Incorrect interpretation of atrial fibrillation
Atrial fibrillation is a condition in which there are hundreds of electrical foci in the atria, causing them to “fibrillate.” In this situation, the main pacemaker – the SA Node – does not work, and the electrical foci in the atria fire hundreds of electrical pulses in its place. On the EKG, you can see f-waves instead of P-waves, which express the electrical foci in the atria. The f-waves look like a straight line with “tremors.” When a patient moves, breathes heavily, or if the monitor patches are not glued ideally (e.g., when the patient is sweating or when the patches are on a lot of hair), we will see a straight line with “tremors,” and sometimes misinterpret them as the f-waves of atrial fibrillation. These are called “artifacts.”
The artifacts in this situation are the result of a technical disorder and not because the patient has an arrhythmia. A patient with normal sinus rhythm may be misdiagnosed with atrial fibrillation.
"EKG test", June 10, 2024
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So, how can you avoid misinterpretation?
There are a few tricks:
- Look at the heart rate over time (at least 10 seconds). If the heart rate is regular – the patient does not have an atrial fibrillation rhythm disorder, as this disorder must be irregular.
- Perform a 12-lead EKG and try to look for P-waves. If P-waves are clearly visible even in a single lead – this is a rhythm that originates from the sinus (SA Node) and not atrial fibrillation.
- In patients connected to the monitor, increase the volume of the voltage in the device settings and try to detect P waves. Even if these exist with tremors – these are still considered P-waves, and the patient does not have an atrial fibrillation rhythm disorder.
Atrial fibrillation rhythm: You can see irregular rhythm and the appearance of f-waves instead of P-waves
Normal sinus rhythm misdiagnosed as Atrial fibrillation: The reason for the misdiagnosis is tremors of the electrical waves misdiagnosed as f-waves. The rhythm can be seen to be regular, and although there are tremors, the P-waves can still be detected.
Incorrect diagnosis of asystole
An asystole is a condition in which there is no electrical and mechanical activity in the heart.
It is a condition of cardiac arrest in which full resuscitation must be initiated, including chest compressions and breaths without defibrillation.
Many things can cause an asystole – severe infection, trauma, hypoxia, pulmonary embolism, myocardial infarction, poisoning, drug overdose, and drug side effects.
Asystole is expressed on the EKG as a straight line since there is no electrical activity in the heart. Sometimes, a patient is connected to a hospital monitor (or pre-hospital), and suddenly, a straight line is observed. Does this mean that the patient has cardiac arrest and has asystole? Not necessarily.
To avoid incorrect diagnosis and unnecessary chest compressions, follow these tips:
First of all – look at the patient and the other vital signs!
If the patient is fully conscious and talking to you, they cannot be in cardiac arrest. During cardiac arrest, there is no blood flow to the brain, and the patient will lose consciousness within a few seconds. So, if they are talking to you, their heart must be beating, and they are not in an asystole state. If the patient is unable to communicate (for example – anesthetized and ventilated) – look at the other indicators on the monitor: If there is a saturation wave or arterial line wave (arterial access to continuous blood pressure measurement) – this necessarily indicates that the heart is beating because these indicate a pulsatile blood flow. If the saturation wave or the arterial line wave shows a straight line at the same time as a straight line is observed on the monitor, that is, all the vital indices show a straight line – then this is a real condition of cardiac arrest, since no sign on the monitor indicates cardiac activity.
Recognize the patient’s clinical condition and whether it makes sense for them to develop a sudden cardiac arrest.
For example – an elderly patient is hospitalized with severe pneumonia when he is anesthetized and ventilated and treated with drugs to raise blood pressure in high concentrations (such as Noradrenaline) – there is a high probability that he will develop a sudden cardiac arrest.
On the other hand – a young female patient who is hospitalized due to a urinary tract infection, without background diseases, is fully conscious with normal vital signs – she is less likely to develop a sudden cardiac arrest.
This patient could certainly theoretically develop a cardiac arrest – but the chance of this is much lower.
Check the connections between the monitor and the stickers.
If you disconnect the monitor cable or the stickers on the patient, you will see a straight line on the device
The monitor shows a straight line in the electrical activity of the heart only. A saturation wave and arterial line can be seen, indicating cardiac activity.
The monitor shows a straight line in all parameters. This condition indicates cardiac arrest.
To avoid incorrect diagnosis and unnecessary chest compressions, follow these tips:
| No | Situation | Significance |
|---|---|---|
| 1 | The patient is fully conscious and speaks | The patient cannot be in asystole because when the heart stops, blood does not flow to the brain and the patient loses consciousness. If the patient is talking, it means the heart is working |
| 2 | Patient cannot communicate (anesthetized and on ventilator) | Check other readings on the monitor: if there is a saturation wave or arterial line, this indicates that there is pulsatile blood flow and the heart is beating |
| 3 | All indicators show a straight line (saturation wave, arterial line) | If all vital signs show a straight line at the same time as the straight line on the monitor, this indicates true cardiac arrest because there is no sign of cardiac activity |
| 4 | Clinical condition of the patient | Assess the likelihood of developing sudden cardiac arrest depending on the clinical condition of the patient. For example, an elderly patient with severe pneumonia has a high probability of cardiac arrest |
Sinus tachycardia or tachyarrhythmia?
