ECG Basics & Fundamentals: you don't always need ST segment elevation to benefit from acute reperfusion therapy

HPI: A 75-year-old male with a history of hypertension presents to the ED with substernal chest pressure. There is no associated diaphoresis or nausea. The following ECG was obtained.

Case ECG

Before watching this week's video, ask yourself these questions:

1. What ECG abnormalities do you notice?
2. Would you emergently activate the cath lab or administer thrombolytics?

Case Interpretation

Posterior MI's are the most common type of missed STEMI!

• 4-10% of STEMI's are isolated Posterior MI's
• Usually associated with inferior or lateral MI due to RCA or circumflex occlusion
• Often misdiagnosed as just ischemia or Non-STE-ACS
• Only 30% are revascularized within 90 minutes
• Look for ST-depression in anteroseptal leads!

 Differential for ST-depression in anteroseptal leads

• Anteroseptal ischemia
• Posterior STEMI
  • Mirror image of septal STEMI in leads V1-V3
  • Look for tall R waves, ST-depression, and upright T waves in V1-V3 on conventional 12 lead ECGs
  • Even 0.5 mm of STE on posterior lead ECGs is diagnostic
• Miscellaneous
  • RBBB
  • Hypokalemia
  • Etc.

Take home Point:

ST-depression in the anteroseptal leads might represent  posterior STEMI. Get posterior leads!

References:

Waldo SW, Brenner DA, Li S, et al. Reperfusion times and in-hospital outcomes among patients with an isolated posterior myocardial infarction: insights from the National Cardiovascular Data Registry (NCDR). American Heart Journal 2014;167(3):350-4. PMID: 24576519

Ayer A, Terkelsen CJ. Difficult ECGs in STEMI: lessons learned from serial sampling of pre- and in-hospital ECGs. Journal of Electrocardiology 2014;47(4):448-58. PMID: 24792903.

Wei EY, Hira RS, Huang HD, et al. Pitfalls in diagnosing ST elevation among patients with acute myocardial infarction. Journal of Electrocardiology 2013;46(6):653-9. PMID: 23890685.

Waldo SW, Armstrong EJ, Kulkarni A, et al. Clinical characteristics and reperfusion times among patients with an isolated posterior myocardial infarction. J Invasive Cardiol 2013;25(8):371-5. PMID: 23913600.

Kudos: Thanks to Drs. Dean Burns and Amir Reyahi for sharing this week's case!

Notes: Questions for Amal? Email him at amalmattu@comcast.net or find him on Twitter @amalmattu.