Intro to EKG Interpretation - A Systematic Approach

[Music] hello everyone it's Eric from Stanford University and as you probably know in this video I'll be talking about EKGs I've had a lot of requests from viewers and from my students for a summary of my systematic approach to interpreting an EKG that is when I pick up an EKG to read it where do I start now to be honest I estimate I've read several thousand EKGs over the over the last decade and I personally no longer strictly adhere to a systematic method however I definitely recommend doing so in first starting out or you're guaranteed to occasionally Miss critical diagnoses so what approach do I recommend well if you're a typical medical nursing PA or paramedic student who has had any prior EXP exposure to EKGs you've probably heard the following sequence before rate Rhythm axis hypertrophy and infarction this specific series of words gets repeated in medical school and Hospital rounds so often it feels like a mantra have you ever wondered where it comes from I'm not positive of the origin of this approach but I am sure of why it's become so ubiquitous it's on account of this book which is by far the most popular book in the the world on EKG interpretation unfortunately despite its popularity it's also not very good and its General approach frames and organizes the interpretation in a way which is illogical and encourages bad habits therefore I recommend something different my Approach has three steps number one assess the Rhythm which will incorporate a measure of the rate since the rate does not stand in isolation from the Rhythm number two assess the QRS complex meaning both the axis and the QRS morphology and number three assess the St segments t- waves and QT interval since abnormalities of these have strongly overlapping ideologies and physical appearance this may seem superficially similar to dubin's approach however this one focuses on individual waveform abnormalities instead of diagnosis among multiple benefits of this are that you won't forget that changes in the waveforms can be caused by things other than hypertrophy and infarction I'm going to walk you through this approach one step at a time and one substep at a time please be aware that I'll be assuming some basic knowledge of EKGs already so if you've come here not knowing the difference between a p-wave in Qs complex or not knowing the difference between limb leads and precordial leads you probably will want to look at some of my other EKG videos first and then come back I've also embedded annotations that will link to other videos on specific diagnoses R relevant step one which is the longest and most complicated of the three steps I've broken down into five parts first measure the rate and determine if it's normal tartic or bra cartic for adults the normal resting heart rate is 50 to 90 beats per minute and not 60 to 100 the fact that most people think it's 60 to 100 is very frustrating and can be detrimental for example I've seen patients referred to cardiologists for a symptomatic heart rates in the 50s which is completely unnecessary and for anyone who is skeptical of this range consider that one of the four criteria for the systemic inflammatory response syndrome or cers is a heart rate greater than 90 which would be a strange criteria if heart rates in the 9s were normal some pearls about the heart rate the maximum predicted sinus rate is approximately 220 minus the patient's age there are some exceptions to this particularly among world class Elite athletes but if you see an 80-year-old patient with a heart rate of 170 you can be very sure that it's not sinus tachicardia and a heart rate of 140 to 150 beats per minute specifically suggests the possibility of atrial flutter with 2:1 AV block 2:1 AV block means that for every two waves of depolarization which reach the AV node only one passes through to depolarize the ventricles if you have no idea what atrial flutter with 2:1 AV block looks like we're going to see some examples of a flutter in a few minutes next determine if the rhythm is regular regularly irregular or irregularly irregular if you're not familiar with those terms those latter two may sound a bit strange so here are some examples first you can already probably recognize a regular rhythm as such formly a regular rhythm is one in which the RR interval is consistent from one beat to the next here's an example of a regularly irregular Rhythm the RR interval varies but does so in a repeating pattern finally in an irregularly irregular Rhythm there is no pattern QRS complexes seem to come at random and unpredictable intervals excluding those which are exceedingly rare there are essentially seven different irregular rhythms I am not going to review these individually in significant detail here as they will be the topics of additional forthcoming videos sinus arhythmia in which p waves are originating from the sinus node but just at irregular intervals often from primary sinus node dysfunction can cause an e regularly irregular Rhythm that can be slow fast or at a normal rate atal fibrillation is the classic cause of an irregularly irregular Rhythm atrial flutter most commonly displays fixed AB conduction that is every second or every fourth flutter wave is conducted resulting in a regular rhythm however sometimes AB conduction can lack any discernable pattern and the Rhythm will be irregularly irregular there is one interesting pattern that atrial flutter can experience in which 2:1 AV conduction alternates with 4:1 conduction in a very repetitive fashion resulting in a regularly irregular rhythm with an overall heart rate of about 100 multifocal atrial tardia in which