Last updated 12/19/24
You’re enjoying a rare, quiet evening when you feel a tap on your shoulder. You turn around and find the local orthopedic surgeon handing you an ECG of their patient and asking, “Dude, is this sinus?”
ECG 1
‣
‣
- Yes (see lead II, III, avF)
‣
- Yes
‣
- Yes appears so
‣
- Yes.
‣
- Yes
‣
- This is likely a sinus rhythm, specifically sinus tachycardia
‣
- This is sinus tachycardia with a rate close to 120
‣
ECG 2
‣
‣
- Yes
‣
- Yes
‣
- No
‣
- No
‣
- No. There appear more P waves than qrs complexes.
‣
- Yes
‣
- This is not a sinus rhythm
‣
- There appears to be no relationship between the p waves and qrs complexes which confirms av dissociation or 3rd degree av block.
- Some key findings:
- Regular P waves at their own intrinsic rate (~70 bpm).
- Regular wide QRS complexes at a slower intrinsic ventricular escape rhythm (~30–40 bpm). Wide QRS complexes indicate a ventricular origin of pacing (outside the normal his purkinje conduction pathways).
- Lack of any PR interval consistency.
‣
ECG 3
‣
‣
- Yes in V3
‣
- in V3 Yes, but can’t tell anywhere else
‣
- Unable to determine
‣
- Yes in V3 but unable to determine in other leads
‣
- Unsure
‣
- Sinus rhythm cannot be determined here
‣
- The rhythm is a bizarre looking, regular and very wide complex rhythm with a rate 60-70, consistent with idioventricular rhythm
- Bizarrre appearance + idioventricular rhythm is hyperkalemia until proven otherwise.
- This is also called sine wave. In hyperkalemia, atrial conduction is suppressed and T waves / QRS complexes fuse together creating wide and bizarre complexes.
- Since there are p waves in V3, this could be also be sinus rhythm with very wide QRS
‣
ECG 4
‣
‣
- No, distinct P waves are not visible in the provided ECG, indicating an absence of organized atrial activity.
‣
- Does not apply
‣
- Does not apply
‣
- Does not apply
‣
- Does not apply
‣
- No, this is not sinus rhythm
‣
- Ventricular escape rhythm at < 20 bpm vs. ventricular escape beats as indicated by
- Wide QRS complexes consistent with ventricular origin
- No atrial activity
- Slow rate
- The differential diagnosis can be hyperkalemia, complete heart block, drug toxicity. In this case the patient had a K ≥ 7.5 meQ/L. Note the peaked T waves in V1-V3
‣
ECG 5
‣
‣
‣
- Yes but hard to find as they may be superimposed into the T wave bc of the rate. See avL for P waves.
‣
- Yes
‣
- Yes
‣
- No
‣
- Difficult to determine. Appear upright in the inferior leads.
‣
- There are sinus beats followed by pacemaker spikes / QRS complex…which will be discussed next
‣
- Atrial sensed, ventricularly-paced rhythm
- The rate is fast (> 120bpm), but appears to be an atrially sensed, ventricularly paced rhythm. See the Prior ECG to confirm this.
- This may be a biventricularly paced as some leads have 2 pacer spikes before each QR complex
- W/ superimposed runs of multifocal PVCS vs. polymorphic VT
- See wide qrs complexes with different morphologies that are not triggered by pacemaker
- This is BAD
‣
ECG 6
‣
‣
- No
‣
- Does not apply
‣
- Does not apply
‣
- Does not apply
‣
- Does not apply
‣
- This is not sinus
‣
- Polymorphic VT specifically Torsades de Pointes with a rate 150-200+
- This is a irregular wide complex tachycardia with QRS complexes that vary in morphology, a hallmark of polymorphic VT.
- The QRS complexes appear to "twist" around the baseline, with amplitudes that progressively increase and decrease in a cyclical pattern (see V1 and V2 rhythm leads) This is characteristic of Torsades de Pointes.
- The rhythm terminated shortly after starting a Mag transfusion and the patient’s K was found to be 2.7 meQ/L. A repeat ECG is below. What’s the QTc?
‣
ECG 7
‣
‣
- Yes
‣
- Yes
‣
- Yes
‣
- Yes
‣
- Yes
‣
- This is a sinus rhythm…but somethings off
‣
‣
- Trigeminy with PACs
- 2nd degree av block type 2
- 2nd degree Sinoatrial block type 2
‣
- Atrial trigeminy
- Premature contractions can cause pauses. If they occur every 3rd beat, this is called trigeminy.
- So is every third beat a PAC? Is the p wave and PR interval and axis different than the preceding 2 sinus beats? No. The P wave is identical to the previous beats so this is NOT a PAC and therefore not atrial trigeminy
- 2nd degree av block type 2 (mobitz II)
- The P: QRS ratio is 1:1 so this cannot be. 2nd degree av block requires a non-conducted atrial beat / accompanied p wave.
- 2nd degree Sinoatrial block type 2
- The pattern is equivalent to 2nd degree av block type 2 except both the P wave and QRS “drop out” out of the rhythm
- The subsequent P wave after the pause arrives on “time”. In other words, the p-p interval after the pause is 2x the duration of the p-p interval between the group beats
‣
- LITFL Sinoatrial Exit Block
- LITFL Premature atrial complex
‣
ECG 8
‣
‣
- Yes they are retrograde. See lead II, III, and avF. There is an inverted p wave at the end of the ST segment (after the qrs complex)
‣
- Yes in leads where retrograde P waves can be identified.
‣
- Not applicable as P wave occurs after qrs complex
‣
- Yes in leads where retrograde P waves can be identified.
‣
- No they are down in the inferior leads and up in avR which is the opposite axis.
