Hello, today I would like to present the one of the most important maneuvers which can help to determine presence of accessory pathway, especially the accessory pathway in the area of bundle of His – says Dr. Michal Peller, Warszawski Uniwersytet Medyczny – WUM. We invite you to the third part of the EP Fans animated handbook!
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A 70-year-old male was admitted to the hospital due to palpitations, dyspnea and decreased exercise tolerance during the last 2 months. The past ECGs were interpreted by the GP as sinus tachycardia resistant to medical treatment.
The patient was treated with maximal tolerated doses of bisoprolol 10mg, although tachycardia 110/min persisted, and the patient was referred to a cardiologist.
ECG at admission revealed wide QRS tachycardia with a heart rate of 110 (fig. 1). Typical RBBB QRS morphology and visible non-sinus P waves with long RP’ interval suggested atrial tachycardia (AT). The patient was qualified for EPS and ablation.
In intracardiac electrograms (IEGMs) concentric atrial conduction was shown (fig. 2). Pacing maneuvers – ventricular overdrive pacing (VOP), cycle length (CL) 500ms confirmed AT – VAAV response (fig. 3). The local activation time (LAT) map of the right atrium (RA) suggest a depolarization wave coming from the broad area of interatrial septum (IAS). The area of the earliest activation was in the LA, close (10mm) to the His bundle potential recorded on the distal HBE electrode. A few applications in the IAS were performed. The arrhythmia terminated during application (fig. 4). The EPS study did not induce AT.
Michał Marchel, MD, PhD
Michał Peller, MD, PhD
1st Department of Cardiology
Medical University of Warsaw
A science that combines physics and physiology seems to be the essential background of knowledge concerning cardiac electrophysiology, but its importance does not decrease with the development of this specialization. Thorough knowledge of biophysics can play a decisive role in the safety and efficacy of the underlying arrhythmia ablation procedures performed. Investing an excessive amount of time in exploring this field is worth doing. It will pay off immensely – convinces Piotr Lodziński, MD, PhD, FESC of 1st Chair and Department of Cardiology, Medical University of Warsaw.
In cardiac electrophysiology, a field dedicated to diagnosing and treating cardiac arrhythmias, biophysics is a discipline describing physics phenomena that affect biological heart tissue and describe the processes essential for its controlled damage.
-Biophysics is one of the fundamental disciplines. In a way, it is a merge between knowledge of physics and physiology. How does this merge benefit us? We know how to effectively and, above all, safely damage the heart tissue to help the patient with arrhythmia. Unfortunately, because of its fundamental character, it is often under-exposed in the cardiology education process. However, knowledge gaps in this area may lead to severe consequences, i.e., the operator may not understand why the procedure failed or why something happened during the procedure that was to be avoided – explains Piotr Lodzinski, MD, PhD.
The knowledge of biophysics is included, among others, in scientific publications constituting a canon of knowledge in this field. As Piotr Lodziński, MD PhD stresses, the age of classical publications covering electrophysiology is a challenge to determine because many works originate from the period when ablation procedures (for research purposes) were performed in animal laboratories, including in vitro and in vivo testing on animals. As far as the needs of today’s electrophysiological operators go, appropriate knowledge update is crucial. Among other things, this is how a lecture on the biophysics of ablation was prepared, included as a part of the EP FANS educational platform, aimed at cardiac electrophysiologists at the beginning of their career.
We decided that the need of embedding a classical knowledge of biophysics in current clinical conditions familiar to today’s operators is indispensable. During the course, we addressed practical situations and tools used in electrophysiological diagnosis and therapy, such as 3D electroanatomical systems or the latest generation of ablation catheters – says Piotr Lodzinski, MD, PhD.
The expert points out that it is not always obvious but vital to urgently follow and correctly interpret all parameters recorded by modern devices during the ablation procedure. Examples include applied power, impedance, or temperature.
– For RF ablation performed with a classical cooled tip catheter, the temperature reading may give the operators a false sense of security. It may appear that since the catheter is cooled and the temperature is maintained at a safe level, which is confirmed by the readings, there is no risk of tissue overheating. Meanwhile, the knowledge of biophysics and energy delivered to the tissue enables a realistic assessment of the situation. We are aware that despite seemingly safe readings, a complication may occur in the too-long application with too much force applied. In terms of procedure safety, this knowledge is priceless – says Piotr Lodziński, MD, PhD.
