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Great cardiology websites : This one is for cardiac radiology !

March 7, 2010 by dr s venkatesan

Hunting for  treasures in medical jungle is no easy job

There are  thousands  of websites for learning  radiology  and then ,

This one  . . .

Hats  off  to   William Herring, MD,

http://www.learningradiology.com/toc/tocorgansystems/toccardiac.htm

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How to identify pulmonary veins in transthoracic echocardiography ?

March 6, 2010 by dr s venkatesan

Even though it is a great vein , often the imaging pulmonary veins by echocardiography is a not a pleasant excercise.

This is due to the following facts

  • The pulmonary veins are posterior structures
  • They occupy the far field of echocardiographic window
  • The pulmonary veins often enter obliquely into the LA
  • The course of PVs are highly variable ( Like RCA origin !) especially in ASDs ,where identifying PVs becomes all the more important

Hence no fixed imaging angle can be advised . But generally a pattern is observed.

  • Right pulmonary veins are best viewed in apical 4 chamber or 5 chamber or in between (Especially RUPV is  seen best in 4.5 chamber view !)
  • Left pulmonary vein , best visualised in  Para sternal  long and short axis view.

Other modalities for imaging pulmonary veins

TEE : Can be  very useful since it is brings the vein closer to the probe .But needs more expertice.

Contrast echo :Probably a simple and best modality often underutilised.

Very useful to clinch the diagnosis when PVs take abnormal course as in PAPVC .

MDCT , Spiral CT, MRI  are the new age modalities that can provide us  with dramatic  3d images of PVs.

The  echocardiogram will always prevail over these sophisticated gadgets for its simplicity and also it’s ability to give us the physiology of pulmonary venous flow which is vital in many diseases(Constriction, Diastolic function etc)

The following illustration is a gross attempt to simplify the imaging of PVs.Please note the rules may not be applicable in all.

Left upper and lower pulmonary veins in short axis view will be posted shortly .

Reference

The images are  based on  personal observations and  an  excellent insight  on the topic from  Department of Cardiovascular Medicine, Guangdong Provincial People’s Hospital, Guangzhou , China

http://ejechocard.oxfordjournals.org/content/9/5/655.full

Posted in Cardiology - Clinical, cardiology -congenital heart disease, echocardiography, Uncategorized | Tagged , , , , , , , , , | Leave a Comment »

A landmark study , but least popular among the interventional cardiologists !

March 3, 2010 by dr s venkatesan

Are the drug eluting stents really better than bare metal stents ?
A million dolor question ? , No . . . a billion dolor question
A study which answered most convincingly with a huge data base  published in LANCET 2007.
  • 38 trials  , Metaanalysis
  • 18 023 patients with
  • 4 year follow-up of up to 4 years.
  • No mortality difference from bare metal stent vs DES
But unfortunately there is  no takers for this  study . The usage of DES continue to  surge ahead  .
The problem facing the medical science in the current era
It takes years  of research to get  into  the truth    and  still   longer time  for  us  to  accept it ! Ironically  falsehoods have immediate patronage and there is no incubation period !

Posted in Cardiology - Clinical, Uncategorized | Tagged | Leave a Comment »

What do we mean by membrane stabilising action of magnesium and lignocaine ?

March 3, 2010 by dr s venkatesan

Human body is a collection of trillions of cells.  Life  is nothing but , a bundle of energy flowing across each of these cells  .Every  organ  has a  specailised mode of communication among themselves and others. When a cell is in an excited state , there is a  likelihood of spontaneous electrical activity.This can happen in nerve cells, cardiac cells , GI tract,  or virtually in  any cell  which has a porous cell membrane and ionic fluxes across it .

  • Each cell membrane has a resting membrane potential . It  varies between -60 to – 90mv in most cells. When this potential increases there a propensity for  arrhythmias in heart  and convulsions in the brain , peristalsis in intestines and so on .
  • Drugs  like local anesthetic lignociane acts by blocking the  Na+ channels and there by neural activation .Similarly magesium  acts on these channels to reduce the excitability of these cells.
  • We know,  the sharp ascending stroke of cellular  action potential is mediated by Na + .Blockage of this channel blunts the action potential voltage and thus  the  early and late after depolarisation is prevented
  • Magnesium sulphate’s anticonvulsant action is directly  attributable  to this membrane stabilising action

Thus , membrane stabilising action  can be termed as “membrane sedating”  action

Posted in Cardiology - Clinical, cardiology -Therapeutics, Infrequently asked questions in cardiology (iFAQs) | Tagged , , , , , , , , | Leave a Comment »

Guideline violations in cardiology

February 28, 2010 by dr s venkatesan

Cardiology  is  among the top medical  specialty  in the current era. It deserves this  special status as it is probably  the  a specialty  which  is based on maximum  scientific evidence and  involves ,   the  most advanced diagnostic and treatment  modalities.

