Cardiac dysrhythmias and tachycardias
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- [Voiceover] In this video, we're going to talk about cardiac ablation, and cardiac ablation is a procedure used to treat arrhythmias. So, an arrhythmia is a problem with the heart's electrical system that causes the heart to have an either abnormal rate, meaning it's too fast or too slow, or an abnormal rhythm. And in the case of the abnormally fast heart rate, that's called a tachyarrhythmia. So in cardiac ablation, diseased heart tissue known to cause an arrhythmia is found and then destroyed. By destroying this problem area that starts arrhythmias, you're hoping to prevent future arrhythmias. Cardiac ablations treat a variety of arrhythmias, such as atrial fibrillation, which is a condition where the atrial walls, or the top chamber walls, spasm. It also treats atrial flutter, which is another type of fast heart rate that stems from the top chambers. Ablation is used to treat ventricular tachycardia, which is a fast heart rate stemming from the ventricles, or the lower chambers, and ablation treats tachycardias caused by accessory pathways. Now an accessory pathway is a connection between the top chamber, the atrium, and the bottom chamber, the ventricle, that shouldn't be there. So basically, electrical signal escapes, instead of going through the AV node, stimulating the ventricles a little too early. Ablation is also used to treat a condition called atrioventricular nodal reentrant tachycardia. This is sometimes called AVNRT. So, AVNRT is a fast heart rate caused by an abnormal loop of electrical activity going around the AV node. So typically, when people have an arrhythmia, they'll go to a heart specialist, and the heart specialist usually prescribes medications to treat the arrhythmia. Sometimes, despite taking the medications, people will still have the arrhythmia. So, if medications don't work, then they might try something called electroshock therapy or cardioversion, and in cardioversion the heart is actually shocked, with the goals of shocking the heart out of the rhythm and into a normal rhythm or rate. Sometimes cardioversion doesn't work, either the person won't convert into regular rhythm or they'll go back in old rhythm and then go back to the arrhythmia. So, when somebody tries medication and cardioversion and are still having the arrhythmia, well then they might try ablation. Now in ablation, we're going in, and we're destroying heart tissue. That sounds pretty invasive. However, ablations are fairly noninvasive, meaning we don't have to go crack open the chest and cut open the heart. Typically, cardiologists can gain access through some sort of blood vessel, and they often use a blood vessel at the groin. Now, just as a side note, in this diagram this heart is not to scale. It's really big. I made this heart big in this diagram just so you could see the vessels. So again, the cardiologist can gain access to the heart through a blood vessel, and like I said, they might go through the groin, and they'll guide a series of tools through the vessels until that vessel reaches the heart. They can either use a vein, or they can go through an artery. Once inside the heart, they're going to use these tools to locate the problem area, and then the tool is used to destroy the problem area. They usually burn it. Sometimes they freeze it, but they usually burn it. So, destroying this area is called ablation, and when they destroy this tissue, it creates scar. So, scar doesn't conduct electrical signal. Therefore, by destroying the tissue at and around the problem area, you're preventing abnormal electrical signal from leaving this area, because again, scar doesn't conduct electricity. Some tachyarrhythmias are caused by focal points, which are basically irritated areas that over-fire. So, an example of this is V-tach or ventricular tachycardia, like we talked about up here. So, this irritated diseased area of tissue over-fires and sends signal out to the rest of the heart, and that causes the tachycardia. The cardiologist will come in, and they'll destroy this problem area, again creating scar and preventing signal from leaving the problem area. The cardiologists are very careful to stay clear of structures that are critical to conduction, such as the SA node and the AV node. They stay clear of all these critical stuctures and only take care of the problem areas that are causing the arrhythmias. Tachyarrhythmias can also come from reentry circuits. So, a reentry circuit is an abnormal loop of electrical activity that goes around and around and around, and that causes a fast heart rate, and in these situations, the cardiologist will go in and find an area called the critical isthmus. The critical isthmus is a point in which all of the wavelengths in this abnormal loop of electrical activity pass. Since everything passes through this area of tissue, by destroying it, you're going to terminate the loop and get rid of the tachycardia. The critical isthmus is always the most narrow area of tissue that's safe to ablate. And again, the cardiologists are going to stay clear of these important structures that are imperative for electrical conduction. They only want to terminate the problem areas. So, some people who experience arrhythmias can sense symptoms when they have them, such as a fast heart rate or palpitations, and a palpitation is basically the feeling or sensation that your heart is beating against your chest wall. Some people also feel dizzy. It's important for these patients to be able to recognize these symptoms, be able to take their pulse, and know to call their healthcare provider in case they're having these symptoms. Why? Well, because these arrhythmias can be very dangerous. Circulation gets so poor that the person might pass out, or they could lead to other serious health problems, such as stroke or even a worse arrhythmia. A classic example is V-tach turning into another deadly arrhythmia, called ventricular fibrillation. In ventricular fibrillation, the walls of the ventricles just spasm, and no blood circulates, and this will lead to death.