In this episode of Think Like a Nurse, Brooke Wallace and her co-host break down the intimidating world of EKG interpretation into a clear, step-by-step process. Using Brooke’s 20 years of ICU experience, they show how to systematically analyze rhythm strips using six key checkpoints: rate, rhythm, P wave, PR interval, QRS complex, and overall interpretation. Listeners learn how to identify life-threatening rhythms like V-tack and V-fib, understand which ones are shockable, and remember key mnemonics like “V-fib = Defib” and “Pulse before paddles.” The conversation emphasizes real-world clinical priorities — from stroke prevention in AFib to pacing for complete heart block — teaching nurses to think beyond memorization and respond with confidence in emergencies.
Systematic Approach (6 Steps):
Rate – Regular: 300 Rule (300 ÷ # large boxes between R waves).
Irregular: 6-Second Strip Method (R waves in 6 seconds × 10).
Rhythm – Regular or irregular?
P Wave – Present before every QRS?
PR Interval – Normal: 0.12–0.20 sec (3–5 small boxes).
If the R is far from P → first-degree block.
QRS Complex –
Narrow (<0.12 sec): supraventricular origin (normal pathway).
Wide (>0.12 sec): ventricular origin or bundle branch block.
Mnemonic: Narrow = Normal, Wide = Worry.
Interpretation – Identify rhythm and appropriate intervention.
Key Rhythms & Interventions:
Normal Sinus Rhythm (NSR): 60–100 bpm, consistent P before QRS. → Routine monitoring.
Atrial Fibrillation: Irregularly irregular, no P waves, wavy baseline. → Stroke prevention with anticoagulants (warfarin or DOACs).
Ventricular Tachycardia (V-tack): Fast + wide complexes. → Check for pulse first!
Pulse + stable → Amiodarone.
Pulse + unstable → Cardioversion.
No pulse → Defibrillate.
Ventricular Fibrillation (V-fib): Total chaos. → Defibrillate immediately.
Mnemonic: “V-fib = Defib.”
Asystole (Flatline): No electrical activity. → CPR + Epinephrine, confirm in 2nd lead.
Rule: Confirm before you code.
Pulseless Electrical Activity (PEA): Electrical activity without a pulse. → CPR + Epinephrine, find reversible H’s and T’s.
Third-Degree (Complete) Heart Block: P’s and QRS march independently. → Immediate pacing.
Mnemonic: “If P’s and Q’s don’t agree → 3rd-degree.”
Shockable vs Non-Shockable:
Shockable: V-fib, Pulseless V-tack.
Non-Shockable: Asystole, PEA.
💡 Nursing Pearl: “If there’s chaos, shock. If it’s flat, compress.”
NCLEX Tip:
Always check for a pulse before paddles — treat the patient, not the monitor.
Welcome to Think Like a Nurse, the show where we take really complex um critical nursing topics and well, we try to break them down, make them easier so you can go from feeling stressed as a student to, you know, confident out there in clinicals.
Yeah. The goal is really to cut through all the noise. This show, it was created by Brooke Wallace. She's got 20 years as an ICU nurse, organ transplant coordinator, clinical instructor, and she's a published author.
She designed this whole thing to give students the perspective they actually need, you know, on the floor. Exactly. And today we are diving straight into uh EKG interpretation. This isn't just like reading squiggly lines on paper.
Definitely not.
This is often the fastest way a nurse figures out if a situation is life or death. So we're giving you the systematic steps that expert clinicians use to well triage a heart rhythm really fast. Yeah.
In seconds basically.
And if you want more resources to go along with our conversation today, please do visit think like a nurse.org. But yeah, right now let's start with that foundation getting that routine. down path. It's mandatory.
Okay, let's unpack that. It's a systematic approach. We talk about method a lot and um maybe nowhere is it more important than with EKGs. You have to be systematic, right?
Absolutely. Every single time when clinicians glance at a strip, they mentally run through six specific steps. Rate, rhythm, Pwave, PR interval, QRS complex, and then finally interpretation.
Right? The RR PPQI method. But let's be real, for that immediate like uhoh moment, which two of Those steps give you the most bang for your buck right away.