As on today ,  a cardiologist  can deliver a stent  anywhere along the coronary tree and even  implant  a valve percutaneously . A surgeon can put multiple grafts in a beating heart  with a patient totally awake !

A  person can live with an  artificial heart for months and a cadaver  heart can give  fresh lease of   life to a terminal heart failure patient .

Why such a glorious filed of cardiology  should often   evoke a pessimistic reaction  in the minds of  public and media ?

This is because  for a   simple reason , in the name of technology , we tend to  indulge in scientific excesses.

This article in Circulation is not a  surprise then . . . Click on the link, Thanks to AHA this  comes free of cost !

For pdf article click on  the image

Note : Non adherence , inappropriate therapy,  Class 2b  indications ,  are  simply semantics in stage  play !

Actually these terminologies are synonymous with

  • Guideline violations,
  • Unscientific ,
  • Empirical.
  • Unethical or  even quackery

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What is off label prescription ?

February 28, 2010 by dr s venkatesan

We generally  believe  drugs  and devices are prescribed  by  physicians with strong scientific basis .Unfortunately  it is  not  true  in many instances.  A drug which is approved for one disease is assumed to be useful in a similar disease  (But not tested in  clinical trials ) and it becomes  an unapproved  indication .This is often termed as off label use (A decent terminology for unscientific usage !) .But ,there are pros and cons to this type of physician behavior .

Pros

The best example  is  the role of sildanafil in pulmonary arterial  hypertension(PAH)  . A drug which was introduced for erectile dysfunction , was found to very useful in regressing pulmonary arteriolar pressure  (Mistaking pulmonary arteriole for penile vasculature  !?) .  A new therapeutic concept was born  for a  hither to difficult problem of PAH. This  successful  discovery  was  attributed   to off label  usage  of a drug .

Cons

But this is a rare  success story of off label therapy.  In real world , we  tend  to  overuse this in many situations and harm is anticipated.

Drug eluting  stents was used extensively in off  label situation ( Acute MI in a thrombotic milieu, very small vessels , in close proximity  to bare metal etc all these are non label or off label  use of coronary stents   which  resulted in many deaths )

Who gave the freedom and liberty for the physicians to use a drug or device off label ?

No body gave  it , we assumed ,  we have it .

When somebody uses a drug for an unapproved indication is it not unscientific  and guideline violation ?

It is a violation , but we can afford to do it because every body does so !

Is there any scientific  body to sanction and desanction off label  usage ?

Unfortunately  not !

So what  is the solution ?

Self regulation  . . . Can it  be  a  fool-proof method  ?

or  Is it foolish  to expect it so  in this   era of commerce  ?

Related video in youtube hosted by me.

http://www.youtube.com/watch?v=d2WfLrTiUks

Related article

Guideline violation in cardiology practice

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The fine art of converting healthy persons into patients .

February 24, 2010 by dr s venkatesan

Common sense would  indicate  medical care is  meant for the sick and ill  . Relieving  the mankind  from all those  suffering  with a healing hand has made the  medical profession noble and sacred .Medical science   grew with this sole aim  many centuries ago  .Some  times  we succeeded   and many times we failed  and the journey is  continuing .

In those days ,scientists were dedicated , inventions were genuine and were driven by a need to conquer a diseases .Some where along the line, (May be in the last 2-3 decades?)   our quest for money power exceeded commonsense  . Commerce entered   every  walk of life and  medical science became the biggest causality.

The purpose of noble   profession was forgotten . Simultaneously   public awareness and quality if life vastly improved in many of the developed countries . So the traditional illnesses  either disappeared  or reduced   to a great extent . Then came the life style diseases.The cost of treating  an illness spiraled too much especially   in the scientifically advanced countries . What was perceived  as great health care system  became  the  most ridiculed  health system in the planet  ?

