Dil Se Technical: June 2011

Wednesday, June 1, 2011

Sino-Junctional rhythm : When a restless pacemaker goes for a walk down the lane !

a new name for a old cardaic rhythm, coroanry sinus rhuthm, juntional rhythm, p cells in sa node, pacemaker current, sino junctional rhythm, sinus node anatomy, sinus node dysfunction, sodium or calcium current in sa node, vagal tone and wandering pacemaker, wandering pacemaker | Categories: cardiac drugs, Cardiology - Clinical, Cardiology - Electrophysiology -Pacemaker, cardiology -ECG, cardiology -Therapeutics, Cardiology-Arrhythmias | URL: http://wp.me/p7rW9-358

SA node is the ultimate power center of heart located in the junction of SVC and right atrium .In normal physiology it fires at a rate of 60 -90 /minute that dictates the ventricular rate .

SA node is a linear spindle shaped structure with a length of 1.5cm . The P cells with unique mitochodria are responsible for pace making activity . The ion responsible for pacemaker current is mainly calcium with the initial 25 % push given by sodium current as well . These cells are predominately under vagal control.Even though pace making activity is normally restricted to the SA node , the vagal innervation is such that the pacemaker has a potential to shifts it's activity both functionally geographically.

In fact , there is constant flux of pacemaker activity with the entire length of SA node.The cranial aspect SA node has more fire power than its caudal tip . It is possible Sinus tachycardia and sinus bradycardia could represent minor changes in the firing focus in its cranio-caudal axis.Further the P cells of sinus node can spill all over the atria and even up to AV node.

What is wandering atrial pacemaker ?

This entity is poorly defined in literature. With pace making cells scattered all around there is no surprise to note dynamic pacemaker shifts even in healthy people. This is especially common in young athletes.

Wandering can occur

Within SA node ( Shift of focus of p cell firing .No visible changes in ECG )
Within SA node and atria
Between SA node and AV node. (Sino-Junctional rhythm )

Effect on ECG

Baseline bradycardia.
Changing P wave morphology
Change in PR intervals
Intermittent absent (Rather concealed ) P wave if is also possible
RR interval can also show minor variation.

Image Modifed from www.eheart.org

Clinical significance of Wandering pacemaker(WAP )

A Benign condition generally has no clinical significance.

It is often an expression of high vagal tone.
Usually transient.
Can be unmasked by beta or calcium blockers.
Severe forms of wandering pace maker can be a marker of sinus node dysfunction and would need further evaluation
In the coronary care units it is associated with infero-posterior MI when the vagal fibers are insulted.

Differential diagnosis .

Some times it need to be differentiated form ectopic atrial rhythm /Low atrial/Coronary sinus rhythm etc .
Sinus slowing followed by a functional escape and reemergence of sinus beat can be a termed as a form of wandering pacemaker

Final message

WAP : This attractive and descriptive ECG entity is largely insignificant in clinical cardiology .

It should not be confused with more dangerous cardiac arrhythmia like sinus pauses and arrest .

Dr.Anil Kumar Gangotia
Sr.D.M.O.( Indian Railway Medical Services)
Former President I.M.A.Gwalior.
Former Director IMA CGP ( M.P.)
District Coordinator for Physicians Trining Initiative ( HIV/AIDS)
A joint programme of IMA,NACO & CHAI ( 2006-07)
Mob.No.+919425301064

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FW: Can you diagnose diastolic dysfunction by ECG ?

From: dranilgangotia@hotmail.com
To: anilgangotia.dilse@blogger.com
Subject: Can you diagnose diastolic dysfunction by ECG ?
Date: Wed, 1 Jun 2011 18:52:59 +0530

Can you diagnose diastolic dysfunction by ECG ?

We presume ECG fails miserably against echocardiography for assessing hemodynamics , while echocardiogram has little value when it comes to studying electrophysiology . Ironically , we often ignore the fact , ECG can provide important long-term hemodynamic data . The pattern of chamber enlargement give us vital clues to the prevailing hemodynamic stress and loading conditions. While echo can be termed as an anatomical and physiologic modality , ECG apart from its unique capacity to record cardiac electrical finger prints , it provides useful , anatomical , hemodynamic information too !

While Doppler is a fascinating modality to measure hemodynamic data in a moment to moment fashion it can never ever tell us , what has been going around in the preceding months or years. This is were chamber size helps which give us chronic physiological information (Chronic Doppler ?)

A simple E:A reversal in mitral inflow doppler can be a innocuous finding in isolation . If it is associated with even minimal grades of LAE it gains huge importance. That is why left atrial size is funnily referred to as HB A1C of diastolic dysfunction ( A marker of chronicity of diastolic dysfunction)

If LAE is so important to diagnose diastolic dysfunction , why we are so obsessed with doppler filling profiles of mitral valve ,pulmonary veins, mitral annular tissue Doppler and what not ! .Many of these sophisticated doppler methods are extremely operator dependent and are subjected to technical and mathematical errors. Especially , with tissue doppler where we magnify the errors as we filter extremely slow tissue motion .

For many decades we have failed to impress ourselves , about the importance of subtle P wave abnormalities in the ECGs of hypertensive patients.

In fact those innocuous looking slurs and notches in P waves , suggest the left atrial stress and a definite marker of underlying LV diastolic dysfunction .

P wave is the only electrical wave that occur in diastole .Hence there is no surprise ,i gives us enormous information about this phase of cardiac cycle .

If only we look at them carefully, zoom it (Now it is made easy with so many softwares) analyse critically we can find a wealth of information about the atrial behavior in hypertension.

Experience from our hypertension clinic with periodic echocardiograms suggest , the following ECG findings can be good markers of significant diastolic dysfunction .

Notched P wave
Wide P waves
Slurred P wave
Bi-phasic P waves

* Surprisingly , these abnormalities correlated with at least grade 1 diastolic dysfunction even in the absence of for LAE or LVH by echocardiogram.

** In an occasional patient P waves can widen due to inter atrial block or conduction delay. This a rare exception for wide P waves without LAE.

Final message

A well recorded and analysed ECG can predict diastolic dysfunction with fair degree of accuracy .This fact need to be emphasized by every one . Next to ECG , LA size and volume by 2d echo are excellent parameters to assess diastolic function in a long term fashion. Sophisticated but error prone , momentary doppler parameters are getting too much attention at the cost of simple , shrewd ECG and 2D echo !