‣
- This is not sinus rhythm. P waves do not occur before each QRS complex
‣
- This is junctional bradycardia with a rate of 48 bpm as evident by
- Regular narrow complex complexes
- Absent or retrograde p waves
- Slow rate
‣
ECG 9
‣
‣
- No
‣
- N/A
‣
- N/A
‣
- N/A
‣
- N/A
‣
- This is not a sinus rhythm
‣
- This is a wide complex regular rhythm with a rate < 100. This is accelerated idioventricular rhythm (AIVR). AIVR is a ventricular rhythm that is too slow to be ventricular tachycardia (typically > 130 bpm) and too slow to be ventricular escape (< 40 bpm)
- Classically, AIVR is associated with reperfusion in the setting of MI and often self-limiting
- Another rhythm on the differential diagnosis is junctional rhythm (see ECG 8) but with a bundle branch block.
‣
ECG 10
‣
‣
- No
‣
- N/A
‣
- N/A
‣
- N/A
‣
- N/A
‣
- This is not sinus rhythm
‣
- This is a regular wide complex tachycardia. The differential diagnosis is:
- Monomorphic VT
- SVT (AVNRT, Orthodromic AVRT) with bundle branch block
- Antidromic AVRT
- This patient was 28 years old and had a history of WPW. If you look at the QRS complexes, they do have delta wave appearance in almost all the leads. Therefore this is likely antidromic AVRT. Patient was given an av nodal blocker and converted to sinus rhythm. If you are unsure, assume the worst and treat as VT. Procainamide can treat both VT and antidromic AVRT in stable patients.
‣
ECG 11
‣
‣
- No
‣
- N/A
‣
- N/A
‣
- N/A
‣
- N/A
‣
- This is not a sinus rhythm.
‣
- This is a irregular wide complex tachycardia with 2 alternating qrs morphologies (see rhythm lead 1). This is a type of polymorphic ventricular tachycardia called biventricular tachycardia.
- For those who haven’t taken their ABEM board exam yet, this can be associated with digoxin toxicity.
‣
ECG 12
‣
‣
- Yes
‣
- Except for the very first beat, they do
‣
- Yes
‣
- Yes
‣
- No. Except for the first beat, the P waves are negative in II, II, avF and upright in avR which is an abnormal axis
‣
- There is atrial communication to the ventricles but this is not coming from the sinus node. This is not a sinus rhythm.
‣
- The rhythm starts off as sinus for 1 beat then converts to an ectopic atrial rhythm as indicated by
- Abnormal P wave axis, suggesting that atrial depolarization is originating from a focus outside the sinus node
- The 1:1 P:QRS ratio and constant PR interval suggest that the conduction through the AV node and ventricles is intact.
‣
ECG 13
‣
‣
- No
‣
- N/a
‣
- N/a
‣
- N/a
‣
- N/a
‣
- Not sinus rhythm
‣
‣
- Monomorphic VT
- Assume this is if any doubts
- SVT (AVNRT, Orthodromic AVRT) with bundle branch block
- This does have RBBB morphology (dominant R wave in V1/V2) but not classic RBBB. There is a monophasic R wave in lead I that is more seen in LBBB. V6 is also atypical for RBBB which typically has R>S (the opppsite is present here). A prior ECG would be helpful.
- Antidromic AVRT
- A history would be helpful. The qrs waves appear less slurred when compared to ECG 10. A prior ECG would be helpful.
‣
- Narrowish wide qrs complexes (closer to 120ms than 200ms)
- Left axis deviation
- RBBB morphology
‣
- LITFL Left Fascicular VT
- LITFL RVOT VT
‣
ECG 14
‣
‣
- Yes
‣
- No (take a look at the rhythm leads). There are multiple morphologies.
‣
- No
‣
- Yes
‣
- Yes
‣
- There is atrial activity and atrial-ventricular communication but this not sinus rhythm
‣
- This is an irregular narrow complex tachycardia with p waves / atrial beats. The differential is
- Atrial flutter with variable conduction - less likely given varying p-wave morphology
- Multifocal atrial tachycardia (MAT) - This is the most likely diagnosis, which requires 3 different p wave morphologies.
‣
ECG 15
‣
‣
- Yes
‣
- Yes
‣
- No
‣
- No
‣
- Yes
‣
- There is definitely atrial activity but this is not sinus rhythm
‣
- There are two qrs morphologies (5 beats total here). Look at rhythm lead II
- QRS #1 and QRS #4 is a sinus beat followed by qrs complex.
- QRS #2-4 are ventricularly paced beats triggered by preceding atrial beat. (Atrial sensed, ventricularly paced)
- Then there are multiple p waves that have no qrs complexes
- Putting this all together: This is an example pacemaker malfunction, likely failure to sense. The pacemaker here only fires 3x when there over 11 p waves on this rhythm strip.
‣
ECG 16
‣
‣
- Yes
‣
- Yes
‣
- Yes
‣
- No. There is 1 p wave to 2 QRS complexes
‣
- Yes
‣
- This is sinus rhythm….but what’s going on here?
‣
- Here you can see grouped beats. A p wave followed by a qrs complex, then another qrs complex without a p wave followed by a pause. The differential diagnosis is
- Bigeminy w/ PAC vs. PJC vs. PVC
- The 2nd QRS complex for each pair is narrow so this is not ventricular bigeminy
- If you look closely, there may be inverted p waves in the inferior leads before each 2nd qrs complex but its hard to tell. This would make this atrial bigeminy
- Conservatively, this is junctional bigeminy where the 2nd beat of each pair is a premature junctional contraction (narrow complex, no p waves or may have retrograde p waves).
- This is also an infero-lateral STEMI
‣
Conclusion: The orthopedic surgeon thanks you for the input and reminds you why all patients should be admitted to medicine.
This post is for education and not medical advice.