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00:00Today we will discuss about ECG.
00:02This is by far the most important topic for all the medicos.
00:06Sometimes you get confused after seeing the ECG for example like this and you think is
00:12this normal should I call the cardiologist.
00:15So in today's video I will try to make ECG very simple in only 10 steps and in the end
00:22you will be able to diagnose majority of heart rhythms on your own.
00:26So let's start.
00:28ECG or electrocardiogram it is the graphical representation of electrical activity going
00:34on in the heart.
00:36Now how to read an ECG in just 10 steps.
00:40Before that we need to check the calibration or speed of the machine which is normally set
00:45at 25 mm per second.
00:48In most of the books on ECG first step is to calculate rate but before calculating the rate
00:53you should know whether the rhythm is regular or not.
00:56I will tell you the reason when I will discuss about the rate.
01:00So we will discuss the ECG interpretation in this manner.
01:04Rhythm, Rate, Axis, P wave, PR interval, Q wave, QRS complex, QT interval, ST segment and
01:13T wave.
01:15Now step 1 is Rhythm.
01:17To check the rhythm we check the RR interval.
01:20As in this ECG RR interval are equal and there is P wave before every QRS complex.
01:27So this is a normal sinus rhythm.
01:31In this second ECG as you can see the RR interval is not equal at any time and there is no identifiable
01:38P wave.
01:39The rhythm is irregularly irregular which occurs most commonly in atrial fibrillation.
01:45Now look at this ECG.
01:48Normal regular rate with regular drop beat.
01:51So rhythm is regularly irregular which is seen most commonly in 2nd degree heart block type
01:572.
01:59It is to calculate heart rate from an ECG.
02:04If the rhythm is regular in ECG heart rate is calculated by 300 divided by large boxes
02:09between RR interval.
02:12And this is an ECG graph paper.
02:14If the speed or calibration of ECG machine is 25 mm per second then one small square corresponds
02:20to 0.04 second and one big square to 0.2 second.
02:25So 5 large squares is equal to 1 second.
02:30Now in this normal sinus rhythm ECG there are 4 large boxes between RR interval.
02:35So the rate will be 300 divided by 4 that comes out to be 75 beats per minute.
02:43But if the rhythm is irregular on ECG as in atrial fibrillation rate is calculated by number
02:50of R waves in 6 seconds multiplied by 10 so as to get rate per minute.
02:56So in this ECG strip there are 9 R waves or 9 QRS complexes.
03:02So the rate comes out to be 90 beats per minute.
03:06So 300 divided by RR interval formula is valid only if the rhythm is regular.
03:12That is why we should first see the rhythm and then should calculate the rate accordingly.
03:17Now step 3 is to calculate the axis.
03:21First of all normal cardiac axis is from minus 30 to plus 110 degree.
03:26And to know about the axis we first need to know about the 12 lead ECG.
03:31There are 3 bipolar leads which are lead 1, lead 2 and lead 3.
03:36And 3 unipolar leads which are augmented voltage lead i.e avia, avial and avia.
03:43So there are 6 chest leads which are from v1 to v6.
03:48Now to calculate the axis most commonly we use perpendicular leads i.e lead 1 and avia.
03:55In this ECG net QRS complex in lead 1 and in avia are positive.
04:01So if we plot these positive deflections on this diagram we will get a vector in the normal
04:06cardiac axis range.
04:08So this is a normal access ECG.
04:11And if net QRS is positive in lead 1 and negative in avia, the net vector will be in left axis
04:18deviation range.
04:20Lead 2 will also be negative in left axis deviation.
04:24And if net QRS is negative in lead 1 and positive in avia, the net vector will be in right axis
04:30deviation range.
04:32Now look at this ECG.
04:34Net QRS in lead 1 is positive and net QRS is negative in avia.
04:40So this ECG showing left axis deviation or LED.
04:44And you can remember this by a mnemonic left leaves where net deflection in lead 1 and avia
04:51are in opposite direction or as if they are leaving.
04:56Whereas in this ECG net QRS is negative in lead 1 and positive in avia.
05:04So this is a right axis deviation and you can remember this by a mnemonic right returns.
05:11Step 4 is p-wave.
