STEMI & NSTEMI: A Nurse’s Comprehensive Guide

STEMI & NSTEMI: A Nurse’s Comprehensive Guide

A STEMI is an ST-Segment Elevation Myocardial Infarction – the worst type of heart attack. This type of heart attack shows up on the 12-lead EKG.

An NSTEMI (or Non-STEMI) does not have any ST elevation on the ECG, but may have ST/T wave changes in contiguous leads.

Patients with STEMI usually present with acute chest pain and need to be sent to the cath lab immediately for reperfusion therapy – usually in the form of a cardiac cath with angiography +/- stent(s).

Ruling out a STEMI is the main reason 12-lead ECGs are obtained, and it is critical that you learn to identify them – even as nurses.

While Physicians/APPs should be laying their eyes on ECGs relatively quickly, this isn’t always the case. The sooner a STEMI is identified, the better the chance for survival for the cardiac tissue as well as for your patient!

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CORONARY ARTERY ANATOMY

The coronary arteries lie on the surface of the heart (the epicardium).

These arteries deliver vital blood flow and oxygen to the myocardial tissue to keep the heart perfused and beating.

The three main coronary arteries are the left anterior descending artery (LAD), the circumflex artery (Cx), and the right coronary artery (RCA).

The Right Coronary Artery (RCA)

The RCA travels down the right side of the heart in the groove between the right atrium and right ventricle. The RCA supplies blood to:

  • Right atria
  • Right ventricle
  • Inferior and posterior surface of the left ventricle (85% of people)
  • SA node (60% of people)
  • AV bundle (85-90% of people)

The Left Coronary Artery

The Left coronary artery begins thicker and is called the left main coronary artery. This branches off into the LAD and the Cx.

The Left Anterior Descending Artery

The LAD lies on the surface of the heart between the right and left ventricles. It often extends to the inferior surface of the left ventricle in most patients. The LAD supplies blood to:

  • Anterior surface and part of the lateral surface of the left ventricle
  • The anterior 2/3 of the intraventricular septum

The Circumflex Artery

The Cx wraps around the left side of the heart in the groove between the left atrium and left ventricle in the back (the coronary sulcus). The Cx supplies blood to:

  • The left atrium
  • The other part of the lateral surface of the left ventricle
  • Rarely the inferior and/or posterior portions of the LV
  • SA node (40%)
  • AV bundle (10-15%)

The Posterior Descending Artery

The posterior descending artery usually branches off from the RCA, although less commonly from the Cx. Whichever one does form the posterior descending artery is considered the “dominant coronary artery”.

ACUTE CORONARY SYNDROME

Acute coronary syndrome (ACS) is an umbrella term referring to any condition which causes decreased blood flow to the heart – also known as ischemia. Prolonged ischemia can lead to infarction – which is cell death of the heart tissue.

This cell death causes the release of troponin into the bloodstream, an enzyme that is not usually found in the systemic circulation.

Cardiac ischemia is usually secondary to atherosclerosis which is a buildup of plaque within the coronary arteries. This is usually caused by unhealthy eating habits, obesity, sedentary lifestyle, hyperlipidemia, smoking, and genetics.

This plaque can rupture, releasing contents into the bloodstream which causes a local inflammatory reaction as well as begins a coagulation cascade.

This blood clot can completely occlude an artery – leading to infarction. 

A Non-ST segment elevation myocardial infarction (NSTEMI) refers to a complete occlusion of a coronary artery that does not cause ST-segment elevation on the ECG.

While some heart tissue dies, this is usually less extensive than a STEMI. The infarction is usually limited to the inner layer of the myocardial wall.

NSTEMIs will often have nonspecific changes on the EKG. These changes include T wave inversion or ST-segment depression with or without T wave inversion in anatomically contiguous leads. However, NSTEMIs could also present with a completely normal ECG.

Troponin levels will be elevated indicating myocardial cell death. However, the ECG does not have ST-segment elevation.

An ST-segment Elevation Myocardial Infarction (STEMI) refers to a complete occlusion of a coronary artery that causes more significant infarction that extends the entire thickness of the myocardium (termed transmural).

A STEMI will have ST-segment elevation in at least 2 contiguous leads on the ECG.

Where this elevation occurs will indicate which heart wall is infarcting, as well as within which coronary artery.

You may also like: “Cardiac Lab Interpretation (Troponin, CK, CK-MB, and BNP)”

ISCHEMIA & INFARCTION (STEMI) ON THE ECG

The ST-segment is the segment on the ECG right after the QRS segment and before the T wave. This represents the initial phase of ventricular repolarization and should be at the isoelectric line.

