Re-entry VT: Termination without Global Capture

Answer: The EGM demonstrates “VT Termination without Global Capture” and has a high probability of indicating that this site is critically involved in the VT circuit. Ablation at this location may abolish VT.

 

Termination without Global Capture

• Refers to a paced ventricular stimulus during VT, providing no “outward sign” of capturing myocardium – i.e no evidence of ventricular capture on ECG or ventricular EGM remote from pacing site.

 

• However, VT terminates immediately after pacing stimulus is delivered.

 

• Usually indicates that pacing site is in critical diastolic isthmus site – and as such this phenomena most often occurs in regions with fractionated EGMs & late potentials mapped during sinus rhythm or RV pacing.

 

 

Explaining Termination without Global Capture

 

 

Optimal timing of the paced stimulus to induce Termination without Global Capture:

• Optimal timing appears to be a paced stimulus during the QRS phase.

 

 

Optimal Location to Pace and induce Termination without Global Capture

 

• Often occurs at sites with “late potentials” and low voltage borderzones, which correlate with the location of critical diastolic isthmuses.

 

• Below is an example of a VT isthmus site, detected through pacemapping, correlating with the borderzone of unipolar low voltage. Pacing at such sites during VT may cause termination without global capture.

 

 

My Two Cents:

• During VT, any pacing stimulus which terminates VT warrants close examination.

 

• If Termination without Global Capture is found, then this is often an indicator to step on the ablation pedal at the location of the pacing site.

 

• Termination without Global Capture strongly correlates with critical diastolic isthmus sites of VT.

 

• Critical diastolic isthmus sites can be found in areas of “abrupt change” in pacemap morphology (as described in previous BeatBoxes here), and correlates with low voltage border zones and regions of isochronal crowding.

 

Thanks for tuning in :)
Cheers
Mitch & CPiP Team

 

This post was based on a Mini-Lecture from the Scar VT Program of EP in Practice. No Compromises. No Shortcuts. Just EP Mastery.

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References:

Katsume Y, Hasegawa K, Ikewaki H, Mohri T, Tashiro M, Nonoguchi N, Hoshida K, Togashi I, Ueda A, Matsuo S, Sato T, Soejima K, Stevenson WG. Termination without global capture: electrocardiographic and anatomical characteristics using 3D-electroanatomical mapping system in reentrant ventricular tachycardia. Europace. 2024 May 24;26(Suppl 1):euae102.332.

 

Katsume, Y, Hasegawa, K, Limprasert, S. et al. Termination Without Global Propagation in Re-Entrant Ventricular Tachycardia: Electrophysiologic Characteristics and 3D-Electroanatomical Mapping Analysis. J Am Coll Cardiol EP. null2024, 0 (0)

 

Hayashi T, Mitsuhashi T, Sugawara Y, Momomura SI. Two mechanisms of termination of idiopathic reentrant ventricular tachycardia originating from the left coronary cusp/right coronary cusp commissure with nonglobal capture. HeartRhythm Case Rep. 2015 Jan 2;1(1):2-5.