Oh, easily. Rate and QRS with if you can nail those two quickly, you immediately get a sense if you're dealing with something minor or, you know, a potentially lethal ventricular issue.
So, skipping steps is a no-go.
Big nogo. It's how patients crash. You absolutely need that routine every single time.
Okay. So, rate first. Let's nail that down. If the rhythm looks regular, like nice, and even normal sinus, maybe what's the fastest way? The shortcut,
we use what's called the 300 rule.
It's pretty simple. You just count the number of large boxes between two consecutive R waves, you know, the big peaks.
And then you divide 300 by that number. So let's say there are uh four large boxes between Rwaves. 300 divided by four, that's 75. So 75 beats per minute.
Got it. Quick math. But what about those messy rhythms? The ones that are all over the place, like AIB, where the space between the Rwaves is totally inconsistent,
right? The 300 rule won't work there. For irregular rhythms, you need the 6-second strip method. You look at the EKG paper, find the markings for a 6-second interval. That's usually 30 large boxes.
Okay?
Then you count how many Rways fall within that 6-second window, and you multiply that number by 10. That gives you a pretty good estimate of the average rate over a minute, even when it's irregular.
Okay, that makes sense. So, we get the rate sorted. Then you mentioned the QRS complex, step five in the process. What's the detective work there? What's it telling us?
Ah, this is like the golden nugget for diagnostics.
The QRS complex, it shows the ventricles depolarizing, right? acting and how wide it is tells you a ton about the path that electrical signal took.
Okay. So, tell us about the widths. There are two critical categories.
Exactly. Yeah.
If the QRS is narrow, meaning it's less than .12 seconds wide, which is about three small boxes on the grid, that tells you the impulse traveled down the normal fast pathway. Think of the hisperkeni system as like um an electrical superighway,
right?
A nuro QRS means the signal zipped right down that highway, right?
So, the impulse must has started above the ventricles. We call that super ventricular.
Okay. Efficient pathway narrow QRS started up high. Got it. And if it's wide, so wider than.12 seconds.
Well, that's usually a sign of trouble. Yeah. A wide QRS means the signal couldn't use that super highway. It's taking the slow inefficient back roads moving cell by cell through the ventricular muscle itself.
Ah.
So that wide often kind of bizarre looking complex means one of two main things. Either the impulse actually started down in the ventricles like in vach or vib or or there's the major blockage on the highway like a bundle branch block forcing it to take that detour.
That really clarifies why the width matters so much. It's not just a number. Okay, we also need those timing windows. The PR interval, that's the time from the start of the Pwave to the start of the QRS,
right? It shows the time the impulse takes to get from the atria through the AV node. Normally that should be between 0.12 and.20 seconds. 3 to five small boxes.
And the QRS complex itself, the ventricular part should be quick, right?
Yeah. Ideally 06 to 0.1 2 seconds. So less than three small boxes. If that PR interval gets longer than 0.20 seconds, it means there's a delay at the AV node. That delay is essentially the definition of a heart block starting.
Okay. Foundation laid. Let's talk baselines. Normal sinus rhythm. That's our gold standard, right?
That's the one rate is between 60 and 100. It's regular. There's nice Pwave right before every single QRS complex. And all those intervals we just talked about, the PR and QRS, they're within normal limits.
Means the heart's natural pacemaker, the SA node, is doing its job perfectly and the whole conduction system is working smoothly.
Exactly. And intervention for NSR basically just routine monitoring. It's the uh the happy heart, the one you compare everything else against.
Right. But then you hit the floor and you see maybe the most common sustained arhythmia out there, atrial fibrillation or aphib. How do we spot that one visually?
Aphib's key feature is that it's irregularly irregular. There's absolutely no pattern to when the QRS complexes appear. They're all over the place. And critically, you won't see clear P waves.
No P waves.
No. Instead, you get this chaotic wavy baseline. That's because the atria aren't contracting properly. They're just sort of quivering, fibrillating. The QRS is usually narrow, though, because the signal is still generally coming from above the ventricles.
