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Essential nephrology for cardiologist : A new molecule scores over creatinine in predicting acute kidney injury !

October 6, 2010 by dr s venkatesan

Bio-chemical diagnosis of cardiac injury or infarction is  well  documented modality for many decades. Now , acute coronary  syndrome is diagnosed  by a battery of tests  that  detects the  proteins leaking from the  injured  myocardium.

Nephrologists have long been aiming for  such a  marker for ischemic  renal injury  (Not withstanding the fact , they are already blessed with two age-old molecules  creatinine and BUN !)

Neutrophil gelatinase associated Lipocalin (NGAL)

  • This is 25 Dalton molecule  richly secreted within renal  cortical cells in response to ischemic injury .
  • It is released without  modification in the  urine  .High urinary levels  of NGAL  reflect  acute renal  injury.
  • Early experience shows it  is a  promising  investigation and could  become a regular biochemical test in the near future.
  • Urine level of  NGAL >250 ng/ml , 2 hours   after cardiac surgery  predicts impending renal failure  in the next 24-48 hours .The advantage is , it NGAL raises well before serum creatinine.

NGAL After cardiac surgery

http://cjasn.asnjournals.org/cgi/content/full/3/3/665

Lipocalin following PCI

Bachorzewska-Gajewska H et al. Neutrophil-gelatinase-associated lipocalin and renal function after percutaneous coronary interventions. Am J Nephrol 2006; 26: 287-292.

www.ngal.com

References for  NGAL

http://www.ngal.com/literature/popular_reviews_of_the_nature_of_ngal_with_a_focus_on_acute_renal_injury

Final message

  • Cardiologists  and cardiac surgeons  have started  performing  complex    PCIs and  CABGs in  patients with   delicately  and precariously balanced renal function.
  • While ,  cardiologists   challenge  the kidneys with high  osmolar contrast agents ,  the surgeons stress it with extra corporeal circulation.  Many of these patients also  have co- morbid conditions .
  • Often , the cardiac outcome is directly linked to pre /post procedural  renal function .Nephrologists usually  arrive  late  into the filed (Creatinine SOS calls !).By this time the full-blown ATN sets in many.

Now , we have a tool to identify impending ARF , it gives us  little more time and  flexibility in managing the issue .

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The paradox of “high cost” low quality medicare !

October 4, 2010 by dr s venkatesan

Medical science is  not like mathematics or economics .

  • It is about how a  bundle of human cells(organs) behave at times of adversity .
  • It is  about how our mind  takes on the body .
  • It is also   about , how the care takers  Heal/Manipulate /Manhandle  these cells at times of distress !

We know, two persons with identical injuries , sustained in a car crash one dies within an hour  , while the other with a  many fold serious injury successfully fight the trauma and walk out of hospital with victorious  .That is the fighting spirit .This  is either  inherited  are  nurtured or both.

This implies , an accidental injury may be an  external , unpredictable  event,  while the  response to  that injury is predetermined or even a predictable response !

In the name of modern science , we “the human animals” are trying to buy this fighting spirit  with money.We are made to believe ,  survival and well-being is a commodity and  can be  bought with high cost  medicines , and high cost care .

Remember  , one of the most astonishing medical  fact is , while we  may struggle to induce  swine flu  in  a laboratory on a given  individual ( Even if ,  H1Ni  viral  concentrate is  infused or inhaled  )   , an  other person gets this disease  , while simply  flying over an  infected country  . Such is the complexity  of  the host response  system in medicine .

So , it is foolish to think health can be bought or maintained  with  money power or modern hi-tech medical care .At best it can save   few lives  with  its   life supporting drugs and devices . Ultimately,    human survival  is determined  by the way we  live  and the way  our  ancestors lived and how we fight the illness.

Yogi’s  of  Himalayas lived for more than 100 years without the need for drug eluting stents and LV assist devices .

Having totally misunderstood  the concept of health and illness the world is wondering how on earth , we can reduce the escalating cost of  healthy living  (pseudo health  !)

An article in the current NEJM ponders over ,  Why in  Grand junction,  Colorado ,USA ,  the health care cost is very much lower ,  without compromising the quality of life and survival.