05:14So first of all see whether p-wave is present or not.
05:18If present see the morphology.
05:20For p-wave morphology we will look at lead 2 and v1.
05:24Height of normal p-wave is less than 2.5 mm in limb leads and less than 1.5 mm in precordial
05:31leads and the width should be less than 0.12 seconds.
05:37In this ECG as you can see in lead 1 p-waves are tall and peaked.
05:43These are called as p-pulminale which is seen in right atrial enlargement.
05:48And if p-waves are bifid or have a notch in between it is called as p-miterial.
05:54Remember m-shape for miterial which is seen in left atrial enlargement.
06:01Step 5 is p-r interval.
06:04It is from the start of p-wave to the start of q-wave.
06:07That is why some call it as p-q interval.
06:11Normally it is 0.12 to 0.2 seconds that is 3 to 5 small squares.
06:17And it is prolonged in AV blocks.
06:21Reduced in WPW syndrome.
06:23In which there is an accessory pathway which conducts impulses faster than the normal.
06:28Reducing shorter p-r interval.
06:30And p-r interval is repressed in pericarditis cases.
06:36Step 6 it is q-wave.
06:39It is called pathological if more than 2 small squares deep and usually indicate current or
06:45past MI.
06:47As you can see deep q-waves in inferior leads 2, 3 and AVF.
06:51So this is ECG of old inferior wall MI.
06:56Step 7 is q-r s complex.
06:59Normally it is 0.08 to 0.12 seconds that is 2 to 3 small squares.
07:05It is widened in ventricle arrhythmias which can be ventricular ectopic or ventricular tachycardia
07:14or ventricular fibrillation or any pathology below bundle of hills.
07:20Step 8 Q-r s is also widened in bundle branch blocks.
07:25In rbbb there is m-pattern in v1 and w-pattern in v6.
07:30You can remember it with a mnemonic marrow where double r is for rbb and m in v1 w in v6.
07:40Similarly you can remember ECG of lbb by a mnemonic william where w-pattern in v1 and m-pattern
07:47in v6 is present.
07:50Step 8 it is q-t interval.
07:53It is from the start of q-wave to the end of t-wave.
07:57As a rule of thumb, normal q-t is less than half the preceding rr interval.
08:02An abnormally prolonged q-t is associated with increased risk of ventricular arrhythmias,
08:07especially tossard depointers.
08:10Step 9 ST segment.
08:13It is the flat isoelectric section of ECG between the end of s-wave i.e. the j-point and beginning
08:20of t-wave.
08:22As in this ECG you can see ST elevation which could be commonly due to acute myocardial infarction
08:29or in pericarditis.
08:32If ST elevation is present in v1-v2 then it is septal wall mi, if in v3-v4 then anterior
08:38wall mi, if present in lead 1 plus avl and v5-v6 then lateral wall mi and if present in
08:472-3 avf then it suggests inferior wall mi.
08:52ST segment depression is seen in n-stemi, myocardial ischemia, posterior mi and many other causes.
09:02Coming on to last step i.e. t-wave.
09:04It is upright in all leads except avr and v1.
09:08Tall, narrow, symmetrically peaked t-waves are commonly seen in hyperkalemia.
09:14Broad, asymmetric, peaked or hyperacute t-waves are seen in early stages of STEMI or ST elevation
09:22mi.
09:24Inverted t-waves are seen in myocardial ischemia or infarction or can be in ventricular hypertrophy.
09:31Now let's discuss about how the ECG looks like in hypertrophy.
09:36In left ventricular hypertrophy add deepest s-wave in v1 or v2 more than 35 mm then lvh
09:43is present whereas in right ventricular hypertrophy there will be right axis deviation, r by s ratio
09:52more than 1 in v1 and less than 1 or equal to 1 in v5 or v6 and also r-wave in v1 is more
09:59than 7 mm.
10:01This is the simplest criteria to detect rvh.
10:05So this is all about ECG.
10:07Always think of these 10 steps in this manner and you will be able to detect majority of
10:12arrhythmias very easily.
10:14And guys if you like the content and information of this video do like, share and subscribe
10:19our channel and also feel free to comment about the video or if you have any doubts about the
10:24topic.
10:25Thanks.