A New Single Chamber Implantable Defibrillator with Atrial Sensing: A Practical Demonstration of Sensing and Ease of Implantation

Implantable Cardioverter defibrillators or ICDs are electrical generators designed to protect patients from sudden cardiac death due to ventricular arrhythmias. However, sometimes the device delivers painful and adequate shock therapy when the arrhythmia is misdiagnosed as being ventricular. While it might be super ventricular in origin, single chamber ICDs may deliver inadequate therapy due to lower detection rates while dual chamber ICDs generally are not used just to improve detection due to complications associated with the second electrode.

Therefore, Biotronic developed a ventricular electrode with atrial detection capabilities called the Linox Smart to be used in conjunction with the Lumax DX system to minimize inappropriate shock therapies. This video describes a placement of a novel single chamber, single electrode implantable ICD, into a patient with paroxysmal atrial fibrillation who is at risk for sudden cardiac death given impaired ventricular function. Atrial sensing and atrial information improves detection and differentiation between supraventricular tachycardia and implantable defibrillators.

With a second electrode, you have a complication rate, an electrode complication rate, which is more than two times as high as with a single electrode with a new electrode from Biotronic. You get the atrial information just with one single electrode. Together with the Lumax DX device, you will thereby improve detection and probably decrease inadequate therapies, which is very important for patient's wellbeing.

The patient is appropriately prepared and draped in a sterile manner. The patient is placed under moderate sedation. A peripheral intravenous line and supplemental oxygen via oral or nasal cannula are recommended with appropriate monitoring for moderate sedation, which includes continuous electrical cardiac monitoring, continuous pulse oximetry, and noninvasive blood pressure monitoring.

Sedation administered is IV midazolam, fentanyl and propofol with judicious application of topical anesthesia. The patient is in propofol sedation is not intubated, is breathing by herself, and we are, we have data from oxygen and we have the blood pressure and everything is fine at the moment. We start with some local anesthesia in the area of interest, The implantation starts with puncture of the left subclavian vein through the intact skin and the placement of a wire in the venous subc clavia.

The correct position is checked by x-ray. This unusual approach is used because interventional electrophysiologists are supposed to be better in transcutaneous punctures than in puncturing. The vein from the pocket, the skin is cut with the scalpel about two centimeters below and parallel to the clavicular after preparation of the pocket.

For the device below the left clavicular, We take care that there is no bleeding anymore because the patient is obviously on antithrombotic therapy. The wire in the vein is drawn to the pocket and a nine french sheath is introduced into the vein. Now this is a new electrode, which is a screw electrode.

As you can see here, this is the tip electrode. This is a coil from the ICD and these two electrodes are supposed to take recording of the right atrium where the proximal electrode is supposed to lie in the venner caver and the other one, the distal one is supposed to float in the right atrium from these electrodes, the atrial signal is received and brought to the ICD. The electrode is introduced into the superior vena cava via the sheath to the right atrium.

After the introduction of a curved wire, the electrode is pushed to the right ventricular outflow tract. After the introduction of a straight wire, the electrode is maneuvered to the right ventricular apex and pushed to the apex of the right ventricle. The positions of the tip of the electrode and the two electrodes in the atrium are controlled by x-ray.

The two atrial ring electrodes should be placed at the junction of the superior vena cava and the atrium. And what we do now, we take we, before we screw it in, we measure the signals. I just want to know what, what the ventricular signal is like before I screw it in.

Okay, now I, I screw it in. Now the screw is out okay, and the electrode is nicely fixed, so we can withdraw the wire a little bit. And now we repeat the measurements from the ventricle with both pacing and atrial signals.

After positioning of the electrode measurements of the atrial and ventricular signals are performed, the pacing threshold for the ventricular electrode is measured. The atrial signal is enhanced four times with the filter setting in the device. And now you see the difference.

We had a measurement of two millivolts before, and now with the filter setting in the device, you increase the sensing by a factor of 2.5. This is important, so you cannot use this electrode with another device without the important filter settings. The atrial signal is around seven millivolts.

