Posts Tagged ‘RF ablation’

Management of recurrent ventricular tachycardia has developed a lot in recent times. Anti-arrhythmic drugs(AADs) were a cornerstone for most recurrent and refractory VTs till recently. Surgeries including CABG,  repair of the aneurysm, and subendocardial resection has helped to control many post-MI ischemic VTs. Soon they became obsolete. Realistically, PCIs had little impact on post-MI VT for some unknown reasons. However, with the advent of ICDs and RF, ablation, a new dimension is added to this field. 

ICDs, though an attractive device, don’t prevent a VT but vow to nullify the consequence of VT. This is problematic. ICDs in spite of their ability to prevent SCD effectively, it has little say in preventing non-sudden deaths of in any form of cardiomyopathy. (In fact, there is some evidence ICDs might increase myocardial damage with inappropriate shocks )

Hence, RF ablation can be called as true curative therapy by extinguishing hot spots of VT genesis. Still, we need to understand ablation is technically creating new dead myocardium (in alreadly  damaged myocardium) and hence, can’t avoid a consequence. More importantly, ablation as a modality is technically more demanding. We have accumulated huge experience with the help of electro-anatomic imaging and cutting-edge hardware in the last few decades. Still, we find it difficult to zero in the target area of RF ablation, with all available techniques of mapping (Activation, substrate, entrainment, and pace mapping) The reason is,  VT circuits can be really complex ones. Not only different loops but also it can travel deep into the myocardium (Intramural or epicardial) making a single approach endocardial often futile. Success rates vary between 60 -70% (Some may claim 90 +)

This post wants the young fellows to take on this fundamental issue and learn in-depth about the arrhythmia circuit.(Get Inspired by Dr. Samuvel Asirwatham of Mayo clinic work )

What is the best site to ablate ventricular tachycardia?

  1. Exit point 
  2. Central isthmus
  3. Entrance 
  4. Inner loop
  5. Outer loop
  • Though logic would tell us we can intercept an arrhythmia by ablating anywhere in the circuit. But the issue here is we need to permanently ablate it. not just interrupting. 
  • The best site to ablate is the exit point or entry point. Maybe isthmus. I am not really sure. But, one thing is clear, the outer and inner loops are not important. Further, live tissues are the culprits and not the scars and infarcted zones. 
  • One more possible answer is to try to ablate all (or maximum) points in the circuits.

How to identify entry points and exit points?

Not a simple answer .EPs apply their life experience to do that, assisted by technology. Not everyone who has a Carto -GPS can do that.

One simple answer for the fellows is, in entrainment mapping,  critical sites can be somewhat arbitrarily labeled as exit, central isthmus, or entrance on the basis of the Stimulus-QRS interval relationship to the TCL. Exit sites will show an S-QRS interval < 30% TCL (QRS onset shortly after pacing), central isthmuses will show an S-QRS interval of 30% to 50% TCL (some delay in QRS onset after pacing), and entrance sites will show an S-QRS interval of 50% to 70% TCL 

Ruairidh Martin et all Circulation: Arrhythmia and Electrophysiology. 2018;11:e006569

Final message 

Key to the successful ablation of VT is the accuracy in choosing the target site. Locating the target is meaningless if we can’t reach that site. Reaching the site is again futile unless we are able to deliver adequate burning or icing with sufficient contact.

Meanwhile, AADs can never be ignored in spite of the apparent side effects, for the simple reason they reach the VT circuits without any fuss. The Pharma industry has almost lost its interest in AAD research and the hyper-talented EP guys are squarely responsible for this unintended consequence.

Future directions

RF energy modification and newer catheter designs will help. While cryoablation shows a promising advantage over RF, it is still to prove its sustained efficiency. Meanwhile, other ablation modes are being tried. Transvascular ethanol ablation and stereotactic radio ablation have both shown promise for arrhythmias that fail other ablation strategies.

Some more questions

  • What is the difference between arrhythmia focus of origin and entry point? 
  • Once the VT is set in, what is the relevance of its origin? 


One of the very good reviews on the topic.