The TP-segment should be used as the isoelectric baseline, but you can use the PR segment if the TP is difficult to see.

The J-point is the point on the ECG where the QRS complex meets the ST segment. This is important for recognizing ST segment elevation.

ST-SEGMENT DEPRESSION

ST-segment depression most commonly identifies cardiac ischemia, as well as reciprocal changes in an acute MI.

It can also indicate heart strain, digitalis effect, hypokalemia, hypomagnesemia, or even be rate related. However, these changes are usually more diffuse as opposed to localized to at least 2 contiguous leads.

ST-segment depression is defined as ≥0.5 mm depression (1/2 small box) below the isoelectric line 80 ms after the J-point (2 small boxes).

Horizontal and Down-sloping ST-segment depression are more specific to cardiac ischemia, whereas up-sloping tends to be less serious although still could indicate ischemia.

De Winter T waves can be seen in 2% of acute LAD occlusions without significant ST-segment elevation. Instead, there will be ST-segment depression at the J-point with upsloping and tall, symmetric T waves in the precordial leads (V1-V6).

ST-SEGMENT ELEVATION

ST-segment elevation usually indicates myocardial infarction when appearing in at least 2 contiguous leads.

Other possible causes of ST-segment elevation include coronary vasospasm, pericarditis, benign repolarization, left BBB, LV hypertrophy, ventricular aneurysm, Brugada syndrome, ventricular pacemaker, increased ICP, blunt chest trauma, and hypothermia.

ST-segment elevation is defined as ≥1 mm elevation (1 small box) above the isoelectric line at the J-point. However, in leads V2 and V3, it needs to be > 1.5mm in women, > 2mm in men >40, and > 2.5mm in men < 40.

Concave ST elevation is considered less ominous and sometimes can indicate benign variant called early repolarization, especially when diffuse.

Convex upward ST elevation is almost always indicative of a large MI. This is termed “tombstoning”.

Q WAVES

Q waves are the initial positive deflection of the QRS complex indicating septal depolarization. These are normal in all leads except V1-V3.

Pathologic Q waves are abnormal Q waves that indicate underlying pathology – usually a current or previous MI.

Pathologic Q waves are defined as >40ms wide (1 small box) and >2 mm deep (2 small boxes).

Any Q waves seen in V1-V3 are always pathologic.

Pathologic Q wave

Q waves can begin hours to days after an infarction begins, and can last for years, even forever.

LBBB OR VENTRICULAR PACED

Recognizing ST-segment elevation or depression can be difficult in the case of a left bundle branch block (LBBB) or ventricular paced rhythm. This is because there is normally some associated ST-elevation and discordant T waves with these conduction abnormalities.

To determine possible ischemia or infarction in a patient with these conduction abnormalities, one of the following should be present:

  • ST-segment Elevation > 1mm in a lead with a positive QRS complex (concordant ST elevation)
  • ST-segment depression >1mm in V1, V2, or V3

These are not always present, but if they are – you should highly suspect ACS in a patient with a pre-existing LBBB morphology.

This is why a new LBBB and acute chest pain or SOB is concerning for acute MI.

You may also like: “How to Read a Rhythm Strip”

STEMI PROGRESSION

STEMIs typically have a normal progression that will be seen on the ECG.

Hyperacute T waves are first seen, which are tall, peaked, and symmetric in at least 2 contiguous leads. These usually last only minutes to an hour max.

Then, ST-segment elevation occurs in at least 2 contiguous leads at the J-point, initially concave, and then becomes convex or rounded upwards.

The ST-segment eventually merges with the T wave and the ST/T wave becomes indistinguishable. This is a “tombstone” pattern.

Reciprocal ST depression may be seen in opposite leads.

The ST segment then returns to baseline after a week or so.

Q waves eventually develop within hours to days, followed by T wave inversion which could be temporary. Over time, the Q wave deepens.

STEMI LOCATION

STEMIs are classified based on where they are located anatomically – so which leads are they are affecting on the ECG.

Contiguous leads simply means leads that are pertaining to the same anatomical region of the heart.

The following leads pertain to each region of the heart:

  • Anteroseptal: V1, V2
  • Anteroapical: V3, V4
  • Anterolateral: V5, V6
  • Lateral: I, aVL
  • Inferior: II, III, aVF

The precordial and lateral leads are often affected together as the area of infarction is not always exact. 

As an example, the EKG below is an inferior wall STEMI:

Inferior wall MI with ST elevation in leads II, III, and aVF, with reciprocal changes in the lateral leads.

ACUTE MANAGEMENT OF STEMI

STEMIs are true medical emergencies.

The patient is at a high risk of significant conduction disturbances and arrhythmias including cardiac arrest.