three or more distinctly different irritable atrial fosi are all firing at seemingly random intervals resulting in irregularly irregular tardia while first and third degree AV block results in regular rhythms second degree AV block results in irregular ones type one also known as wanky Bach AV block results in a regularly irregular Rhythm while type two results in an irregularly irregular one note that type 2 second degree block is not seen in tardus finally the collection of very similar rhythms of atrial biny and triy and ventricular byy and triy cause regularly irregular rhythms here are just two examples of the more unusual of The aformentioned rhythms first atrial flutter with alternating 2:1 and 4:1 conduction and then ventricular bymany in which every normal sinus beat is immediately followed by a PVC which then blocks the subsequent sinus beat from occurring in ventricular trigeminy um you have two sinus beats followed by PVC then two sinus beats followed by PVC um but otherwise looks very similar after rate and regularity the next parameter to assess is whether the QRS complex is narrow or wide a narrow complex is one in which the width is under 120 milliseconds or three small boxes a wide complex is 120 milliseconds or greater regarding the ideologies of a wide complex uh common ones include bundel branch block a ventricular origin of the Rhythm as in ventricular tardia shown here left ventricular hypertrophy and a pacemaker uncommon ideologies include class 1 a and 1 C anti rythmics the wolf Parkinson White pattern which we'll see later and profound hyperemia evaluate the atrial activity specifically look for p waves if they're there what is their morphology cus p waves should be upright in Lead 1 and down in AVR if they do not display this polarity it strongly suggests that the origin of the p waves is somewhere other than the sinus node when looking at p-wave morphology also take a moment to look for evidence of atrial enlargement if there are no p-waves look to see if there are fibrillation waves which are typically very small amplitude irregular undulations in the Baseline if there are flutter waves typically described as sawtoothed and easiest to see in the inferior leads or occasionally in lead V1 the final part of the assessment of the rhythm is to identify the relationship between atrial and ventricular activity for example is the PR interval normal at between 120 and 200 milliseconds is it short or is it prolonged a PR interval that is consistently above 200 milliseconds is indicative of first-degree AV block by definition also look to see if the PR interval changes um and if there is a one toone correspondence between p waves and QRS complexes and if there is not a one:1 correspondence if there is any association between the two at all here's an example of a changing PR interval due to type 1 second deegree AV block you may also notice that there are more p waves in QRS complexes since every third P wve does not get conducted here's an example of fixed 2:1 AV block which may be either type 1 or type two and last here is an example of complete dissociation of p waves and QRS complexes as a consequence of third degree AB block also called complete heart block also ask if the p waves come before or after the QRS complexes with which they are associated although it's uncommon to see p waves following the complexes it can occur in a select few types of super ventricular tardas such as one called orthodromic AV re-entrant tardia shown here noticing these retrograde p waves which occur after the QRS and are inverted will help to suggest an otherwise difficult to make diagnosis so in summary when assessing the Rhythm first measure the rate then determine if the rhythm is regular regularly irregular or irregularly irregular determine if the QRS complex is narrow or wide evaluate the atrial activity and finally identify the relationship between atrial and ventricular activity going through these five components to Rhythm assessment thoughtfully and deliberately will result in an accurate diagnosis of the Rhythm for all but the most unusual and difficult of EKGs let's move on to step two assess the QRS access and morphology so first here is the access a normal QRS access for an adult is between -30 and positive 90 it is not 0 to 90 as commonly claimed by dubious medical texts and various internet sites the ideologies of access deviation are many right Axis deviation can be a normal variant in children and young thin adults rvh COPD in the absence of rvh left posterior facular block a lateral wall Mi an ectopic ventricular Rhythm or the wolf Parkinson White pattern left axis deviation has analogous ideologies normal variant in older obese adults LVH an elevated diaphragm for any reason such as Market as cites or pregnancy left anterior facular block and inferior Mi an ectopic ventricular Rhythm and once again wpw then look at the QRS morphology when looking at the morphology there are five to six key diagnoses to look for first pathologic Q waves which are usually indicative of a prior Mi look for evidence of ventricular hypertrophy and if the QRS complex is wide for a bundle branch block consider whether the pattern has low voltage that is if the amplitude of every QRS complex is unusually low ideologies of this usually involve some insulating material or substance coming between the heart's conduction system and the electrodes on the skin moving outside in this includes excessive adapost tissue in obesity excessive air and hyperinflation from COPD plural or pericardial affusions and infiltrative diseases of The myocardium such as amiloidosis and Sarcoidosis finally through a mechanism unknown to