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Archive for the ‘Cardiology – Animations’ Category

Ventricular pressure volume loop is an Important ( often feared !) concept to learn for cardiology fellows . . . I would say , It is not that hard to understand !

These loops tell us the secret  hemodynamic story of a 300 gram “mass of muscle” called the heart  and how It handles about 100 ml of blood every beat and successfully ejects around 70 ml into Aorta and Pulmonary artery *

108356heart_beating

While doing this life sustaining job , It would seem the heart muscle  conducts a perfect, non stop, hemodynamic orchestra with 4 electro-mechanically coupled phases which is depicted as classical ventricular pressure volume  loop. Mind you, this loop is plotted pressure volume data from a single heart beat and it can’t be time correlated with heart sounds or ECG as the two parameters loop around in same time cycle.

Watch this animation , carefully and read the appearing annotation that come along with each phase.That should suffice to understand the basic. (For Audio version go the video link in the reference )

Modified from a clipping from Giphy.com.Original source of this Image is not located. Whoever has done this thanks and it’s a great attempt.(I have tried a fusion Image of doppler mitral Inflow in diastole and Aortic pressure curve during ssytole to bring PV loop an anatomical perspective.)

*Note: When we say PV loop it means about by LV by default . We do have seperate RV ,LA (even RA?) PV loops.

Is there clinical application for  PV loops ?

It may not have any direct use , but understanding  how a ventricle works in normal conditions or at distress especially during acute decompensations or after surgery  is vital. With modern gadgets like LV assist devices,  Impella used widely and to assess hemodynamic efficiency of transplanted (Very soon total artificial hearts) , PV loop analysis of both RV/LV will be critical.

Is there any simple Lab modality that can draw this Loop curve instantaneously ?

echocardiography lab methods for ventricular pressure volume loop

 

Very few companies make it . AdInstruments that make power lab monitors, enable us to visualise PV loops invasively .

 

Can we get PV loops non invasively by Echocardiography ?

Echocardiography  provide us both volume  and pressure data.With improving accuracy of data it should be possible to plot the loop manually with some effort. (Still , we can’t get pressure in all points of cardiac cycle )

I guess, sooner 3D volumetric machines with automated online doppler pressure data across the valves  can help us draw the ultimate LV functional  curve live on real time.If that happens cardiologists will be further enriched and hemodynamically enlightened !

Final message

The shape , size , timing and the slopes of this loop  givs us vital info about the functional aspects of ventricle. First one should understand the normal loop , then , we can dwell on the effects of acute and chronic lesions like regurgitations, cardiomyopathy ,cardiogenic shock etc.

Reference 

An excellent knwoledge base on the topic with a  video 

Dr. Richard E. Klabunde, PhD

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Failure of  enocardardial  cushions  to separate and reach the  predesignated destination  ie  right and left AV valve is the basic embryological feature in AV canal defect .This brings whole AV ring  down and stretches the distance between  the semi-lunar valve (especially aortic)  with that of LV , thus elongating  the LVOT into a classical  goose neck deformity.The defect  has a profound  impact on how the AV node and its branches penetrate the ill-formed AV junctional tissue and fan out into the ventricle. There are  four basic issues  that are responsible for the various conduction defects in AV canal defect.

  1. Postero- inferior  displacement of the A-V node is the key abnormality .
  2. Hence  AV node penetrates the ventricle at the level of crux which is abnormal .This results in short his bundle  (AV node short of compressed with His  early direct origin of the left bundle branching)
  3.  Left bundle branching system by itself is also abnormal  with hypoplasia   left anterior bundle branches.
  4.  Right bundle branch is relatively long and elongated

Physiological effects

  1. Prolonged PR interval (50%)
  2. QRS  axis shift can be extreme right or left , but superior direction is a rule .Typically its around -180 . Left axis deviation is distinct in downs syndrome (Counter-clock wise rotation q in lead 1 and  AVL ) .It should be learnt , the ECG features (due to  anatomical defects in AV conduction system  ) can be be  easily modified by the hemodynamic stress of  ventricles  due to associated conditions and classical pattern may non exist )
  3. Surprisingly high grade AV blocks are rare (“viz a viz” LTGV )

Electro-physiology

Short HV interval is documented  in AV canal defects inspite of prolonged PR due to small his bundle length.

membranous ventricular septum 2

conduction system in av canal defect vsd

A large Inlet VSD , simply takes over the place meant for the conducting system and its pushed down and out

Reference

Robert Feldt from Mayo clinic did excellent work about this issue and published in Circulation, Volume XLII, September 1970

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Left main ostial lesion remains a  challenging task .A new stent design is  proposed here.