According to the expert, knowledge of biophysics also allows the proper treatment design, i.e., defining its strategy and contingency options. A well-thought-out plan and possible alternative scenarios allow the procedure to be performed in a shorter time, more safely and effectively.
27-year-old male with a history of palpitations for the last 10 years. Finally, ECG during tachycardia was recorded (Fig 1). The patient was scheduled for EPS and ablation. Here you can find a few of his intracardiac recordings from EPS (Fig 2-4). What kind of tachycardia might it be?
Do you remember our riddle: https://lnkd.in/eBRG8deV? Dr. Michal Marchel & Dr Michal Peller agreed to reveal the solution! 🙂
27-year-old male with a history of palpitations for the last 10 years. Finally, ECG during tachycardia was recorded (Fig 1). The patient was scheduled for EPS and ablation. Here you can find a few of his intracardiac recordings from EPS (Fig 2-4). What kind of tachycardia might it be?
Fig.1: Narrow QRS tachycardia, in aVF negative P waves hidden in QRS complexes (red arrows). RP<PR. Sinus beats, PVCs.
Fig.2: Programed pacing 100×8 + 340ms, extrastimuli conducted by slow pathway and nodal echo is present (red square). Double pathway physiology, stepdown conduction through the slow pathway, retrograde conduction through the fast pathway.
Fig.3: Ventricle overdrive pacing (VOP). Pacing with CL 270ms during tachycardia (CL 290ms). Tachycardia not terminated by VOP makes analysis of V and A response possible. VAV response excludes AT (figures). Late atrial capture following “transition zone” makes AVRT uncommon (red square).
Fig. 4: Para-Hisian pacing. High output pacing makes His capture possible (narrow QRS). SA short (70ms) – retrograde conduction through physiologic pathways (His-AVN) (red line). Low output pacing and loss of His bundle capture when local ventricular myocardium is captured (wide QRS) results in longer SA (120ms) – conduction through physiologic pathways (ventricle myocardium-Purkinie-His-AVN) (blue line). This kind of response excludes presence of the para-Hisian accessory pathway.
Diagnosis: Typical slow-fast AVNRT.
Treatment: In the EPS following slow pathway ablation in the postero-septal region no tachycardia was induced. No palpitation in 6-month follow-up were reported.
Today in our EP handbook Michal Peller, MD from Warszawski Uniwersytet Medyczny – WUM talks about the idea of incremental pacing. Let’s see!
Although its idea has been known for more than 30 years, it is currently more widely used in clinical practice due to technical progress. Bipolar ablation may be the only practical alternative for a specific group of patients with heart rhythm disorders. Piotr Futyma, MD, PhD, Associate Professor at the University of Rzeszów and Cardiac Electrophysiologist at St. Joseph’s Heart Rhythm Center in Rzeszów, talks about the current position of this procedure and Polish scientific and technological projects.
We refer to bipolar ablation when we use a second ablation catheter located near the application site, connected to a radiofrequency (RF) generator instead of a dispersive patch. Our goal is to surround our predefined ablation target with two ablation catheters coupled into a single circuit to maximize the RF current near the area of interest.
Bipolar ablation was, in fact, an original idea for performing ablation procedures. Publications from the early 1990s documented the first cases of accessory pathways treated with RF current delivered in bipolar fashion (1). At that time, the bipolar ablation appeared to be rather inconvenient. Firstly, it was necessary to provide full control over not only a single one but two separate ablation catheters. Secondly, the biophysics of RF application was not that well known back then. So, it was challenging to take into account and coordinate many parameters of both ablation catheters located in the patient’s heart.
In the very first landmark paper on ablation in WPW syndrome, researchers led by Professor Warren Jackman switched to unipolar ablation after treating their first eight patients, ultimately with the bipolar technique. The unipolar ablation has been considered the classic ablation method since then. By using only one ablation catheter and a dispersion patch located at the patient’s body, it was easier to control RF delivery because it required parameters maintenance of a single ablation catheter only. It is worth mentioning that the use of RF current those days was an alternative to high-energy discharges performed with a direct current (2) – a method that is now returning to clinical electrophysiology as an irreversible electroporation, also called pulsed-field ablation.
