Posts Tagged ‘m mode echo of vpds’

VPDs are the most common arrhythmia  that  confront  us  in  cardiology clinics .While  it can be a totally  benign   manifestation in some  ,  it may signify a sinister condition in others. ECG  is the easiest  and surest way to identify VPD.However  a shrewd echocardiographer can detect the VPDs while imaging the heart.It is often missed if one do not concentrate on the mitral valve motion.

Note :The VPD convert the typical M pattern into a inverted U pattern in mitral valve.

One of the important hemodynamic side-effect of VPD is intermittent mitral regurgitation.

Effect of VPD on mitral valve opening .

By  conventional thinking   VPDs  are expected   to impact  more on the  mitral  valve closure than it’s  opening .In reality it has indirect influence on mitral valve  opening as well. The retrograde  conduction(VA conduction) of the VPD determine the timing of atrial contraction and hence the   mitral valve opening. If the VPD gets blocked retrogradely  within AV node , the normal sinus impulse will activate the atria in an antegrade fashion .Note ,  he atrial activity  occur randomly when multiple VPDs occur.This makes the cardiac cycle too complex to assess especially the diastole. (In fact true  physiological diastole  may  not occur here !)

If  the mitral valve opening  is interfered by a   VPD  (Early diastole is  the  favorite time  for VPDs to  appear  !  )   .When it occurs the AML is    suddenly pushed  upon superiorly  by the premature ventricular activity and hence resets the  mechanical diastole. Please note electrical resetting of atrium is different from mechanical resetting.

It is also possible atria and ventricle contract simultaneously .This is the time , a cannon wave  may occur inside LA .VPDs can result in pulmonary venous canons and may even elevate pulmonary venous pressure   if  this  occurs repetitively .

Another possibility  is ,  VPDs  may not initiate a ventricular  contraction at all .It may be  simply  be an electrical event. That’s why  we changed the name of extra systole  and premature contraction into just   premature depolarisations.

Why is it important to know about M Mode motion of VPDs

Cardiologists  continue to  engage wide qrs  tachycardias   in the  wrong side  of their   brain for many  decades .The ECG debate about wide qrs tachycardia  is expected to  continue  for generations . !  Few smart cardiologists would  rapidly put  the echo probe  over the mitral valve and able to  differentiate  instantly a VT form SVT   with fair  degree of accuracy.

Detection  of regular M shaped mitral AML  will exclude a VT with a high degree of precision .(AV dissociation by echo )*

Even  presence of trivial  MR*  (More often diastolic )   which occur  irregularly  will  definitely indicate it is VT . SVT  hemodynamically   can not result in this  MR is gives us evidence for AV dissociation

* No reference for these observed indices in our lab. (Class 1 Level C expert opinion(  No one calls me as expert though ! )

What is the mechanism  of VPD induced  mitral regurgitation ?

It is well-known VPDs can cause   mitral regurgitation .Not every VPD cause MR.

  • The timing is important .
  • It can be  either systolic or diastolic MR .
  • If VPD occur in early diastole (After the T wave , the MR jet  will collide with  diastolic mitral flow. )
  • Paradoxical septal motion induced by VPDs can alter the pap muscle alignment transiently and result in MR
  • We dot not know how a LV apical VPD  differ from RVOT  VPD in the genesis of MR.
  • Logic would suggest RVOT  VPDs are unlikely to result in MR as there is  a time lag for the impulse to reach the LV base

What is  the effect of  VPD and Aortic valve opening ?

While  every VPD promptly  hits the mitral valve ,  aortic valve may or may not open with VPDs .Again timing and focus of VPD could be  important.This is the reason during  multiple  VPDs  only few open the aortic valve , that  explains  pulse deficit. (The so called missed beat )

Final message

Anterior mitral leaflet (AML) is the most mobile structure  of  the heart . Hence ,  it is not surprising to note  sudden unexpected ventricular contraction will  have maximum impact on this valve .

When VPDs occur in clusters or at random it has a complex effect on the mitral valve motion. This is responsible for  palpitation , minimal mitral regurgitation and rarely trouble some pulmonary venous cannons and raise in pulmonary venous pressure .

Careful analysis of  AML motion can give us useful clues to differentiate VT from SVT during wide  qrs tachycardia

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