The answer is very simple .There is some body in that county , who  dares to think beyond  raw  science  and adds  little  bit of common sense ! Obviously he has to be rewarded and  this  model need to be replicated  elsewhere.

http://healthpolicyandreform.nejm.org/?p=12706

This article discusses the phenomenon  of  high quality , low cost medical care , but what it misses out is , the reverse could also be true !

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Lesser known cardiac arrhythmias ! What is 1 : 2 AV conduction

October 2, 2010 by dr s venkatesan

AV node is the  “Go slow” region in the cardiac highway .Every impulse is delayed  for about 120ms and then pursue its  onward journey to depolarize the ventricle.

Since  AV node  has inherently slow conduction properties , it is not  surprising  this zone  is vulnerable  for developing  AV block .We know AV junction and the adjacent his bundle  is the site  for many types of AV block. In  classical  Mobitz type  2 AV block ,  for every two or three supra ventricular impulse only one is  conducted and we call this as   2:1  or 3: 1 AV block ( More appropriately AV conduction  )

Can we have reverse of the above situation ?  That is , for each supra ventricular  impulse  can ventricles  fire twice or thrice   ?

Yes it can  ,  what looks like a funny situation ,  could be more common   .We are not recognising it often.

How is  this possible ?

This can happen only if there are two different  tracts of conduction from atrium to ventricle and  both of them conducting  fully to  reach ventricle and complete the depolarisation.

This situation can  occur in

  • Dual AV nodal pathway*
  • Triple nodal pathway**
  • Multiple AV accessory pathways (All contributing  AV conduction )

* Exact incidence in general population is not known ,but it could be higher than what  we believe !

** Very rare

 Some what  related  phenomenon , never the less , it   mimics 1:2 or 1 : 3 AV  conduction

  • AV nodal echo beats
  • Non sustained AVNRTs

How is simultaneous conduction possible in dual AV nodal  physiology  ?  Will ( it not  ! ) the first impulse make the ventricle refractory to the following impulse ?

Under normal physiological conditions simultaneous conduction*  is not possible .It happen if  . . .

  • The first impulse goes relatively fast  and activate the ventricles .
  •  The second component of the first impulse, ie  through  the slow path conduction   is sufficiently  slow ,  it  reaches the ventricle and  able to depolarize it , well after  the  first beat’s  refractory period .
  • A Further requirement is , the initial  fast response fails to block the incoming slow  response  by a retrograde   slow path block .

* It need to be further clarified , even in physiology ,  simultaneous conduction is possible , but it is  often incomplete . At best it can result in ventricular fusion beat as in pre -excitation beat or it can be a concealed one travelling halfway through the AV node or the bundle.

Why recognising this 1:2 conduction  is important ?

  • It is traditional  to  think  , an unexpected beat  occurring prematurely  in a given strip of ECG is always thought to be an ectopic beat .This is not the case. An  unexpected premature narrow QRS  complex  with out a  p wave , should  make us suspect   dual AV nodal conduction .
  • If  this  dual AV nodal  pathway  is intermittently  conducting or conducting with  varying velocities ,  it becomes  an     irregular narrow QRS  rhythm  .This  can ,  very well  be confused with  atrial fibrillation.
  • If  one of the paths in the dual AV pathway  is conducted aberrantly   it  mimics a  VPD.

Final message

1:2  AV conduction may not be rare . Cardiac physicians are encouraged to look  for this phenomenon whenever they encounter an abnormal  early  narrow  QRS  beat without preceding P waves. Apart from academic curiosity , it can  solve many mysteries in CCUs and EP labs .

 Reference :

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2267891/

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The happiness dissociation curve

September 30, 2010 by dr s venkatesan

Mankind’s  elusive pursuit of happiness  has an  interesting relationship with human physiology.The recent research  from  Princeton  university has confirmed a concept about the relation between  happiness and the economic well being .It was strange it exactly mimicked a famous physiological concept involving hemoglobin and oxygen.

Two simple questions were asked

  1. Can money bring happiness to life ?
  2. Is there a linear relationship  between money  and happiness ?

The answer to the first question is  “yes” it can.

The answer to second  looks complicated but , it is actually simple !