The longer you wait – the more heart cells will die, leading to worse cardiac outcomes as well as increasing the possibility of patient death.

A 12-lead ECG should be obtained within 10 minutes of any patient with significant cardiac symptoms including chest pain or SOB.

Women, older adults, and diabetics may have atypical presentations including a “silent” MI, where they don’t even have chest pain.

There are many actions that need to be taken in a short amount of time, and many medications that will need to be administered before the cath team gets there.

A code STEMI should be activated (or whatever your facility’s version of it is), so the interventional cardiologist and the cath team can be alerted ASAP.

The patient should be hooked up to the monitor, vital signs obtained, IV access x 2 should be established (preferably an 18g), labs drawn and sent including troponin and PT/PTT, and the defibrillation pads should be applied.

Any abnormal vital signs should be addressed, and any arrhythmias should be managed via ACLS guidelines.

STEMI medications

Oxygen should be administered to maintain O2 >90%.

Aspirin 324mg should be chewed and swallowed. A rectal suppository of 300mg can be given if the patient cannot tolerate PO for some reason.

Antiplatelet therapy with P2y12 receptor blockers such as Plavix or Brilinta should be given in addition to the aspirin.

Nitroglycerin should be administered 0.4mg SL x 3 q5min if the patient has persistent chest discomfort, HTN, or signs of heart failure.

However, do not give if they have used phosphodiesterase inhibitors like Viagra or Cialis within the last 24h.

Don’t give Nitro if they have a low blood pressure, if they have severe aortic stenosis, or if there is a possibility of a right ventricular infarct (sometimes presents with inferior wall MIs). Nitro can cause severe hypotension in these patients.

For persistent symptoms, an IV nitro drip can be used.

Anticoagulants like an unfractionated heparin drip should be given. Other options include Lovenox.

If the patient has signs of left heart failure, treat with nitro as above, loop diuretic like Lasix, +/- Bipap.

Morphine 2-4mg slow IVP q5-15min can be given for persistent severe chest pain or anxiety. However, there is research indicating an increased risk of death when morphine is given in STEMI.

It is possible that morphine may interfere with the antiplatelet effect of P2y 12 receptor blockers. So morphine should be avoided unless absolutely required for pain control.

Atorvastatin 80mg PO should be given ASAP, preferably before PCI in those who are not already on a statin. If the patient on it already, their dose should be increased to 80mg.

Primary percutaneous coronary intervention (PCI) is the preferred reperfusion method and should happen ASAP.

This is when the interventional cardiologist will take the patient to the cardiac cath lab and perform angiography and stent placement to open up the occluded vessel.

Fibrinolytics can alternatively be given, specifically if there is no access to a cath lab within a reasonable time frame (120 min), as long as symptoms < 12 hours and no contraindications (i.e. risk of bleeding).

Beta-blockers are initiated within 24 hours, unless they are contraindicated such as with bradycardia, HF, or severe reactive airway disease. This can be started after PCI.

You may also like: “Adverse Drug Reactions Nurses Need to Know”

Non-ST Segment Elevation Myocardial Infarction (STEMI)

As the name suggests, an NSTEMI does not have ST elevation seen on the ECG, but it is still a heart attack.

An elevated and rising troponin level is associated with an NSTEMI.

The ECG can be completely normal, or it can have nonspecific T wave changes or even ST depression in contiguous leads.

Management of an NSTEMI is similar to a STEMI in terms of medications. However, they are not given fibrinolytic and are not emergently brought to the cath lab. They may or may not get a cardiac cath during their hospital stay.

Instead, medication therapy is maximized like the ones described above. The patient is continued to be monitored, and troponin levels are trended usually every 6-8 hours.

STEMIs and NSTEMIs are critical emergent events that nurses need to know well! You will be running into this at some point in your nursing career, and you want to know exactly what you’re doing when it happens! Being able to recognize a STEMI on the ECG is the first step!

Want to learn more?

If you want to learn more, I have a complete video course “ECG Rhythm Master”, made specifically for nurses which goes into so much more depth and detail.

With this course you will be able to:

  • Identify all cardiac rhythms inside and out
  • Understand the pathophysiology of why and how arrhythmias occur
  • Learn how to manage arrhythmias like an expert nurse
  • Become proficient with emergency procedures like transcutaneous pacing, defibrillation, synchronized shock, and more!

I also include some great free bonuses with the course, including:

  • ECG Rhythm Guide eBook (190 pages!)
  • Code Cart Med Guide (code cart medication guide)
  • Code STEMI (recognizing STEMI on an EKG)

You can use the code “SPRING2021” for a limited time 15% discount, exclusive to my readers!

Check out more about the course here!