In the following years, RF current proved to be an optimal solution for sufficient control of effective ablation procedures in a broad spectrum of arrhythmias. Unipolar RF delivery has become an efficient therapy for ablation of accessory pathways and turned out to be highly effective for the treatment of atrioventricular nodal reentrant tachycardia. The next step was to use unipolar RF ablation to treat right and left ventricular outflow tract arrhythmias (3). In the last decade, RF ablation was established for the treatment of post-infarction ventricular tachyarrhythmias and pulmonary vein isolation for atrial fibrillation (4).
In the early development of ablative electrophysiology, there was a brief intriguing return to the use of the bipolar method for some more complex cases. In the early 1990s at St George’s Hospital, the bipolar technique was used for the ablation of septal accessory pathways that could not be successfully eliminated using the classic approach (5). At the beginning of this century, single reports from Spain, the Czech Republic and the United States showed up demonstrating the possibility of effective ventricular arrhythmias treatment with the use of bipolar ablation (6). The first Polish reports appeared in the last decade; for instance, the first Polish publication concerning bipolar ablation came from our St. Joseph’s Center in Rzeszow and described the treatment of atrial flutter in a patient with an anatomical variant (7). Almost simultaneously, a team from Poznań led by Prof. Artur Baszko performed an emergency bipolar ablation of ventricular septal tachycardia (8), and several such procedures have been performed in Poznań since then. In Rzeszów, we focused mainly on bipolar ablation of arrhythmias from a relatively complex area of the heart, which is the left ventricular summit (9). Arrhythmias originating in the left ventricular ostium can sometimes cause significant difficulties for electrophysiologists, mainly due to unique anatomical relationships and tissue heterogeneity in this area. That’s why arrhythmic substrates located there are sometimes refractory to classical RF applications, either from the left ventricular outflow tract, from the aortic cusps or from the great cardiac vein. The long-term efficacy of classical ablation in the left ventricular summit area is also suboptimal (10). The first reports on the possibility of effective treatment of tachycardias originating from the left ventricular summit came from Poland, with the main participation of our center in Rzeszow (11,12), and this is what I am particularly proud of. Today, we have the honor and pleasure to share our knowledge and skills with colleagues from other centers in Poland and worldwide.
Possibilities for the use of bipolar ablation are significant. In particular, patients after multiple and extensive unsuccessful ablation attempts frequently appear to be good candidates for this procedure. Not only patients with refractory septal arrhythmic substrates may particularly benefit from bipolar ablation, but also relatively young patients with idiopathic arrhythmias, i.e., those without structural heart disease, with the emphasis on the left ventricular summit cases.
One of the most challenging patients was a male after six ventricular tachycardia (VT) ablations. After these unsuccessful attempts using the classic approach performed at four different expert centers, the decision was made that the patient would ultimately live with his recurrent VT or should be scheduled for heart transplantation. Together with Prof. Piotr Kulakowski in our center in Rzeszów, we’ve performed the 7th procedure, this time using the bipolar technique. The case lasted over five hours and required bipolar applications for a total duration of approximately 30 minutes – it was so difficult to get to the source of the arrhythmia. However, this challenging case was ultimately successful (13). Until this day, nearly five years after the procedure, the patient has no VT recurrence and remains symptom-free. Similar results are frequently observed in other patients treated with this method.
Bipolar ablation is a technique attracting increasing interest from clinicians and researchers. The 2019 expert consensus on ablation of ventricular arrhythmias includes a paragraph dedicated to bipolar ablation, highlighting some limitations of the procedure (14). There are regular publications, usually single-center or consisting of a relatively small group of patients from several centers, describing the effects of this therapy. We are currently waiting impatiently for the results of prospective studies. We are also aware of certain limitations and difficulties. The group of patients who may benefit most from bipolar ablation is a relatively challenging group in the view of clinical trials – these patients frequently underwent long-term antiarrhythmic drug treatment and many extensive ablations as well.
Technical issues are essential aspects of bipolar ablation. Centers often use customized equipment or available off-label connections in order to plug in ablation catheters into a bipolar circuit. The first models of RF generators capable of deriver energy in bipolar fashion have been recently developed. Here in Rzeszow, we’ve constructed a connection device dedicated for bipolar ablation based on my original project. This adapter allows to collect and track substantial information from the catheter plugged into the position of the return electrode connected instead of a dispersive patch, which results in reasonable control of bipolar ablation.
