The Lead Episode 18: A Discussion of Substrate Mapping Alters Ventricular Tachycardia Inducibility-Circulation Arrhythmia and Electrophysiology

Circulation Arrhythmia and Electrophysiology

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A recent study published in Circulation: Arrhythmia and Electrophysiology has shown that substrate mapping during ventricular tachycardia (VT) ablation procedures can alter the inducibility of VT. The researchers hypothesized that substrate mapping may mechanically disrupt critical sites within the re-entry circuit, leading to changes in VT inducibility. <br /><br />The study included 28 patients with scar-related VT who underwent VT ablation. The patients were divided into two groups: Group I underwent substrate mapping before repeated programmed electrical stimulation (PES), while Group II had additional imaging and transeptal puncture performed without substrate mapping before repeated PES. The response to the second PES was categorized as Type I if the same VT was induced, Type II if a different VT was induced, and Type III if VT was not inducible.<br /><br />The results showed that substrate mapping commonly altered the inducibility of VT. In Group I, the second PES induced the same VT in only 21% of patients, a different VT in 64%, and no VT in 14% of patients. In contrast, in Group II, the same VT was induced in 71% of patients, a different VT in 21%, and no VT in 7% of patients.<br /><br />The findings have important implications for catheter ablation procedure planning and the assessment of outcomes. They suggest that substrate mapping can transiently disrupt parts of re-entry circuits, potentially preventing the inducibility of clinically relevant VTs. This can lead to a misperception of successful ablation when VT is no longer inducible.<br /><br />The researchers recommend considering modifications in procedural strategies, such as performing VT induction prior to ventricular mapping. They also suggest that initial mapping during VT, rather than creating a sinus rhythm substrate map, may be beneficial for identifying critical substrate sites. Additionally, a targeted hybrid approach that combines initial mapping and ablation with subsequent electrophysiology study could be considered in some patients.<br /><br />It is important to note that the study had some limitations, including a small sample size and potential operator bias in group allocation. However, the findings highlight the need to carefully assess the inducibility of VT after substrate mapping in order to accurately evaluate procedural outcomes.

Keywords

ventricular tachycardia

substrate mapping

ablation procedures

VT inducibility

re-entry circuit

programmed electrical stimulation

catheter ablation

procedural strategies

electrophysiology study

procedural outcomes