Hi. I’m Mark from ACLS Certification Institute. In today’s Megacode review, we’re going to cover narrow-complex irregular tachycardias because the treatment is different than that of regular narrow-complex tachycardias.
Quick review: What makes a narrow-complex tachycardia a narrow-complex tachycardia? We’re looking at the width of the QRS complex. The width of the QRS should be less than 0.12 seconds. If it’s 0.12 seconds or less, it’s considered a narrow-complex tachycardia. If the QRS is wider than 0.12 seconds, we call that a wide-complex tachycardia, and we’ll cover that a little later. Sometimes it’s difficult to discern a regular from an irregular tachycardia. What you’re looking for is irregularity in the morphology, the shape of the waveform. What is the appearance of this EKG? Look at the R waves. The R waves march out. Are they an equal distance from each other, and is this equal distance maintained and consistent throughout the run of the rhythm? If the morphology, the appearance, starts to change throughout the run of the same rhythm, that means there are different parts of the heart generating that impulse, causing that different shape in the waveform. That’s a polymorphic tachycardia, and the treatments vary a little bit from regular. One of the most common causes of a narrow-complex irregular tachycardia is an underlying atrial fibrillation. In atrial fibrillation, the atrial chambers aren’t fully contracting. They’re not fully ejecting all the blood out of those chambers. In atrial fibrillation, the atrial chambers are just quivering, so blood tends to accumulate inside those chambers. You have blood pooling inside the atrial chambers because it’s not being fully ejected. The risk is that clots can start to form inside this pool of blood. Any patient who has been in atrial fibrillation longer than 48 hours before they present to you and is stable probably shouldn’t be cardioverted right away. Again, the risk is they could throw a clot. If it’s been longer than 48 hours, the risk of a clot forming in the atrial chamber increases. If we convert them to a sinus rhythm, fully eject that blood and that clot out of the chamber, that patient runs the risk of a stroke or another event.
In A-fib with RVR (rapid ventricular response), we may not necessarily want to convert this A-fib to a sinus rhythm for other reasons, minimizing the risk of a clot and so on, but we want to get control of the ventricular response. The ventricular rate is way too fast. That’s the problem. With an A-fib with RVR, we want to focus on rate control, ventricular rate control. One of the big differences between narrow-complex regular and narrow-complex irregular tachycardias is the drug of choice. Our drug options change. Remember, for a narrow-complex SVT, our drug of choice is adenosine. We really don’t want to use adenosine in irregular complex arrhythmias. Has it been used before? Absolutely. Did the patient die? No. I had a student come to me the other day and go, “Mark, Mark, look what I did,” and he hands me a strip of a patient he had who he had converted with adenosine. After the conversion, I could see that the patient was in an underlying atrial fibrillation. Did the patient die? No. Is adenosine indicated for an A-fib with RVR? No. Does it happen? Absolutely. Did the patient die? Of course not. However, it’s not indicated and generally shouldn’t be used in irregular rhythms. The drug of choice for a narrow-complex irregular tachycardia is a calcium channel blocker. A couple options exist. One is verapamil 5 mg slow IV push over 5 minutes. Some literature says over 2 minutes, but 5 over 5 is how I remember it. Second drug is Cardizem 0.25 mg/kg, again, over 2 to 5 minutes. Both of these drugs are calcium channel blockers and are designed to help slow the ventricular response in these tachycardias.
Any narrow-complex tachycardia—whether it’s regular or irregular doesn’t matter—if the patient is showing serious signs of shock (low blood pressure, poor color, altered mental status), immediate synchronized cardioversion. Again, whether the complex is narrow regular or irregular, a patient with serious signs of shock with this tachycardia is going to receive immediate synchronized cardioversion.
There is a little difference in the amount of energy they recommend between regular and irregular narrow-complex tachycardias. For a narrow-complex regular tachycardia, the literature is suggesting starting around 50 J, synchronized cardioversion at 50 J. If the narrow-complex tachycardia is irregular, like an A-fib with RVR, they recommend bumping the joules up to about 200 J. In A-fib with RVR, synchronized cardioversion at 200 J. The topic always comes up of sedation. Let’s say you have a narrow-complex tachycardia. The patient’s hemodynamically unstable. Blood pressure’s in the 80s. They look a little funky to you, but they’re still with it. They’re still talking to you. You know, you’re coming at them with the paddles, and they’re going, “Ahhhhh!” You know, you may want to give them a little sedation. However, never without emergent cardioversion for a truly unstable patient to administer sedation. If you can get it into him quick, fantastic. Give him a little ‘groovacaine,’ make him feel a little bit better. If not, shock him.