Our adapter enables the delivery of the bipolar ablation as well as temperature measurements from the electrode tip, which allows avoiding overheating and subsequent formation of charring and related complications. Another functionality of the adapter is the ability to transfer signals from the catheter electrodes, which allows 3D reconstruction of the catheter in the electroanatomical mapping system and provides signal recordings obtained directly from the catheter electrodes. The device works with most of the available RF generators and with a spectrum of currently available ablation catheters.
After the device received a CE mark in 2020, we successfully implemented bipolar ablation in several leading European centers (15). Apart from the St. Joseph’s Heart Rhythm Center in Rzeszów, the bipolar ablation device is currently used in the main EP centers in Frankfurt, Cologne, Essen, Basel, Zurich, and London. The results of bipolar ablation with the use of the adapter and the feedback concerning the use of our tool are very satisfactory. In my opinion, this is an excellent proof that the original idea of using bipolar ablation was not a mistake. It is beneficial to develop technological concepts and ideas due to true clinical demands, and it is worth cooperating — exchanging views, experiences, sharing knowledge and skills. This way, we can help a number of challenging patients who just recently had barely any alternative.
Assoc. prof. Piotr Futyma, MD, PhD
Finalist in the Innovation Stage competition at the 2019 EHRA Congress in Lisbon. Member of the Heart Rhythm Society (HRS) Communications Committee. In 2021 accepted as a Fellow of ESC (FESC) and Fellow of EHRA (FEHRA). Author of 5 patent applications.
He participated in implementation bipolar ablation technique at several leading electrophysiology centres in Europe, including Cardioangiologisches Centrum Bethanien in Frankfurt, Germany, Universitatsspital Basel, Switzerland, Klinik Hirslanden in Zurich, Switzerland, St. Georges University Hospital in London, UK, and several others.
- Jackman WM, Wang XZ, Friday KJ, Roman CA, Moulton KP, Beckman KJ, McClelland JH, Twidale N, Hazlitt HA, Prior AL, et al. Catheter ablation of accessory atrioventricular pathways (Wolff-Parkinson-White syndrome) by radiofrequency current. N Engl J Med. 1991 Jun 6;324(23):1605-11. Doi: 10.1056/NEJM199106063242301. PMID: 2030716.
- Chen SA, Tsang WP, Hsia CP, Wang DC, Chiang CE, Yeh HI, Chen JW, Ting CT, Kong CW, Wang SP, et al. Catheter ablation of accessory atrioventricular pathways in 114 symptomatic patients with Wolff-Parkinson-White syndrome – a comparative study of direct-current and radiofrequency ablation. Am Heart J. 1992 Aug;124(2):356-65. Doi: 10.1016/0002-8703(92)90598-p. PMID: 1636579.
- Zhu DW, Maloney JD, Simmons TW, Nitta J, Fitzgerald DM, Trohman RG, Khoury DS, Saliba W, Belco KM, Rizo-Patron C, et al. Radiofrequency catheter ablation for management of symptomatic ventricular ectopic activity. J Am Coll Cardiol. 1995 Oct;26(4):843-9. Doi: 10.1016/0735-1097(95)00287-7. PMID: 7560606.
- Andrade JG, Champagne J, Dubuc M, Deyell MW, Verma A, Macle L, Leong-Sit P, Novak P, Badra-Verdu M, Sapp J, Mangat I, Khoo C, Steinberg C, Bennett MT, Tang ASL, Khairy P; CIRCA-DOSE Study Investigators. Cryoballoon or Radiofrequency Ablation for Atrial Fibrillation Assessed by Continuous Monitoring: A Randomized Clinical Trial. Circulation. 2019 Nov 26;140(22):1779-1788. Doi: 10.1161/CIRCULATIONAHA.119.042622. Epub 2019 Oct 21. PMID: 31630538.
- Bashir Y, Heal’ SC, O’Nunain S, Katritsis D, Camm AJ, Ward DE. Radiofrequency current delivery by way of a bipolar tricuspid annulus-mitral annulus electrode configuration for ablation of posteroseptal accessory pathways. J Am Coll Cardiol. 1993 Aug;22(2):550-6. Doi: 10.1016/0735-1097(93)90063-7. PMID: 8335828.
