Accessory pathway ablation

Just thought I’d put out a post from my work last week. A woman in her 30’s had been getting palpitations. They were much worse during her pregnancy, but continued even after delivery. We had caught a supra-ventricular tachycardia (SVT) on ECG monitoring.

I did an Electrophysiology study to assess the heart’s wiring system. I passed 4 wires through the veins at the top of the leg up into the heart, under local anaesthetic. It was easy to set off the SVT and there was evidence of an extra pathway (called an accessory pathway) on the left side of the heart.

I did a puncture across the atrial septum to get access to the left atrium. We set up to use a 3D anatomical mapping system (Carto) to localise the pathway. I then delivered a series of ablation lesions to get rid of the pathway and terminate the tachycardia. This should be enough to fix the problem and prevent future episodes.

The video shows the map that we created, using the open window mapping method. The heart was being paced from the right ventricle and electricity is passing from the ventricle (in red) up into the atrium (in magenta). The white line shows the mitral annulus (where early meets late signals) and the colours reveal the wave front passing through the accessory pathway.

A series of lesions here abolished conducting through the pathway and terminated the tachycardia. The lesions are shown as the red points, with the catheters visible on the shell.

The diagnosis was not Wolff-Parkinson-White syndrome as the resting ECG was normal. This is explained by the fact that this accessory pathway did not conduct antegradely from the left atrium to the left ventricle, but only conducted backwards from the left ventricle to the atrium. This was sufficient to allow atrio-ventricular re-entry tachycardia with a circuit down the normal conduction system and back up the accessory pathway.

The ablation was performed under sedation and with painkillers. Whilst the total procedure time was a few hours, the ablation time was only 4 minutes. This is definitely a case where the adage “measure twice, cut once” is important! The pathway fibres did seem to fan out so a few lesions were required.

If you have palpitations it is worth getting it checked out. There may be nothing serious, but it can be something like this which can be sorted out. Monitoring your own heart rhythm using a Smartwatch pulse monitoring or indeed the ability to capture your own ECG.

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