Paucis Verbis: Sgarbossa’s Criteria with LBBB
It is difficult to determine if a patient with a left bundle branch block (LBBB) has an acute myocardial infarction (AMI) because ST segments are “appropriately discordant” with the terminal portion of the QRS. That means if the QRS complex is negative (or downgoing), the ST segment normally will be positive (or elevated). Similarly if the QRS complex is positive (or upgoing), the ST segment will be negative (or depressed).
PV Card: Sgarbossa’s Criteria
In 1996, Sgarbossa et al looked through the GUSTO-1 trial patients with LBBB and AMI. They derived 3 criteria which may help diagnose the “hidden” AMI. The criteria are:
1. ST elevation ≥ 1 mm concordant with QRS complex (most predictive of AMI of the 3 criteria)
2. ST depression ≥ 1 mm in lead V1, V2, or V3
3. ST elevation ≥ 5 mm where discordant with QRS complex
Use these criteria with caution though. None of these criteria are perfect. They are to help you risk-stratify. For instance, criteria #3 (ST elevation ≥ 5 mm) can exist in asymptomatic patients with LBBB because of concurrent left ventricular hypertrophy and high voltages.
How do you risk-stratify undifferentiated chest pain patients in the Emergency Department? There are a multitude of causes for chest pain. We are always taught to think of the 5 big life-threats: ACS, PE, aortic dissection, tension pneumothorax, and pericardial tamponade.
The treatment of shock should focus on correcting the underlying pathophysiology. With persistent hemodynamic instability, a vasopressor and/or inotrope should be selected. Reviewing receptor physiology can help you select the best-fit agent for the patient’s clinical condition. There is an especially useful table on medication selection in the reviewed 2008 EM Clinics of North America article.
A few days I wrote about my “peripheral brain” note cards that I carry with me on each ED shift. These cards contain brief summaries of updated guidelines, evidence based literature, and clinical pearls. I constantly get requests for a copy of them, but they are fairly outdated now that I’m out of residency.