Electrophysiologic Studies and Catheter Ablation of Abnormal Conduction Pathways

Electrophysiologic studies involve the placement of special multipolar catheters within cardiac chambers to define the mechanism, origin, and pathways of arrhythmias and to determine the best therapeutic options.^[130] Vascular access is usually through the femoral artery and vein, and frequently, additional catheters are placed through the internal jugular vein, with obvious implications for airway management. Programmed electrical stimulation is performed at various locations with the use of standard transvascular catheterization techniques. By using specifically timed electrical impulses, the arrhythmia is reproduced under controlled conditions and is monitored through both the catheters and the surface ECG leads. Electrical energy delivered through appropriately positioned catheters can then be used to ablate arrhythmogenic foci or accessory pathways. Another intervention that may also be performed in the laboratory is to place the electrodes precisely for subsequent connection to an implantable defibrillator.

Antiarrhythmic drugs are stopped before these studies and are avoided during the procedure because they may prevent detection of the accessory conducting pathways and arrhythmogenic foci. These studies use multiple catheters and often take several hours to perform. To ensure patient comfort, adults and older children are usually sedated with midazolam and receive analgesics such as fentanyl. The total administered doses of these drugs may seem quite high at the end of the procedure, but the procedures are long, and the pain resulting from the RF ablation may be severe during the burn. Brief periods of general anesthesia with thiopental or propofol may be needed during ablation^[131] or if cardioversion is required for supraventricular arrhythmias that cannot be terminated by overdrive pacing via the catheters. Care must be taken during mask ventilation that any internal jugular venous catheters are not moved and the operative site is not contaminated. Similarly, care must be taken during endotracheal intubation or placement of an LMA should conversion to general anesthesia prove necessary. Electrophysiologic studies in younger children are usually performed under general anesthesia, as outlined in the section on cardiac catheterization. Intravenous and volatile anesthetic techniques have both been used successfully in electrophysiologic testing.^{[132] [133]} One study has shown that general anesthesia with controlled ventilation improved the conditions for electrophysiologic studies. ^[134] As for cardiac catheterization, consistent anesthetic techniques should be used in a given institution to ensure diagnostic accuracy.