Let’s get into our Megacode review of narrow-complex irregular tachycardias. Today we’re working pre-hospital. We’re back in the ambulance. Let’s get started.
Paramedic: “Hey there, can brother get a donut?”
Radio: “Ambulance 158, respond to a call at 153 Turnberry for a female with chest palpitations. The patient states she weighs 600 pounds, lives in a 6th floor apartment, and the elevator’s broken. 158, the donut shop’s right across the street. I can see you through the window.”
Paramedic: “Yeah, ambulance 158, we’re ---. Come on, ---, let’s roll.”
Paramedic: “Thanks to our rocket-powered ambulance, we made it to the scene in no time. When you get to the scene, you find a 55-year-old female who about 30 minutes ago had sudden onset of a fluttering in her chest, started to feel a little dizzy, and called the ambulance.”
We have a 55-year-old female. As the team leader, I immediately start assigning roles, like I do in any code or any emergency. I want her on oxygen immediately because she’s symptomatic. We’re going to start her on high-flow oxygen. I have another paramedic getting her connected to the monitor. Another paramedic is starting an IV. We get her hooked up to the monitor and we see this: narrow-complex tachycardia, rate of about 168. Her blood pressure is 110/70. Respiratory rate is 20, clear bilaterally. Room air SPO2 is 95%. She’s symptomatic, but she’s hemodynamically stable. She’s not showing any serious signs of shock. We have some wiggle room here. We have some time. My partner’s looking at the monitor and he’s debating is this regular or irregular. He’s really not sure. Before we move forward and since we have some time, we’re going to do a 12-lead EKG and get a better look at this heart to see what’s going on. The 12-lead shows an underlying atrial fibrillation, so what we have now is A-fib with RVR. This is a sudden onset. The patient said it started about 30 minutes ago, and she has no history of A-fib. Our drug of choice? Cardizem 0.25 mg/kg over 2 minutes. To better demonstrate the difference between regular and irregular rhythms, I want to slow down the A-fib. Let’s take a look at that. Notice that when you’re looking at a slower A-fib rhythm, the R waves don’t march out. The timing between the R waves is different. That’s because it’s not one focus firing. It’s multiple foci within the atrium firing off, causing this quivering of the atrium. Because we have that and not one, say the sinus node, firing off, we don’t have a P wave. There’s no discernable P wave in this rhythm. The P wave would normally be round, upright, and preceding a QRS complex. We don’t have that. We have a quivering atrium and a ventricle that fires off intermittently, irregularly. My partner’s starting to draw up the Cardizem. The other paramedic keeps reassessing, reassessing, reassessing the patient. He now tells me that her blood pressure has dropped to 80. The patient starts to look pale. She starts falling off her chair. We help her down to the ground. Now that the patient has become hemodynamically unstable—she has altered mental status, her blood pressure has dropped, she is hypotensive—we’re going to move immediately to synchronized cardioversion. The difference between regular and irregular narrow-complex tachycardias and synchronized cardioversion is the amount of energy you use. For regular SVT narrow-complex tachycardia, the literature says you can start around 50 J. For A-fib with RVR, we’re going to start at 200 J synchronized. Fire it up to 200. Remember to set your defibrillator to defibrillation. Set it to sync. Remember, in sync we’re going to see those hashmarks over the R wave. The monitor should say “sync” and we should see those hashmarks. That lets us know we’re in synchronized cardioversion mode. We delivered the shock and the patient converted to this: Still in A-fib, but we have rate control now. You see her rate has slowed down. Reassess her vital signs. Blood pressure is now 130/70. Heart rate has come down. Respiratory rate is still 20, clear bilaterally. Her mental status has improved. Her color has improved. We’re going to continue the oxygen therapy. In the literature, it often says “consult experts.” Get an expert consultation. If you’re in the field, your expert consultation is medical control. Call your resource hospital. In this case, they wanted us to start a Cardizem drip at 5 mg/h. We started that. What do you do when you don’t know what to do? You consult the expert.
Remember, when assessing narrow-complex tachycardias, first, is your patient stable or unstable? If they’re unstable, immediate synchronized cardioversion. If they’re stable and you have some time, some wiggle room, do further investigation. Get a 12-lead EKG. Get somebody else’s opinion on what’s going on and really identify what this rhythm is. If it’s regular or irregular, pick the appropriate drug of choice.
I’m Mark for ACLS Certification Institute. Thank you for watching.