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 )
Posted in cardiology congenital heart disese, Clinical cardiology, dr s venkatesan -Personal, My presentations, Uncategorized, tagged a wave in jvp, difference between left atrial v wave from right atrial v, jugular venous pressure, jugular venous pulse, jvp in congenital heart disease, mean jugualr pressure, sternal angle, v wave in jvp, vertical distance jvp on March 11, 2012| 1 Comment »
Posted in Cardiology - Clinical, tagged angle of lewis, cvp, jugular venous pressure, jugular venous pulse, sternal angle, two scale vs one scale in jvp, ultrasound and jvp, vertical column of blood on September 3, 2010| 2 Comments »
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
Soon , your mobile will double up as ultra-portable echocardiogram
Read this related article in this blog .
Posted in Cardiology - Clinical, cardiology -ECG, Clinical cardiology -JVP, Infrequently asked questions in cardiology (iFAQs), Uncategorized, tagged cannon sounds, cannon waves, cardiac auscultation, clinical cardiology, ECG, giant a waves, heart sounds, high pitched sound, jugular venous pulse, long pr and muffled s1, loud first heart sound, loud s1, neck viens, pr interval, pr interval and heart sound, pr interval in s 1, relation of pr interval to heart sound, s1 vs s2, short pr and loud s1 on February 21, 2010| 1 Comment »
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.
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.