1.Gustavo S. Guandalini, Jackson J. Liang, Francis E. Marchlinski, Ventricular Tachycardia Ablation: Past, Present, and Future Perspectives,
JACC: Clinical Electrophysiology, Volume 5, Issue 12, 2019, 1363-1383,
2;,W.G. Stevenson, H. Khan, P. Sager, et al.  Identification of reentry circuit sites during catheter mapping and radiofrequency ablation of ventricular tachycardia late after myocardial infarction Circulation, 88 (1993), pp. 1647-1670

3.M.E. Josephson, L.N. Horowitz, H.L. Waxman, et al.Sustained ventricular tachycardia: role of the 12-lead electrocardiogram in localizing site of origin Circulation, 64 (1981), pp. 257-272

Read Full Post »

AV nodal reentrant tachycadia(AVNRT) is the commonest mechanism of SVT. It is divided into slow-fast, fast-slow, slow-slow , representing the two limbs of he circuit.

Slow -Slow circuit is  the rarest  type of AVNRT.  It should be appreciated  ,  the scientific validity of  slow-slow circuit is  applicable  only in relative terms . A virtually  similar antegrade and retrograde limbs with identical conduction velocity and refractory  properties  , can neither  initiate  nor  sustain an AVNRT.

Caveat in the definition of slow -slow AVNRT.

Even though ,  we call it   a  slow-slow  tachycardia , one of the limbs need to be faster than the other.  So , every slow -Slow AVNRT in reality will have  two types

  • Slow- Slow ( Still , faster than antegrade slow) mimic a slow-fast physiology
  • Slow( Faster than retograde slow )  -Slow closely mimic typical  fast slow .

Implication for electrophysiologists  and   points of contention for the ablationist !

  • In Slow -Slow AVNRT ablation we do not know exactly ,  which of the slow pathway is being ablated , unless we specifically  analyse  the post ablative  data.
  • Very often it is not done.Every one in the lab is happy , for breaking the tachycardia circuit. Only after the procedure is over , we may realise the tachycardia is not really killed as it finds an alternate highway to complete  the short circuiting of heart.
  • We need to  suspect this type of AVNRT   prior to the  procedure .Electrophysiologist  shall  spend little   more time and a wide area ablation done , in the vicinity  of coronary sinus ostium can be attempted. .

It is not a smart practice to advocate  wide area ablation as a routine protocol in all AVNRT

as it directly  increase the rate of complication >

Final message

A   hurriedly  done slow pathway ablation  which  may  temporarily terminate the AVNRT ,only to recur later as  the retrograde  slow pathway may again form  a substrate  .The area of slow conduction  acts as a turnaround gateway and capture  the  retrograde fast  pathway which  could be  available in plenty in the anterior aspects of AV node  .   (Note : The unablated  slow pathway  now  form the antegrade  circuit )

Read Full Post »

Management of  atrial fibrillation has been a  big puzzle for cardiologists  for many  decades  till  it became a corporate game , and  now in the era of recession it has become  medicare’s  night mare !

So , we  were  made to dance to the tunes of the so called evidence based cardiology . . .

  • From only rhythm control to . . . in 1990s
  • Either rhythm or rate control  . . .       in early  late 1990s
  • Then cost control  was found  more important than rate control  . . .
  • . . . So rate control became superior to rhythm control in early 2000s

In 2010 , even the  rate control  became  a luxury ,  here comes the  real ace !   ” Casual rate control may be  suffice in most cases of AF “

Read this article  from  NEJM , which tries to  make  sense out of nonsense  and judge for yourself

Probably the most influential  article  in electrophysiology over  the  next decade

Click  below to reach Nejm article



Gist of the trial

Technically and literally it  means a  “Take it easy attitude” as long as patient is comfortable , even a rate  of  more than 100 is allowed . Few years back the above concept could be termed a “non sense”

Final message

In this  perennial  management issue  of AF  ,  Whether ,   we were successful in  restoring   sinus rhythm or not , we have restored  the common sense*  Thanks to RACE 2 investigators.

