Electrocardioversion

Voiceover: Let's talk about electroshock therapy. So sometimes healthcare providers use electrical shocks to bring patients out of irregular heart rhythms or irregularly fast heart rates. And the goal is to re-establish a normal heart rate and rhythm. So you probably seen scenes in movies or on TV where there is a patient in the hospital and all of a sudden the patients eyes rollback. And there's pandemonium in the room, someone yells, "The patient's heart stopped." The doctor comes running into the room, puts two paddle in the patient's chest and then yells "Clear!" In this scene or scenario, the healthcare provider is using something called a defibrillator. Which is a machine that shocks the heart. So in the movies, usually the patients knocking on death's door and has no heart beat. But in reality, electroshock therapy is actually use to treat a number of different abnormal heart rates and rhythms. For example it's use to treat atrial fibrillation, and that's where the upper chambers of the heart are spasming. So atrial fibrillation sometimes this known as Afib for short. Another rhythm that treats is ventricular tachycardia or Vtach, where the ventriculars are beating way too fast. In addition to Afib and Vtach, there are a number of other different rates and rhythms that are treated with shock therapy. And we'll talk about those in a second. So again, in the movies the patient is usually unconscious and has no heartbeat. But in reality, sometimes the patient's actually awake until just before the shock. And these patients will receive sedating medication just before the shock, to help them fall asleep. Because you can imagine that getting a shock to the chest hurts. And again in the movies, we typically see that people are getting shocked in emergency situations, but in reality electroshock therapy isn't always an emergency. There are some situations were people actually book this shock therapy as an outpatient procedure. So a defibrillator can shock a patient in one of two settings. The first is, synchronized electrical cardioversion. In synchronized electrical cardioversion, the defibrillator delivers a shock in sync with the R wave on the QRS complex. So again, the shock is delivered and synced with the R wave. Which is why it's called synchronized cardioversion. Synchronized cardioversion is use for certain arrhythmias such as atrial fibrillation or Afib like we talked about up here. It's also use to treat atrial flutter which is another type of supraventricular tachycardia just like Afib. It's use to treat atrioventricular nodal reentrant tachycardia, which is a fast heart rate cause by an abnormal loop or circuit of electricity going around the AV node. And synchronized cardioversion is used to treat someone with Vtach who has a pulse. Now why do we care about the pulse? In someone with Vtach, whether or not they have a pulse actually determines how we treat this patient. So if the person has a pulse and is stable meaning that they have normal blood pressure and no chest pain and they have a normal mental status, they are not coming in and out of consciousness. These people will receive medication for treatment. And someone with Vtach with a pulse who is unstable, meaning that their blood pressure is low or they are experiencing chest pain because their heart beating so fast they can't circulate blood well enough to the heart to get oxygenated blood. Or if they have an alter mental status meaning that, they are falling in and out of consciousness or they are confused. These people who are unstable with a pulse in Vtach will undergo synchronized electrical cardioversion. Someone in Vtach without a pulse, well they are going to go straight to defibrillation, which is the second setting on the defibrillator. Again so, Vtach without a pulse, defibrillation. In defibrillation, the electrical shock is given at any point in the cardiac cycle. So again it's given anytime in the cycle. It's not in sync with the R wave or any wave for that matter. So sometimes defibrillation is called asynchronous cardioversion. A, meaning, no synchrony, because it's not synchronizing to any part of the cycle. Defibrillation is use on patients who are a seconds away from death and who have no pulse. It's use in ventricular fibrillation, where there is no electrical activity in the heart. Instead, the ventricular is just spasming and there's no pulse. So what's another arrhythmia where there's no pulse? Remember sometimes Vtach doesn't have a pulse. And in the case of Vtach, without a pulse, we're going to treat that with defibrillation. Another difference in the two settings is that, in defibrillation, a higher energy level is used. So defibrillation is going to use a higher energy level when delivering the shock. So how does electroshock therapy work? Shock therapy works by shocking all of the hearts all at once and depolarizing all of the heart cells at the same time. What happens after depolarization? Repolarization. And the cells go into their refractory periods. The refractory period is sort of like the recovery time or the window of time where the cells can't create another action potential. So depolarizing all of the heart cells simultaneously briefly prevents the tissues from being able to transmit electrical signals because the cells are busy recharging. They are in this refractory period. This is the last time for the heart to reset and allows the heart pacers to sort of reclaim their dominant pacing role. In short, it's kind of like when your computer starts to act up. What do you usually do when your computer starts acting up? Well usually reboot. And so just like you reset your computer, you're resetting the heart. So next time you reboot your computer, it's almost like you're putting paddles on it and yelling "Clear!"