European Heart Journal Advance Access originally published online on April 18, 2006
European Heart Journal 2006 27(10):1134-1136; doi:10.1093/eurheartj/ehi862
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Non-fluoroscopic mapping systems for electrophysiology: the ‘tool or toy’ dilemma after 10 years
Department of Cardiovascular Sciences, Ospedale di Circolo e Fondazione Macchi, University of Insubria – Varese, Viale Borri, 57, IT-21100 Varese, Italy
* Corresponding author. Tel: +39 0332 278934; fax: +39 0332 393309. E-mail address: rdeponti{at}alice.it
This editorial refers to ‘Radiofrequency ablation of arrhythmias guided by non-fluoroscopic catheter location: a prospective randomized trial'
by M.J. Earley et al., on page 1223
Searching in PubMed for the string ‘tool or toy’ in the title of medical papers, we found that over the past three decades about 50 papers brought up the dilemma concerning whether a novel technology is a useful tool, or merely an expensive toy. The papers are from 15 different medical disciplines spanning from radiology, neurology, anaesthesia, and surgery. Surprisingly, in almost half of these papers the ‘tool or toy’ dilemma is posed for new technologies introduced in the cardiovascular field. Several of them, such as stress echocardiography and transoesophageal echocardiography, have become widely diffused and have definitely become routine practice. Although this analysis of the medical literature is gross, the result underlines that this dilemma is not so rare. In fact, new technologies are periodically proposed and the reaction of the medical community is usually quite ambiguous, varying from the hardest scepticism to the warmest enthusiasm. Actually, far from being an expression of physicians' uncertainty, the dilemma is justified by the fact that on one hand new technologies, especially in their early phases, are associated with high costs for equipment acquisition and their disposable parts, that the field of application is not well defined, and that the initial version is usually not completely developed because the engineer's work requires physician's feedback to ameliorate and render user friendly, brand new technologies. On the other hand, the introduction of new technologies may be the first step in a revolution which advances the frontiers of medical science and therapeutic approaches by providing more effective treatments in an always increasing cohort of patients.
In 1996, the in vivo use of a non-fluoroscopic magnetic technology for endocardial navigation and mapping of the heart was reported.1 Although initially the focus was on the fact that the position of the catheter could be precisely established without fluoroscopy, subsequently it turned out that this was not the only use of the system. Actually, its peculiar feature was the ability to perform a three-dimensional electroanatomical reconstruction of the heart in which spatial information is complemented by the electrical information recorded in a given rhythm, with both used to reconstruct the activation sequence and voltage amplitude on a colour-coded map.
Two years later, another new system was introduced in clinical electrophysiology.2 It was capable of virtually reconstructing the endocardial activation during a single heart beat, processing endocavitary signals simultaneously recorded in a non-contact way by a multielectrode array adequately placed in a heart chamber by using the inverse solution of Laplace's equation. A catheter could be navigated in a map obtained without fluoroscopy using a low-current ‘locator’ signal. Subsequently, the system was modified so that multipolar catheters could be located and navigated without the multielectrode array using only externally applied high-frequency electrical fields from cutaneous patches.
In the following years, another two systems that used microcurrents or ultrasounds to locate multipolar electrophysiology catheters were introduced into clinical use. Because conventional electrophysiology was made of paper recordings of intracavitary signals and fluoroscopy, these systems were classified as non-conventional. In fact, their technological content allowed for something outside the ‘conventional’ limits. Over the years, the question of whether crossing the border of what is conventional and orthodox was clinically useful (e.g. non-conventional systems a new tool) or simply fun for the bored electrophysiologist (e.g. non-conventional systems an expensive toy) was asked several times. Our feeling is that non-conventional systems are progressively changing the course of modern electrophysiology and maybe if these systems had not been introduced into clinical practice, it would not be the same. A long and detailed literature overview would be required to define the contribution of these systems into new electrophysiological developments.
In a few lines, we may try to delineate what these new technologies have changed and are still changing in the field of cardiovascular medicine, limited not just to arrhythmia diagnosis and treatment. In this process, technology did not work a miracle per se, but every new achievement was the result of hard work and large investments of physicians' time and resources.