- Koruth JS, Dukkipati S, Miller MA, Neuz’l P, d’Avila A, Reddy VY. Bipolar irrigated radiofrequency ablation: a therapeutic option for refractory intramural atrial and ventricular tachycardia circuits. Heart Rhythm. 2012 Dec;9(12):1932-41. Doi: 10.1016/j.hrthm.2012.08.001. Epub 2012 Aug 2. PMID: 22863684.
- Futyma P, Futyma M, Maciołek M, Kułakowski P. Bipolar Radiofrequency Ablation of Typical Atrial Flutter. J Cardiovasc Electrophysiol. 2016 Jul;27(7):874-5. Doi: 10.1111/jce.12908. Epub 2016 Feb 4. PMID: 27405451.
- Baszko A, Telec W, Kałmucki P, Iwachów P, Kochman K, Szymański R, Kłopocki J, Ożegowski S, Szyszka A, Siminiak T. Bipolar irrigated radiofrequency ablation of resistant ventricular tachycardia with a septal intramural origin: the initial experience and a description of the method. Clin Case Rep. 2016 Aug 25;4(10):957-961. Doi: 10.1002/ccr3.648. PMID: 27761246; PMCID: PMC5054470.
- Futyma P, Wysokińska A, Sander J, Futyma M, Kułakowski P. Bipolar Endo-Epicardial Radiofrequency Ablation of Arrhythmia Originating from the Left Ventricular Summit. Circ J. 2018 May 25;82(6):1721-1722. Doi: 10.1253/circj. CJ-17-0782. Epub 2017 Oct 18. PMID: 29046505.
- Chung FP, Lin CY, Shirai Y, Futyma P, Santangeli P, Lin YJ, Chang SL, Lo LW, Hu YF, Chang HY, Marchlinski FE, Chen SA. Outcomes of catheter ablation of ventricular arrhythmia originating from the left ventricular summit: A multicenter study. Heart Rhythm. 2020 Jul;17(7):1077-1083. Doi: 10.1016/j.hrthm.2020.02.027. Epub 2020 Feb 28. PMID: 32113894.
- Futyma P, Sander J, Ciąpała K, Głuszczyk R, Wysokińska A, Futyma M, Kułakowski P. Bipolar radiofrequency ablation delivered from coronary veins and adjacent endocardium for treatment of refractory left ventricular summit arrhythmias. J Interv Card Electrophysiol. 2020 Sep;58(3):307-313. Doi: 10.1007/s10840-019-00609-9. Epub 2019 Aug 11. PMID: 31402415.
- Futyma P, Santangeli P, Pürerfellner H, Pothineni NV, Głuszczyk R, Ciąpała K, Moroka K, Martinek M, Futyma M, Marchlinski FE, Kułakowski P. Anatomic approach with bipolar ablation between the left pulmonic cusp and left ventricular outflow tract for left ventricular summit arrhythmias. Heart Rhythm. 2020 Sep;17(9):1519-1527. Doi: 10.1016/j.hrthm.2020.04.029. Epub 2020 Apr 26. PMID: 32348845.
- Futyma P, Głuszczyk R, Futyma M, Kułakowski P. Right atrial position of a return electrode for bipolar ablation of the left posterosuperior process ventricular tachycardia. Pacing Clin Electrophysiol. 2019 Apr;42(4):474-477. Doi: 10.1111/pace.13554. Epub 2018 Dec 9. PMID: 30461031.
- Cronin EM, Bogun FM, Maury P, Peichl P, Chen M, Namboodiri N, Aguinaga L, Leite LR, Al-Khatib SM, Anter E, Berruezo A, Callans DJ, Chung MK, Cuculich P, d’Avila A, Deal BJ, Della Bella P, Deneke T, Dickfeld TM, Hadid C, Haqqani HM, Kay GN, Latchamsetty R, Marchlinski F, Miller JM, Nogami A, Patel AR, Pathak RK, Sáenz Morales LC, Santangeli P, Sapp JL, Sarkozy A, Soejima K, Stevenson WG, Tedrow UB, Tzou WS, Varma N, Zeppenfeld K; ESC Scientific Document Group. 2019 HRS/EHRA/APHRS/LAHRS expert consensus statement on catheter ablation of ventricular arrhythmias. Europace. 2019 Aug 1;21(8):1143-1144. doi: 10.1093/europace/euz132. Erratum in: Europace. 2019 Aug 1;21(8):1144. Erratum in: J Arrhythm. 2020 Jan 12;36(1):214. Erratum in: Europace. 2020 Mar 1;22(3):505. PMID: 31075787; PMCID: PMC7967791.