Sinus rhythm means electrical activity starting from the SA Node (=Sinus)
Sinus tachycardia means – sinus rhythm above 100 beats per minute (in an adult)
Tachyarrhythmia – rapid heart rhythm disorder, over 100 beats per minute (in an adult)
Occasionally, we see a rapid heart rate in a patient on the monitor. When the rhythm reaches very high speeds – usually over 150 beats per minute, it is difficult to identify what rhythm we are seeing. Is there a sinus-derived heart rhythm, or is there an arrhythmia such as PSVT, atrial flutter or atrial fibrillation?
For the differential diagnosis – we need to checkifthere are P-waves. If they exist, it is not an arrhythmia but rather a fast rhythm that originates from the sinus. A differential diagnosis here is necessary, as treatment is different for sinus rhythm and arrhythmia.
So, what can be done to diagnose the heart rhythm correctly? Several methods can be used:
The classic method is to perform a 12-lead EKG and look for P-waves in one of the leads.
Even if P-waves appear in only one lead – this is a sinus rhythm. In the above case, it is a sinus tachycardia rhythm since the rhythm is over 100 beats per minute in an adult.
It is important to note that this method is excellent for hemodynamically stable patients who are not in a life-threatening situation.
Unstable patients – there is not always time to perform a full EKG because we do not want to waste precious time and cause the patient’s condition to deteriorate. In this situation, try the following methods.
Change the monitor settings and increase the spacing between the electrical waves.
When the space is enlarged, the electrical waves are “less adjacent” to each other.
In this method, if they exist, P-waves can be more easily identified.
Decrease the heart rate.
When the pulse is slower, it is easier to detect the electrical waves observed on the monitor.
The first method to slow the pulse is with an operation called a vagal maneuver. This method activates the vagus nerve, which belongs to the parasympathetic system.
Ask the patient to perform a movement, such as a bowel movement in the toilet, while applying light pressure to the abdomen with your hand (this should not be done in patients who have recently undergone surgery in the abdominal cavity!).
Another method of vagal maneuver is to ask the patient to blow into a 20cc syringe to push the plunger out.
When performing a vagal maneuver, look at the monitor. If the pulse does indeed decrease during the operation – try to identify whether there are P-waves.
The second method is to slow the pulse by drug therapy from the beta blockers group – such as metoprolol.
Monitor settings – You can change the gain, volume and the speed in order to look for p waves.
In this image – P waves are seen very clear
To correctly interpret the heart rhythm on an EKG, it is important to consider the presence of P waves. If P waves are seen in at least one lead, this indicates sinus rhythm rather than arrhythmia, which can have a significant impact on the choice of treatment
Sagi Tzabari - ICU nurse, paramedic
Incorrect diagnosis of ischemia manifested by T-wave inversion in lead AVR
Inversion of T-waves or depression of an ST segment can indicate cardiac ischemia.
At least two leads in the same anatomical area are necessary to diagnose ischemia (or myocardial infarction).
For example – V2 + V3 leads face the front wall.
Another example – leads II, III, AVF – all three face the lower wall of the heart. Only two of them will show signs of ischemia to diagnose cardiac ischemia.
A common error that often occurs is the diagnosis of T-wave inversion as ischemia in lead AVR.
T-wave inversion in this leadis normal and does not indicatecardiac ischemia.
This is because lead AVR is inverted in the direction of electrical activity in the heart. Therefore, it will always be negative.
When T-waves appear positively in lead AVR (i.e., they are not inverted), this is because the connections of the limbs (RA, LA, LL, RL) were connected oppositely, so you get the wrong picture of the electrical waves on the EKG.
Check the limb connections if lead AVR is not negative.
Note: Sometimes, an inverted T-wave appears in lead V1 as well, and this is normal.
Incorrect diagnosis of myocardial infarction manifested by imitation of ST elevations
Myocardial infarction is a condition in which there is a blockage of a coronary artery due to a rupture of plaque.
In this situation, the body recognizes the rupture of the plaque as an injury. Therefore, it sends platelets to the affected area to stop the bleeding. However, at the same time it also blocks the coronary artery.
Signs and symptoms appearing in this condition include a feeling of pressure or burning in the chest, shortness of breath, radiation to various places in the body, nausea and vomiting, and extreme anxiety.
Myocardial infarction will be expressed on EKG as one of the following two situations:
NSTEMI – non-ST elevation myocardial infarction.
This type of myocardial infarction will appearwithout ST elevations in the EKG.
STEMI – ST-elevation myocardial infarction
This type of myocardial infarction will appearwith ST elevations in the EKG.
ST elevations are expressed in EKG as an ST-segment elevated at least 1 mm above the isoelectric line (except for V2-V3 leads, where the criteria are slightly different).
There is a situation where there are ST elevations in the EKG. However, theseare ST elevations that do not express myocardial infarction.
This condition occurs due to early repolarization (also called “high-take off”) and is completely normal.
This pattern can be seen in the EKG in young people and athletes.
A pattern of early repolarization that mimics real ST elevations is expressed on the EKG according to the following criteria:
Positive deviation at the beginning of the ST segment accompanied by positive QRS.
Elevation in the ST segment of 0.1mv at the J point accompanied by a pointed or unclear QRS shape.
Sagi Tzabari
ICU nurse, paramedic
Sagi Tzabari is a nurse who works in the general ICU department as well as a paramedic. I’m addition to his daily job, he teaches at a nursing school on topics including EKG interpretation, emergency medicine, general surgery, nursing calculations, and pharmacology.
Sagi Tzabari is a nurse who works in the general ICU department as well as a paramedic. I’m addition to his daily job, he teaches at a nursing school on topics including EKG interpretation, emergency medicine, general surgery, nursing calculations, and pharmacology.