* Do not unnecessarily trouble a  asymptomatic  patient with those powerful  and costly  antiarrhythmic drugs .

Read Full Post »

This is a real life experience of  a patient who underwent a electrophysiology study and   ablation   procedure for atrial fibrillation  .The blog describes  how the procedure became a nightmare .Written in a  most  readable fashion .  Interventional cardiologists need  not get hurt by this  narration  instead  they should  do a  reality check on the dangers  of  the some  of the  complex  procedures !

Adventures in Cardiology

Click over the  image to  read the real  time experience of   Pulmonary vein  ablation

Image courtesy Mayo clinic

The message from the above story  :

  • Atrial fibrillation is  one of the  relatively  benign  cardiac arrhythmia , that  can be treated  with   simple and effective  drugs . Now we have strong evidence to say rate control is equally , if not more effective than the rhythm control  modalities .
  • The RF  ablation  , which aims at rhythm control  is a too complex a procedure with  lots of expertise  technology  .
  • This should be  reserved  as a last resort  in an occasional patient who had exhausted all other  options .
  • Patients should  realise ,  the consent forms they sign  before any new and innovative  procedure is always  incomplete and  he may be the first person to experience  a new complication  hitherto unreported .
  • A cath lab is run by a team ,  you can’t  expect  the chief doctor to be on your  side always.   Many of the procedures  are  done by either experienced or inexperienced  fellows . That’s  only the  way medicine  can be practiced !
  • So beware all patients , many times, modern medicine is nothing but  experiments on live humans  !

Read Full Post »

Traditionally we believed VT can originate only  from the ventricular myocardial cells . Then we realised many of the VTs shared the characteristics of SVT. When these were analysed , it was found VTs , after all ,   do not have   a big deal of   difference wth SVT s ! especially when it arises from the high septum .Contary to the conventional teaching  the AV node is not a anatomically distinct and discrete  structure  .Instead it is made up of  thousands of specialised cells located in AV junctional area .These cells ramify both superiorly and inferiorly like an octopus . Hence  , it does not require great academics to understand AV Nodal properties extend downward into the IVS for some distance . In some individuals   clusters of cells with  slow conducting  property (Which is a hall mark of AV nodal tissue )  may invade deep into the IVS .The interface of  these slow conducting tissue with that of  fast septal purkinje fibres , make it a  perfect platform for  the potential slow-fast reentry within IVS. This forms the basis of fascicular  VT.

Clinical features

  • Since it shares the  properties of SVT , the natural history is also relatively beningn
  • Occurs in young
  • Hemodynamically stable ( More physiological conduction : Superi inferior Like SVT)
  • Narrow qrs (Narrow because the VTdoes not travel by cell to cell instead  run through the normal conduting system for most part in the circuit)
  • Verapamil sensitive .(Mimic AV nodal Tach)
  • Degeneration into VF is  rare  and hence  SCD is not a big  issue
  • Tachycardic myopathy can occur.

fascicular vt ventricular tachycardia  ecg  svt avnrt avrt wpw


Fascicular tachycardia is also known in several names.

It forms the bulk of the causes for  idiopathic left ventricular VTs .Other being LVOT VT.

Described first by Cohen in 1974 , followed by Zipes , when they noticed  it was possible to reproduce atrial induction of VT.

Belhassen in 1984 found the verapamil sensitivity of this VT

Other synonyms some times used are

  • Septal VT
  • Narrrow qrs VT

Download high resolution table

Fascicular tachycardia

Read Full Post »


The debate of rate control verses rhythm control in atrial fibrillation  goes on and on. The AFFIRM, RACE,PIAF, STAF the HOT CAFE all went against sinus rhythm in the last 10 years . This was one of the settled contoversies in cardiology . The conclusion was ventricular  rate control was no way inferior to rhythm control in patients with SHT, CAD population .This made the electrophyiologists wonder how can a natural rhythm fare bad ! . But the findings  were consistent .Rhythm control neither improved the quality of life nor  it reduced the incidence of stroke. The later finding was very surprising but the explanation was convincing as stroke in elderly was more related to SHT, CAD, DM etc than  AF itself. The source of emboli in ischemic stroke could come any where distal to LA .The big assumtion that all strokes in elderly  should come from LA appendage or the body  of LA was  premature and  wrong. What prevented stroke in AF was not restoration of SR but administration of oral anticoagulants with adequate INR.(2-3)

Having failed to document superiority in elderly  population   , the  logic machine  strongly suggested restoring SR  in patients with CHF,  will atleast provide hemodynamic and also survival  benefit .