- CorSystem announces first use of Bipolar Ablation Adapter. Cardiac Rhythm News, 10th March 2021
Although in terms of anatomy, a child’s heart does not differ significantly from an adult’s heart, each organ has its specific characteristics from the electrophysiological point of view. What are the secrets of the youngest patients’ hearts and what should be remembered regarding electrophysiological diagnostics and therapy, reveals Artur Baszko, MD, PhD (2nd Department of Cardiology and Pediatric Electrophysiology Centre, Poznań University of Medical Sciences).
Let’s start with a fundamental issue: is a child’s heart, apart from its size, the same as an adult’s?
From the moment of birth through all stages of further development until adulthood, the child’s heart changes very little in terms of quality. It is, of course, much smaller, has thinner walls and large vessels that supply and drain blood from the heart. However, anatomically it is practically the same as an adult heart. The difference lies in the heart’s functionality, where significant differences exist. A child’s heart works much faster than an adult’s, and children have also lower blood pressure.
Your main specialty is cardiac electrophysiology. What differences do you observe between children and adults in this area?
It is worth knowing what electrophysiology is. It is the science of the electrical activity of the heart. We can compare the action of the heart to the action of an automobile engine – without electric sparks, the heart would not be able to contract, i.e. pump blood. These sparks are generated in the sinus node at the base of the heart’s right atrium and then propagate through a specialized conduction system to the atria and ventricles, leading to a synchronized contraction, first of the atria and then of the ventricles. However, there are few differences in the electrical properties between a child’s heart and an adult’s heart. One of the most significant is a considerably higher heart rate. Whereas the heart rate for adults fluctuates around 60-80 beats per minute, it is well over 100 beats for children. The heart rate can be up to 140 beats per minute in the newborn period!
What about other differences?
Another difference concerns the speed of impulse conduction and the so-called refractory time. Impulses are conducted much faster in children, and the individual heart structures have significantly shorter refractory times, leading to substantially higher heart rates in the case of tachycardia.
It is worth to mention that the neonatal period favors the development of rhythm disturbances that rarely occur in adults. Moreover, some of these rhythm disturbances may disappear as the child’s heart develops and the autonomic system matures.
Do children have different heart rhythm disorders than adults?
Rhythm disorders related to an accessory pathway (overt or concealed WPW syndrome) are more common in children than in adults. Ectopic tachycardia (especially atrial) and nodal reentrant tachycardia are also more frequent. The type of predominant rhythm disturbances changes with age. In adolescents and young adults, nodal reentrant tachycardia and tachycardia related on the accessory pathway are most frequent. Still, ventricular disturbances in the absence of structural heart disease (arrhythmias from the right and left ventricular outflow tract and the so-called fascicular tachycardia) are more common.
Which arrhythmias are more likely to develop in adults, including seniors?
In adults, atrial fibrillation and arrhythmia caused by other heart diseases (such as myocardial infarction or cardiomyopathies) are important electrophysiological problems. There is also an increasing incidence of bradyarrhythmias in the elderly population, i.e. diseases of the stimulus conduction system that slow down heart rate (sinus bradycardia) or block conduction through atrioventricular node or the left bundle branch. Many patients with sinus node or atrioventricular node disease require the implantation of a pacemaker. In children’s, these problems are rare and are usually congenital or result from a corrective operation on a heart defect. Out of more than 1100 ablation procedures in our centre, we have implanted 168 epicardial pacemakers in infants and small children and 48 endocardial systems in older children.
In terms of implantable devices, how common is it to safeguard children with cardioverter-defibrillators?
