okay so this is a brand new lecture that I just put together for the winter of 2023 um and what I'm trying to do in this lecture is I'm going to explain I'm not going to talk specifically about drugs in this lecture and it's a very short lecture it's only 15 slides but it what I'm trying to do here is show you some common Concepts that will that we will see when we look at cardiac medications in particular those cardiac medications which have a dual purpose and I'll talk about what those are as we go to the next bunch of slides foreign so what we have to remember here is when we talk about modifying cardiac function and as you probably know from as you're as you're doing in pathology we know that we need to sometimes modify the function of the heart uh based on whether or not the heart is whether or not there's hypertension going on whether or not there is heart failure going on whether or not there's a combination of hypertension and heart failure usually there's a little bit of both and there are when it comes to drugs there are a couple of ways that we can affect that function of that that heart we can do one of we can do one of three conceptual things we can change the timing of the heart and so whether or not it makes sense to you or not I have a metronome here so tick tick tick tick how quickly or how fast or slow the heart actually uh for it actually beat so we're talking about the rate of the heart or the when we talk about the timing of the heart how fast it beats we can also talk about the force of contractions as well so the heart muscle itself how strong is that contraction of the heart muscle so and when we talk about drugs that do either one of these two these are drugs that affect directly the heart muscle of of the heart so we're talking when we talk about the heart as a whole we're talking about the The myocardium we're talking about the the cardiac muscle itself and all the nerve Pathways that are within that heart to help facilitate that contraction we would say that a drug that affects directly that function of the heart as I said does specifically as concerned with the timing of the heart or force of contractions we can also modify how hard the heart Works indirectly and the way that we do that is through vascular resistance so this is what we can come up with and then we come up there's a couple of terms that we're going to come up with there's a couple of special terms that we use when we talk about timing and force of the contraction of the heart when we're using a drug that directly affects cardiac muscle and this is why I have these things here in in different colors when we talk about timing of the heart the term is going to be chronotropic okay when we talk about affecting how well the heart contracts the force of contraction we are trapping talking about inotropic and we will see that as I said before these are drugs that will have direct cardiac effects so think about it here if I have a drug that directly affects the chronotropic activity of the heart or the inotropic activity of the heart we could say that these drugs and you won't find this in the textbook but this is me trying to put it into a way that you can understand that drug has direct cardiac effects directly affecting the heart muscle or the nervous tissue that is within the heart we will have chronotropic inotropic effects if we're looking at if we're looking over here about playing around with the vascular resistance of the heart and the workload that's imposed on the heart well we can look at that as an indirect effect drugs that have an indirect effect on cardiac function are affecting the force that the drug has to work against so when you think about this if I either increase or decrease the the um the resistance that the heart has to work after it's sort of like the heart has to work hard but is what's the heart pushing against well those indirect effects if we have a drug that has indirect cardiac cardiac effects or indirect effects on its cardiac function we're pretty much modifying what goes on in the periphery of the body okay or it could have and there are some drugs we're going to talk about one drug that has a direct effect on the vasculature of the heart we will refer to that drug as a direct cardiac effect but we will see that that some drugs will have a bit of both okay and this is the part I'm pointing out through there's not one drug that will do one or the other there will be a the drug will do a little bit of both okay the question is what does it do better and what are we and what function are we using that drug for what indication are we using that drug for okay this height this sort of this sort of uh mimics back to the for or sort of points back to one of the first lectures I did when we talked about what is the pharmacal Dynamics of this heart or what are the pharmacodynamics of a drug what are you using the drug for because we know that drugs don't have soul isolated effects on the body but we will see that some drugs have really big direct cardiac effects and other ones that have indirect effects and when will we use one or the other well it's going to depend on the situation and what was indicated for that drug so depending on what the drug does best is what we will use it for okay either it's Direct effects or it's indirect effects and when we look at those when we look at those direct cardiac effects because there's going to be several drugs that we're going to talk about about using this for and it's going to pop up in semester three as well we have some we have some terms here that we will use as I started should have said inotropic chronotropic these are the big effects that we try and play with there's also a third one and you're going oh sir you just added a third term we have to know yeah and I'm going to explain why okay we have to add this third term for our purposes in this course and what you need to know is that the beneficial effects that we are going to get out of a lot of these drugs are going to be from inotropic or chronotropic effects there is a third effect which is called a dromotropic effect and this one well it's kind of the one we we watch out for okay in the sense of whether or not we're going to have negative effects or bad outcomes Okay so dromotropic we're talking about something that deals with cardiac nerve impulses and specifically we're talking about changes to the transfer of nerve impulses that go from The Atrium down to the ventricles and a lot of the times we're looking at the speed or the conduction of those impulses from The Atrium down to the ventricles okay I'm going to point this out a little bit close more more specifically and I'll outline this a little bit more and and some diagrams that I made up specifically for this lecture but let's look at some of these pharmacological terms just and see how they actually work so we talk about inotropic