Archive for September, 2015

Pulmonary valve should open shortly after the onset of RV systole , when RV pressure exceeds the PA end diastolic pressure which  will  be around 10-15 mmHg.

We know  cardiac valves open and close with reference to the pressure difference across the valve .So, in any part of cardiac cycle , if RV pressure exceeds  the pulmonary  arterial pressure , pulmonary valve is bound to open. (The pulmonary  leaflets simply doesn’t bother whether  RV is in systole or diastole )

What are the situations RV pressure may exceed PA pressure during diastole ?

Yes, if  RVEDP raises for any reasons beyond 15 mmhg it can prematurely open the pulmonary valve in late diastole. This often coincides with right atrial  contraction  that make the   RVEDP to spike  just before systole.  In chronic right heart dysfunction  the premature opening can occur  much earlier in diastole and not dependent on RA contraction. It can even be noted with AF if the mean RVEDP exceeds PA pressures.

This typically happen in constrictive pericardits and any  isolated RV failure  without pulmonary hypertension.(Please note , for premature  pulmonary valve opening to occur  one important prerequisite is,  PA pressure should be normal or low and hence its precluded in significant pulmonary hypertension )

Conditions associated with premature PV opening

1. Constrictive pericarditis.

2. Isolated RV restrictive cardiomyopathy (Lofflers etc .Note :Biventricular restriction would prevent premature opening  as PA pressure is raised. )

3. Ebstein anomaly

4.Some  patients with with RSOV .(Acute raise in RVEDP)

5.Post tricsupid valvotomy




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Pacemaker implantation is one of the few high impact interventions done by cardiologists.Traditionally , RV apex was paced for many decades with tined or screwing leads. Serious concern was raised in recent years about the ideal site of pacemaker lead position. .Today, some argue  pacing RV from RV apex is a electro-physiological crime (Of-course it appears  more of hyped up fear ! )

What is the concern with RV apical pacing  ?

RV apical pacing is  unphysiological .To mimic physiology we have to move the lead as  cranial as possible within RV. (*Obviously  pacing anywhere in RV is non-physiological .Best would be atrial pacing . This is possible only  in sinus node dysfunction with Intact AV conduction.) Hence RVOT and mid septal pacing was proposed and practiced as a relatively  more physiological site as the spike could capture the natural conduction system early and ventricle is activated from above down.

How to localise the RV lead in mid septum ?

Inter ventricular septum , hardly occupies an area of 5/5 sq cm  with a  complex structure , shape and alignment with RV and LV cavity .In pathological states it can further get distorted. To catch it’s profile in fluoroscopy and imagine the plane requires a mind of “cardiac architect”.So, to locate the  IVS various views are suggested. Currently LAO 40 is typically  used for fixing  mid septal position. In midseptal position ECG is expected to show small q  in lead 1 and AVL. QRS axis will be more left .We seemed to agree with this.

rv pacing mid septal postion rvot rv apical
Image courtesy: Pavel Osmancik Circulation: Arrhythmia and Electrophysiology. 2013; 6: 719-725 Fluoroscopic examples of 2 patients. One with correct lead placement in the septum (A–C) and the other with the lead placed in the anterior wall (D–F). See the similarity of the left anterior oblique 40 view, the difference of the right anterior oblique 30 and the location of the lead on computed tomography image.

And suddenly  this paper  from  the picturesque  city of  Prague , Czechoslovakia throws a stunner.

What we have been thinking as  mid septal pacing with LAO protocol turns out to be   anterior RV pacing in 60% of times.The study showed LA0 40 view  failed to differentiate anterior RV pacing from mid septal pacing .CT scan correlates have documented this . Further ,we have never given a thought to the wayward trabecuale coming across mid septal zone. It has happened time and again (Atleast i have witnessed) the lead would  just fall short of IVS and get screwed in the trabeculae  with high risk for dislodgement . RAO 30 view  consistently separates the mid septal lead from anterior  RV position.It is suggested a carefully done per-procedure echo would also be useful in locating the lead tip .

What hemodynamic implication of mid vs RV anterior pacing ?

Could be significant . No reliable data available. It s tempting to think the hemodynamic inadequacies of an improperly placed mid septal RV pacing may not be different from a conventional RV apex pacing .

Final message

The complex shape of RV and IVS in  fluoroscopy can fool us. If you really want to pace the mid septum, please ensure with multiple views and confirm with RAO 30  . Also remember echocardiography is not a forbidden tool for localising pacemaker lead.


1.The Insufficiency of Left Anterior Oblique and the Usefulness of Right Anterior Oblique Projection for Correct Localization of a Computed Tomography–Verified Right Ventricular Lead Into the Midseptum Pavel Osmancik, Petr Stros, Dalibor Heart 2013; 6: 719-725

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