Why ?  The simplest answer to this q  is

In the name of science  and  modernity , medical treatment  was glorified beyond the level it deserves ,  and hence  the  cost of treatment is  kept at artificially  & foolishly high  (This often involves  diagnostic   exploration of human body with modern gadgets without any meaningful   purpose )  .

ie , In  a  nutshell  of modern medicine is   often a medical mirage than a miracle . We know ,  the chances of success  as we  try  to chase it. If we think the  world is   waking  on this issue .

We are in for a surprise ! Even as  every one  is asking for outcome analysis in modern health care

more and more countries just imitate the failed ( Scientific and moral failure ) western models of health care .

When major illness are reducing in a society what will the health care providers do ?

Feel happy ?  Yes that’s what   a  sane   mind  would   do .  In a capital  rich ,   health conscious ,   knowledge  driven  society the opposite happens .

When  the patient  input  into a top hospital  reduces , the MBAs   in  them plan strategies  to bring  increase the bed occupancy rate and  maintain  patient  parity.

If sufficient  patients  are not there in a community what shall we do ?

Create  more  patients

Creating  new patients is a too dangerous game ,  what shall we do ?

In the  name  of preventive screening   let  us  label   normal  persons as patients .

How to do it ?

The following examples  are personal observation made in  huge city of educated elite  in a developing country . Excuse me if it offends a few  . . .

Define, redefine all criteria that define the disease (There are

  • Make, 130/85mmhg of blood pressure as pre hypertension and make them visit our HT clinic every month.
  • In the  name of risk stratification do CRP, Micro HDL , Apo a   etc and  catch them  for primary risk reduction for a non existing illness
  • Let us  label  all the   age related  bone loss as  deadly osteoporosis and do bone graft.
  • Let us  call  the occasional post dinner stiff stomach as non ulcer dyspepsia   and  insert a  endoscope  into the patient tummy .
  • Do a 64slice CT  in a master health check and convert many  of the healthy  normals into carriers   soft  coronary plaques.
  • Do a ultra sound scan  in every one who takes alcohol and  give our brains a temptation to label  the normal  fatty streaks  as infiltrative  fat disorder .
  • Do routine pelvic scan and detect  sub clinical fibroid uterus as potentially  malignant and  post them for hysterectomy on the next operation day.
  • Convert all healthy women as a  potential cervical cancer  and administer  herpes vaccine and help  the vaccine company share  move up in wall street !
  • Finally , screen  all  our  playful   kids for   learning disability and   label them as slow attention deficit disorder  and  make their  life permanently   miserable .

The list is endless  . . .

Final message

We  are in a  era ,  where  even   a  simple  illness  ( common cold ? )  can be converted into a billion dollar industry . ( Are you aware of H1N1 fiasco ,  The role of   WHO  and  mystery labeling of pandemic !)

While the above  misadventure  with scientific excesses   goes  on merrily  , lest we forget , millions of children  and adults  suffer in misery for want of  live saving  investigations and drugs  in any country .

When a person with a head injury dies due a  missed   subdural  hematoma for want of CT scan in one hospital  ,  ” in the adjacent hospital”  a wealthy and healthy man  ( who got admitted for master health check up ) undergoes  a series of scans  all over the body   even as he is  watching   the  satellite TV in  the comfort of a  five star suite   !

God will never  forgive  the  noble professionals   if they are part of this  negative health care  forces

Finally  ending with a very positive note !

The new   initiative by  Obama   , ” Health care  for  the uninsured ” is to be welcomed as great move  and will do a world of good .

But , our  only  request  to WHO ( or related   bodies )  is to create a forum or authority  to  impeach all fancy diseases from the medical   literature  !

Posted in bio ethics | Tagged , , , , , , , , , , , , , , | 1 Comment »

What is the mechanism of deafness in Jervell and Lange-Nielsen syndrome ?

February 22, 2010 by dr s venkatesan

The same channels , that  create the  deadly prolonged  QT interval  by  delaying the  repolarisation  in the heart  is  responsible in the for the deafness  as it interfere with inner ear

Mechanotransduction of sound into neural signals .

