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Posts Tagged ‘CABANA trial’

AF is not only the most common cardiac arrhythmia,it is also an extensively researched entity in cardiology literature. We are trying to rein in, this arrhythmia for the past three decades with multiple strategies. Drugs, pacemakers, ICDs devices, surgical cuts, RF catheters, and the latest technique is trying to frostbite the atrial electrical circuits with ICE. ( Karl-Heinz Kuck,N Engl J Med 2016 )

It is believed that up 60% of AF originate from pulmonary veins. What does it mean?  So, when we blindly suggest PV Isolation routinely for all PAF,  there is 40% futility straightaway! Apart from the hugely variable anatomy of the pulmonary veins, there are prohibitive levels of recurrence due to  PV reconnections. Maybe, will find new technical solutions as we are now moving in 2nd or third generation cryo balloons, 4D imaging, contact force sensing, etc. But let us not forget there are other sources of focal electrical activity too  

Importance of non-PV ectopic beats initiating  AF(Ref 1,2)

  1. Superior vena cava (SVC),
  2. left atrial posterior free wall (LPFW),
  3. LA appendage
  4. crista terminalis (CT),
  5. coronary sinus ostium (CSO),
  6. Ligament of Marshall
  7. Interatrial septum (IAS) 

Ablation or no ablation, we need to reflect on two things in the management of AF.

1. AF can be triggered by totally different mechanisms like intermittent hypoxia, adverse electrolytic flux, diffuse atrial interstitial pathology or amyloid, etc. Before calling the appointment desk of the EP guy’s office please rule out all the systemic causes. This could be your last (lost) chance to save the atria from pulmonary burns.

2. This one is more important. Read carefully. It is not a divine protocol that demands us to restore sinus rhythm in all patients with AF. There is an excellent knowledge base, backed up by wonderfully done studies. (Need not mention the trial name, I think) that should effectively neutralize our compulsive &  misplaced urge to bring back sinus rhythm in all chronic AF.

With respect to the overall outcome, It hardly matters whether you treat the AF by rate control or rhythm control. While there is major technological leap in our fight with AF.It is heartening to know simple measures like regular exercise can control or reverse AF by atrial fatty mass regression.

Final message

We have played with fire for quite some time within the innocent lesser chambers of the heart  (RF ablation) and burnt our reputation considerably. Now, silently we have decided to fall for a more friendly weapon ICE. But we must remember our obsession with the pulmonary vein as the only source of initiation of AF is essentially flawed. Further, all these hyper-technology-based combat of AF is indicated only in a fraction of our patients (Maybe 5-10%) 

Reference 

1.Chen SA, Tai CT, Yu WC, Chen YJ,  Right atrial focal atrial fibrillation: electrophysiologic characteristics and radiofrequency catheter ablation. J Cardiovasc Electrophysiol. 1999 Mar;10(3):328-35. doi: 10.1111/j.1540-8167.1999.tb00679.x. PMID: 10210494.

2.Lin, Wei-Shiang, et al. “Catheter ablation of paroxysmal atrial fibrillation initiated by non–pulmonary vein ectopy.” Circulation 107.25 (2003): 3176-3183.

Postamble

If you think this write-up is too biased, please read the CABANA trial fully before ditching this post into the dustbin.

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There is a tough ongoing rivalry between drugs and catheters to conquer the commonest electrical chaos in human heart, namely Atrial fibrillation (AF). Mind you,the confusion about the importance of this arrhythmia is huge and real.Bulk of these episodes are transient , paroxysmal and do not require rigorous management.While stroke prevention seems to be the major aim and target , the real world scenario seems to tell a different story.

The nomenclature conundrum

AF may be classified as many ways a learned cardiologists can think . Often it’s done with reference to etiology, duration , rate, neural (sympathetic or parasympathetic) humoral , cardiac or non cardiac , reversible or irreversible ( Endocrine, Electrolytic, hypoxia etc).

Unlike VT , bifurcating AF with reference to the presence or absence of structural heart disease is rarely meaningful.Subclinical atrial interstitial fibrosis in elderly is so common especially so in hypertensive individuals making all lone atrial fibrillation as true structural disease.

Classifying AF with reference to atrial enlargement again is problematic as any sustained AF can dilate these thin atrial chambers in few weeks time making it a sequel to AF rather than a cause to it.

Adding further fuel to the confusion is the recent man-made (read cardiac scientists!) problem .Linking the etiology of AF with the presence or absence of valves pathology is definitely not helping us. In the process , we forget a casual fact that valvular AF needs aggressive valvular Intervention and not arrhythmia Intervention !*A patient with dilated cardiomyopathy with mitral regurgitation and LA enlargement with AF is considered non valvular AF in spite of clear pathology in mitral valve apparatus.(Is there myocardial AF by the way ?)

What is the current role for catheter ablation in AF ?

The question of advanced catheter based management boils down to a minority of refractory, fast , troublesome AF which has failed by most available drugs. More Importantly the long-term success of ablation is lowly 20% ( PV reconnection, geographical miss, atrial focus etc) and follow-up medication is absolute must even after successful ablation. Its well-known , severe the underlying heart disease more likely is the recurrence .Ironically these are same ones that attract the catheters.

The previous debate of rate control vs rhythm control gave sufficient lessons that complex modalities to restore sinus rhythm is unwarranted . As scientific cardiologists we continue to be adamant and don’t learn from our mistakes and blindly adore and adopt technological excessess.

Now, thanks to CABANA* the ablation for AF has proven to be a fruitless process considering the time ,effort and potential (& real )complications.

*The Catheter Ablation Versus Anti-arrhythmic Drug Therapy for Atrial Fibrillation . Just presented in HRS annual meet at Boston MAy 2018.

The bright spot is even in these commercial medical world the study like CABANA is a silver lining. Mind you it’s partly sponsored by Industry , still went against them. Three cheers to the genuine medical research team of CABANA for bringing out a truth. Now, I am optimistic more such trials in cardiology will be proposed

A companion to CABANA from UK

A 2018 landmark paper from published in BMJ reveals a dramatic truth that the risk of stroke continues to persist even after resolved Atrial fibrillation, largely concurring with CABANA.(Nicola J Adderley, Risk of stroke and transient ischaemic attack in patients with a diagnosis of resolved atrial fibrillation: retrospective cohort studies BMJ 2018;361:k1717)

So, how to get out of these AF conundrum ?

Practically , an extreme simplification of AF classification is warranted . It should answer these couple of questions !

1. Will the AF in a given patient require long-term oral anticoagulants or not ? (or ok with antiplatelet drug !)

2. Should I make any meaningful attempt to convert the AF to sinus rhythm at all* ?

* You can also redefine the second question , does this AF deserve a EP consult or not ?

Final message

AF is largely a benign arrhythmia in global perspective . However, In those patients were its troublesome , safe and effective drugs are available to tackle it.We shouldn’t Insist to make it complicated.
Meanwhile . . .the anxious pulmonary veins seems to enjoy the moment as they escape from the fire .No wonder they will thank and celebrate the CABANA.

Reference

http://www.acc.org/latest-in-cardiology/clinical-trials/2018/05/10/15/57/cabana

Post-amble and counter point

The RF ablation is a high risk procedure , as we develop less injurious cryo balloons the results of Invasive ablation procedures may score over drugs.Let us wait and don’t prematurely ditch the catheters.

https://1drv.ms/v/s!Ahm_xjThT-nXgY5EtHnqjxFkb_PWtQ

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