Posts Tagged ‘companion’

Cadiac resynchrnonisation (CRT) therapy , is  the most famed  as well as  ridiculed treatment modality for refractory failure . It is facing a real tough time for survival now .(At least in class 4 CHF.)

Confident and  authentic data  are emerging  now , that CRT should not be  used  in advanced heart failure .(This is in total contrast with the original concept  ,  when CRT was introduced nearly  a decade ago !  more  of class 3 and 4 were enrolled ) . Bad outcomes are expected in advanced CHF. This is something similar to whipping the tired horse concept  which  found inotropes   to increase the mortality in severe heart failure .

The article in the current issue of circulation  shows  no mercy to CRT  in advanced CHF


So what  is  the answer to the ailing CRT industry ?

Go and catch class 1 and class 2 CHF population* .You will get plenty  , of course  it got ratified by MADIT -CRT trial .

* It is attractively called prevention of cardiac failure

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Atrial fibrillation and CHF are close companions. Either it   precipitates  CHF  or  follows it.In advanced heart failure of any etiology  the incidence of AF can be up to 40% .Medical therapy of AF is fairly effective in patients with normal LV function  .But when associated with refractory cardiac failure  it becomes  too complex to control .

Currently CRT with ICD  is becoming the standard OF care for advanced CHF. The efficacy of CRT is being rigorously being assessed . Even as the controversy  about  the wideness of QRS is being settled , the issue of optimal  timing of CRT has risen  . Now ,  the MADIT-CRT has answered this issue “Earlier it  is better , it can be  indicated even for  class 1 patients”

While MADIT -CRT will increase the number of CRT implants , we  have no clear cut answer for the  efficacy of CRT in patients with AF .( Of course , the MUSTIC and CARE HF sub group analysis suggested AF has no significant impact on CRT efficacy )

atrial fibrillation crt cardiac resynchronisation therapy icd madit crt care chf

Why is AF important in CRT ?

There are two issues that need analysis

  1. A patient who  has chronic AF at the time of CRT
  2. Development of  new onset AF after CRT implantation.

Impact of AF during CRT

  • Inter atrial synchrony is lost. ( Significance not clear . . . makes AF permanent)
  • AV synchrony is lost
  • Rapid AV conduction : May trigger   too much of Bivi pacing if sensed by LV lead

Presence of AF at the time of CRT gives us an opportunity to tackle this issue.

How to tackle  sudden AF induced CRT response ?

There are variety of algorithms available to

  • Ventricular sense response
  • Conducted AF response
  • Atrial tracking recovery

In dual chamber pacing mode switching converts DDD into VVI  .This happens  at the cost of loss of AV synchrony .This may have profound implication in CRT .

Then the big question comes  . What is the use  of  having Intraventricular  and interventricular  synchrony without AV synchrony ?

When nothing works .The best strategy is ( Rather deemed to be best ! )

  • To ablate the  AV node  pace  the atrium and ventricle  (RV & LV)  .

Note : Ablation of AV node and putting a dual chamber pacing can never guarantee a physiological pacing as the atrium continues to fibrillate and AV synchrony is rarely there .

Final message

For CRT is to be successful , there should be maximal Bi-Vi capturing , of course this capture has to optimally timed , and must reverse the three pathological asynchronies , namely intraventricular , Interventricular  and  atrio  ventricular  asynchronies.

It is obvious , presence of AF complicates the issue as it demands  constant monitoring and programming of the device (Of course  now most  of them are automated) . It may   require  knocking down of AV node , which  not only carries a risk of SCD *  ,  it also make these  patients   permanently  dependent   on the RV pacing  . This  adds on ,  another  risk ,  for an  acute complication   if the RV lead fails for some reason.

Reference :

*Sudden death after radiofrequency ablation of the atrioventricular node in patients with atrial fibrillation
Journal of the American College of Cardiology, Volume 40, Issue 1, Pages 105-110

EP experts generally take  too much liberty in adopting this  strategy for the simple reason it solves the nuisance of atrial impulses  interfering with   ventricular  leads  function that result in  inappropriate ventricular capture fusion or ultimately poor BiVi pacing . But it is not an easy decision  atleast for the patient ! This article , emphasises the dangers involved in ablate and pace strategy for uncontrolled AF.

Further reading

  • Fung, J. W H, Yip, G. W K, Yu, C.-M. (2008). Does atrial fibrillation preclude biventricular pacing?. Heart 94: 826-827 [Full Text]
  • Khadjooi, K, Foley, P W, Chalil, S, Anthony, J, Smith, R E A, Frenneaux, M P, Leyva, F (2008). Long-term effects of cardiac resynchronisation therapy in patients with atrial fibrillation. Heart 94: 879-883 [Abstract]
  • Buck, S., Rienstra, M., Maass, A. H., Nieuwland, W., Van Veldhuisen, D. J., Van Gelder, I. C. (2008). Cardiac resynchronization therapy in patients with heart failure and atrial fibrillation: importance of new-onset atrial fibrillation and total atrial conduction time. Europace 10: 558-565 [Abstract] [Full Text]

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