me hypothyroidism can also cause low voltage although it's rare electrical alternance is an important diagnosis to be aware of it's characterized by alternating amplitude of the various waveforms usually most prominent in the Qs complexes when the entire 12 lead EKG is available one can actually see large alternating shifts in the QRS axis this usually indicates the presence of a large paracardial fusion um and is caused by the heart literally shifting back and forth uh in this big ball of fluid though this is not necessarily indicate paracardial tanod the last major morphologic abom of the QRS to look for is delta waves these are an initial shallow upstroke before each QRS complex that results in a technically widened QRS complex and usually they're not always a short PR interval delta waves are indicative of an accessory pathway an accessory pathway is an abnormal tract of conductive myocardium that connects the Atria to the ventricles without needing to pass through the AV node thus these are also sometimes referred to as bypass tracks on EKG the presence of delta waves QRS widening and a short PR interval is collectively known as the wolf Parkinson White pattern and when it's associated with parisal tardas it's called The Wolf Parkinson White syndrome onto step three assess the St segments t- waves and QT interval the first thing to look for is St ation which is generally only notable if the elevation is 1 mm or more in at least two anatomically contiguous leads by far the most well-known ideology of St elevation is an st elevation Mi however there are many more most notable of which are left bundle branch block left ventricular hypertrophy and a normal variant frequently called early repolarization the elevations seen with these three are usually limited to leads V1 through V3 the remaining causes include pericarditis an LV aneurysm vasospasm severe hyperemia hypothermia an inherited sodium Channel defect called bugata syndrome and a rare cause of acute heart failure called tacos suboc cardiomyopathy frequently referred to in the American Press as broken heart syndrome of almost equal importance is ST depression the most notable cause here is again either coronary esea or infarction other causes include tacac cardia even in the absence of aeia dexin even at therapeutic doses hypokalemia bundle branch blocks and ventricular hypertrophy ST depression due to the last two are usually referred to as secondary repolarization abnormalities since the reason that the sequence of repol ization is abnormal is the abnormality in depolarization the others are referred to as primary repolarization abnormalities when we look at inverted t- waves and their ideologies the interesting and helpful thing is that the list is nearly identical to that of St depressions there are just a couple of rare additions intracranial hemorrhage late stage pericarditis and hypothyroidism remember that isolated t-wave inversions in leads 3 AVR and V1 are common and normal aside from t-wave inversions the only other significant t-wave abnormality to look for is to see if they are peaked which suggests hyperemia an acute stemi can occasionally cause a similar morphology of the t-wave very early on before the development of St elevation this is usually called a hyperacute t-wave and is rare to see because usually the patient experiencing the Mi has already transitioned to the St elevation phase by the time he or she is seen by medical personnel the very last component to consciously examine on a typical EKG is the QT interval keeping in mind that the QT interval should be corrected for the heart rate although there is an equation to do this as a quick rule of thumb the QT interval should be less than 1/2 the RR interval ideologies of a prolonged QT include congenital Long QT syndrome a relatively long list of medications and all of the hypos that is hypocalcemia hypothyroidism and hypothermia a number of resources list hypokalemia also as a cause of prolonged QT but the most authoritative of sources suggest that this is erroneous the confusion regarding QT prolongation and hypokalemia arises for two reasons first when the uwave becomes prominent as it can in hyposmia there can be Fusion of the T and U waves and when measuring the QT interval one can inadvertently measure the Q interval instead which will necessarily be longer the second reason for the confusion is that hypokalemia is particularly dangerous when superimposed on pre-existing QT prolongation which is independent of the electrolyte disorder an unusually Short QT interval is also a pathologic finding albeit an extremely rare one the ideologies of this are hypercalcemia and the very rare congenital Short QT syndrome both Long QT and Short QT syndromes are associated with an increased risk of sudden cardiac death so that's the grand summary of my systematic approach to the EKG if you found that went through some of the examples very quickly or you want to know more about the EKG features of some of the AP forementioned abnormalities you may want to view my specific topic videos listed here please remember to like or share this video if you found it helpful or interesting and feel free to leave questions or comments [Music]

Channel: Strong Medicine

Views: 902,633

Keywords: EKG, Electrocardiography (Invention), ecg, ekg interpretation, interpreting ekgs, ecg interpretation, method, approach, rhythm, heart rhythm, qrs complex, st elevation, st depression, long qt, Long QT Syndrome (Disease Or Medical Condition), t wave inversion, short qt, ekg analysis, analysis, ecg analysis, ekg intro, ekg introduction

Id: ENyBhCJ2llY

Length: 20min 56sec (1256 seconds)

Published: Fri Mar 14 2014