Implantable Cardiac Defibrillator

So as a lead-on to pacemakers, other devices that we place in patients are defibrillators, and we implant defibrillators in specific group of patients, and these are patients that either have had very fast abnormal heart rhythms or are at risk of developing abnormal fast heart rhythms, which can be potentially life-threatening. So, what I tell patients is that a defibrillator is very much like a pacemaker that can regulate the heart rate and rhythm, but it can also deliver a small shock to get your heart back into the normal rhythm should it develop a life-threatening fast abnormal heart rhythm. So, it's slightly akin to having a paramedic on your shoulder 24-7 that watches your heart rhythm and your heart rate and then it treats abnormally fast heart rhythms if you develop them with a small electric shock. Normally patients when they do develop this abnormally fast heart rhythm or have passed out so when you actually get the shock you'll be unconscious and you won't realize getting the shock. In terms of the actual procedure and putting in the defibrillator it's almost exactly the same as a pacemaker and but the actual hardware that we put in is slightly different. So the wires that we put into the heart are different from the wires of the pacemaker because this defibrillator wires have what we call shocking coils which then allow the defibrillator generator to then shock the heart between the coils. The actual generator or the battery of the defibrillator is also a lot more complex because if you can imagine it's not only producing impulses to make the heart beat faster or regulating the heart but it actually needs to be able to distinguish abnormally dangerously abnormally fast heart rhythms for it to be able to then get you out of that normal rhythm with a shock what we call defibrillates you. And with the improved, the more complex machinery in it, it's almost always larger than a pacemaker. But with again modern technology, they're not actually terribly large and unless you're very thin, the generator box normally isn't terribly visible from the outside. The defibrillator has a lot of implications for a patient and a lot of the times it's largely because of driving. So if you have a defibrillator put in and depending on the indication to why the defibrillator was put in, you may well have a driving ban between one to six months and it is actually the onus on the patient to inform DVLA when you have the defibrillator put in and DVLA would then get in touch with your physicians to get a bit more information. Again the follow-up for defibrillators we have are very similar to pacemaker follow-ups where you have a check four to six weeks after you've had the defibrillator implanted, six months thereafter, every year, you will have an emergency contact number to get in touch with the physiologist or the doctors should the defibrillator actually fire. The physiologist will explain to you in greater detail how and what to do if you have the defibrillator shock you or fire off. And the defibrillator also has numerous alarms that can sound and this might indicate some sort of malfunction or the battery being depleted or something worrying that it's detected. What's really good about current defibrillators is that in the majority of patients nowadays, we don't actually need the patient to come in physically to the defibrillator or the pacing clinic and what we have this technology that allows the defibrillators to be monitored from home, what we call remote monitoring. So you'll be given a set of equipment very much like a router for your broadband at home and the defibrillator when you're at home normally can automatically communicate with the router and this information can then be passed through to the hospital and if there's any abnormalities it's picked up by one of the physiologists who then will contact you and get you in for further checks if need be. So the complication rates of defibrillators are again very similar to the complication rates in terms of the actual implant there's no additional complication, but the only extra bit that we do when we do implant a defibrillator is we actually do a defibrillator threshold test. So what we actually do is that we actually put you into a dangerously abnormal heart rhythm and then allow the defibrillator to detect it and actually treat the abnormally fast heart rhythm with a shock. Obviously this will be done with you being sedated so you won't be completely awake and the likelihood is that you won't remember this segment of the procedure and this is to ensure that the defibrillator is actually working well and will be able to get you out of a dangerously fast heart rhythm. One important aspect of patients having the defibrillator is that ultimately these defibrillators are machines and machines can make mistakes and sometimes patient might get treatment in terms of shocks when they actually don't need the treatment what we call inappropriate shocks or inappropriate therapies and it should that happen unfortunately you need to call 999 and get into hospital straight away and normally it happens when you actually get receive a shock when you're actually completely wide awake and the reasons why it could happen is a software malfunction and more commonly actually the leads can degenerate over time and can fracture and when this leads fracture they can create noise in this leads which then feeds back to the generator and the generator then detects it as an normally fast heart rhythm and treats you inappropriately. Of note, even if you get a shock when you didn't need a shock, what we call an inappropriate shock, you will unfortunately still be banned from driving for a month after that. So it does have driving implications. In some patients where the defibrillator has been put in when they are relatively young, these wires all have a certain amount of shelf life, in the sense that they have wear and tear and they malfunction over time. For example, if a patient gets a defibrillator when they are 18, by the time they are 40, it may well be that they are outliving some of the material components of the defibrillator. And if that happens, we can detect any signs of wear and tear. One of the options is actually to remove the defibrillator and we extract the leads and the wires out and we can put in a new set of wires in and out and essentially give you a fresh defibrillator with new wires and a new battery. This procedure isn't taken very lightly because it has quite a significant risk of damaging the veins or the arteries that leads to the heart and needing cardiac surgery but once again as I said it doesn't happen in everyone and fortunately most defibrillators are put in to the elderly population where the defibrillators actually outlive the patients rather than the patients outliving the defibrillators.