You may also like:

How to read an EKG Rhythm Strip - Pin Share

How to Read an EKG Rhythm Strip

How to Read an EKG Rhythm Strip

This post may contain affiliate links, which means I get a commission if you decide to purchase through my links, at no cost to you. Please read affiliate disclosure for more information

Learning how to read an EKG rhythm strip is an essential skill for nurses!

This skill becomes especially handy for nurses on Med-Surg, Telemetry, the Emergency Department, or Critical Care units.

If reading an EKG rhythm strip is new to you – this is the perfect place to start!

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What is a Rhythm Strip?

An EKG or ECG stands for Electrocardiography, which is the electrical activity of the heart traced on paper (or a monitor).

A rhythm strip is at least a 6-second tracing printed out on graph paper which shows activity from one or two leads.

Leads are “views” of the heart. There are 12 leads that are traditionally obtained with a 12-lead EKG, but most portable and bedside monitors only monitor 3-5 leads at a time.

Luckily – interpreting a single rhythm strip is much easier than a 12-lead EKG. Most rhythm strips are interpreted from Lead II as this gives a great view of the heart.

The goal of reading an EKG rhythm strip is to determine the rate and rhythm of the patient. This is great for identifying baseline cardiac rhythm as well as any arrhythmias or ectopy that may occur (like a premature beat).

A 12-lead EKG also looks at the rate and rhythm, but additionally gives nearly a complete 360° view of the heart.

This means it can be used to assess for things like cardiac ischemia or infarction, conduction delays, and even enlarged chamber size.

The ECG Rhythm Strip Tracing

As I said earlier – an ECG Rhythm tracing is the electrical activity of the heart recorded on paper or a monitor.

This is traditionally printed out on a 6-second strip. This can make it easy to determine the rate of an irregular rhythm if it is not given to you (count the complexes and multiply by 10).

Thick black lines are printed every 3 seconds, so the distance between 3 black lines is equal to 6 seconds.

As you can see, a printed ECG rhythm strip is comprised of boxes – both small boxes and large boxes. 5 small boxes make up one large box.

Each small box is 1mm wide, signifying 0.04 seconds or 40 milliseconds (ms).

Each large box is 5 small boxes, signifying 0.20 seconds or 200ms.

This becomes important to remember when determining the rate of regular rhythms. The boxes and lines are also important in recognizing whether a rhythm is regular or irregular.

The PQRST

Okay so that covers the paper, but what about the actual tracings? That’s where the alphabet comes into play. By alphabet – I mean PQRST.

An electrical tracing of the heart is made up of waves, lines, complexes, and intervals, and each of these represents specific conduction within the heart. This is the key to interpreting a rhythm strip.

P WAVES

P waves represent atrial depolarization. This means that the electrical signal that starts in the SA node (the normal pacemaker of the heart) is traveling through both atria (top chambers of the heart) during the P wave.

A P wave should look smooth and upright in most leads including lead II.

The 3 things you’ll want to specifically look for in P waves in a rhythm strip are:

  • Are there P waves before each QRS complex?
  • Are there any P waves that do not have a QRS complex that follows?
  • Do all the P waves look the same / have the same shape?

Keeping these 3 questions in mind will help you determine where the rhythm originates from (i.e. the sinus node), if there are any potential extra beats, or if there could be certain heart blocks present.

An inverted P wave means there is anterograde conduction to the atria (backwards direction). This means the electrical impulse originates from near, at, or below the AV node. Examples of this include Junctional rhythm, certain PACs, and PJCs.

QRS COMPLEXES

The QRS complex represents ventricular depolarization. This means that the electrical signal is traveling through both ventricles (the bottom chambers of the heart). In a healthy heart – this should correlate with the pulse.

The QRS complex is actually made up of 1-3 waves, the Q wave, the R wave, and the S wave. Depending on which lead you look at and the specific heart, any combination of these waves may be present.

In lead II, usually all three waves are present. This includes an initial downward deflection (Q wave), an upward deflection (R wave), followed by a downward deflection (S wave).

The presence of a QRS complex indicates that the ventricles are receiving the electrical signal. These should follow shortly after a P wave in a sinus rhythm.

The main abnormality that can occur is a wide QRS complex. This either means that there is aberrant conduction (like a bundle branch block), or that the electrical signal starts in either the left or right ventricle (i.e. a PVC or Ventricular Tachycardia).

A bundle branch block just means there is a delay in the conduction tissue transmitting the signal to either the right or left ventricle. If the widened QRS is preceded by a P wave, it is probably a sinus rhythm with a BBB.

If there is no preceding P wave, you may have a PVC or even VTACH if it is sustained.