The relationship between money and happiness is  linear initially  , till it  hits the flat  section of  the curve  at 75000$ /year . (In India it may at 12,0000 lakhs/year)

Like hemoglobin , which   gets saturated  with oxygen  at  Pa o2 of  90  %  ,

Beyond  a particular point , however much you increase  your salary , the  mind can not be enriched with further happiness !  , as all the happiness receptors  get  saturated !

Link to Princeton university paper

Another  curious phenomenon is ,  the more time you spent  in pursuit of happiness less likely you get it  !

(The following  illustration  is from the original Princeton paper which i got from  NDTV  website )

http://profit.ndtv.com/news/show/the-odd-relationship-between-money-and-happiness-102103

Hemoglobin Oxygen dissociation curve

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MRI in new Avatar : Journal of cardio vascular magnetic resonance imaging

September 25, 2010 by dr s venkatesan

Cardiology is probably the most rapidly growing field  in medicine. Radiology is closely following .When both combine together there is  bound to be  plenty of action ! That’s what is happening with this journal .

Knowledge is power , do not bother if you do not have such  a machine in your work place.Just know what is happening in the world of cardiac imaging.

http://jcmr-online.com/

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Laughter and enothelial function

September 24, 2010 by dr s venkatesan

  • Endothelium is the largest vascular organ in the body .
  • It is constantly being serviced by both the circulating blood  from the luminal side as well as from the abluminal plane.

  • The discovery of nitric oxide and endothelin  was a breakthrough .
  • They are under neural, mechanical and endocrine control .
  • Negative emotions like anger and depression has a high correlation with hypertension and cardiac event
  • Positive emotions like laughter and happiness is expected to have good vascular tone

This fascinating  study from Japan and USA (Texas)  published  in American journal of cardiology , discusses how a comedy movie possibly releases nitric oxide profusely from our endothelium

Link placed with the courtesy of AJC

http://www.ajconline.org/article/S0002-9149(10)01050-7/abstract

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Regulating the regulators !

September 24, 2010 by dr s venkatesan

The world of  medical science is  moving in a alarming speed.In any field , speed is always dangerous ! That’s why we have speed breakers , traffic police , speed cameras , etc etc . The medical world  is flooded with new devices, drugs , procedures . Though the mankind is benefited with many of them , a equal number could do the opposite.

How to identify which is causing benefit and which doing harm ?

It is a horrible fact , this is the most difficult exercise  for the  medical academia   . . . Still worse , harm will masquerade as benefit ! Further ,  beneficial concepts are  often buried alive if  it lacks  glamor  or  commercial value (Eg: The Digoxins,)

Lay public (as well as )  the physicians   are fed with half-baked ( Often quarter baked !) medical information .Many  of the medical journals,  guidelines , sponsored  seminars  ,  some times  even text books do a clandestine  campaign  . Even after a completion of major trial,  real truths rarely  come out . Funnily ,  they call them aptly , as blinded study ! Who is blinding whom is a different issue .

So ,  in  this  new millennium , thousands of innovations are on the pipeline. These pipes are often  infested with trivial , duplicate or even  harmful  concepts waiting for a grand release into human domain.

Take the story of coronary stents

In 1977 , Gruntzig mastered the  opening  of  the obstructed coronary  arteries with a simple balloon without any add ons . That patient is still alive  without  angina  . In the next 30 years we have ridiculed (Rather , we were compelled  to ridicule it ! * Read the related article  Is  there a role for  plain balloon angioplasty ?

Technology made  it  possible to introduce a  gamut of intra coronary  devices .We used (?abused ) all sort of anticancer drugs within the tender human coronary arteries .In 2002 , we claimed to  have climbed the summit and conquered  the restenosis with DES. And in 2010 , every one knows  what is happening to DES .

The malaise is  deep rooted  in every specialty . Next  came the  Stem cell fiasco ? and more  recently huge  conflicts of interest exposed  in the  vaccines  against H1NI

Final message

Who is going to regulate the menace ?  Hmm . . . . then  . . . Who will regulate the regulators ?

Is there a way out for our patients ?  or  they  have to suffer with it  along with the disease . The later is  more realistic option !

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50th anniversary of cardiac resucitation had just gone by . . . silently !

