Lots of great comments and it was good to see the depth of discussion on the appropriate treatment and transport for this patient!
This is the conclusion to 64 year old female CC: Trouble Breathing.
When we left off our crew was attending to an elderly female patient in respiratory extremis. Pulmonary edema was present and their initial 12-Lead was concerning.
Many readers correctly noted the normal sinus rhythm, a 1° AV Block, and a wide QRS. Other readers pointed out the apparent Left Bundle Branch Block due to a negative QS complex in V1. Only a few readers picked up on the abnormal presentation of the LBBB: lead I has an rS complex and there is right axis deviation! Right axis deviation is a very uncommon finding in LBBB .
Just as it is important to know what a normal 12-Lead looks like, we also need to know what our abnormal 12-Leads should normally look like. In the case of LBBB, we expect V1 to be negative and leads I/V6 to have broad, monomorphic R-waves.
We also expect the T-waves to be discordant with the dominant deflection of the QRS. A picture is worth a thousand words in this case:
In our case we have three troubling findings:
- An rS complex in Lead I with Right Axis Deviation, which is very uncommon in LBBB.
- Concordant ST-segments in leads V5 and V6.
- Excessive ST-segement elevation in leads V2 through V4.
Many readers stated that a Left Bundle Branch Block is a STEMI mimic and precludes an activation of a STEMI alert until an old 12-Lead is used in comparison. However, criteria exists to diagnose a STEMI in the face of a LBBB or Paced rhythm.
Additionally, this patient's 12-Lead does not show a normal LBBB, but rather a non-specific intraventricular conduction defect or IVCD. Dr. Garcia would encourage, "considering the company it keeps,"  which includes acute myocardial infarction!
Sgarbossa's criteria (and its modifications) for diagnosing STEMI in the face of LBBB or a Paced Rhythm has been covered in depth before so we'll only cover the positive criteria found on our 12-Lead:
- Is there ST-segment elevation ≥1 mm that is concordant with the QRS complex? Yes.
- Is there ST-segment depression ≥1 mm in leads V1, V2, or V3? No.
- Is there ST-segment elevation ≥5 mm, or ≥20% the depth of the S-wave, that is discordant with the QRS complex? Yes.
With 2 of the 3 criteria met (only 1 is required), we can be very confident that we're looking at a STEMI. Additionally, any concordant ST-elevation present should always suggest a STEMI.
The paramedic in this case recognized the concordant ST-elevation and the abnormal LBBB, called in a STEMI alert, and transported the patient to the PCI capable center. The patient improved significantly on the non-rebreather and CPAP was not necessary. Prior to arrival a second 12-Lead ECG was acquired:
Enroute the patient proved to be difficult for IV access, and received external jugular access in the ED. Labs were drawn while they waited for the cath lab team to arrive.
In the cath lab a 100% occlusion of the LAD was found and corrected with stenting.
For QA purposes an old ECG was retrieved after the call to compare to the field ECG:
Given this prior ECG, the new LBBB alone would likely cause a STEMI activation. However, in the absence of our more definitive changes this is a very weak criteria for activation .
Even without the prior ECG, we have an abnormal LBBB (most likely IVCD due to a peri-infarction block) with concordant ST-elevation and a patient presenting with signs of actue left sided heart failure: all of which point to an acute myocardial infarction!
This case highlights the importance of knowing what abnormal should normally look like and understanding that not every patient fits the protocol. We hope you enjoyed this case as much as we did, so be sure to continue the discussion below.
- Childers R, et al. Left bundle branch block and right axis deviation: a report of 36 cases. J Electrocardiol, 2000; 33 Suppl:93-102. [PubMed]
- The Art of Interpretation Series. http://www.12leadecg.com/
- Jain S, et al. Utility of left bundle branch block as a diagnostic criterion for acute myocardial infarction. Am J Cardiol, 2011; 107(8):1111-6. [PubMed]