Letâ€™s switch gears a little bit and discuss irregular or polymorphic wide complex tachycardias.
First I need to tell you a story.
A few years ago I was teaching ACLS to a group of mostly nurses at the local community hospital. I volunteered to teach Bradycardias, Tachycardias, and the Hypotension/Shock/Acute Pulmonary Edema algorithm.
At first the education coordinator was thrilled! Apparently not many ACLS instructors feel comfortable teaching the Hypotension/Shock/Acute Pulmonary Edema alogrithm.
Keep in mind, I was following along with the AHA ACLS PowerPoint slide set. I wasnâ€™t freelancing. I was explaining and elaborating, but I wasnâ€™t introducing material that is outside the scope of the ACLS objectives.
I arrived at Irregular (or Polymorphic) Wide Complex Tachycardias.
I had just written on the board the differential diagnosis, which included:
- Atrial fibrillation/flutter or (multifocal atrial tachycardia) with bundle branch block
- Polymorphic VT
- Torsades de Pointes
- Atrial fibrillation with Wolff-Parkinson-White Syndrome (WPW)
When suddenly, the education coordinator yelled out from the side of the room, â€œYouâ€™re scaring the hell out of them!â€
I was struck dumb!
I didnâ€™t know what to say. I looked back at the screen, and I looked at the dry erase board where I had just written the differential diagnosis, and then I looked back at the education coordinator, shrugged my shoulders, and said, â€œWhat do you want me to do?â€
To be honest, this wasnâ€™t the first run-in I had had with this particular education coordinator.
A couple of years prior, I was a student in one of her ACLS classes. She handed out a cardiac rhythm strip test. I identified one of the heart rhythms on the test as 2:1 atrial tachycardia. She marked it wrong. When I asked about it, she said the correct answer was sinus tachycardia with 2Â°AVB and 2:1 conduction.
I laughed and said, â€œIs the atrial rate > 100?â€
She said yes.
â€œAnd you agree there is 2:1 conduction?â€
She agreed that there was.
â€œSo you acknowledge that 2:1 atrial tachycardia is technically correct?â€
She gave me look of utter contempt, leaned forward, and said quietly, â€œWhat do you think you are? A cardiologist?â€
Iâ€™m not entirely sure this person likes firefighters. Letâ€™s just say she used to be married to one, and leave it at that.
All of this to say, the differential diagnosis of irregular (or polymorhpic) wide complex tachycardias is a very neglected subject, both in paramedic school, and in ACLS class! But you have to know the differential diagnosis to select the correct treatment modality!
You can kill a patient who presents with an irregular (or polymorphic) wide complex tachycardia if you select the wrong drug!
That should â€œscare the hell out of youâ€ far more than the differential diagnosis written out on a dry erase board.
Letâ€™s start with atrial fibrillation.
Atrial fibrillation with intraventricular conduction defect (including right and left bundle branch block) can be considered a VT mimic at high rates, because the higher the heart rate, the more difficult it is to pick up on the irregularity that is normally the hallmark of atrial fibrillation!
In training (using the heart rhythm simulator) I sometimes give paramedics a scenario like this:
89 year old female contacts 9-1-1 complaining of chest pain and shortness of breath
On arrival, respirations are 36 and labored
Skin is pale and diaphoretic
Begin your assessment!
When they attach the monitor, they see atrial fibrillation with a nonspecific intraventricular conduction defect at a rate of 160.
I take that back. What they see when they attach the monitor is a wide complex tachycardia.
This example from Wide Complex Tachycardia: ECG Differential Diagnosis. Am J Emerg Med 1999; 17:376-381 should give you an idea what it looked like when printed out (which is different from how it looks on the monitor).
When they asses breath sounds (if they assess breath sounds) I say â€œwheezes with a poor tidal volumeâ€.
When they assess the SpO2 (if they assess the SpO2) I say â€œ72â€.
Can you guess whatâ€™s wrong with this patient?
If you said â€œheart failureâ€ move to the head of the class!
You would be frightened amazed to know how many paramedics immediately lie the patient flat and prepare her for immediate synchronized cardioversion!
In the debriefing that follows, when I ask why the decision was made to start shocking the patient, the ones that have clear rationale will say, â€œBecause she was in unstable VT!â€ or â€œBecause she was in unstable AF with RVRâ€.
When I asked what made the patient unstable, they will say, â€œthe chest pain!â€ Some will say â€œthe shortness of breath!â€
Others will want to say the BP, but then they realize they never assessed it.
Thereâ€™s a fine line between symptomatic and hemodynamically unstable.
For any patient who presents with a tachycardia, one of the most important and difficult questions you have to answer is:
Is the tachycardia causing the signs and symptoms, or are the signs and symptoms causing the tachycardia?
To put it another way:
Is this some type of compensatory tachycardia?
For the heart failure patient, atrial fibrillation and bundle branch block are extremely common. Have you ever seen acute, decompensated heart failure patient that did not present with tachycardia?
This is just my opinion, but I would try oxygen (CPAP if possible) and nitroglycerin before lying a heart failure patient flat and proceeding directly to synchronized cardioversion.
The next question you need to answer is:
Does the risk/benefit analysis favor treating this tachycardia in the field?
If you read the AHA ECC 2005 guidelines, you will see this statement featured prominently in the irregular (or polymorphic) wide complex tachycardia section.
â€œWe recommend a 12-lead ECG and expert consultation if the patient is stable.â€
Was the patient in this example â€œstableâ€? No!
Was the instability cased by the atrial fibrillation and rapid ventricular response?
In my opinion, no.
The BP of 160/110 gives you â€œroom to playâ€ so to speak. Nitroglycerin is a potent vasodilator. Why not give it, along with supplemental oxygen, and take some preload off the heart?
The heart rate will probably come down on its own when the SpO2 is back > 90.
You can always simultaneously prepare for cardioversion!
Differential diagnosis of wide complex tachycardias – Part 5