T WAVES

The T wave represents ventricular repolarization. This means that the myocardial cells within the ventricles are recovering and “getting ready for the next beat”.

This should be smooth and upright in most leads, including lead II.

Sometimes, the T wave can be inverted or flipped. This is nonspecific but can indicate cardiac ischemia or infarction, especially if it is in at least 2 contiguous leads (pertaining to the same anatomical area of the heart).

People may have flipped waves in certain leads at baseline after a heart attack, with a bundle branch block, or with a PVC, VTACH, or ventricular paced rhythms.

Tall or tented T waves are those that are > 1 large box in lead II and may be particularly pointed. This could be normal for the patient, but can also indicate hyperkalemia (high potassium).

PR INTERVAL

The PR interval is from the beginning of the P wave to the beginning of the QRS complex. This represents the time it takes for the electrical signal to reach the ventricles from the SA node.

This should be 3-5 small boxes or 120-200ms. If longer, this is considered a first degree AV block.

A short PR interval could be from a a PAC, a junctional rhythm (associated with an inverted P wave), or Wolff-Parkinson-White syndrome.

QT INTERVAL

The QT interval is the time between the start of the QRS complex to the end of the T wave. This will change depending on the heart rate, so a QTc (QT corrected) is calculated.

This should be 350-440ms in men, and 350-460ms in women. A QT interval >500ms predisposes the patient to deadly ventricular arrhythmias such as Torsades de Pointes.

QT prolongation can be caused by ischemia, electrolyte abnormalities, or from medications such as psych medications, Zofran, Azithromycin, Cipro, etc.

While you can calculate the QT interval from a single strip, a 12-lead EKG should be obtained and it will be listed on the EKG for you. Otherwise, there are online calculators which can be used to determine the corrected QT interval for the heart rate.

Arrhythmias on the ECG Rhythm Strip

An arrhythmia is any abnormal rhythm other than normal sinus rhythm – the baseline rhythm of the heart. This can be a benign variant (like sinus arrhythmia), or it could be deadly (like ventricular fibrillation).

In order to know how to read an EKG rhythm strip, you need to first be able to understand what normal sinus rhythm (NSR) looks like.

You should be comparing every rhythm strip to NSR. Recognizing where the rhythm differs from NSR will help you identify the rhythm.

Normal Sinus Rhythm (NSR)

Normal sinus rhythm is the gold standard. This is what a normal functioning heart beat should look like.

The “sinus” in the name indicates that the electrical signal is coming from the Sinoatrial node (SA node), the “normal” pacemaker of the heart.

The presence of sinus rhythm means the cardiac conduction system is functioning appropriately (although certain blocks may still be present).

The rate of NSR is 60-100 bpm.  Slower is sinus bradycardia, and faster is sinus tachycardia. This just means that the heart is functioning at altered rates, possibly due to sleep, medications, infection, exercise, etc.

All sinus rhythms should be regular, meaning each of the QRS complexes are mapping out.

You can do this by measuring the R-R interval between any two beats, and then making sure the R-R interval stays constant throughout the strip. Some people use calipers, but I recommend a good old-fashioned alcohol pad or piece of paper and a pen.

Additionally, a P wave should precede each QRS complex.

The QRS complex should be narrow unless there is a bundle branch block present.

The ECG Rhythm Strip Interpretation

To read an EKG rhythm strip, you should do so in a systematic way, so that you don’t miss anything.

  1. Is the rhythm regular? Is every R-R interval equal?
  2. What’s the rate? This is usually printed for you
  3. P wave: Are there P waves before every QRS?
  4. PR interval: Is it wide >200ms?
  5. QRS: Is the QRS narrow or wide (>100-120ms)?
  6. T waves: Are the T waves upright and normal-appearing?

Using this systematic approach should help you interpret what each rhythm is. But you need to be familiar with most of the arrhythmias out there.

Systematic approach to reading a rhythm strip

Other Sinus Rhythms

Other sinus rhythms are rhythms that may still “normal”. I include paced rhythms in this section as this replaces NSR once a pacemaker is placed.

Sinus Bradycardia (SB)

Sinus bradycardia is the same as NSR, but the HR is <60bpm.

This can be normal for well-conditioned individuals like athletes, can be normal if the patient is on a beta-blocker or similar medication, and can also be normal while sleeping.

The most important thing when the patient has SB is

  1. Is it new or severe (<40bpm or so)
  2. Are they symptomatic? (dizziness, lightheadedness, syncope, SOB, chest pain, etc)

Since this is often a normal variant – if the patient is asymptomatic there’s usually nothing that needs to be done.

Make sure a slow HR is actually SB and not a heart block!

