Understanding 12 Lead EKG: Basic Cardiac Arrhythmias
In the second part of 12 lead EKG interpretation, we will look at simple heart arrhythmias that can be detected by 12 lead EKG or just a primary lead EKG strip. By basic I mean those rhythms that you can look at only one primary lead (usually lead 2) and tell what it is. There are other EKG abnormalities that needs you to look at more than one lead, the position of the heart (also called axis), specific segments, amplitude and voltage of the leads. But don’t let this make you run away from 12 lead EKG interpretation because it is quintessential you understand it. If reading this can make you save only 1 life, then it is all worth understanding 12 lead EKG interpretations. Needless to say, more lessons are coming about: –
- Understanding 12 ECG/EKG lead placement
- Understanding the circulation of the heart and which arteries when blocked caused AMI
- Understanding which leads on EKG are positive, negative or neutral in polarity.
- Understanding the normal axis of the heart and what deviation from normal axis mean (Have you ever seen some numbers at the top of EKG graph and you wonder what they mean? Just understanding those numbers points you to the problem area and when you look at specific waves, you are just confirming. This is a key to successful 12 lead EKG interpretation
The following are the common arrhythmias of the heart that you probably already know about. They are straight forward to diagnose and most of them has no emergent attention command
- Sinus Bradycardia:AKA Sinus Brady is a regular heart rhythm with less than 60 beats per minute. It should be noted that sinus bradycardia has regular beats. There must be P waves before every QRS at a ratio of 1:1, meaning per every 1 P wave, there is 1 QRS complex. The distance between P wave and the beginning of QRS complex (PR interval) must be between 0.12-0.20 seconds. Each small box in EKG measures 0.04 seconds, meaning a normal PR interval has 3-5 small boxes. Got it? Are you sure? Soon we will find out because if you see a rhythm of 45 and call it sinus bradycardia before measuring PR interval, you could be misdiagnosing with junctional rhythms.
- Sinus tachycardia:AKA Sinus Tach is a regular rhythm with more than 100 beats is a minute but less than 150 beats. Why less than 150? If a rhythm has more than 150 beats, it is not possible to see the P-Wave as the beats succession is so rapid. This is what is called supraventricular tachycardia and recently renamed as narrow complex tachycardia. We will look into this soon. Sinus tachycardia must have a normal P-Wave before each QRS complex and PR interval must be the same. The distance from one R wave (top of QRS) to the other must be the same (R-R). If R-R wave is not regular, you might be looking at atrial fibrillation AKA A-Fib. Are you feeling like you might have misdiagnosed sinus Tachycardia already? Most likely not but keep reading
- Sinus Arrhythmia: What? Never heard of that! Sinus arrhythmia is an irregular heart rhythm usually seen in ICU or telemetry patients on continuous monitoring. The heart rate is variable depending on inspiration or expiration. With inspiration, the heart rate increases and with expiration, the heart rate decreases. All other parameters are normal like 1:1 ratio of P-wave and QRS complex, PR interval of 0.12-0.20 and QRS complex less than 0.10 seconds.
- Premature Atrial Complex (PAC):This is yet another rarely heart arrhythmia that is benign in nature. You never call a rhythm PAC but rather mention the underlying rhythm with PAC. Example, Sinus rhythm with PAC or Sinus Bradycardia with PAC’s. So what is it? There is an ectopic beat once in a while. The ectopic beat originates from atrial heart cells firing before they are supposed to. Except the ectopic beats, all other beats are normal with normal measurements. Patients may complain of feeling as if the heart stopped for a beat, something also reported in A-Fib
- Atrial Flutter: The so called saw tooth wave form is one of the easiest for many of us to diagnose. The atrial beats (firing) could be as many as 230-350 times in a minute but ventricular conduction may be normal (60-100 beats). These saw tooth like waves are called U-Waves. Aha! U-Waves. QRS is normal in morphology and measurements. Of course, there are no P-Waves as they have been replaced by U-waves.
- Atrial Fibrillation: A-fib is a silent killer FYI due to clots formation in the right atria. Nothing about A-Fib is regular. The rhythm is irregular meaning that there are variable R-R wave distances between each beat. The baseline may look like a wavy line with irregular U-Waves. It is an irregular irregularity in simpler terms. There are no P-waves but U waves. QRS is upright and normal in measurements (<0.1 second).
- Supra Ventricular Tachycardia (SVT) also called narrow complex tachycardia (NCT).This is a super fast sinus tachy is simpler terms. The heart is so fast, between 150-250 beats a minute. Do you know how it is treated? Ever heard of adenosine?
- Junctional Rhythms:There are 3 types of junctional rhythms namely Junctional escape(40-60 beats a minute, less than normal), accelerated junctional rhythm (61-99 beats, normal heart beats a minute) and junctional tachycardia (100-140 beats a minute). How do you know if it is a junctional rhythm?