The most common risk of sudden cardiac death among adults is coronary artery disease with acute myocardial infarction, its consequences and various types of cardiomyopathies such as dilated, hypertrophic, and arrhythmogenic. Cardiomyopathies also occur in children but are rarely associated with a risk of sudden death. This group is dominated by genetic diseases, the so-called channelopathies: long QT syndrome, catecholaminergic ventricular tachycardias and Brugada syndrome). For life protection, a cardioverter-defibrillator is implanted in adults in strictly defined cases, whereas the need for such a system in children is relatively rare.
What are the critical differences in treating arrhythmia patients according to age group?
On the one hand, most of the youngest patients respond well to pharmacological treatment, so it is not always necessary to undertake interventional therapy or implant a device. Secondly, it can happen that children “grow out” of certain rhythm disorders over time. In the case of children under 5, we sometimes prefer to prescribe antiarrhythmic drugs rather than perform an ablation procedure. These are generally accepted recommendations. At the same time, however, there is a group of children for whom drug therapy is ineffective, poorly tolerated or has serious side effects. In these cases, ablation is necessary. The most common issues are WPW syndrome, atrial and nodal tachycardias. In Poznań Pediatric Department, we have performed almost 90 such procedures on small children. The youngest patients were 3-4 weeks old. I can immodestly admit that we have a very high ablation efficiency in this group of patients, and so far, we have had no complications.
Sounds impressive. Let us stop at the stage of diagnosing heart rhythm disorders in children. What does a diagnosis of arrhythmia mean for the youngest patients?
A good example are children actively involved in sports who have been diagnosed with WPW syndrome at periodic check-ups. The presence of an accessory pathway connecting the atria to the ventricles, bypassing the conduction system, may in some situations result in the risk of tachycardia and sudden death. Fortunately, the latter happens rarely. However, the problem of WPW syndrome is essential in qualifying for sports. In the case of symptomatic patients, i.e. those with paroxysmal tachycardia or atrial fibrillation, ablation is necessary. In the absence of parental consent for this procedure, sports participation is not recommended, as it is potentially risky for the child.
The management is slightly different in children who show features of pre-excitation on ECG but are entirely asymptomatic. Exercise stress test or Holter test, in which we find only intermittent pre-excitation (we call it intermittent WPW syndrome), suggests a relatively safe form of the accessory pathway. If there is constant pre-excitation, only an electrophysiological study can show whether the pathway is safe or potentially dangerous, i.e. whether it can lead to tachycardia or has a very short refractory time, associated with the risk of cardiac arrest in case of atrial fibrillation.
What does a children electrophysiological study look like?
Electrophysiological examination of children is usually performed under general anaesthesia. We should bear in mind that anaesthesia affects the haemodynamic parameters and can also influence electrical heart properties. In order to exclude the sedative effect of anaesthesia on the heart, the patient is administered a short-acting beta-mimetic intravenously – isoprenaline – a drug acting similarly to adrenaline. After its application, it is possible to see how the accessory pathway behaves under “stress” conditions. It allows a more reliable assessment of the electrophysiological properties of the accessory pathway and the stimulus-conduction system.
In this group of patients with WPW syndrome, we also have a subgroup with the so-called parahisian accessory pathway. This term means that the accessory pathway runs very close to the conductive system, especially the His bundle. The ablation in these patients always carries an increased risk of atrioventricular block. The use of a 3D cardiac reconstruction system with electroanatomical mapping improves the precision of the procedure, and the use of cryoablation improves its safety. We have performed cryoablation in over 120 children with a parahisian arrhythmia without observing any atrioventricular conduction system impairment. However, the efficacy of this technique is slightly lower than the efficacy of classical radiofrequency ablation. Nevertheless, we assume that the procedure can be repeated if necessary – the most important thing is to avoid complications that may remain for life.
Which groups of youngest patients are the most challenging to treat?
A category of children problematic in this context is the subgroup with rhythm disturbances and congenital heart defects, especially after previous cardiac surgical interventions, often of multiple stages. Among patients with particular difficulties performing ablation procedures, I would select children with a common atrioventricular canal with a hypoplastic heart due to underdevelopment of the left or right side. After many hospital stays, these children often have an occluded part of the venous system due to previously inserted catheters for administering drugs or performing cardiac catheterization. It significantly limits access to the heart.
How does the strategy differ in the electrophysiological surgical treatment of adults and children?