Sinus Tachycardia (ST)

Sinus tachycardia is the same as NSR, but the HR is >100bpm and usually <150bpm, at least while at rest.

This can often be seen with exercise, but ST at rest often indicates anxiety, certain drugs, sepsis, dehydration, or volume loss. ST is usually a response to an underlying cause within the body.

You never treat the ST, but rather treat the underlying issue (i.e. give fluids with volume depletion).

Paced Rhythm

Paced rhythms will look different depending on the location of the leads. If the lead is in the right atria, the rhythm will appear like NSR but with a pacer spike before the P wave.

If the lead is in the right ventricle, it will look like a slow VTACH with a pacer spike before the QRS. There can also be both of these at the same time.

Some monitors only show the pacer spike if you turn that function on – if you see a very slow VT – ask the patient if they have a pacemaker and adjust the monitors appropriately.

Other Cardiac Arrhythmias

Heart Blocks

Heart blocks are when there is significant delay or blockage in transmitting the signal from the atria to the ventricles. This is usually associated with a junctional or ventricular escape rhythm.

First degree AV block is generally “no big deal” and common in older age and with beta-blockers. The PR interval is consistently >200ms.

Second degree type 1 AV block or Wenckebach, is when there is a progressive lengthening of the PR interval which eventually leads to a dropped QRS complex.

Second degree type 2 AV block or Mobitz II is when there is a consistent PR interval but QRS complexes are randomly dropped.

Third degree AV block or complete heart block is when there is complete dissociation of the atria and the ventricles.

Atrial Fibrillation (AF)

Atrial Fibrillation is a very common type of arrhythmia that you will definitely run into in the hospital. AF could be new-onset, RVR (rapid ventricular response), could be intermittent (paroxysmal), or chronic/persistent.

AF is an irregularly irregular rhythm, meaning that there is no rhyme or reason for the regularity of each QRS complex.

This is usually from a structurally diseased heart where both atria are quivering rapidly, termed fibrillation. This leads to fast ventricular rates (AF RVR), as well as poor blood flow through the atria – predisposing the patient to blood clots.

This is why these patients are started on rate-control medications such as metoprolol or Cardizem, and usually anticoagulants like heparin, Eliquis, etc.

AF will not have p waves but instead, have a fibrillatory baseline. The QRS complexes will usually be narrow, and will not map out with each other in any way.

Rates >100bpm are considered AF RVR.

Atrial Flutter

Atrial Flutter (Aflutter) is similar to Atrial fibrillation and is treated largely the same.

This is when the atria aren’t fibrillating but rather “fluttering”. This is usually from a reentrant loop near the AV node.

This will usually lead to a conduction ratio of 2:1, and a HR around 150bpm. Conduction ratios can be 3:1 (100bpm), 4:1 (75bpm) and variable as well.

You will see saw-tooth P waves termed “f waves”. Depending on the conduction ratio, you will see 2 (3 or 4) F waves per QRS complex. Aflutter is usually regular.

Supraventricular Tachycardia (SVT)

Supraventricular Tachycardia is an umbrella term referring to any fast tachycardia that originates above the ventricles. However, in clinical terms, this usually refers to AV Nodal Reentrant Tachycardia (AVNRT).

This occurs when there is an abnormal pathway of conduction tissue near/within the AV node, termed a “reentrant loop”.

If a PAC or PVC comes at the wrong time, this can send the electrical signal around and around this loop of conduction tissue, leading to very fast heart rates.

SVT can be as “slow” as 140bpm to as fast as 220bpm. The faster the heart rate, the more symptomatic the patient usually is.

In SVT, P waves are usually not present, there is usually ST depression, and the rhythm is regular with narrow QRS complexes.

Treatment for this involves vagal maneuvers and often adenosine or Cardizem.

Ventricular Tachycardia (VTACH or VT)

Ventricular Tachycardia is a fast tachyarrhythmia originating within the ventricles. This leads to very fast heart rates with or without a perfusing rhythm.

This means the patient may not have a pulse and may be a code blue. Either way, VT is a very serious arrhythmia.

VT is usually caused by Coronary heart disease, like a previous or current MI.

The rhythm is regular, and the rate is anywhere from 100-330bpm, and the QRS complex is wide (>140ms).

P waves are usually absent or undetectable, but 60% of cases can have AV dissociation present.

If there is no pulse, you use ACLS cardiac arrest algorithm.

If there is a pulse, you utilize the ACLS Adult tachycardia with a pulse algorithm.

Ventricular Fibrillation (VF or VFIB)

Ventricular Fibrillation is a deadly ventricular arrhythmia. There will not be a pulse, and the patient will be coding.