And thus came the AF-CHF trial  published in NEJM 2008

Alas !  AF-CHF  also found there is no useful purpose of restoring sinus rhythm in patients  with atrial fibrillation and cardiac failure. In fact patients in SR fared little worse !

 Why . . .  why . . . why ?

Should we ask the seemingly absurd question !

Is sinus rhythm poorly tolerated by cardiac failure  patients ?

It is some times possible atrial fibrillation by itself could be a mechanism to amplify the  cardiac reserve by which it provides a  relatively high ventricular rate to improve the cardiac index  . Even though the optimal ventricular rate in AF is around 80-90 at times of need it has to increase to 120-130. Patients in class 3 CHF and AF often achieve this in times of demand .This is not possible in patients who are getting rhythm control drugs and further patients in SR can  not increase the HR suddenly from 80 -130  .

So is this a  wild imagination !   AF could be a safety valve mechanism in CHF to increase the HR . Where the atria come to the rescue of ventricle like a rate adaptive pacemaker .

The other logical* ! argument is that  there  is nothing wrong with restoring  SR , but the  methods to achieve and  maintain SR  is too cumbersome and results in adverse outcome .The currently available  drugs are too toxic for the purpose  .

If we have a simple and safe way to restore SR in these patients it should always be superior to AF .

But it is a well  known fact  that , whatever be the rhythm or rate the ultimate outcome will be dictated by the LV function, mitral valve function etc.

 Read abstract of AF-CHF

Rhythm Control versus Rate Control for Atrial Fibrillation and Heart Failure

Denis Roy, M.D., Mario Talajic, M.D., Stanley Nattel, M.D., ., for the Atrial Fibrillation and Congestive Heart Failure Investigators


Rhythm Control versus Rate Control for Atrial Fibrillation and Heart Failure

Denis Roy, M.D., Mario Talajic, M.D., Stanley Nattel, M.D.,  the Atrial Fibrillation and Congestive Heart Failure Investigators* –>ABSTRACT

Background It is common practice to restore and maintain sinus rhythm in patients with atrial fibrillation and heart failure. This approach is based in part on data indicating that atrial fibrillation is a predictor of death in patients with heart failure and suggesting that the suppression of atrial fibrillation may favorably affect the outcome. However, the benefits and risks of this approach have not been adequately studied. Methods We conducted a multicenter, randomized trial comparing the maintenance of sinus rhythm (rhythm control) with control of the ventricular rate (rate control) in patients with a left ventricular ejection fraction of 35% or less, symptoms of congestive heart failure, and a history of atrial fibrillation. The primary outcome was the time to death from cardiovascular causes.
Results A total of 1376 patients were enrolled (682 in the rhythm-control group and 694 in the rate-control group) and were followed for a mean of 37 months. Of these patients, 182 (27%) in the rhythm-control group died from cardiovascular causes, as compared with 175 (25%) in the rate-control group (hazard ratio in the rhythm-control group, 1.06; 95% confidence interval, 0.86 to 1.30; P=0.59 by the log-rank test). Secondary outcomes were similar in the two groups, including death from any cause (32% in the rhythm-control group and 33% in the rate-control group), stroke (3% and 4%, respectively), worsening heart failure (28% and 31%), and the composite of death from cardiovascular causes, stroke, or worsening heart failure (43% and 46%). There were also no significant differences favoring either strategy in any predefined subgroup.
Conclusions In patients with atrial fibrillation and congestive heart failure, a routine strategy of rhythm control does not reduce the rate of death from cardiovascular causes, as compared with a rate-control strategy.








Read Full Post »