Electrophysiology Catheters and EP Tracing in Ventricular Pacing

Transcript of the video: Just before discussing about an electrophysiology tracing in ventricular pacing, we will have a look at how the electrodes are placed. This is the left anterior oblique view and right anterior oblique view on fluoroscopy. Multiple catheters can be seen here. Those marked by yellow arrows are not catheters, they are the surface electrodes on the chest, pasted over the chest using usual dot snappers. And, intracardiac electrodes this one is coming from above. It is introduced through the jugular vein, into the coronary sinus. It is a decapolar catheter, meaning 10 poles are there. The poles are numbered like this. Distal most one is 1, next is 2. So when these two are taken together it will be one bipolar electrode, usually 1-2. Then it will be 3,4, 5,6, 7,8, 9 and 10. The proximal most will be 9-10, pair will be 9-10. Introduced from the jugular vein. Then there is a quadripolar catheter at the His bundle. This is the right ventricular quadripolar catheter. Distal pair is RV distal and proximal is RV proximal. This is another view of the same catheter, decapolar catheter in coronary sinus. Quadripolar in His bundle region. These are the two proximal electrodes and these are the two distal electrodes. Ablation catheter is different from the other types of catheters. The tip is bigger, and having more surface area. 8 mm catheters, 4 mm catheters are all available. These are smaller, they are meant to record the intracardiac electrical activity, while this is meant for delivering high power, may be 50 Watts of radiofrequency current into the heart to produce a tiny burn, to abolish the lesion. So this has to have a bigger surface area. That is the difference you can see. These are diagnostic catheters. This is an ablation catheter.

Proximal ends of the catheters are connected, multi-electrode catheters connected to a junction box, which is taken to the EP recorder and from which you have tracings displayed on the monitor. The timing is displayed here in milliseconds. The speed of sweep of tracing is much higher than in conventional ECG, which is only 25 millimeters per second, this could be 200 millimeters per second, fast tracing, so that all the complexes will be wider. This is a normal narrow QRS which also appears wide because of the fast sweep speed. These are some surface electrodes which have been taken into this monitor screen, I, aVF, V1, V6 and these are the coronary sinus, CS proximal to distal. And this is His distal, His proximal. This is right ventricular, which appears to be not connected here, as there is no recording seen over here. Instead it is probable that the His catheter is pushed into the right ventricle for pacing. Sometimes this is done to reduce the number of catheters in the heart, to make the procedure simple. This is most probably His bundle catheter has been pushed into the ventricle and ventricle is paced. This is normal activation. You can see that the sequence of activation in the left atrium. Coronary sinus electrode represents left atrial activation. This is the distal, proximal. So activation comes in the proximal portion of the coronary sinus electrodes and then proceeds distally. This is the lateral portion, this is almost the central portion. So atrial activation from right atrium to left atrium is in this direction. That is known as the A waves. And these are the V waves in intracardiac electrogram, representing the ventricular tracing. This is normal narrow QRS. This is a wide QRS, preceded by a pacing spike. You can see a pacing spike. This is the pacing spike recorded, intracardiac pacing spike. This is surface electrode pacing spike. And pacing spike can be recognized by a associated polarization artifact in the lead from which the pacing is delivered. So you can see that it is the electrode, distal His bundle electrodes which are being used for pacing, as the polarization artifacts have been picked up well in His bundle distal electrode. And ventricular depolarization is seen in proximal electrode also after the pacing. And this is the atrial activation. The sequence is the same as this. So this could be a spontaneous P wave which has occurred at that time. But this is different. Here activation in the proximal coronary sinus electrode is coming earlier. So it is possible that ventricular pacing is spreading retrogradely into the left atrium from proximal to distal. That is possible in this case and there is a good VA interval also. So this is possibly a different sequence of atrial activation. Ideally you should have right atrial electrodes also.