- The heart rate is regular, meaning R-R is regular
- The P-wave is inverted instead of facing upright OR
- There is no P-Wave in front of every QRS complex
- The PR interval is larger than 1.20 seconds
- Ventricular Tachycardia:V-Tach (Code blue) is a life threatening emergency rhythm that must be intervened immediately or sudden death will occur. This monster is between 100-250 beats a minute with no P-waves. There is no QRS complex, meaning that the heart is NOT perfusing itself or other organs and cardiopulmonary resuscitation (CPR) is warranted. The waves in this rhythm are through to be bizarre looking QRS complexes. If you see this rhythm (monitor alarms will scream at you even before you see it if you have your alarms set and armed), immediately call for help, assess ABC’s and start CPR. Remember, this is a NON PERFUSINGrhythm and CPR is warranted unless the patient is awake and alert. Guess what, the patient cannot be awake and alert if they are in true V-Tach. If the monitor shows V-Tach and you see them moving, it could be a false rhythm caused by insecure leads or movement. If it is a true V-Tach, they will be unresponsive and you must start CPR NOW! Do you hear me? It is also a shockable rhythm per ACLS algorithms.
- Ventricular Fibrillation: Call Code blue and start CPR ASAP. Just like V-Tach, V-Fib is a NON-PERFUSING Rhythm. You cannot see any P-Waves, no heart rate, no QRS complex, just a wavy line.
In one of the future articles, I will talk about other rhythms that you may never see easily but can tell you that a life threatening emergency is likely. Example, Torsades de Pointes, which may be seen during long resuscitation due to low magnesium or calcium level. It can also be caused by Haldol IV-Push. (Always give haldol as I.M. and never as IV although you might say… we do this all the time and even doctors order it as I.V. Consider yourself warned!
In the next article, we will look at heart blocks, how to recognize them easily by just checking key areas and then we will go back to interpreting 12 Lead EKG. After heart blocks, we will look at how 12 Lead EKG leads are placed, what they mean, what side of the heart are they are looking at, and what lead correspond to what side of the heart. We will also look at the axes of the heart because understanding axes can accelerate your 12 lead EKG interpretation.
By replying here with comments, describe in as many words as you can: –
- A life threatening emergency you have ever taken part in. Tell us what happened and what was done to save the patient. Did the patient survive? Do not mention names or locations.
- Have you ever been in a code blue and how did it go? Did you participate? CPR? How did that go?
- There are other rhythms that are not mentioned here. Can you identify any?
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Anita Stringer says
Hello…..I am a RN and have worked at Marion General Hospital in Columbia Ms for 15 years. I work Med Surg, ER and ICU. I myself have a hx of SVT and wanted to share with you how my life has changed since that night…when I was awakened at 2 o’clock in the morning…with my heart beating faster than I could count. It was TERRIFYING!!!! I kinda figured I was in SVT because rate was regular and that I should do the common things we advice our pts to do…..hard cough, ice water in face, or vagel man….but, the fact that I lived deep in the woods and was alone scared me so bad that I just wanted to wait on AAA to get to me. I was afraid that I may go into another, more dangerous rhythm…such as vtach. Anyway, as I talked to paremedic via cell phone….and gave him directions…my symptoms were getting worse. I .became short of breath….clammy….PETRIFIED…making heart rate even faster. I finally after much persuation on AAA’s part, coughed 3 times and converted priot to their arrival. Was transpoterd to MGH and was fine when I got there. This happened again for the next two nights. Wound up having cardiac workup, echo, stresstest…all normal…but have been on Tenormin and Lanoxin since. I hate taking these medications too…..took me a few weeks to get used to them Felt horrible…became depressed….which as you know, is a side effect of the Temormin. This went for months and FINALLY I had had enough….and now I am on antidepressant which has helped alot. I have realized that my life in general….abusive mother…alcoholic father…sexual abusive family members…ALL predisposed me to having problems with anxiety…which eventually led me to having the SVT. Alsoo, my mother had history of A-fibI. have not been the same person since, but, I am doing good. If my kt drops or I get really scared or upset over something…it acts up. Otherwise, I do fine. Just wanted to share that with you all. I have given Adenosine many times and I PRAY I NEVER HAVE TO HAVE IT!!!!!!!!!!!!!! HAPPY NEW YEARS TO YOU ALL AND KEEP UP THE GREAT WORK OF HELPING THE SICK!!!!
Mike Lee Toris says
Great article! I’ll be following this series from now on.
Anyway, I think this statement is a little misleading:
“Guess what, the patient cannot be awake and alert if they are in true V-Tach.”
There ARE true VT wherein the patient remains awake and alert. I’ve experienced caring for a patient that had pulseless VT and had to be defibrillated, after restoring her to normal sinus rhythm and regaining consciousness the cardiologist put her on Lidocaine drip. Several hours after the attack and while on Lidocaine drip, she would have episodes of non-sustained VT lasting only several seconds (10 seconds at most). She would remain awake and alert all through out the episode with no apparent symptom except for changes in her EKG and complaints of moderate light-headedness. About 12 hours after starting the Lidocaine drip, her NSVT episodes disappeared and never went back. So yeah, I think what you’re referring to is “Pulseless VT” not “True VT” because you can have VT while retaining your consciousness. Just my 2 cents.
