Implantable Cardiac Defibrillator (ICD) Pacemaker

00:01 Now, there's a special kind of pacemaker called an ICD pacemaker.

00:05 It cannot only pace just like a, you know, the DDD pacemaker cuz that's what it is.

00:11 It's a DDD pacemaker but in addition, if the patient goes into a dangerous malignant arrhythmia and we're gonna talk about those in a subsequent lecture when we talk about ventricular arrhythmias.

00:22 They're the cause of cardiac arrest, and the ICD pacemaker shocks the heart back to a normal rhythm when a dangerous ventricular arrhythmia develops.

00:32 So, for example, fast ventricular tachycardia or ventricular fibrillation.

00:36 I'm gonna have a lot of time to spend on that when I get to the ventricular arrhythmia lecture.

00:41 But those are both malignant arrhythmias that can lead to sudden death.

00:45 And the pacing component works just like the other pacemakers described, but the shock or defibrillation component occurs only when the pacemaker recognizes a dangerous life-threatening arrhythmia.

01:00 And here you see them inserting - you see it's inserted in the same way.

01:04 The ICD pacemakers are larger cuz they have to carry a bigger battery because that battery has to be able to shock a lot more than just the impulse.

01:12 The shock for causing a little impulse is tiny.

01:16 The shock for defibrillating the heart is substantially larger so it needs a bigger battery.

01:21 And here, you see it's in the same position under the skin, the wires are the same way, the wires are a little heavier as well for the ICD pacemaker.

01:30 And here's an example. So here we see an electrocardiogram of a patient in ventricular fibrillation.

01:36 This is a cardiac arrest, so this is a regular 12 lead ECG. Notice leads I, II and III, aVR, aVL, aVF and the precordial leads V1 through 6.

01:46 Notice that the patient is continuously in ventricular fibrillation and if you look down at the bottom line that's a rhythm strip.

01:54 You see the patient's in ventricular fibrillation and then there's a big spike there; that's the shock.

02:00 And the beat after the shock is a paced QRS. So, the ICD successfully terminated ventricular fibrillation and then paced the patient until the patient's own rate came - would come back normally.

02:15 All pacemakers also contain what I call - they have a little tape recorder and they store any beats that occur.

02:25 So actually, if there are arrhythmias, you can actually find that out from the pacemaker.

02:29 The pacemakers are usually checked every 3 to 6 months.

02:32 And during that time, there's a readout of what has happened in terms of electrical activity in the pacemaker.

02:39 So, any arrhythmias that occurred during that time period are identified and the physician is alerted.

02:44 For example, there could be short periods of atrial fibrillation.

02:48 When that occurs, you know, it's seen and recorded in the little pacemaker recording area.

02:55 And the - when the pacemaker is checked, they report to the doctor, "Oh yes, we saw X number one, two, three episodes of paroxysmal atrial fib and they lasted for so and so long."