Pace mapping to unmask isthmus sites in post MI VT

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Raja Selvaraj, JIPMER

VT substrate in post MI VT

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VT substrate in post MI VT

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Circuit and the ECG

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Isthmus pacing during tachycardia

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Some times VT is

  • Not inducible
  • Not mappable

Pacing in sinus rhythm - Attractive idea

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Pacing in sinus rhythm - Reality

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Pacing in sinus rhythm useful to delineate isthmus

  • Do not expect perfect pace match
  • Adjacent bystander cannot be differentiated

Evidence

Parts of VT reentry circuit isthmuses can be traced during sinus rhythm

  • 11 patients
  • Match defined as 10/12
  • Pace match at short S-QRS - 85%
  • Pace match at long S-QRS - only 27%

Corrina B …. Williaim Stevenson. Identification of the ventricular tachycardia isthmus after infarction by pace mapping. Circ 2004;110:652-659

Pacemapping matches

  • Isthmus exit - 84%
  • Isthmus entrance - 32%
  • Central isthmus - 59%

Christian de Chillou … Francis Marchlinski. Localizing the critical isthmus of post infarct ventricular tachycardia: The value of pace-mapping during sinus rhythm. Heart Rhythm 2014;11:175-181

Color coding the match - Pacemapping map

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Christian de Chillou … Francis Marchlinski. Localizing the critical isthmus of post infarct ventricular tachycardia: The value of pace-mapping during sinus rhythm. Heart Rhythm 2014;11:175-181

Practical ? - Old AWMI with recurrent VT of one morphology

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Delineating the circuit

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Usefulness

  • Most post MI VT, substrate based ablation superior to targeting specific VTs (1)
  • But some patients with single dominant VT, useful to target VT
  • In these cases, when VT is not inducible / not mappable / to deduce circuit in SR
  • But be aware of limitations when using pacemapping
  1. Di Biase …. Natale. VISTA multicenter randomized trial. JACC 2015;66:2872-2882