asystole can occur as a rare complication especially in elderly and very young (Cataract /Squint surgery) .
  2. Cardiac events and  strokes  are clustered around opthalmic surgery in many elderly  for some unknown reason ( OCR triggered ?)
  3. OCR can unmask hidden sinus node dysfunction in elderly.Routine cardiac evaluation before eye surgery may be recommended .
  4. Orbital fracture especially Medial orbit can elicit dangerous bradycardia (BMJ Case Rep. 2014 Apr 15;2014.)
  5. Rarely sudden death has been reported (Smith R (1994). “Death and the occulocardiac reflex.”. Can J Anaesth 41 (8): 760. )
  6. OCR for termination of SVT/AVNRT : , One can use the eyeballs  to stimulate the brain stem nucleus of vagus to terminate a rapid supraventricular tachycardia (Like carotid sinus message) .Cold water immersion of eye is effective way to stimulate the vagus.(Diving  reflex -Mathews 1981)

Neural control of heart how Important it is ?

Many sudden cardiac deaths are now believed to be neurogenic in origin . Though,  somatic nerve  supply of heart is least important except over pericardium , extensive sympathetic and parasympathetic nerve supply is present . They can  now be visualized by  adrenergic receptor imaging  . Neuro cardiology is distinct developing field. A hyperbole:  Of course  one could argue , these connection has less overall significance as a person can live with an entirely new donor heart with zero neural connection with brain.

Reference

1.Lang S, Lanigan D, van der Wal M (1991). “Trigeminocardiac reflexes: maxillary and mandibular variants of the occulocardiac reflex.”. Can J Anaesth 38 (6): 757–60

2.Mathew PK (January 1981). “Diving reflex. Another method of treating paroxysmal supraventricular tachycardia”. Arch. Intern. Med. 141 (1): 22–3.

3.Borumandi F1, Rippel C, Gaggl A.BMJ Case Rep. 2014 Apr 15;2014.Orbital trauma and its impact on the heart.

 

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William  I am Harvey first discovered human circulatory system in the year 1628 .Published his work in  De Motu Cordis” (otherwise known as “On the Motion of the Heart and Blood”) as a 72 page booklet in Frankfurt book fair. The world of medicine changed  forever , and new system of human circulation was born.

Read this now

Who first invented human circulation william harveyExcerpts  from   Chinese classic of Internal medicine , written  2000 years before William Harvey,

All the blood is under the jurisdiction of the heart .Twelve blood vessels are deeply hidden between the muscles and cannot be seen.Only on the outer ankles are visible because there is nothing to cover. All other blood vessels that are on the surface are  veins. The harmful effects of wind and rain enter the system first through the skin , being conveyed to the capillaries. When these are full , the blood goes in and turn empty into the big vessels .The blood current flows continuously in a circle and never stops

Post-amble

Of course , this in no way takes credit away from any body .William Harvey collected  every data on circulation available at that time , and  came with that classic De Moutu Cordis ,  the importance of which is undisputed. But ,history time and again tell us there are silent restless brains pondering over important  concepts all over the globe .Whoever has the access to scientific  facility , proves the same  point ,  publishes first and gets attention . After all thoughts are never rewarded in human domain ! (God , does it I guess  !)

Reference

1.Hume E.H Medicine in china ,old and new,American medical history 1930; 2;272-280

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