VF is a similar concept as AF, except the ventricles are the ones fibrillating. Coronary artery disease is again one of the main causes of VF. Severe electrolyte abnormalities can also cause VF.

VF is irregular and has no pattern. There is either coarse or fine fibrillation, eventually degenerating into asystole if not shocked back into a normal rhythm.

These patients need fast defibrillation, high-quality CPR, Epinephrine, antiarrhythmics, etc (Code blue algorithm).

Asystole

Asystole is the absence of cardiac activity. This is essentially a straight wavy line but may have occasional p waves initially. The patient is dead. Follow ACLS algorithms as above.

Pulseless Electrical Activity (PEA)

PEA appears like a normal rhythm (Usually NSR or SB), but there is no actual mechanical contraction (no pulse). The patient will be unresponsive, pulseless, and this is a code blue as well (follow ACLS).

Want to learn more?

Hopefully this gave you a good idea about how to read an EKG rhythm strip. Unfortunately, I couldn’t include every single arrhythmia or detail, but this definitely should give you a good understanding of the basics!

If you want to learn more, I have a complete video course “ECG Rhythm Master”, made specifically for nurses which goes into so much more depth and detail.

With this course you will be able to:

  • Identify all cardiac rhythms inside and out
  • Understand the pathophysiology of why and how arrhythmias occur
  • Learn how to manage arrhythmias like an expert nurse
  • Become proficient with emergency procedures like transcutaneous pacing, defibrillation, synchronized shock, and more!

I also include some great free bonuses with the course, including:

  • ECG Rhythm Guide eBook (190 pages!)
  • Code Cart Med Guide (code cart medication guide)
  • Code STEMI (recognizing STEMI on an EKG)

You can use the code “SPRING2021” for a limited time 15% discount, exclusive to my readers!

Check out more about the course here!

You may also like:

Heart Blocks EKG Rhythm Infographic

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Vagal Maneuvers: How to Stop your Patient’s SVT

Vagal Maneuvers: How to Stop your Patient’s SVT

Vagal maneuvers are used in the clinical setting to slow down fast heart rates – primarily for supraventricular tachycardia (SVT)  and sometimes rapid atrial fibrillation (AF RVR).

There are numerous physical maneuvers that can slow down the heart rate – and there is an important modified technique which can almost triple your chances of success!

Vagal maneuvers for SVT fbook image

Svt and Vagal Maneuvers

Supraventricular Tachycardia (SVT) is a very rapid regularly arrhythmia caused by a reentrant loop within the heart.

Essentially – the signal goes around and around in a circuit, producing very fast heart rates.

reentrant loop gif

While SVT is an umbrella term for any tachycardia originating above the ventricles of the heart, it usually is used in reference to AV Nodal Reentrant Tachycardia (AVNRT). This arrhythmia is due to a reentrant loop within/near the AV node itself.

Some patients have abnormal conduction tissue in this area, and if a premature beat comes at the wrong time – it can throw them into this very fast heart rhythm.

This condition occurs more often in younger patients, females, and can be secondary to certain triggers like exercise, stimulants, or even alcohol.

Patients will usually be symptomatic and feel palpitations, fatigue, or dizziness. They can also have chest pain, SOB, or syncope.

Remember when the heart is beating this fast, the cardiac chamber’s ability to fill is decreased, and cardiac output can suffer – leading to symptoms.

When a patient comes in with SVT, their heart rate is usually very fast, with rates often between 150-200 bpm.

AVNRT-svt

We want to stop or “break” this rhythm as soon as possible, so the patient does not decompensate.

If we look at the Adult tachycardia ACLS algorithm, we can see that the first thing we do to attempt to stop the SVT in a stable patient is vagal maneuvers.

The Vagus nerve and the Heart

In order to understand vagal maneuvers, you first need to understand how the vagus nerve works.

The vagus nerve is the primary method that the parasympathetic nervous system affects the body.

This is the 10th cranial nerve which travels from your brain throughout the body. This is how the brain controls certain automatic functions.

When the vagus nerve is activated, the following effects on the body occur:

  • Bronchial constriction
  • Pupillary constriction
  • Increased blood flow to the stomach’
  • Increased digestion

Remember – “rest and digest”

Regarding the heart, the vagus nerve also has important physiological effects on the cardiac system. These include:

  • Slowing of the heart rate
  • Slowing of the conduction velocity of the AV node
  • Decreases the strength of contractions

As you can see, stimulation of the vagal nerve can be utilized to slow the conduction and increase the refractory period of the AV node which hopefully breaks the SVT reentrant loop, leading to conversion back to normal sinus rhythm (NSR).

