Inducibility Conundrum for Ablation of Ventricular Tachycardia
Are We Done Yet?
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See Article by Oloriz et al
The application of programmed electrical stimulation (PES) by Wellens et al1 to the evaluation of ventricular tachycardia (VT) in humans was a landmark achievement establishing a method that has led to pathophysiologic insights and improved VT diagnosis and therapy for >4 decades. The ability to initiate VT, ablate, and then demonstrate that VT is no longer inducible has been fundamental to assessing the acute effects of catheter ablation. Although there has been substantial progress with ablation in patients with heart disease and scar-related reentry and it is superior to escalating antiarrhythmic drug therapy in many situations, multicenter trials continue to report arrhythmia recurrences in 20% to 50% of patients.2,3 Recurrences are more frequent for nonischemic dilated cardiomyopathies and are associated with increased mortality and hospitalizations.2,4,5 Can PES shed light on the reasons for ablation failure? Or is its use to assess the acute procedural endpoint part of the problem? When one ablates an accessory pathway, the arrhythmia is no longer inducible, but we also confirm that the pathway is gone. Does use of noninducibility as an endpoint obfuscate the goal of abolishing the substrate?
There are many limitations and caveats in the use of PES for assessing procedure outcome. VT inducibility is probabilistic and influenced by drugs, autonomic state, and the nuances of the stimulation protocol. The pacing sites, number of extrastimuli, and manner in which the extrastimuli are applied vary among laboratories. Some patients do not have inducible VT at baseline. Initiation of reentrant VT demonstrates that the substrate for reentry is present but is not informative about the existence of initiating triggers. Programmed stimulation is generally performed from sites remote from the reentry circuit, whereas recordings of spontaneous VT initiation often show that …