For proper auditory function  , the cochlear hair cells   needs  a continuous flow of endolymph which  maintain a voltage gradient for  nerve  signal  transmission  .The lymph secretion is  is regulated by potassium channels  KCNQ1 and KCNE1 . Mutations of this gene impairs  the K + content of the endolymph. It results in  a compromised  endocochlear potential (Difference between peri lymph and endolymph potenial )  .This result in irreversible deafness .

Link to   a good   illustration from Medical physiology

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What is a cannon sound and what is a cannon wave ?

February 21, 2010 by dr s venkatesan

Cannon Sound

A loud first heart sound (S 1)   which is  heard intermittently in patients with complete heart block (CHB)  is  often referred to as  cannon sound .

What is the mechanism of loud S1 in CHB ?

We know , the intensity of S 1 is  mainly determined by the  relative position of mitral leaflet (To be precise, the  anterior mitral leaflet(AML) )   at the onset of systole.  We also know the  PR interval  has an intricate relationship to  mitral leaflet  position .

The shorter it is ,  wider the leaflet separation  and a longer PR interval makes a mitral leaflet assume a almost closed position   by the time the ventricle contracts.this happens because  a long drawn PR interval fills the ventricle more completely and LVEDV  reaches the maximal levels and LV blood column lifts up the mitral leaflets , and hence the LV  contraction  which follows does not close it with a  bang. In a short PR interval the opposite happens and hence a loud S1 .

In CHB we have variety of PR intervals ranging between  very short to long   ( falling just before the qrs complex) It is not difficult to understand this , as P waves are totally dissociated with the QRS complex  in CHB.In fact p waves have a liberty to fall any where in the ECG tracing , some call this as marching through the qrs complex !.

Hence typically the S1 is variable in intensity , varying between loud to soft.  When  P wave falls just behind a QRS complex , it generates a very  loud S 1  that is called cannon sound .This happens intermittently.

Cannon wave

This is entirely different phenomenon except that it shares the word cannon . Cannon a wave is  a visual finding on the jugular venous pulse.(JVP) .It is a systolic event . It is also seen in CHB as like a cannon sound

This is a giant a wave  in  JVP  when the right atrium contracts against a closed tricuspid valve. In physiological situations atrium contracts with an open AV valves , so that ventricle gets  filled . So atrial contraction  does not does not cause any reflux of blood back into vena cava.

But, when the atrium  contracts and  finds , the AV valve closed  there is no other option   for the incoming blood  to reflux  back into  the neck veins. This is seen as giant a waves called as cannon ” a “waves

With reference to ECG  location ,  this cannon”  a” wave occurs   whenever p wave falls within the ventricular systole ie  the QT interval .The cannon waves also occur intermittently like the  cannon sounds.

What is the  peculiar relationship between cannon a wave and   sound ?

In fact , it is  a non- relationship.  Though  , both the sound and wave   can occur in a given  patient with CHB ,   they can not occur simultaneously .This is because ,  for cannon sounds   to occur  the  P  wave has to fall before  QRS  and for cannon waves to occur the  p   waves must fall after QRS  ie with QT interval .

Clinical significance  of  cannon wave

Complete heart block is the most common situation for cannon waves to occur.

Ironically ,the VVI pacemaker which is used  to treat CHB does not prevent the cannon waves , and atrial contractions continue to occur at random , causing various degrees of intermittent venous reflux into the veins .This may produce, worrisome venous palpitation in some (Usually settles down after few weeks !)

Some attribute , the so called pacemaker syndrome ie giddiness, dizziness to this abnormal venous waves triggering the carotid baroreceptors (Venous -artery spillover )

Will DDD pacemakers  eliminate venous cannon waves ?

We hoped so , it does in fact . But,  it really happens only if the A sense V pace mode . A pace V pace mode with programmed PR interval is not a realiable way to produce AV synchrony. It is  common ,  many of the DDD pacemakers fall back to VVI mode either intentionally or by mode switching  for various reasons.

//

Posted in Cardiology - Clinical, cardiology -ECG, Clinical cardiology -JVP, Infrequently asked questions in cardiology (iFAQs), Uncategorized | Tagged , , , , , , , , , , , , , , , , , , | 1 Comment »

Lesser known cardiology journals . . . but with excellent content !

February 21, 2010 by dr s venkatesan

There are many  cardiology journals we read , trust , and celebrate  . . .

Many of us are not aware of   few other excellent journals

This is one is different

It is  from  Scandinavia &  deserves a special status.

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