There are various physical maneuvers that can stimulate the vagus nerve – and many you may do without trying. These include:

  • Coughing
  • Vomiting
  • Cold water immersion

Then there are certain physical maneuvers termed “vagal maneuvers” that we can perform in the hospital to intentionally cause vagal response and hopefully slow down a tachyarrhythmia such as with SVT.

These maneuvers include the Valsalva maneuver and the carotid sinus massage.

But did you know that by modifying the Valsalva maneuver – you can almost triple your chances of success?

The Modified Valsalva Maneuver

The Valsalva maneuver is the classic vagal maneuver used to stimulate the vagus nerve and stop SVT.

This is used on patients who are stable (stable vital signs) and can follow commands.

To perform the Valsalva maneuver, the patient intentionally “bears down” or strains for 10-15 seconds.

This has a 17% success rate in converting SVT. However, by modifying the Valsalva maneuver we can almost triple this success rate!

The Modified valsalva or the positional valsalva maneuver has a significantly higher success rate of 43%!

That’s almost half of your patients with SVT who this can convert back to NSR without any additional medications or interventions.

To perform the modified Valsalva maneuver:

  1. Have a Physician or APP at the bedside
  2. Place the patient in a semi-recumbent position (45° Semi-fowlers)
  3. Have the patient take a normal breath in
  4. Have them forcefully exhale with a closed glottis (bearing down) for 15 seconds
  5. Immediately place them supine and raise their legs to 45 degrees for 15 seconds
  6. Return to semi-fowlers position and watch for up to 1 minute for resolution of the SVT

Clinical Tip: If the patient has trouble bearing down, you can place an empty 10-mL syringe in their mouth and have them blow hard enough to see the plunger move.

As you can see, this technique requires a few assistants, but it is clearly the better option when attempting to convert SVT with vagal maneuvers.

The modified valsalva maneuver infographic

The Carotid Sinus Massage

The carotid sinus massage is a vagal maneuver that you can perform on someone who cannot follow commands.

The carotid sinus is an area located just below the internal carotid artery at the level of the thyroid cartilage, near the pulse.

This area is very sensitive to mechanical pressure, and mechanical pressure to this area can stimulate the vagus nerve.

To perform the carotid sinus massage:

  1. Place the patient supine with their neck extended toward the opposite side
  2. Ensure there is no carotid bruit with your stethoscope
  3. Locate the carotid sinus. This is inferior to the angle of the mandible at the level of the thyroid cartilage near the pulse
  4. Apply firm pressure for 5-10 seconds
  5. You can repeat on the other side if needed

The carotid sinus should never be performed in the following circumstances:

  • Without a physician / APP at the bedside
  • On both sides simultaneously
  • In someone with TIA or stroke within the last 3 months
  • In someone with known carotid stenosis or active carotid bruit

Carotid sinus massage infographic

Complications of Vagal Maneuvers

Any side effects from vagal maneuvers are usually short-lived and an “over-exaggeration” of expected effects.

These include sinus pauses, brief asystole, bradycardia, AV blocks and hypotension.

These will usually fix themselves within seconds to minutes.

Strokes are a major concern with the carotid sinus massage and can happen in <1% of patients.

This is why those with potential carotid stenosis or recent history of strokes should not have the carotid sinus massage.

References:

Aehlert, B. J. (2017). ECGs made easy (6th ed.). Elsevier Health Sciences.

Burns, E. (2019). Supraventricular tachycardia. In ECG Library. Retrieved from https://litfl.com/supraventricular-tachycardia-svt-ecg-library/

Frisch, D. R., Zimetbaum, P. J. (2020). Vagal maneuvers. In UpToDate. Retrieved from https://www.uptodate.com/contents/vagal-maneuvers

Grauer, K., MD. (2014). ECG Pocket Brain: Expanded Version (6th ed., pp. 65-68). Gainesville, FL: KG/EKG Press.

Knight, B. P. (2020). Atrioventricular nodal reentrant tachycardia. In UpToDate. Retrieved from https://www.uptodate.com/contents/atrioventricular-nodal-reentrant-tachycardia

Tintinalli, J. E., Brady, W. J., Laughrey, T. S., & Ghaemmaghami, C. A. (2016). Cardiac Rhythm Disturbances. In Tintinalli’s emergency medicine: A comprehensive study guide (8th ed., pp. 126). McGraw-Hill Education.

Want to Learn More?

If you want to learn more about vagal maneuvers, SVT, and every other cardiac arrhythmia – check out my ECG Rhythm online video course out now!

It’s specifically designed for nurses, and not only teaches you how to identify each arrhythmia, but also why and how they occur, and what to do about it!

If you’re not ready to take that leap yet but still want to learn more about ECG rhythms – be sure to download my free ECG Cheat Sheet below!

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