A male in his 40s presented to the ED by ambulance with acute chest pain, possibly waxing and waning. He had been working out and felt dizzy and weak in addition to the chest pain.
He had a pacemaker in place that he stated was due to a congenital problem, later found to be due to congenital absence of atrial activity. He had no history of coronary disease.
Here is his first ED ECG (ECG 1):
ECG 2: 25 minutes later
ECG 3: His prehospital ECG was located; it had been recorded 25 minutes before the first ED ECG:
ECG 1:
1. There are no P-waves. The rate is slightly above 60. There are no pacer spikes, so either the pacer is not working or its rate is set below 60.
2. There is an RBBB and LAFB morphology, which means that either the junction is escaping and there is RBBB + LAFB, or there is a posterior fascicular escape. A rate of 60 suggests that it is junctional and not fascicular.
3. V2 lacks the normal ST depression that one sees in RBBB. In RBBB, the ST segment is usually discordant (opposite to) the positive R'-wave, with up to 1 mm of ST depression, also usually with an inverted T-wave, as seen in the "normal RBBB" ECG below.
4. Concordant STE in lead I
5. Notice the slight ST elevation in V3, with up-down T-wave. This is highly suggestive of ischemia.
6. There is very poor R-wave progression from V3-V6.
7. There are Proportionally large T-waves from V3-V6.
In this situation, all these features are all but diagnostic of LAD occlusion.
Normal RBBB
ECG 2:
Same analysis, except that now there is new ST elevation in V4-V6 and dynamic T-waves in V2 and V3, with slightly increased ST elevation in aVL with reciprocal ST depression in lead III.
ECG 3: Prehospital ECG:
1. This one is paced!! (Also at a rate slightly above 60)
2. Look at lead V6. There is proporionally excessively discordant ST elevation at 2.5 mm. Divide that by the preceding S-wave (6 mm), and the proportion of 2.5/6 = 42%. I believe this is diagnostic of coronary occlusion.
3. The T-waves in V3-V6 are very abnormally large, highly suggestive of acute occlusion.
ECG in Ventricular Paced Rhythm with Coronary Occlusion
The Modified Sgarbossa criteria for left bundle branch block (LBBB), which I apply to ventricular paced rhythm, uses a hard cutoff of 25% in just one lead to diagnose coronary occlusion. This is the third criterion (1st criterion is concordant STE of 1 mm in 1 lead, and 2nd is concordant ST depression of 1 mm in one of leads V1-V3); any one of the 3 makes the diagnosis. Our research would indicated that the normal discordant proportional ST elevation is about 11% and that anything above 15% is very likely to be occlusion. A 25% ratio was 99% specific, but a 20% proportion was still 94% specific in the validation study!
We are in the midst of a multicenter, international study to assess the Modified Sgarbossa Criteria in Paced Rhythm. It is called the PERFECT study! (Paced ECG Requiring Fast Emergent Coronary Therapy). https://clinicaltrials.gov/ct2/show/NCT02765477
Many physicians still do not believe that STEMI can be diagnosed in the presence of ventricular paced rhythm.
One of my mentors, K. Wang, put up an image on Medscape of a Paced ECG that clearly showed STEMI and quizzed the readers and received this answer:
Case Continued:
The cath lab was activated emergently and the patient was found to have 100% occlusion of the first Diagonal off the LAD. It was opened and stented.
The peak trop I was 33.9 ng/mL.
A subsequent echo showed:
--Normal left ventricular size, thickness estimated left ventricular ejection fraction is 50-55 %.
--Regional wall motion abnormality-distal septum anterior and apex,dyskinetic.
--Regional wall motion abnormality-distal inferior wall, dyskinetic.
--Asynchronous interventricular septal motion nonspecific.
Learning Points:
1. RBBB can obscure LAD occlusion, but you should suspect it in the absence of normal discordant ST depression in V2 and V3, or with hyperacute T-waves.
2. Paced rhythm obscures MI far less than believed. Coronary occlusion can definitely be diagnosed in the presence of ventricular paced rhythm.
3. Even in normal conduction, acute coronary occlusion is frequently not evident on the ECG. This is also true with RBBB, LBBB, and Paced Rhythm. There is little evidence supporting the notion that it is far more difficult in the latter three.
He had a pacemaker in place that he stated was due to a congenital problem, later found to be due to congenital absence of atrial activity. He had no history of coronary disease.