The lesion

Left main  ostial  stenting lesion003

The hardware 

left main ostial coronary stent drsvenkatesan

The technique

Left main  ostial  stenting lesion002

Final message

This thought came  when I  recently encountered a patient with a left main ostial  stent which was projecting well into aortic root .It is an open access patency ,whoever is capable of converting this idea  to a clinically applicable technique is welcome to proceed !

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Click over the Image  for animation

ptca balloon for PTMC inoue 002

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Cannon waves occur when Atria contracts against a closing tricuspid valve of  right ventricle .( There  would be a equivalent left atrial cannon which  goes into pulmonary vein as well  , it is discussed elsewhere !)

Cannon waves  happen only when P waves fall within QT interval in ECG as QT represents the electro-mechanical systole of  ventricles.  (Since P wave represents atrial systole , it is simple to understand when it falls within QT both atria and ventricular contractions collide to produce a cannon wave into the neck or pulmonary veins.)

The following two images of cannon waves  taken from the legend  Dr Paul woods own tracing  .

irregular cannon waves in jvp  complete heart block

regular cannon waves in jvp  svt avnrt  11 va conduction  002

Regular cannon waves

Occur during SVT  with 1:1 VA conduction.*

1 : 1  VA conduction  can be considered as  absence of  AV dissociation  (Rather  disciplined  VA association with every beat ) This is essential to create a hemodynamic  milieu for regular cannon waves.

* In AVNRT , VA conduction in strict  sense  is a misnomer  .It is simply a retrograde conduction thorough  the AV node .

Irregular cannon waves 

  1. Complete heart block .
  2. Multiple random VPDs
  3. Some patients with VT.*(Who are those patients ?  Those with AV dissociation when retrograde “P” wave falls  within QT interval cannon occurs. As expected this occurs in random fashion  which makes  the cannon fire irregular.

Can we get regular cannon in VT ?

Yes , but rare . As explained earlier this can happen only if AV  association occur on a retrograde fashion.

Further reading in this site

What-is-a-cannon-sound  , how is it related to cannon wave ?

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Pacemaker current is   strangely  referred  by physiologists  as  funny current (I f ) . I am yet to find the exact reason .  This is the current  that  sustain  our life right from the day 22  of  embryonic life when the  cardiac jelly beats for the first time.   SA node  solemnly  follow our  entire life  before  making  a  bid-adieu !

pacemaker  potential sa node 5

 

pacemaker current if funny current poential 002

pacemaker current if funny current poential 003

What is contribution of  If  current in the overall Pace-making  activity ?
This  has not been quantified . The fact that ,  Ivabradine induced  If  current  blockade does not result in serious bradycardia indicate  , SA node has alternate reserve currents as well . ( SA node  is a such a mystery  structure , it would never be a  surprise , if we  find many more  “not so funny”  currents !)

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Squatting is a simple physical  maneuver that can  be done in bed side.

  • Squatting  increases  systemic venous return.
  • Raises aortic after load and SVR

It is  ideal to do  “Stand -Squat -Stand” sequence to appreciate the attenuation during squatting and augmentation during standing

squatting dynamic auscultation mvps mitral valve prolapse

Hemodynamics

MVPS-MR is  a pre load (LV volume )  dependent phenomenon.The degree of prolapse is inversely proportional to the LV size.

Squatting increases the venous return and after load both tend to  increase the LV volume. More blood in the LV  , means mitral leaflet floats much closer to the  mitral annulus . Hence the  force of LV contractility is not only  less on the prolapsing  leaflet , it  reaches late ,  hence the click is delayed  and murmur is short (It may be less intense as well * )

(* Squatting increases aortic after load hence the murmur of MR  may  get amplified .)

Reference

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