chronotropic or dromotropic okay we are talking about again one the contractility and it can have either a positive contractility or A negative contractility effect so these drugs are these are the sort of the adjectives we use to describe what's going on do we have a positive inotropic effect which means are you increasing the force of contraction or are you having a negative ionotropic effect of a drug which means it decreases the force of contraction do we have a chronotropic effect which is a positive chronotropic effect which means increases the heart rate or do we have a drug that has a negative chronotropic effect which means it slows the heart rate and in particular that's going to affect the SA node okay now this term dromotropic as I sort of pointed out before if you have a drug that has a positive dromotropic effect it would speed up the conduction of electrical signals from The Atrium to The ventricle if we have a negative one then it slows the rate of Electro conduction and this is where we're going to see a lot of the drugs we're going to talk about this term in semester two are going to have these negative dromotropic effects and these negative dromotropic effects have a little problem that come with it and we'll get to that just a couple of slides all right so and what this sort of brings up and I've mentioned it already a couple of times so this means that when we look at the drugs from about this point onwards we will see that these drugs have sometimes dual cardiac effects they will have direct cardiac effects on the heart which we may or may not want or and they will also have an indirect effect on the workload of the heart looking at the the resistance that the heart has to work against so we're going to see dual effects of these drugs and this is why we will see some hypertension drugs being used for either directly modifying what the heart muscle does or it can also be used to reduce blood pressure and you're like well which one to use it for well the question is which indication are using are you just trying to reduce are you just trying to reduce blood pressure then maybe you want to choose one cardiac drug over another one maybe we don't want one that has a lot of direct cardiac effects maybe you do want one that has direct cardiac effects and indirect cardiac effects depending on the pathology that's going on and what we will do is we will see that we will use we will see that we'll see some drugs used both for heart failure and hypertension but the question is once and you decide well which drug do you choose well you depends on what that drug does best okay and we will see as we get into we talk about each of the drugs I will have some diagrams specifically when we get to the hypertension drugs that will indicate that oh this drug has a bigger inotropic effect than it does a chronotropic effect so your choice to use it for would be for x or y and we'll talk about that specifically when we get to those drugs but this is the concept that you have to have in your head prior to going in and doing and before us actually talking about drugs themselves and what these drugs are used for you have to have an idea of what's going on when we talk about chronotropic inotropic andromotropic because we will talk about these drugs and say this one has a this you know drug X has a really big chronotropic effect but not so much an inotropic effect well maybe we want to use that for a drug that for a situation where there is a issue with the SA node either firing too much or firing too little and then which one would you actually choose and use okay so keep that in mind we need to know these terms because I'm going to use these terms chronotropic inotropic andromotropic when we talk about the effects either positive or negative effects of the drugs of of the cardiac drugs all right so let's look at this specifically the dromotrophic because I said the dromotropic effects is it really something that we want or that we're going to see are really beneficial in in the drugs that we're talking about this semester okay and the drugs that are going to be referring to you so you need to know that the dromotropic is there because the dromotropic is something we as is an adverse effect and possibly an adverse event that we're looking out for okay so for example when we look at this one right here when we look at what the heart does and let's go back to Anatomy for a second very simplistic Jerry would not say this is anatomically correct or Sharla in the anatomy course but let's let's look at what you know very simplistically what is happening this is something I as I've sort of told you guys I learned my Best by whether or not I could conceptually sketch something out on a uh on a piece of paper or if I'm at a restaurant on a on a napkin so this is where conceptually this is a very conceptual diagram it is not anatomically correct by any state or form so if we look at this diagram right here we have a heart we have the SA node in the AV node respectively one at the top and one at the bottom and we see that the SA node starts off and as we as you'll go through in more in more detail in anatomy you will see that the SA node is the is is the is the timer of the heart it initiates it initiates a heartbeat and we see that there is impulses that are sent out through the atrium and then we will see that a nerve impulse is transmitted to the AV node and that part of that nerve transmission is there is a decrease in timing this is why one part of the eight one part of the heart beats before the next that they don't part beat at the same time there is a little synchronous dance that needs to go on here so once the SA node has sent out its signals there's a transmission to the AV node the AV node then distributes that pulse to the rest of the heart after this after the after the atrium has has slowed down and finished its contraction we then see that the AV node then that distributes that impulse and then does its beat and then at infinite and we just keep going back and forth and back and forth if we had a situation where we had a positive inotrope dromotropic effect we would see that a positive dromotropic effect we would see an increase in that transmission to that AV node so we would see the AV node actually Contracting a little bit sooner than it would if there was a positive dromotropic effect because we would see that signals are the speed at which the signal went from the SA node to the AV node is increased we don't have a lot of drugs and I don't think there's any drugs in semester two that we're going to be talking about as a positive dromotropic effect what we do have in semester two is the following a negative dramotropic effect that's why I did the little hash mark right here with the with in the diagram we will see that the that there is actually a slowing of that transmission from the SA node to the AV node now