Excerpts from EP summit

Excerpts from EP summit

8 – 10% of atrial tachycardias may be adenosine sensitive

Optimal site of pacing

The shorter distance the impulse have to travel before engaging the conduction system, the better the hemodynamic response
RVOT pacing is not beneficial in HOCM and in situations with diffuse infra Hisian conduction system disease

Principles of entrainment

What is entrainment? It is a stable condition with a definable periodicity due to interaction of two rhythms – one of the tachycardia and the other of the pacing.

It is a method to try to identify the mechanism of tachycardia. Entrainment establishes the mechanism of tachycardia as re-entry.

Four criteria (any one is enough for establishing entrainment):

1. Pacing during tachycardia yields constant fusion on the ECG except for the last captured beat which is not fused.
   This last beat is at the cycle length of paced beats, but is not fused.
2. Progressive fusion while pacing at two different rates.
3. Pacing termination of tachycardia yields localized conduction block followed by activation of that site with a shorter conduction time
4. Demonstration of a change in both the conduction time and electrogram morphology at a recording site when overdrive pacing is performed at two different constant sites. (A combination of criteria 2 and 3).

Concealed fusion occurs in entrainment occasionally. Concealed entrainment does not rule out ‘bystander pacing’.

For reentrant circuit, the QRS morphology does not predict site of successful ablation. The QRS depends on the site of exit of the tachycardia and not on the slow zone which has to be targeted for ablation.