September 23, 2010 by dr s venkatesan

In 1960 , exactly 50 years ago , a group of doctors from Jhon Hopkins published their observation in 20 cases. It went on to become , one of the most remarkable discovery  in the history of cardiology .

They taught us how to use  a pair of hand  ,  as an  artificial  heart and save lives

They are . . .

  1. Dr Kouwenhoven*
  2. Dr  James R. Jude, and
  3. Dr G. Guy Knickerbocker .

* He was not a medical doctor but an electrical engineer at Hopkins but he worked in the medical school as well .

They meticulously documented , each patient’s case history ,  whom they were able to successfully revive , (It was in the same  period , the  AC/DC shock was also invented  in the  Hopkins ) .One of  the  highlights of their paper was ,  with each chest compression  they were  able to elevate the carotid pressure  up to 90mmhg and was recorded in a pressure tracing .

We have to thank the  JAMA (Journal  of American medial   association )  for  making this  original  article   available  free in their website .

Must read for every cardiologist

http://jama.ama-assn.org/cgi/reprint/173/10/1064?ijkey=33bb40fe3062331bae50e10c8a04263f3e26b317

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Harvey Cushing : Getting Inspiration from an unparalleled life of a neurosurgeon !

September 22, 2010 by dr s venkatesan

We owe a lot  , to  our ancestors for making our  journey   smooth  and purposeful   in  our  pursuit ,   of   healing the   mankind  . It is because of their  meticulous  clinical acumen , passion  , dedication ,sacrifice we are enjoying  the fruits  of success .

Though there are thousands of them , one life that always fascinates  me is that of Harvey Cushing. His fame went  to dizzy heights  after his publication of  biography of William Osler .

A book every medical  professional must read and cherish especially the elite cardiologists !

I wonder  ,what  Harvey Cushing  ,  if alive would make  a difference  in the current  world of medical  science contaminated with commerce ,  hyped up technology ,  and  the near extinct bed side clinical skills.

Links to life of Harvey Cushing http://www.med.yale.edu/library/historical/cushing/peter.html

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SHIFT trial : Ivabradine shining in Beta blocker’s glory ?

September 20, 2010 by dr s venkatesan

We now understand , heart rate reduction  could be the single most important factor  in the management of heart failure .Beta blockers have proved this time and again.We know heart rate has a linear relationship between survival .

SHIFT trial has  proven  that  Ivabradine  has a major role in the management  of chronic heart failure therapy .It is an If current blocker .  No hemodynamic  side effects was noted.

How does Ivabradine act ?

It acts on the phase 4 diastolic depolarisation in SA node by slow I f  currents.

SHIFT trial Link to lancet

SHIFT study official website

In this trial , the usage of  optimal Beta blockers  was  only in 25 %  . Patients  who received   complete beta blockade did show much benefit with Ivabradine . Further, the usage of  digoxin was only around 20% .This does not represent  the realistic  population of  cardiac  failure in many  countries  .In India , almost 70-80 % receive  it . Digoxin , the wonder drug does have an important vago mimetic action, to  reduce the heart rate .

Another  contentious issue   in SHIFT study  is , the Class 4 patients constituted <2% of the study population .It is ironical , these are the patients , one would  like to try a new rate control drugs like Ivabradine  , because we  are worried about beta blockers in this population  .A great opportunity was  lost as Ivabradine could have  been tried in this population.

We need a study  like this .

  • One to one comparison   of  beta blocker  and   Ivabradine  in cardiac failure  . Such a study will ever happen ? My guess is , it is  next to impossible !
  • Efficacy of  Ivabradine in patients with class 4  failure  , where beta blockers were contraindicated  or could not be administered.

Final message

Ivabradine , a new generation  negative chronotropic agent  is a great concept drug. But , the worthiness of this drug  is questionable , when we have  proven , well tolerated  drugs namely , the beta blockers to reduce the heart rate.. However , if the beta blockers are poorly tolerated  Ivabradine may be tried.Last , but not the least, never under-estimate the greatness of digoxin in heart failure.It is the only drug that has a positive  inotropic  properties coupled with  negative chronotropic action . Both benefits patients in CHF  . It can do wonders than any other drugs .(DIG trial was the most misunderstood by cardiologists!)

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