An ICD is a device that is implanted under the skin on the left side (usually) but it could be the right side and a lead inserted into a vein under the collar bone called the subclavian vein. This vein leads to the right atrium of the heart. The wire is inserted to the right ventricle and the wire touching the inside part of the heart called the endocardium (a fancy way of saying the heart’s inner wall). The wire is then sutured down.
Why would someone need a device like this? If someone had a life threatening arrhythmia like Ventricular Tachycardia or Ventricular Fibrillation a shock would need to be delivered as soon as possible; the sooner the better the chances of surviving greatly improve. Wiring of the heart can get messed up, so much so that these rhythms are common place. Since getting to a hospital is sometimes out of the question. The shocks can be delivered instantaneously.
An implantable cardioverter defibrillator works with the wire touching the inner aspect of the heart. The computer that is implanted on the chest wall monitors signals from this wire. Once it detects a life threatening rhythm such as VT or VF it delivers shocks. First it will attempt a low shock like a pacer shock which is measured in volts. The ICD gives a few of these shocks, which are not felt by the patient and waits for a signal back indicating success. If the heart is still not corrected it delivers a cardioversion shock (milder than placing your tongue on a 9V battery). The level is set by the cardiologist depending on the condition of the patient. The wearer usually reports a weird sensation such as a thud or fluttering in the chest. If still uncorrected the device delivers a larger defibrillator shock, which is 3.5 volts in 0.4 ms and will keep giving shocks until the rhythm is corrected at predetermined intervals (i.e 380ms). The wearer reports a jolt which can be very surprising to say the least. If for some reason the feeling doesn’t subside or shocks persists, usually the doctor will advise the patient to seek immediate medical attention.
ICD’s and pacemakers are exactly the same in appearance. They only differ in programming and lead placement. As I said earlier the implantable internal defibrillator's leads are placed in the right ventricle touching the inner wall. Pacemakers’ leads are placed in the right atrium wall and right ventricle wall. Obviously, the programming (telling the pacemaker what to do) would be slightly different too. The voltage would be the same, however, the rate the pacemaker would pace at would be different and in a straight forward pacemaker no large shocks would be given. You can get different types of devices that can do a combination of things, such as a pacemaker/defibrillator.
It sometimes happens that ICD’s give inappropriate shocks (which these days are few and far between). Like all equipment they can fail so patients are advised to seek medical attention for these special circumstances as well. We can stop the ICD from working by placing a very strong ring magnet over the device, by doing so the practitioners remove the ICD out of the equation and focus on the underlying problem. An ICD can malfunction if there is an infection at the insertion site or nearby and if left unchecked can find its way into the device and interrupt the devices circuitry. Very rarely do devices malfunction from faulting wiring from the manufacturer. Usually if they do malfunction it is from software problems not hardware issues. If it is determined that a software problem is the culprit, the hospital staff would call the ICD manufacturer using the card the patient has on them. At which time the manufacturer will send out a technician with a portable computer anytime of the day to correct the issue. They can also download information from the device such as ECG’s and event logs to bring up a history of the problem, to which, they can prevent any future problems from happening.
Wearers are advised to stay away from microwave ovens or other magnetic devices. Wearers are advised to carry with them device cards.
Patients come to the emergency department for many reasons. It was the beginning of summer and it had been dry for some time now. A patient arrived in the emergency triage line pale, tired and barely able to hold her head up in the wheel chair. She was conscious and it was obvious something serious was wrong with her. We wheeled her into one of our critical beds. We proceeded to change her and assess her more closely with vitals and an ECG. Her vitals signs were: Blood Pressure 78/40, Temperature 36.4, Pulse 25 respirations 12, and oxygenation 100%. At the same time we inserted an intravenous and started to give her fluids. The doctor arrived soon after her arrival. The ECG showed 3rd degree AV block or complete heart block. Then we placed external pacer pads on her chest and began to pace her heart. We gave some medication for the pain and some slight sedatives to help relax her. She is 68 and quite alert but someone can’t live with a big machine externally pacing. She responded well to the treatment, requiring only mild medications to help her blood pressure. Since she was in a 3rd degree AV block she requires a permanent pacemaker to be inserted. Our hospital doesn’t insert pacemakers therefore she needed temporary pacer wires inserted while she waited for a pacemaker.
A 48 year old man arrived in triage complaining of a nagging left sided chest pain that started 3 days ago. In the last 3 hours it became constant and thought he’d better get it checked out. Due to his age and cardiac risk factors he was brought to an urgent area and was told to change into a patient gown. We began to assess him with some questions and an ECG and some vital signs. He remained alert and oriented and advised us that he has no previous history of chest pain. Vital signs: Blood pressure 90/58, Temperature 37.0, Pulse weak 170, Respirations 14, Oxygenation 98%. A large bore intravenous was started and his ECG showed Ventricular tachycardia. The doctor arrived soon after the patient’s ECG was done and because the patient remained alert and oriented we prepped him for a conscious sedation electric cardioversion. The electric cardioversion was ordered due to the patient’s blood pressure and it could be argued that the rhythm started 3 hours ago, but it is uncertain. Life threatening rhythms need to be treated. We cardioverted him with no problems he remains on blood thinners today. After this procedure he continued to have three more episodes of VT to which an ICD was scheduled to be inserted.Do you have a Patient story to tell, Tell it here!.