The Patient:  A 75-yr-old man called Emergency Services because of chest pain and shortness of breath. He had just returned from a 15-mile bicycle ride, during which he had to stop several times to catch his breath, not normal for him.  He was so diaphoretic, they were not able to get a good 12-lead ECG. While the paramedics were assessing him and preparing for transport, he went into ventricular fibrillation. He was defibrillated at 360 joules within seconds of onset, and converted to sinus rhythm with pulses.

The ECGs:

11:24 am:  This ECG is obtained after defibrillation, and there is return of spontaneous circulation (ROSC).   The rhythm is sinus at 78 bpm.  The QRS is slightly wider than normal at .12 seconds. (It is my opinion that the ECG machine read the QRS wider because of the J point and ST changes.) Other intervals and frontal plane axis are within normal limits. R wave progression is normal.

There is marked ST elevation in Leads II, III, & aVF, with reciprocal ST depression in Leads I, aVR, & aVL. (inferior wall transmural injury). There is ST elevation in V5 and V6 (low lateral transmural injury), and ST depression in V1 through V4 (posterior-lateral transmural injury with reciprocal changes in these leads.)

 11:25 am:  The rhythm has changed.  There are no clear P waves, and the rhythm is irregularly-irregular. This is atrial fibrillation, with one PVC.  Not only that, the ST changes are completely different.  The inferior wall now has ST depression, with reciprocal elevation in aVL.  There is now ST elevation in right sided chest leads V1 and V2, as well as ST depression in V5 and V6.  The ST changes of acute M.I. can vary as the supply-demand ratio shifts.  As demand increases, or supply decreases, the ST segments will elevate, indicating transmural ischemia/injury.  If demand decreases or supply increases (arterial dilation, increased cardiac output, etc.), the ST elevation will disappear, and ST depression will represent ischemia that is not transmural.  BEWARE:  Unless this occurs after catheterization and angioplasty or pharmaceutical thrombolytics, the obstruction is still there, and will probably increase again.

 11:32 am:   The rhythm is still atrial fibrillation, with a tendency to be fast at times. The ST elevation is back in the inferior and low lateral walls.  There are “appropriate” reciprocal changes in the limb leads I, aVL, and aVR.  V1 through V4 have ST depression reflecting the ST elevation that is on the back of the heart.

 Outcome:  The patient was taken to the cath lab on admission to the hospital.  He was found to have a non-dominant right coronary artery (RCA), which was patent.  His dominant left circumflex artery (LCx) was 100% occluded.  The posterior descending artery (PDA), which supplies the inferior and posterior walls, arises from the right coronary artery in 70-80% of the population.  The PDA arises from the LCx in 8-10% of the population.  In 10-20% of people, the PDA is supplied by both the RCA and the LCx.

This patient had a successful recovery, and was discharged from the cardiac ICU after two days, with a Cerebral Performance Category of 1 (CPC-1) – no neurologic deficits.  This is a great case to illustrate two important points:  1)  During an acute occlusive event, the ECG can change minute-to-minute.  It is important to obtain serial ECGs on anyone having chest pain or other symptoms suggestive of M.I.  Remember, IF THE PATIENT IS SWEATING IN A COOL ENVIRONMENT, YOU SHOULD BE, TOO.   2)  Early, prompt treatment by personnel capable of defibrillation and resuscitation, along with access to an interventional cath lab, makes a huge difference in survivability in an occlusive M.I.  (OMI).  There is great disparity between geographical locations regarding the availability of defibrillators (including Automatic External Defibrillators), people trained to use them, quick response and transport times, and nearby hospitals that have comprehensive cardiac services. This patient was fortunate to arrest in an area with very advanced EMS agencies and nearby hospitals with a full range of cardiac services

               Our thanks to Ashley Terrana, Paramedic, for contributing this case.