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Video transcript

torsades the point is a type of ventricular tachycardia or v-tach specifically it's a polymorphic ventricular tachycardia and the polymorphic v-tach in torsades always follows long QT intervals so in torsades ii of a long QT has followed by a polymorphic v-tach what does all that mean well this is a lot to swallow so let's break this down morphic refers to the QRS intervals and poly just imply that there are multiple there are multiple QRS intervals torsades the point is actually French for twisting of the points and what does that mean well imagine you have a party streamer and say you take the ends of that streamer and you twist them what you'll get is a twisted party streamer that's going to look a lot like this you notice the dips and waves in the twists this is what a polymorphic v-tach looks like on EKG it looks like this twisted party streamer we have high amplitude QRS waves and low amplitude high amplitude low amplitude high amplitude and it keeps on going back and forth the QRS is appear to flip around a horizontal axis and remember in torsades the polymorphic v-tach is always preceded by a long QT ok so let's go over QT here we have a single beat on EKG so we're going to have the P wave and the q r s interval and the T wave and the QT interval is from the beginning of the Q all the way to the end of the T wave that's the QT interval it represents when the ventricles are depolarizing and when they're repolarizing so the QT interval represents the length of time or the interval when the ventricle is depolarize and repolarize now people with a long QT typically have some sort of delay and repolarization and this delay could be due to either genetic mutations and ion channels or from certain medications but for whatever reason they have a delay in repolarization and that delay affects the refractory periods or the recovery times of heart cells now the heart likes it when it cells work in unison so if there are differences in refractory times in neighboring heart cells that can set you up to have a ventricular tachycardia because you're messing with the conduction system when you're messing with the repolarization and the refractory periods something else to note is that the QT interval is rate dependent now what does that mean so let's say you have a heart rate and it's going very fast you can imagine that the QT interval here is going to be pretty short because the heart's beating so fast and on the other hand if you have a heart rate that's going really slowly you can imagine that your QT interval might be long and drawn-out so the rate of the heart affects how long the QT is and given that there's some rate dependence there are formulas created that adjust the QT interval you can calculate what's called the Qt C where the C stands for corrected so this is just the corrected QT and the Qt AC in certain situations is considered to be more accurate than the regular qt and the only reason I bring this up is just in case you're looking at an EKG and you see if those two Qt and a QT C and I want you to know what the difference is between the two now what's normal for a QT interval well in adults females typically have a slightly longer QT interval than males so in a normal adult male the QT should be less than zero point four three seconds and a normal adult female it should be less than 0.45 seconds a QT interval is considered to be prolonged an adult male if it's greater than zero point four five seconds and prolong in a female if it's greater than zero point four seven seconds now if you're just eyeballing EKGs it's impossible to tell a difference between zero point four three seconds and 0.45 seconds but again if you're just eyeballing EKGs here's something good to know every large box represents zero point two seconds so if the QT C is longer than two large boxes or larger than zero point four seconds then you want a closer look at the QT or the Qt C typically the machine itself will calculate it for you or you can even take out calipers which are these little measuring tools and you can measure it yourself so remember on EKG and someone put torsades you're going to have the long QT syndrome or you have a prolonged QT and you're also going to have this polymorphic ventricular tachycardia so you'll have the long QT and the polymorphic v-tach now having a long QT doesn't usually give you symptoms to come into the hospital however people who are experiencing a ventricular tachycardia might have symptoms where they want to come to the hospital so often they present in v-tach and you're not going to see the long QT on EKG what you can do though is look at old EKGs you can look at the old EKG and see if you notice a per long QT interval which has now turned into this polymorphic v-tach here is an EKG of someone with polymorphic v-tach you have these short amplitude waves followed by these large amplitude qrs's and then short again and then large amplitude you notice that the QRS is are wide complexes and because it's a tachycardia the heart rates greater than 100 people with torsades who are in a polymorphic v-tach and have heart rates at up to 250 even 300 beats per minute which is dangerously high these people might not be able to circulate blood effectively to the body because our heart's beating so fast and there's not enough time for the heart to fill with blood and pump that to the rest of the body also v-tach can turn into another deadly heart rhythm called ventricular fibrillation also called v-fib and in v-fib the heart doesn't even beat instead the walls are spasming and blood can't circulate so rest of the body now why would someone have a prolonged QT interval or long QT syndrome well a person can have a prolonged QT for a couple of reasons there is congenital long QT syndrome and congenital means that you're born with it so these people are born with a genetic mutation where they have abnormal ion channels and these abnormal ion channels will prolong their QT there's also acquired long QT meaning it comes from some sort of outside source the most popular culprit for long QT well that's medications so different medications can make you more likely to develop long QT it's not all medications but there's definitely a certain list of medications that will do this and ironically certain types of antiarrhythmics will put you an increased risk of developing long QT so that seems kind of funny the medications we use to prevent arrhythmias can cause them when you think about the mechanism it makes sense certain antiarrhythmics will delay repolarization of ventricular cells and like we said earlier this can set up an environment for heart to go into v-tach since people with congenital long QT are always at a higher risk of developing torsades it's good to know about this condition and to think about it if they develop an abnormal rhythm also in this group of people education is really important because you can advise these people on what meds to avoid to prevent going into torsades and depending on the patient and their circumstances the patient may opt for the implantation of an internal defibrillator now an internal defibrillator is a machine that's implanted into the heart and it will shock the heart back to a normal rhythm if it develops or disintegrates into a deadly rhythm remember we said that torsades is type of v-tach and v-tach is dangerous because it can turn into ventricular fibrillation or v-fib and if that's not reverse immediately then the result is rapid death now why does v-tach turn into v-fib well and v-tach there's either an irritated area of the ventricles or some sort of add neural circuit that's going around in circles firing away making the heart beat really fast however v-tach is still an organized rhythm however in some patients usually patients with a sick heart or heart that's irritated due to either electrolyte abnormalities or medications this organized rhythm can disintegrate into random chaotic electric wavelets these wavelets don't generate unifying contraction of the ventricles and instead ventricular walls with spasm and blood can't circulate if no blood circulating the body that's what causes death