The ventricular signal is around eight millivolts. Now we take the sheath outside a little bit and take the sheath out altogether. After that, we have to repeat the atrial signal measurements.

With this sensing and pacing threshold, the electrode can be fixed at the entrance of the subclavian vein, So it's nicely fixated. The electrode, we recheck the position, the correct position in all views, L-A-O-R-A-O-N-A-P. So the electrode is in a nice position, all three views, and now we repeat all measurements ventricle and the atrium as well.

To finalize the implantation. The electrode is then connected to the defibrillator. Now we place the device in the pocket putting the rest of the electrode below the device so that whenever the device is exchanged, the, the physician runs no risk really to touch the electrode when he cuts into the pocket.

Okay, now all measurements are rechecked with the device, and this is important because obviously the device has a different filter setting than the measurements taken before. So it's important to, to realize that all the sensing that we have is via the device. And you will see the difference between the measurements before and afterwards.

All measures will be rechecked and ventricular fibrillation will be induced by T-wave shock via the defibrillator and automatically terminated by the device mind the stability of the atrial signal. Even after ventricular fibrillation, induction and termination, There's T-wave shock to induce vf. Now there is VF going on.

The device detects it. There is a shock and terminates vf. So device, the device is properly functioning and now we recheck all the positions of the electrode after the shock and the electrode is in the correct position.

Still everything is very nice. The patient will be brought to the ward and stays in the hospital until the next day when x-rays will be taken and sensing and pacing thresholds rechecked up to four hours of observation. Recovery and monitoring are required after the implantation.

Since we are talking about primary prevention of sudden deaths, we use a VT zone and the VF zone. The VT zone is usually programmed around 190. In the specialist case is 188.

For VT detection, we use the smart algorithm, which is an algorithm differentiating between VT and vetric tachycardia, using also the atrial signal and the atrial formation. And for VF detection we have the program the zone to 231. For the F detection, one more, and as a therapy we use three attempts of antitachycardia pacing with a burst and three antitachycardia attempts with a ramp.

And afterwards in the VT zone we have maximum shock energy, which is in this special device, which is a high energy device, four 40 joules, and we have eight shocks of 40 joules at hand. And we come to the VF zone. And what we have, we have one antiar pacing during detection, which is standard nowadays in order to avoid shocks in the VF zone because most fast VTS can also be terminated by antitachycardia pacing.

Afterwards, we have eight maximum energy shocks with 40 jewels throughout. You can see here also a special feature of this device we have here also ho the the facility of home monitoring, which means that all the data are transferred via a little device that the patient has with him and via satellite with an SMS technology to the implanting center. So all important aspects of follow up are transferred via satellite where distance is not important anymore.

We can also get the information from this patient if he's on holidays, let's say in South America or in Canada. We get the information if something is wrong with the device with in a very short time, which is a special feature called home monitoring in this device. Now this is the, the biotronic cardio messenger, which can be placed besides the bedside and the, the transfer of the information is during the night when the, the patient doesn't realize anything of it.

So the patient need not do anything except for plug it in, which makes this kind of transfer of information so easy. With this device, the so-called cardio messenger, you get a better differentiation between ventricular and sup ventricular tachycardia with the atri information. The second important aspect is this lady has intermittent atrial fibrillation and we can nicely control any therapy of atrial fibrillation with this device because the atrial signal is, can also be seen during atrial fibrillation.

So we know whenever the patient gets atrial fibrillation and when we start the therapy for atrial fibrillation, we can monitor the therapy effect. And with this device we can certainly detect any atrial fibrillation episode during follow-up. The new linox electrode is as easy to implant as any single chamber electrode.

It is not thicker and it is not stiffer. The only thing that you have to take care of during implantation is that the two atrial electrodes are positioned close to the contact between valar cava superior so that you have the proximal electrode at the wall and the distal electrode free floating in the right atrium. And with this you will gain excellent signals, which with a filter setting in the device are usually much bigger than the atrial signals that you gain from atrial electrodes.