Conscious sedation for diagnostic electrophysiology and catheter ablation of supraventricular tachycardia

This editorial refers to ‘Effects of conscious sedation on tachycardia inducibility and patient comfort during ablation of supraventricular tachycardia: a double blind randomized controlled study’ by R.J. Selvaraj et al. on pages 142–146.

Approaches to sedation/analgesia in modern electrophysiology laboratories range from conscious sedation to general anaesthesia.^1,2 Certain procedures, especially in paediatric patients or for complex cases that require precise electroanatomical mapping, are being carried out under general anaesthesia. The majority, however, of diagnostic and ablation procedures can be safely accomplished following mild or no sedation/analgesia, and this is particularly true for supraventricular tachycardias (SVT).³ Mild sedation/analgesia appears to be the most logical approach, ensuring patient comfort and relative amnesia. Two issues have prohibited its unanimous adoption.

First, concerns about sedation-related side-effects as well as restrictive legislation in several countries necessitate the presence of an anaesthetist even for mild sedation/analgesia, at the increase of procedural complexity and costs. However, we now have ample evidence espousing the notion of intravenous sedation that can be proceduralist-directed nurse-administered, i.e. the so-called PDNA model.^1,4 With the exception of certain circumstances such as patients at high risk of hypoventilation or aspiration, as well as prolonged procedures in anxious patients and children in which deeper sedation or even general anaesthesia is required during the procedure, mild sedation/analgesia for most diagnostic and ablation cases can be safely and effectively accomplished through a PDNA model.^1,4

Second, and perhaps more important, ‘conventional wisdom’ may dictate that mild, and especially deep sedation, reduce the chances of tachycardia inducibility or even render the clinical tachycardia non-inducible. Several observations support this notion: the role of the sympathetic component of the autonomic nervous system is well established in arrhythmogenesis, not being restricted to apparently catecholamine-dependent clinical entities, the potentially ensuing lower blood pressure following sedation may preclude the extensive use of isoprenaline and aggressive induction manoeuvres, and certain drugs may have electrophysiological effects, albeit of questionable clinical significance: propofol causes dose-related depression of the sinus node and His-Purkinje conduction, whereas ketamine enhances conduction and promotes tachycardia inducibility.¹

In this issue of EP-Europace, Selvaraj et al., provide solid evidence, as derived from a randomized, double-blind comparison, that conscious sedation with intermittent midazolam and fentanyl reduces patient discomfort during electrophysiology study and ablation of SVT, without affecting tachycardia inducibility and effectiveness of the procedure. In addition, sedation administered according to the PDNA model in the absence of an anaesthetist is safe.⁵ There has been an abundance of previous observational evidence that, with the possible exception of automatic atrial tachycardia,⁶ sedation does not considerably affect basic electrophysiologic properties or inducibility of SVT.^7–9 This is true not only for the opiate–benzodiazepine combination but even for propofol,⁹ and dexmedetomidine, an a-2 adrenergic agonist that is an attractive sedative due to its short half-life and lack of respiratory depression, but had been associated with cardiac conduction abnormalities, and hypotension.⁹

It seems, therefore, that in the current era of free availability of isoproterenol, we should not ablate SVT by subjecting our often young patents, to an unpleasant procedure. A point that merits consideration in this context is the regime used for sedation. Although, an approach that both prevent inadequate sedation (a common shortcoming of benzodiazepine–opiate regimens) and the adverse haemodynamic and respiratory effects of deep sedation has been sought, no such ideal regimen exists. The opiate–benzodiazepine combination is rather safer that propofol¹ but does not necessarily comprise only midazolam and fentanyl. Emulsified diazepam offers a much cheaper alternative than midazolam and avoids the irritating effects of intravenously administered diazepam, and morphine or diamorphine that lacks the emetic effects of morphine (available in the UK), are alternatives to fentanyl. Dexmedetomidine is also an emerging alternative to the opiate–benzodiazepine combination.¹ Individual drug choices depend on the legal environment of different countries, the experience of the involved medical and nursing personnel. The important message is that, in contemporary electrophysiology practice, all patients subjected to ablation for SVT should be given the chance of a comfortable procedure in a friendly environment of mild sedation/analgesia and pleasant music, with Beethoven’s chamber music masterpieces and Callas arias especially indicated for this purpose. Apart from avoiding a rather traumatic experience, patients may even forgive potential tachycardia recurrences…

Conflict of interest: none declared.

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