Here is his first ED ECG (ECG 1):
 |
| What do you think? (It is NOT paced) See analysis below. |
ECG 2: 25 minutes later
 | |
| What do you think? (Still not paced) See analysis below. |
ECG 3: His prehospital ECG was located; it had been recorded 25 minutes before the first ED ECG:
 | |
|
ECG 1:
1. There are no P-waves. The rate is slightly above 60. There are no pacer spikes, so either the pacer is not working or its rate is set below 60.
2. There is an RBBB and LAFB morphology, which means that either the junction is escaping and there is RBBB + LAFB, or there is a posterior fascicular escape. A rate of 60 suggests that it is junctional and not fascicular.
3. V2 lacks the normal ST depression that one sees in RBBB. In RBBB, the ST segment is usually discordant (opposite to) the positive R'-wave, with up to 1 mm of ST depression, also usually with an inverted T-wave, as seen in the "normal RBBB" ECG below.
4. Concordant STE in lead I
5. Notice the slight ST elevation in V3, with up-down T-wave. This is highly suggestive of ischemia.
6. There is very poor R-wave progression from V3-V6.
7. There are Proportionally large T-waves from V3-V6.
In this situation, all these features are all but diagnostic of LAD occlusion.
Normal RBBB
 |
| Normal RBBB, with normal ST depression, up to 1 mm, in V2 and V3, and inverted T-waves. Note the absence of ST elevation and the size of the T-waves in lateral precordial leads. |
ECG 2:
Same analysis, except that now there is new ST elevation in V4-V6 and dynamic T-waves in V2 and V3, with slightly increased ST elevation in aVL with reciprocal ST depression in lead III.
ECG 3: Prehospital ECG:
1. This one is paced!! (Also at a rate slightly above 60)
2. Look at lead V6. There is proporionally excessively discordant ST elevation at 2.5 mm. Divide that by the preceding S-wave (6 mm), and the proportion of 2.5/6 = 42%. I believe this is diagnostic of coronary occlusion.
3. The T-waves in V3-V6 are very abnormally large, highly suggestive of acute occlusion.
ECG in Ventricular Paced Rhythm with Coronary Occlusion
The Modified Sgarbossa criteria for left bundle branch block (LBBB), which I apply to ventricular paced rhythm, uses a hard cutoff of 25% in just one lead to diagnose coronary occlusion. This is the third criterion (1st criterion is concordant STE of 1 mm in 1 lead, and 2nd is concordant ST depression of 1 mm in one of leads V1-V3); any one of the 3 makes the diagnosis. Our research would indicated that the normal discordant proportional ST elevation is about 11% and that anything above 15% is very likely to be occlusion. A 25% ratio was 99% specific, but a 20% proportion was still 94% specific in the validation study!
We are in the midst of a multicenter, international study to assess the Modified Sgarbossa Criteria in Paced Rhythm. It is called the PERFECT study! (Paced ECG Requiring Fast Emergent Coronary Therapy). https://clinicaltrials.gov/ct2/show/NCT02765477
Many physicians still do not believe that STEMI can be diagnosed in the presence of ventricular paced rhythm.
One of my mentors, K. Wang, put up an image on Medscape of a Paced ECG that clearly showed STEMI and quizzed the readers and received this answer:
 |
| 50% gave the wrong answer: you cannot diagnose infarction in ventricularly paced rhythms. |
Case Continued:
The cath lab was activated emergently and the patient was found to have 100% occlusion of the first Diagonal off the LAD. It was opened and stented.
The peak trop I was 33.9 ng/mL.
A subsequent echo showed:
--Regional wall motion abnormality-distal septum anterior and apex,dyskinetic.
--Regional wall motion abnormality-distal inferior wall, dyskinetic.
--Asynchronous interventricular septal motion nonspecific.
Learning Points:
1. RBBB can obscure LAD occlusion, but you should suspect it in the absence of normal discordant ST depression in V2 and V3, or with hyperacute T-waves.
2. Paced rhythm obscures MI far less than believed. Coronary occlusion can definitely be diagnosed in the presence of ventricular paced rhythm.
3. Even in normal conduction, acute coronary occlusion is frequently not evident on the ECG. This is also true with RBBB, LBBB, and Paced Rhythm. There is little evidence supporting the notion that it is far more difficult in the latter three.
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