So, the atria are just kind of jiggling, not pumping effectively.
Okay.
Okay. Here's the big clinical question, then. If your patient has AIB, but they seem stable, vital signs are okay, what's the number one priority?
Stroke prevention, hands down. Because those atria aren't squeezing blood out properly, blood can pull in there, and pulled blood tends to form clots, right?
Those clots can then get pumped out and travel, potentially causing a stroke. It increases the risk massively. So, the nurse's first thought should be assessing that stroke risk and getting anti-coagulation started. Often, Warfin or more commonly now, the DOAC's, the direct oral anti-coagulants.
So, before even worrying too much about fixing the rhythm itself, you're thinking clots.
Exactly. We do also manage the heart rate often with beta blockers or calcium channel blockers to slow things down if it's too fast and sometimes we try to convert the rhythm but for a stable patient managing that clot risk is absolutely primary.
That's a huge takeaway for students risk management over rhythm management and stable aphib. Okay, let's pivot now from risk management to immediate danger the ventricular emergencies. Let's start with ventricular teacardia VTEC.
Okay, VTEC think fast and wide. The rate is tip typically fast anywhere from 100 up to maybe 250 beats per minute and you see those wide bizarre looking QRS complexes we talked about
because the signal is starting down in the ventricles
precisely yeah it's originating low down taking that inefficient path and because things are happening so fast in the ventricles you often can't even see any P waves they get buried in the QRS
okay you see that on the monitor what is the absolute single most crucial first step
check for a pulse
yeah
always always check for a pulse first I remember, you know, early in my career, seeing Vatch on the monitor is terrifying. Your first instinct might be to grab the paddles.
Yeah, absolutely.
But my mentor stopped me once, reminded me, treat the patient, not the monitor. The strip is just information. You have to know if that electrical activity is actually generating a pulse, actually pumping blood.
Okay. And how does finding or not finding a pulse change what you do?
It changes everything. If they have a pulse and seem relatively stable, maybe just some palpitations, who typically use anti-arithmic medications like amiotarone.
Okay.
If they have a pulse but are unstable, meaning they're hypotensive, confused, having chest pain, signs of poor profusion,
then you need synchronized cardio version, a controlled shock timed with their QRS.
And if there's no pulse,
pulseless VTAC, then you treat it exactly the same way you treat the next rhythm, VIB. That means immediate defibrillation,
which brings us right to ventricular fibrillation. VIB. This is where the heart muscle is just quivering, right? No coordinated pumping at all.
Exactly. Total chaos electrically. The strip looks like well just a messy, disorganized scribble. There's no discernable P waves, no QRS, no T- waves. It's just chaotic electrical firing that isn't moving any blood.
And the key thing to burn into your memory for VIB,
the pneummonic VIB equals defib. Ventricular fibrillation requires defibrillation. It is a shockable rhythm because there is electrical activity, albeit chaotic, that you might be able to reset with a shock.
So the intervention sequence kick off immediately
instantly. Defibrillate first, then high quality CPR. Push epinephrine, shock again if needed, then consider anti-arithmics like amiodarone or lidocaine between shocks. Time is absolutely critical. Brain cells are dying.
Okay. Def for VIB. Then we hit the grim one. Acy, the flatline.
Yeah. Acy. Flatline. Basically, no electrical activity visible on the monitor at all.
Okay. You run into a code situation. You look up and you see that flatline. It's high pressure. How do you manage that urge to just jump straight into full code mode versus making sure it's real.
That's a great point. It is stressful, but again, you stick to your systematic approach. You start CPR immediately and you give epinephrine according to ACLS protocols.
But crucially, before assuming it's true assist, you have to confirm it.
Confirm how?
Check the patient first. Are they responsive breathing? Check the equipment. Are the leads properly attached? Is the monitor gain turned up? Sometimes a loose lead can mimic a flatline. And most importantly, confirm the rhythm in a second lead. Look at it from a different electrical angle. Never ever pronounce someone or run a full code solely based on seeing a flatline in just one lead.
