A woman in her 90s with a pacemaker for heart block but no history of coronary artery disease presented to the ED for 45 minutes of nonradiating, nonpleuritic chest pain that woke her from an afternoon nap. She had no syncope, palpitations, shortness of breath, fever, cough, or other symptoms. Nitroglycerin was given by the paramedics, and may have helped slightly.
Her vital signs were within normal limits, and her exam was otherwise normal. The initial differential diagnosis included GERD, acute coronary syndrome, and gallstones. The computer read the ECG as the patient having an electronic AV pacemaker and an abnormal rhythm. Do you agree with the computer? What should you do next?
The computer read was incomplete. This ECG was diagnostic of a proximal left anterior descending artery occlusion by two of three of the Smith-modified Sgarbossa criteria. This was a potentially deadly occlusion MI. There was concordant ST elevation >1 mm in multiple leads: I, aVL, and V2, and there was discordant ST elevation >25% of the QRS height in leads V5 and V6 and perhaps V4.
There was also concordant ST depression >1 mm in leads III and aVF and perhaps lead II, which was concerning but not the third criterion, which for a right bundle branch block (RBBB) pattern paced rhythm is concordant ST depression in one of the leads, V1-V6. It is V1-V3 for left bundle branch block (LBBB).
The cardiologist declined to take the patient to the cath lab based on age, and could or would not come to the ED to see the patient. He did call a second cardiologist to see the patient. That cardiologist did a bedside echo and recommended heparin but not tPA. The patient's troponin I was <0.01, drawn about one hour after pain onset (99% URL <0.030: troponin I immunoassay, Abbott). The second troponin drawn two hours after pain onset was 0.07 and five hours later was 2.1. The peak troponin was >77.0.
The patient survived the hospitalization, but was left with severe congestive heart failure.
- Know the criteria identifying STEMI in LBBB and RBBB. For most pacemakers, there will be an LBBB-like pattern. This one had more of a RBBB pattern, however.
- The traditional Sgarbossa criteria using >5 mm of appropriately discordant ST elevation as criteria C are about 56% sensitive and 97% specific. The Smith-modified Sgarbossa criteria using appropriately discordant ST elevation >25% of the height of the preceding QRS as criteria C is better, with about 86% sensitivity and 97% specificity.
- It is not appropriate to withhold PCI based on age. Even thrombolytics should not be withheld based on age.
This article was peer-reviewed by Stephen W. Smith, MD, ofDr. Smith's ECG Blog.
Dr. Pregersonis an emergency physician at Tri-City Hospital and Scripps Coastal, both in Oceanside. He is the author of the EMN blog Bradycardia athttp://bit.ly/EMN-Bradycardia, and of Emergency Medicine 1-Minute Consult, Tarascon Emergency Department Quick Reference Guide, A to Z Emergency Pharmacopoeia & Antibiotic Guide, Don't Try This at Home, and Think Twice: More Lessons from the ER. Follow him on Twitter@EM1MinuteGuru, and visit his website atEMresource.org.