Posts Tagged ‘jugular venous pulse’

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This was presented in the cardiology fellow training course in Chennai – March 2012

(Acknowledgement : Paul wood collection , J.K Perloff , Credit to Images from open source )

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Looking at the neck veins for hours  together  has been a favorite pastime of our cardiology ancestors.Thanks to those sharp intellect , that has led us to this height of cardiovascular revolution. Measuring JV pressure by itself was considered a big science. Putting a patient in 45 degrees , marking the sternal angle, identify the  oscillating venous column,  measuring   the vertical distance  etc . . .

Now in 2010 , with bedside hand-held echo one can rapidly  rule out an elevated  central venous pressure by imaging the jugular vein directly . Here is an article from American heart  journal


Simon MA, Kliner DE, Girod JP, et al. Detection of elevated right atrial pressure
using a simple bedside ultrasound measure. Am Heart J 2010; 159:421–427.

Soon , your mobile will double up as ultra-portable  echocardiogram

Read this related article in this blog .

Coronary care in your pocket

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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.


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