The child’s heart anatomically differs slightly from the adult heart, as I mentioned before. The differences mainly concern the size and thickness of walls of the individual heart cavities, the diameter of venous and arterial vessels. The distances between unique structures are also smaller. It is important when performing an electrophysiological examination and ablation procedures. Firstly, the puncture of the vessels is more difficult due to the size and degree of filling the vessels with blood. Such procedures are almost always performed under general anaesthesia, and anaesthetic drugs reduce blood pressure. We often use ultrasound to puncture the vessels, especially in young children. We use practically the same diagnostic electrodes for electrophysiological examination as in adults. Sometimes the catheters are slightly thinner. Due to narrow veins in children, we have to limit their number to the necessary minimum. When introducing catheters into the heart, we must be cautious not to cause any perforation of the vessel wall or heart.
What are the other things the operator should pay attention to?
It is essential to be aware of the minimal distances between the endocardium and the arteries running on its surface. The spaces between the structures forming the Koch’s triangle, at the top of which runs the bundle of His, are also very small. For left-sided arrhythmias, it is necessary to pass the ablation electrode through the aortic valve, which has very thin and delicate leaflets in children, unlike in adults. The literature has described the aortic valve dysfunction after ablation procedures performed with the transaortic technique. There has also been damage to the femoral artery wall requiring reparative surgery.
For this reason, for more than 10 years we have been performing the majority of procedures – if not almost all of them – using the transseptal technique. Here, the atrial septum has to be pierced with a transseptal set – the same set used in adults whose hearts are several times bigger. The structure that needs to be punctured has a few millimetres in diameter. It is located close to the aorta and the atrial free wall. We have already performed several hundred such operations, fortunately without any complications. Conditions resulting from the anatomy of a child’s heart and equipment dedicated to performing procedures in adults significantly impact the safety of procedures performed in this area.
Is it necessary to perform additional tests before the procedure regarding children?
Indeed, sometimes the changed anatomy of the heart also requires additional imaging studies before the planned ablation. We use cardiac tomography or rotational angiography performed during the procedure. The advancement of the electrophysiological system allows us to perform a 3D reconstruction of these examinations, which dramatically improves the orientation of the highly altered anatomy of the heart and vessels. The most challenging group of patients are children after the Fontan operation. All venous flow is redirected directly from the upper and lower body to the pulmonary artery (so-called TSPS). Suppose the tunnel turning blood from the lower body to the pulmonary artery is connected to the atrial part by a small hole (so-called fenestration). In that case, some procedures can be performed by slightly extending this opening or using the access through the aorta. Needless to say, the manipulation of ablation electrode in such altered anatomy is considerably tricky, even in the ablation of focal tachycardias or those related to WPW syndrome. The degree of difficulty is exceptionally high when dealing with macro-reentry tachycardias dependent on previous surgical scars. It is then necessary to perform an exact bipolar and propagation map with the identification of scar and slow conduction zones. After analysing such an electroanatomical map, we plan the application system to eliminate all possible tachycardias.
You’ve drawn attention to the aspect of using electroanatomical systems during paediatric procedures. What is their role?
I’ve mentioned before that one of the most important principles when performing ablation procedures in children is safety. Electroanatomical systems improve the precision of ablation procedures and are therefore often used in more difficult ones. We were the first in Poland to start performing “freezing” or cryoablation procedures in children for safety reasons. So far, we have performed over 120 such procedures in cases where the classical ablation procedure was utterly impossible from the standpoint of complication risk. We were the first to use the Ensite system to perform ablation in children to entirely or almost entirely eliminate X-rays. We have now completed practically 800 such procedures. The system allows us to map and perform ablation procedures with all available electrodes accurately. Our initial idea was to eliminate potentially harmful X-rays, assuming that the procedures could be prolonged by this, as the initial publications indicated. However, after years of using this technique, we discovered that not only did we reduce the dose of X-rays tenfold, but in 70% of cases, we performed the procedure wholly fluoroscopically free. It turned out that treatments with the Ensite system are significantly shorter and that we achieve an effective ablation procedure by performing fewer applications.
Thank you for this talk!
Steerable sheath is a gamechanger in complex left atrial ablations says dr. Bartłomiej Bińkowski (MSW Hospital in Łódź, Poland), and presents step by step approach to transseptal puncture carried out directly with steerable sheath.