That is such a critical safety check. Confirm in a second lead. And this non-shockable status also applies to another rhythm, right? PA,
correct? PA, pulseless electrical activity. This is where you do see organized electrical activity on the monitor. Could even look like sinus rhythm sometimes, but when you check the patient, there's no pulse. The electricity is there, but the heart must isn't responding mechanically.
So bottom line for assisty and pea
they are non-shockable rhythms. You cannot defibrillate them because there's either no electrical activity assistly or the existing activity isn't the problem pea. The treatment focuses on excellent CPR giving epinephrine and urgently trying to find and fix any underlying reversible causes. We often call these the hes and t's.
Got it. Shock vib and pulseless vet. Don't shock acy in pea. Okay, let's shift gears slightly to the blocks. This is where the communication between the atria and ventricle starts to break down. Let's start with the mildest one. First degree AV block,
right? There's a little rhyme for this one that helps. If the R is far from P, then you have a first degree. What it means is that the PR interval that time from the start of the Pwave to the start of the QRS is consistently long. It's greater than that .20 second upper limit.
But importantly, every Pwave still does eventually get through and cause a QRS complex. Just takes a little longer than usual to get through the AV node.
So, the signal gets there just slowly and every atrial beat still leads to a ventricular beat. Intervention is usually minimal then
pretty much mostly just monitoring.
Mhm.
Maybe review the patient's medications. Things like beta blockers or dyin can sometimes cause or worsen this slight delay, but usually it's benign and doesn't cause any symptoms on its own.
Okay. Simple delay, usually no big deal. Now, let's jump to the other end of the spectrum. Third degree AV block, also called complet Complet heart block sounds serious.
It is. This is complete AV dissociation. The atria and the ventricles are electrically divorced. They're beating completely independently of each other.
So the signals from the atria aren't getting through to the ventricles at all.
Not at all. The SA node is firing away creating regular P waves. And somewhere lower down usually in the ventricles or the AV junction an escape pacemaker is firing creating regular QRS complexes. But if you look closely the Pways in the QRS complexes have absolutely Absolutely no relationship to each other. They just walk out across the strip at their own rates. Completely unrelated.
Total communication breakdown. Okay. Clinical scenario. Your patient has this on the monitor and they are symptomatic, maybe dizzy, hypotensive, confused. What is the absolute priority intervention?
Immediate pacing.
Yeah,
usually transcutaneous pacing first. You have to externally take control of the ventricular rate because the heart's own system has failed completely. While you're getting the pacer pads on and setting it up at the really stable, you might give meds like atropene or start dopamine or epinephrine drips to try and support their pressure and rate temporarily. But pacing is the definitive firstline treatment for an unstable patient in a thirdderee block.
Pacing is key for unstable advanced blocks. Okay, this really brings us back to that crucial distinction we touched on earlier, shockable versus non-shockable rhythms. It dictates the immediate action.
Absolutely. It synthesizes everything. You only use the defi defibrillator paddles when there's chaotic or inappropriate electric activity that you hope to reset. So, your shockable rhythms are VIB and pulseless vetch.
And the ones where grabbing the paddles is the wrong move where it's all about CPR and meds.
That's a cyal and pulseless electrical activity, pea. No useful electrical activity to reset means no shock. You focus on compressions, airway, breathing, drugs, and finding those reversible causes.
Wow. Okay. We've really covered a huge amount today from that essential systematic approach, the RRPPQI, right through identifying these critical rhythms. and knowing the immediate lifesaving interventions.
Yeah. And the real goal here isn't just to be able to name the rhythm on a test. It's using that systematic process to instantly know what to do, look at the strip, figure out where the problem is originating based on things like QRS with and prioritize the right action. Whether that's anti-coagulants for aib risk, defib for VIB, or immediate pacing for complete heart block. That is how you really start to think like a nurse.
Absolutely. We really hope this conversation helps. you move past maybe feeling intimidated by those EKG lines and helps you feel more confident in practice knowing why you're doing what you're doing.
And if you found this helpful, please do check back for more conversations each week and definitely visit think like a nurse.org. There are lots more great resources over there.
Definitely. Until next time, stay sharp, keep practicing that systematic approach and always, always check the patient first.