that nerve impulse that comes from the SA node to the AV node helps to regulate sort of tells the AV node when to go off okay so we see that with negative dromotropic effects reduces the speed of that transmission also reduces the regulation of that AV nodes that timing telling when the AV node to fire yes or no when does it need to go well if you're slowing down the transmission then sometimes and you know lack of a better term the AV node might get a little impatient okay this is what brings us to here so there's serious risks with um with drugs that have negative dromotropic effects what would happen is that if the AV node is looking up at the you know you can think of it as two little people who regulate the heart if the AV node is looking up at the SA node and saying hey I'm waiting for your signal to go and the signal doesn't come in time and the AV node gets impatient the AV node will not will start to self-regulate on its own without the commands coming from the SA node so if if that if that dromotropic effect is negative which means you have a very slow signal coming down from the SA node to the AV node the AV node might go off on its own it might fire on its own and the more and more you slow that that signal coming from the SA node you can lead to if if it fires off on its own every now and then then you might get a dysrhythmia going on where you see a one little you see the AV node firing off on its own and firing off out of sequence if that drama that negative dromotropic effect progresses and gets even slower then we can lead to something called AV block where the signal going from the SA node to the AV node is significantly blocked which means the AV node will fire off even more on its own and AV block if left too long can lead to something that is an adverse event a huge adverse event is ventricular fibrillation and this is a complete disjointed firing of The ventricle and Atrium and it leads to complete and utter heart failure and can lead to an arrest situation so we would see that and if we were to put this on a little um if we were to put this on on our on our scale of what is considered an adverse effect to an adverse event we would see that a dysrhythmia is an adverse effect that we don't want we don't want the AV node firing off every now and then okay where it becomes an adverse I would say an artist an adverse event is where we would have not an adverse effect adverse effect might be the a dysrhythmia or an occasional dysrhythmia going on where the AV node fires off once or twice every now and then AV block which can what's left untreated can progress to ventricular fibrillation would be an adverse event okay not something that you want this is life-threatening AV block and ventricular fibrillation not good so this is where I say that we still need to know about the or we still need to be aware of even though that when we're looking at the good effects of the drugs which we want we want inotropic and chronotropic effects to sort of modify the function of the heart and heart failure and in hypertension we don't want the nasty drummotropic effects with come from that and we're going to see and I'm just going to give you an example of some of these drugs that we're going to talk about some this semester and then some next semester as well in semester three but here's some of the ones that have some of these effects inotropic effects digitalises the next drug we're going to talk about um we talk about oh look at isoproterenol well that's actually a respiratory drug that we're going to talk about um in the next coming weeks when we talk about some of the respiratory drugs we're going to talk about epinephrine as a respiratory drug as well and then you're going to talk about it in semester three as as a as a medication that's used in other sort of indications we're going to talk about propanolol this semester okay these ones for next semester but propanolol we're talking about this semester isoproterenol we're going to talk about digitalis you know right after this lecture um we're going to see some drugs have some chronotropic effects okay we're going to see um acetylcholine acetylcholine you'll see that in next semester we will see that there are a couple of hypertension drugs this semester that have some chronotropic effects on them as well we're going to see dromotropic for mapper Mill it is a blood pressure medication okay that also can be used for direct cardiac modification as well we're going to see this drug this semester okay when we talk about it in two two lectures from now and then this one next semester is a drug that is an is an anti-seizure medication and you're going to see that as positive dromotropic effects actually speeds up the heart rate so what does this tell us well if we know what the effects of the heart of effects of some of these drugs are we know what they're going to do for us and we know what to look for we know what we you know if we're using if we're using digitalis which is also called digoxin for and we were using it for positive inotropic effects well that's a good thing that's what we want to look out for if we're looking at negative dromotropic effects we could see that oh my God we could sum of these negative dromotropic effects we have to look out for as I just stated on the previous slide we have to look out for any dysrhythmias possibly and then any AV block or possibly even worst case scenario ventricular fibrillation not a good thing when we're using this one so this is what we would look out for for this drug semester three when you're looking at a at some of the anti-seizure medications well we know it's going to have a direct dromotropic effect on the on the heart as a positive effect so we have to watch for rapid heart rates and uh and Rapid ventricular firing in semester three so you see how using these drugs okay we can see how using these drugs and knowing whether or not they have one or two of these sort of effects we already know what to look for either as a positive outcome of the effect of the drug or a negative effect of the drug Okay so this is one of those lectures you might need to want to reread again in your head and maybe go over it one more time it wasn't that long of a lecture it was only about 20 minutes but it's something you might have to re-go over again and say what did he mean by that when we get to the actual drugs can come back to this lecture re-look at it again and say oh now I get what's going on okay but it's just a good starting point before we get into the actual drugs themselves but you will see that knowing these three terms are very useful in looking at the positive or the you know the therapeutic or the non-therapeutic outcomes that we will get from each one of these drugs or or specific drugs going forward through semester two and it's a semester three all right so that is the end of this very very short lecture