First, non-conventional mapping systems have largely contributed to improvements in the approach to complex arrhythmias, namely atrial fibrillation (AF), atypical atrial macroreentrant tachycardia/flutter, and ventricular tachycardia. For AF, the approach is now so sophisticated that left atrial ablation can be supported by the integration of three-dimensional cardiac computed tomography into the electroanatomical system which allows for navigation of the ‘real anatomy’ with clear and precise identification of the pulmonary vein–left atrial junction, target for ablation.3 The complete course of re-entry can be reconstructed, and the most suitable isthmus for ablation defined by non-conventional systems in atypical atrial macroreentry, even in association with relevant heart disease, improving the outcome of the ablation procedure4 when compared with the conventional era. Non-conventional systems have greatly contributed to the development of new ablation strategies for non-tolerated or non-inducible ventricular arrhythmias, triggering repeated interventions of implantable defibrillators. These new approaches are based on attempts to reconstruct the arrhythmia course in a single beat5 or on electroanatomical voltage mapping of the ventricular substrate during sinus rhythm to identify tachycardia-related channels in patients with prior myocardial infarction.6
Secondly, these non-conventional systems can be used merely as an advanced diagnostic tool, not directly finalized to ablation therapy. Although we are at a very early stage of this application, one good example is a paper by Corrado et al.7 Their study demonstrates that electroanatomical voltage mapping of the right ventricle enhances the accuracy for diagnosing arrhythmogenic right ventricular cardiomyopathy/dysplasia when compared with conventional criteria. Interestingly, the presence of altered electroanatomical voltage patterns in patients with this disease correlated with the findings of endomyocardial biopsy and reached borderline statistical significance in the correlation with events such as syncope, palpitations, and sustained ventricular arrhythmias. We are confident that this is just the beginning and many other studies will follow in this line of research.
Thirdly, these non-conventional systems proved to be a very useful method for research in pathophysiological studies by providing new answers to old questions. Just two examples will be mentioned. Some times ago, we reported the electroanatomical pattern of sinus activation in intact normal human atria,8 whereas only animal or open-chest surgical data were available previously. Defining the normal electroanatomical pattern with possible individual variations, the prevalent role of the Bachmann's bundle among interatrial connections and the discordant activation of the right and left aspects of the atrial septum shed new light on apparently well-known phenomena and posed a new basis for further research. A couple of years ago, Auricchio et al.,9 using non-conventional mapping systems, characterized left ventricular activation in patients with heart failure and left bundle branch block. They provided data that left bundle branch block is a rather complex electrical disease resulting from conduction delay, located at several anatomic levels of the activation sequence that cannot simply be detected by surface ECG. Proposing the concept of an individual intracavitary activation pattern of what is recorded simply as left bundle branch block on surface ECG, they proposed a milestone for further research not yet completely perceived in the applicative field of biventricular pacing.
Earley et al.10 report the interesting results of their prospective randomized trial on catheter ablation of cardiac arrhythmias supported by non-fluoroscopic systems in comparison with the conventional method. Complex arrhythmias such as AF, atypical atrial flutter, and ventricular tachycardia with structural heart disease were excluded from the randomization, because the authors perceived that ablation of this arrhythmia would definitely benefit from a non-fluoroscopic mapping system. Even in this patient population with conventional arrhythmias, the authors demonstrate that the two systems used in this study show the advantage over the conventional approach of reducing the fluoroscopy time without compromising the duration, effectiveness, and safety of the ablation procedure. This implies that after all the above-mentioned research, non-conventional mapping systems, going back to their origin, can be used simply as a non-fluoroscopic navigation tool even in the cases in whom arrhythmia complexity is not expected. In contrast, one could argue that the clinical relevance of reduced fluoroscopy times is minimal when an optimized modern X-ray system is used and that this benefit is obtained at a generally higher cost than using conventional systems. However, the authors conclude that there might be long-term benefits of reduced radiation exposure for the community and the laboratory staff.
After all these considerations, we find it very hard to put in a final word on the tool or toy dilemma. In any case, if our predecessors had not progressively introduced and developed new technologies over the past centuries, we would probably still use horse-drawn carriages and smoke signals, whereas fully equipped cars and cellular phones make everyday life safer and more comfortable.
Conflict of interest: R.D.P. is a member of the Clinical Advisory Board of Biosense-Webster, Inc.
Footnotes
The opinions expressed in this article are not necessarily those of the Editors of the European Heart Journal or of the European Society of Cardiology.
doi:10.1093/eurheartj/ehi834 
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[Abstract/Free Full Text] - Earley MJ, Showkathali R, Alzetani M, Kistler PM, Gupta D, Abrams DJ, Horrocks JA, Harris SJ, Sporton SC, Schilling RJ. Radiofrequency ablation of arrhythmias guided by non-fluoroscopic catheter location: a prospective randomised trial. Eur Heart J 2006; 27: 1223–1229. First published on April 13, 2006, doi:10.1093/eurheartj/ehi834.
[Abstract/Free Full Text]
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- Radiofrequency ablation of arrhythmias guided by non-fluoroscopic catheter location: a prospective randomized trial
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EHJ 2006 27: 1223-1229.[Abstract] [Full Text]
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