@ Mike, non-sustained V-Tach is a V-Tach of less than 12 beats. Above 12 beats, pt would lose conciousness in a matter of seconds.
Pulseless VT is a non-perfusing V-tach and pt cannot be alert unless someone is misdiagnosing it as pulseless.
Rule of thumb is… Pulseless = unresponsive = CPR IMMEDIATELY
With pulse = start anti-arrythmics immediately, usually 300mg of Amiodarone IV Push, then start a drip.
deborah Adebayo says
I remember how awful you feel , ,I was in the plane when I noticed that my heart rate was beating faster, I used to have palpitation frequently, though I am a staff nurse but I never bothered to do anything about it as I am so scared,.
That day I rushed myself to Emergency Dept, my heart rate was 235/hr, was scary, weak clammy thinking I was goint to collapse any minute but I was treated, i used to have blood pressure as high as 200/120, no medication has ever worked for as am from black ethnic group, my doctors does not know the best medication to use, I just fed up and live the life as it comes.. I was given adenoscine6+6
Chris Tartaglia says
When I was an EMT I went on a call to an office building where a young cleaning woman who was pregnant complained of feeling funny and being dizzy. I took her vital signs and found her pulse to be so fast that I couldn’t count it. Paramedics were right behind us – they put her on the monitor and found what they said to be was V-tach. The monitor did look like V-tach as you showed the strip above – heart rate was 220. Patient was conscious and alert. Medic administered adenosine and told me to drive like this woman’s arm was cut off. It took two more doses before we got to the hospital and her NSR returned. I don’t understand why you said the patient would be unconscious with V-tach, because this young mom wasn’t and thankfully, baby and mom are fine today.
Does the v-tach thing sound absurd to anyone else? “Remember, this is a NON PERFUSINGrhythm and CPR is warranted unless the patient is awake and alert. Guess what, the patient cannot be awake and alert if they are in true V-Tach.” As someone else mentioned, ACLS identifies V-Tach with a pulse and a complete treatment algorithm for it. Obviously, it is a perfusing rhythm because the patient has a pulse!!!! And you certainly can be awake and have a pulse, can’t you? I have witnessed several pts with a pulse, awake and alert, in V-Tach.
I have also witnessed perfusing V-Tach especially in open heart patients. The longest I have seen lasted about 2 minutes and the patient was awake and with a pulse. However, he lost the pulse second time it happened although we had already put him on amiodarone drip with a loading dose. Good thing, when it happened the first time, we had pads on and connected to defibrilator. 200KJ shock once converted him back to his baseline.
I tell my students always to attach pads on if a patient has 12 or more v-tach beats even if they converted back, call MD immediately and get anti-arrhythmic ordered. Depending on how often or how severe the patient condition is, cardiologists may order a loading dose. Others may just order 1mg/kg/min X 6 hrs then 0.5mg/kg/min X 18 hrs. Others may order it continous.
I stand to be corrected
I was thinking the exact same thing!
Adenosine is not for V-Tach. it is for supra ventricular tachycardia (SVT). When the heart rate is in 200’s, to most, it may look like VTach. V-Tach is a non-perfusing rhythm and a patient cannot be concious
A person CAN be conscious with V-tach. It’s called stable VT under ACLS guides lines. Amiodarone 150mg given over 10minutes is the recommended tx. V-Fib is the rythym you can’t be conscious with. Paramedic 11years, I have seen this many times.
sal bellantoni says
I badly need to pass the ekg exam and the ekg strips strip i’ve seen your web page are great!
Would please send me all ekg strips and meanings like you show rhythms that would indicate atrail fib
for example. You’ve shown a few on the website but not all of them.
[ Please send those to me i would greatly appreciate it ]
Is it possible for you to include the management and nursing considerations for each of the above cited arrhythmias? TY!
Sarvatma Sharma says
A rhythm is Junctional if it’s PR interval is less than .12 not over .20. Over .20 is considered a First Degree AV Block. Monitor Tech
Joe D AEMT-CC says
Junctional rhythms may or may not have PRi as there may or may not be p waves although p waves will always be inverted or have irregular morphology such as biphasic, however if they are inverted the PRi has no indication in whether or not it is Junctional. If all QRS complexes are preceeded by an upright p wave it is not Junctional and therefore greater than .2 would be 1st degree block and less than .12 consider wpw
Joe D AEMT-CC says
V-Tach is most often a non-perfusing rhythm and will always progress to non-perfusing if not corrected however you must check for a pulse before beginning CPR as there are different treatment modalities for Pulseless V-Tach and Stable V-Tach(a misnomer as all V-Tach should be thought of as an unstable patient). If there is a pulse start treatment with Amio or Lido per order or protocol. New York State AEMT-Critical Care and former AHA instructor