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Dawn's picture

Large Anterior Wall M.I. and Effect of Lead Reversal

Submitted by Dawn on Mon, 05/23/2022 - 15:52

EDIT: Please refer to the comments below this text. The second ECG in this series shows unexpected QRS and ST-T morphology changes, which I tried to explain by way of the patient's long anterior descending coronary artery. However, Dave Richley, who is a very well-known cardiac physiologist and ECG Guru took the time to analyze these morphologies and realize they can be explained by an inadvertent ECG LEAD MISPLACEMENT. This patient does have a proximal lesion of the LAD, proven and repaired in the cath lab. But the inferior wall does not have the injury it appears to have in this second ECG. Thanks to Dave for reminding us to slow down and look closely when things don't look "right".

The Patient:   These two ECGs, taken 26 minutes apart, were obtained from a 50-year-old man who complained of sudden onset of chest pain.  He denied history of coronary artery disease. He was Covid-positive, and the rest of his medical history was unremarkable.

ECG No. 1:  This ECG was obtained by paramedics enroute to the hospital.  For your beginner-level students, it will be easy to demonstrate the large ST elevations in V3 through V6. The machine’s measurements at the bottom confirm that this ECG meets any field criteria for ST elevation M.I. “STEMI”.

But there is so much more to see! Taking a methodical approach, and starting with rate and rhythm, we see sinus bradycardia at 57 bpm. Intervals and frontal plane axis are within normal limits. R wave progression in the chest leads is stalled in V1- V3 due to loss of initial r waves (narrow QS). The transition to positive deflections in V4 – V6 is abrupt.  These q waves in the V1 and V2 appear narrow, but V3 appears to have a Q wave that is almost wide enough to be considered pathological.  Narrow Q waves may be a transient sign of injury, while wide ones (>40 ms) are an ECG sign of necrosis.

Dawn's picture

Anterior Wall M.I. With Bifascicular Block

Submitted by Dawn on Sat, 03/25/2017 - 15:13

This ECG is taken from an 82-year-old man who called 911 because of chest pain.  He has an unspecified “cardiac” history, but we do not know the specifics. 

WHAT IS THE RHYTHM?  The heart rate is 69 bpm, and there are P waves before every QRS complex. The underlying rhythm is regular, with one premature beat that is wide without a P wave.  The PR interval is slightly prolonged at .25 seconds.  The rhythm is normal sinus rhythm with first-degree AV block and one PVC. 

WHY THE WIDE QRS?   The QRS complex is wide at .14 seconds. The QRS in V 1 has a wide R wave after a small Q wave.  This in consistent with right bundle branch block pattern, with loss of the normal initial small r wave (pathological Q waves).  The diagnosis of RBBB is further corroborated by the wide little S waves in Leads I and V6.  The QRS frontal plane axis is -66 degrees per the machine, and clearly “abnormal left” because the QRS in Lead II is negative, while the QRS in Leads I and aVL are positive.  This is left anterior fascicular block, also called left anterior hemiblock.  The combination of RBBB and LAFB is a common one, as the two branches have the same blood supply.  It is also called bi-fascicular block. 

WHAT ABOUT THE ST SEGMENTS?  The ST segments in leads V2 through V6 are elevated, and their shape is very straight, as opposed to the normal shape of coved upward (smile). Even though the amount of ST elevation at the J points appears subtle, the shape of the segments, the fact that they appear in related leads, and the fact that the patient is an elderly male with chest pain all point to the diagnosis of ANTERIOR WALL ST elevation M.I. (STEMI).  Additional ST changes include a straight shape in Leads I and aVL and ST depression in V1 and aVR.  

PATIENT OUTCOME  The patient was transported to a cardiac center, where he received angioplasty in the cath lab.  The left coronary artery was found to be occluded, and was repaired and stented.  He recovered without complications and was sent home in a few days.

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